<?php

/* the glue that holds it together / everything else. */

class ABJ_404_Solution_PluginLogic {

	/** @var ABJ_404_Solution_Functions */
	private $f = null;

	/** @var ABJ_404_Solution_DataAccess */
	private $dao = null;

	/** @var ABJ_404_Solution_Logging */
	private $logger = null;

	private $urlHomeDirectory = null;

	private $urlHomeDirectoryLength = null;

	private $options = null;

	/** Track whether we're already in the method that updates the database that may be called recursively.
	 * @var bool */
    private static $instance = null;

    private static $uniqID = null;

    /** Use this to avoid an infinite loop when checking if a user has admin access or not. */
    private static $checkingIsAdmin = false;

    /** Allowed column names for orderby parameter. */
    private static $allowedOrderbyColumns = ['url', 'status', 'type', 'dest', 'code', 'timestamp', 'created', 'lastused'];

    /** Allowed values for order parameter. */
    private static $allowedOrderValues = ['ASC', 'DESC'];

    /** @return ABJ_404_Solution_PluginLogic The singleton instance of the class. */
    public static function getInstance() {
    	if (self::$instance == null) {
    		self::$instance = new ABJ_404_Solution_PluginLogic();
    		self::$uniqID = uniqid("", true);

    		// these filters allow non-admins to have admin access to the plugin.
    		add_filter( 'user_has_cap',
    			'ABJ_404_Solution_PluginLogic::override_user_can_access_admin_page', 10, 4 );
    	}

    	return self::$instance;
    }

    /**
     * Constructor with dependency injection.
     * Dependencies are now explicit and visible.
     *
     * @param ABJ_404_Solution_Functions|null $functions String manipulation utilities
     * @param ABJ_404_Solution_DataAccess|null $dataAccess Data access layer
     * @param ABJ_404_Solution_Logging|null $logging Logging service
     */
    function __construct($functions = null, $dataAccess = null, $logging = null) {
    	// Use injected dependencies or fall back to getInstance() for backward compatibility
    	$this->f = $functions !== null ? $functions : ABJ_404_Solution_Functions::getInstance();
    	$this->dao = $dataAccess !== null ? $dataAccess : ABJ_404_Solution_DataAccess::getInstance();
    	$this->logger = $logging !== null ? $logging : ABJ_404_Solution_Logging::getInstance();

    	$urlPath = parse_url(get_home_url(), PHP_URL_PATH);
    	// Fix MEDIUM #1 (5th review): Distinguish between parse failure (false) and no path (null)
    	if ($urlPath === false) {
    		$this->logger->warn("Malformed home URL detected: " . get_home_url());
    		$urlPath = '';
    	} else if ($urlPath === null) {
    		$urlPath = '';
    	}

    	// Fix HIGH #2 (4th review): Decode subdirectory for consistency with runtime processing
    	$decodedPath = rawurldecode(rtrim($urlPath, '/'));
    	// Fix HIGH #3 (4th review): Remove null bytes and control characters for security
    	$this->urlHomeDirectory = preg_replace('/[\x00-\x1F\x7F]/', '', $decodedPath);
    	$this->urlHomeDirectoryLength = $this->f->strlen($this->urlHomeDirectory);
    }
    
    /** This replaces the current_user_can('administrator') function.
     * 
     * Use the following to add a filter.
     * // -------
     * add_filter( 'abj404_userIsPluginAdmin', 'my_custom_function' );
     * function my_custom_function( $value ) { 
     * 	  // validate user can access the plugin here.
     * 	  return $value;
     * }
     * // -------
     * 
     * @return bool true if $abj404logic->userIsPluginAdmin()
     */
    function userIsPluginAdmin() {
    	// avoid an infinite loop.
    	if (ABJ_404_Solution_PluginLogic::$checkingIsAdmin) {
    		return false;
    	}
    	
    	ABJ_404_Solution_PluginLogic::$checkingIsAdmin = true;
    	try {
    		// Capability checks should not trigger DB upgrade checks (which can throw and lock users out).
    		$options = $this->getOptions(true);
    		$f = $this->f;
    		global $current_user;

    		// Baseline: admins have access. Prefer capability checks over role-name checks.
    		$isPluginAdmin = current_user_can('manage_options') || current_user_can('administrator');
    		if (function_exists('is_multisite') && is_multisite() && function_exists('is_super_admin') && is_super_admin()) {
    			$isPluginAdmin = true;
    		}

    		// check extra admins.
    		$extraAdmins = $options['plugin_admin_users'] ?? array();
    		$current_user_name = null;
    		if (isset($current_user)) {
    			$current_user_name = $current_user->user_login;
    		}
    		if ($current_user_name != null && $current_user_name != false) {
    			$check = false;
    			if (is_array($extraAdmins)) {
    				$extraAdmins = array_filter($extraAdmins,
    					array($f, 'removeEmptyCustom'));
    				$check = true;
    			} else if (is_string($extraAdmins)) {
    			    $extraAdmins = $this->f->explodeNewline($extraAdmins);
    				$check = true;
    			}
    			if ($check && in_array($current_user_name, $extraAdmins)) {
    				$isPluginAdmin = true;
    			}
    		}

    		// do the filter in case someone wants to add one
    		return apply_filters('abj404_userIsPluginAdmin', $isPluginAdmin);
    	} finally {
    		ABJ_404_Solution_PluginLogic::$checkingIsAdmin = false;
    	}
    }

    /**
     * Verify a nonce for admin-link actions, without depending on the browser's Referer header.
     *
     * WordPress core's check_admin_referer() can fail in environments that strip referrers; in that
     * case we fall back to wp_verify_nonce() using the same nonce value.
     *
     * @param string $action Nonce action string used in wp_nonce_url()
     * @param string $queryArg Nonce query arg name (default '_wpnonce')
     * @return bool
     */
    private function verifyLinkNonce($action, $queryArg = '_wpnonce') {
        // Prefer check_admin_referer when available, but don't die on failure.
        if (function_exists('check_admin_referer')) {
            $ok = check_admin_referer($action, $queryArg, false);
            if ($ok) {
                return true;
            }
        }

        if (!function_exists('wp_verify_nonce')) {
            return false;
        }

        if (!isset($_REQUEST[$queryArg])) {
            return false;
        }

        $nonce = sanitize_text_field(wp_unslash($_REQUEST[$queryArg]));
        if ($nonce === '') {
            return false;
        }

        return wp_verify_nonce($nonce, $action) !== false;
    }

    /**
     * Get the current user's settings mode preference.
     * @return string 'simple' or 'advanced'
     */
    function getSettingsMode() {
        $user_id = get_current_user_id();
        if (!$user_id) {
            return 'simple';
        }
        $mode = get_user_meta($user_id, 'abj404_settings_mode', true);
        return ($mode === 'advanced') ? 'advanced' : 'simple';
    }

    /**
     * Set the current user's settings mode preference.
     * @param string $mode 'simple' or 'advanced'
     * @return bool|int Meta ID on success, false on failure
     */
    function setSettingsMode($mode) {
        $user_id = get_current_user_id();
        if (!$user_id) {
            return false;
        }
        $valid_mode = ($mode === 'advanced') ? 'advanced' : 'simple';
        return update_user_meta($user_id, 'abj404_settings_mode', $valid_mode);
    }

    /** Allow the user to be an admin for the plugin. 
     * @param $allcaps
     * @param $caps
     * @param $args
     * @param $user
     * @return array an array of the capabilities
     */
    static function override_user_can_access_admin_page( $allcaps, $caps, $args, $user ) {
    	// if it's not an admin page then we don't change anything.
    	if (!is_admin()) {
    		return $allcaps;
    	}
    	
    	$abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
    	
    	$isPluginAdmin = false;
    	$isViewing404AdminPage = false;
    	
    	// is the user supposed to have access?
    	if ($abj404logic->userIsPluginAdmin()) {
    		$isPluginAdmin = true;
    	}
    	
    	if ($isPluginAdmin) {
    		$userRequest = ABJ_404_Solution_UserRequest::getInstance();
    		$queryParts = $userRequest->getQueryString();
    		
    		// are we viewing a 404 plugin page?
    		if (strpos($queryParts, ABJ404_PP) !== false) {
    			$isViewing404AdminPage = true;
    		}
    	}
    	
    	if ($isPluginAdmin && $isViewing404AdminPage) {
    		$allcaps['manage_options'] = true;
    	}
    	
    	return $allcaps;
    }
    
    /** If a page's URL is /blogName/pageName then this returns /pageName.
     * @param string $urlRequest
     * @return string
     */
    function removeHomeDirectory($urlRequest) {
    	// PHP 8.2+: Handle null input gracefully
    	if ($urlRequest === null) {
    		return '/';
    	}

    	$f = $this->f;
    	$urlHomeDirectory = $this->urlHomeDirectory;

    	// Fix CRITICAL #1 (5th review): Skip processing for root installations
    	// When WordPress is at domain root, urlHomeDirectoryLength is 0
    	// Without this check, substr($url, 0, 0) == '' is always TRUE, incorrectly stripping leading slash
    	if ($this->urlHomeDirectoryLength === 0) {
    		return $urlRequest;
    	}

    	// Fix CRITICAL #1 (2nd review): Check path boundary to prevent false positives
    	// e.g., /blog should match /blog/page but NOT /blogpost or /blog-archive
    	if ($this->f->substr($urlRequest, 0, $this->urlHomeDirectoryLength) == $urlHomeDirectory) {
    		// Verify path boundary: next character must be '/', '?', '#', or end of string
    		$nextChar = $this->f->substr($urlRequest, $this->urlHomeDirectoryLength, 1);
    		if ($nextChar === '/' || $nextChar === '?' || $nextChar === '#' || $nextChar === '') {
    			// Fix CRITICAL #2 (3rd review): Don't strip query/fragment markers
    			if ($nextChar === '/' || $nextChar === '') {
    				// Strip subdirectory + slash for paths: /blog/page → /page
    				$urlRequest = $this->f->substr($urlRequest, ($this->urlHomeDirectoryLength + 1));
    			} else {
    				// Fix HIGH #1 (4th review): Add leading slash for query/fragment
    				// Strip subdirectory, add leading slash: /blog?q=1 → /?q=1
    				$urlRequest = '/' . $this->f->substr($urlRequest, $this->urlHomeDirectoryLength);
    			}
    		}
    		// else: false positive (e.g., /blogpost when subdirectory is /blog) - don't strip
    	}

        return $urlRequest;
    }

    /**
     * Normalize URL to relative path by removing WordPress subdirectory.
     * This ensures URLs are stored/matched independently of subdirectory changes.
     * Fixes Issue #24: Redirects now survive WordPress subdirectory changes.
     *
     * @param string $url Full URL or path
     * @return string Relative path without subdirectory
     */
    function normalizeToRelativePath($url) {
        // Fix Issue #5: Handle empty or null URLs explicitly
        if ($url === null || $url === '') {
            return '/';
        }

        // Fix HIGH #2: Trim whitespace
        $url = trim($url);

        // Fix CRITICAL #2 (4th review): REMOVED rawurldecode() - URLs already decoded by UserRequest
        // Subdirectory decoding is now handled in constructor for consistency

        // Fix HIGH #2: If full URL, extract path only
        if (preg_match('#^https?://#i', $url)) {
            $parsed = parse_url($url);
            if ($parsed === false || !isset($parsed['path'])) {
                return '/';
            }
            $url = $parsed['path'];
            // Preserve query and fragment
            if (!empty($parsed['query'])) {
                $url .= '?' . $parsed['query'];
            }
            if (!empty($parsed['fragment'])) {
                $url .= '#' . $parsed['fragment'];
            }
        }

        // Fix HIGH #2: Handle protocol-relative URLs (//example.com/path)
        if (strpos($url, '//') === 0) {
            $parsed = parse_url('http:' . $url);
            if ($parsed !== false && isset($parsed['path'])) {
                $url = $parsed['path'];
                if (!empty($parsed['query'])) {
                    $url .= '?' . $parsed['query'];
                }
                if (!empty($parsed['fragment'])) {
                    $url .= '#' . $parsed['fragment'];
                }
            } else {
                return '/';
            }
        }

        // Remove home directory if present
        $relativePath = $this->removeHomeDirectory($url);

        // Fix Issue #5: Check if removeHomeDirectory() returned empty unexpectedly
        if ($relativePath === null || $relativePath === '') {
            // Return root path for empty results
            return '/';
        }

        // Fix HIGH #2: Normalize multiple slashes to single slash
        $relativePath = preg_replace('#/+#', '/', $relativePath);

        // Ensure consistent leading slash (but not multiple)
        $relativePath = '/' . ltrim($relativePath, '/');

        return $relativePath;
    }
    /** Forward to a real page for queries like ?p=10
     * @global type $wp_query
     * @param array $options
     */
    function tryNormalPostQuery($options) {
        global $wp_query;

        // this is for requests like website.com/?p=123
        $query = $wp_query->query;
        // if it's not set then don't use it.
        if (!isset($query['p'])) {
            return;
        }
        $pageid = $query['p'];
        if (!empty($pageid)) {
            $permalink = urldecode(get_permalink($pageid));
            $status = get_post_status($pageid);
            if (($permalink != false) && 
            	(in_array($status, array('publish', 'published')))) {
            	$homeURL = get_home_url();
            	if ($homeURL == null) {
            		$homeURL = '';
            	}
            	$urlHomeDirectory = parse_url($homeURL, PHP_URL_PATH);
            	if ($urlHomeDirectory == null) {
            		$urlHomeDirectory = '';
            	}
            	$urlHomeDirectory = rtrim($urlHomeDirectory, '/');
                $fromURL = $urlHomeDirectory . '/?p=' . $pageid;
                $redirect = $this->dao->getExistingRedirectForURL($fromURL);
                if (!isset($redirect['id']) || $redirect['id'] == 0) {
                    $this->dao->setupRedirect($fromURL, ABJ404_STATUS_AUTO, ABJ404_TYPE_POST, 
                            $pageid, $options['default_redirect'], 0);
                }
                $this->dao->logRedirectHit($fromURL, $permalink, 'page ID');
                $this->forceRedirect($permalink, esc_html($options['default_redirect']));
                exit;
            }
        }
    }
    
    /** 
     * @global type $abj404logging
     * @global type $abj404logic
     * @param string $urlRequest the requested URL. e.g. /404killer/aboutt
     * @param string $urlSlugOnly only the slug. e.g. /aboutt
     */
    function initializeIgnoreValues($urlRequest, $urlSlugOnly) {
        $abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
        
        $options = $abj404logic->getOptions();
        $ignoreReasonDoNotProcess = null;
        $ignoreReasonDoProcess = null;
        $httpUserAgent = array_key_exists('HTTP_USER_AGENT', $_SERVER) ? 
                $this->f->strtolower($_SERVER['HTTP_USER_AGENT']) : '';
        
        // Note: is_admin() does not mean the user is an admin - it returns true when the user is on an admin screen.
        // ignore requests that are supposed to be for an admin.
        $adminURL = parse_url(admin_url(), PHP_URL_PATH);
        if (is_admin() || $this->f->substr($urlRequest, 0, $this->f->strlen($adminURL)) == $adminURL) {
            $this->logger->debugMessage("Ignoring admin URL: " . $urlRequest);
            $ignoreReasonDoNotProcess = 'Admin URL';
        }
        
        // The user agent Zemanta Aggregator http://www.zemanta.com causes a lot of false positives on 
        // posts that are still drafts and not actually published yet. It's from the plugin "WordPress Related Posts"
        // by https://www.sovrn.com/. 
        $userAgents = $this->f->explodeNewline($options['ignore_dontprocess']);
        
        foreach ($userAgents as $agentToIgnore) {
            if (stripos($httpUserAgent, trim($agentToIgnore)) !== false) {
                $this->logger->debugMessage("Ignoring user agent (do not redirect): " .
                        esc_html($_SERVER['HTTP_USER_AGENT']) . " for URL: " . esc_html($urlRequest));
                $ignoreReasonDoNotProcess = 'User agent (do not redirect): ' . esc_html($_SERVER['HTTP_USER_AGENT']);
            }
        }
        
        // ----- ignore based on regex file path
        $patternsToIgnore = $options['folders_files_ignore_usable'];
        if (!empty($patternsToIgnore)) {
            foreach ($patternsToIgnore as $patternToIgnore) {
                $patternToIgnoreNoSlashes = stripslashes($patternToIgnore);
                $_REQUEST[ABJ404_PP]['debug_info'] = 'Applying regex pattern to ignore\"' . 
                    $patternToIgnoreNoSlashes . '" to URL slug: ' . $urlSlugOnly;
                $matches = array();
                if ($this->f->regexMatch($patternToIgnoreNoSlashes, $urlSlugOnly, $matches)) {
                    $this->logger->debugMessage("Ignoring file/folder (do not redirect) for URL: " . 
                            esc_html($urlSlugOnly) . ", pattern used: " . $patternToIgnoreNoSlashes);
                    $ignoreReasonDoNotProcess = 'Files and folders (do not redirect) pattern: ' . 
                        esc_html($patternToIgnoreNoSlashes);
                }
                $_REQUEST[ABJ404_PP]['debug_info'] = 'Cleared after regex pattern to ignore.';
            }
        }
        $_REQUEST[ABJ404_PP]['ignore_donotprocess'] = $ignoreReasonDoNotProcess;
        
        // -----
        // ignore and process
        $userAgents = $this->f->explodeNewline($options['ignore_doprocess']);
        
        foreach ($userAgents as $agentToIgnore) {
            if (stripos($httpUserAgent, trim($agentToIgnore)) !== false) {
                $this->logger->debugMessage("Ignoring user agent (process ok): " . 
                        esc_html($_SERVER['HTTP_USER_AGENT']) . " for URL: " . esc_html($urlRequest));
                $ignoreReasonDoProcess = 'User agent (process ok): ' . $agentToIgnore;
            }
        }
        $_REQUEST[ABJ404_PP]['ignore_doprocess'] = $ignoreReasonDoProcess;
    }
    
    function readCookieWithPreviousRqeuestShort() {
        $cookieName = ABJ404_PP . '_REQUEST_URI';
        $cookieNameShort = $cookieName . '_SHORT';
        
        if (array_key_exists($cookieNameShort, $_COOKIE) && 
            array_key_exists($cookieName, $_COOKIE)) {
    		return $_COOKIE[$cookieName];
    	}
    	
    	return '';
    }
    
    /** Set a cookie with the requested URL (path only, no query string).
     * Security: Query strings may contain sensitive data (tokens, auth codes, etc.)
     * so we only store the path portion of the URL.
     */
    function setCookieWithPreviousRequest() {

        $requested_url = urldecode($_SERVER['REQUEST_URI']);
        // remove ridiculous non-printable characters
        $requested_url = preg_replace('/[^\x20-\x7E]/', '', $requested_url);

        // Security: Strip query string to avoid storing sensitive params (tokens, auth codes, etc.)
        $requested_url = preg_replace('/\?.*$/', '', $requested_url);

    	// this may be used later when displaying suggestions.
    	$cookieName = ABJ404_PP . '_REQUEST_URI';
    	$cookieNameShort = $cookieName . '_SHORT';
    	try {
    		setcookie($cookieName, $requested_url, time() + (60 * 4), "/");
    		setcookie($cookieNameShort, $requested_url, time() + (5), "/");

    		// only set the update_URL if it's not already set.
    		// this is because multiple redirects might happen and we want to store
    		// only the user's original requested page.
    		if (!isset($_COOKIE[$cookieName . '_UPDATE_URL']) ||
    				empty($_COOKIE[$cookieName . '_UPDATE_URL'])) {
    			// Also strip query string from UPDATE_URL for consistency
    			$update_url = preg_replace('/\?.*$/', '', urldecode($_SERVER['REQUEST_URI']));
    			setcookie($cookieName . '_UPDATE_URL', $update_url,
    				time() + (60 * 4), "/");
    		}

    	} catch (Exception $e) {
    		$this->logger->debugMessage("There was an issue setting a cookie: " . $e->getMessage());
    		// This javascript redirect will only appear if the header redirect did not work for some reason.
    		// document.cookie = "username=John Doe; expires=Thu, 18 Dec 2013 12:00:00 UTC";
    		$expireTime = date("D, d M Y H:i:s T", time() + (60 * 4));
    		$c = "\n" . '<script>document.cookie = "' . $cookieName . '=' .
     		esc_js($requested_url) .
     		'; expires=' . $expireTime . '";</script>' . "\n";
     		echo $c;
    	}

    	$_REQUEST[ABJ404_PP][$cookieName] = $requested_url;
    }
    
    /** The passed in reason will be appended to the automatically generated reason.
     * @param string $reason
     */
    function sendTo404Page($requestedURL, $reason = '', $useUserSpecified404 = true) {
        $abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
        
        $options = $abj404logic->getOptions();
        
        // ---------------------------------------
        // if there's a default 404 page specified then use that.
        $dest404page = (isset($options['dest404page']) ?
                $options['dest404page'] : 
            ABJ404_TYPE_404_DISPLAYED . '|' . ABJ404_TYPE_404_DISPLAYED);
        
        if ($useUserSpecified404 && $this->thereIsAUserSpecified404Page($dest404page)) {
           	// $idAndType OK on regular 404
           	$permalink = ABJ_404_Solution_Functions::permalinkInfoToArray($dest404page, 0, 
           		null, $options);
            
            // make sure the page exists
            if (!in_array($permalink['status'], array('publish', 'published'))) {
            	$msg = __("The user specified 404 page wasn't found. " .
            			"Please update the user-specified 404 page on the Options page.", 
            			'404-solution');
            	$this->logger->infoMessage($msg);
            	
            } else {
            	// dipslay the user specified 404 page.
            	
	            // get the existing redirect before adding a new one.
	            $redirect = $this->dao->getExistingRedirectForURL($requestedURL);
	            if (!isset($redirect['id']) || $redirect['id'] == 0) {
	                $this->dao->setupRedirect($requestedURL, ABJ404_STATUS_CAPTURED, $permalink['type'], $permalink['id'], $options['default_redirect'], 0);
	            }
	            
	            $this->dao->logRedirectHit($requestedURL, $permalink['link'], 'user specified 404 page. ' . $reason);
	            
	            // set cookie here to remmeber to use a 404 status when displaying the 404 page
	            setcookie(ABJ404_PP . '_STATUS_404', 'true', time() + 20, "/");
	            
	            // the 404 page...
	            $abj404logic->forceRedirect(esc_url($permalink['link']), 
	            	esc_html($options['default_redirect']),
	            	'404Solution-404-page');
	            exit;
            }
        }
        
        // ---------------------------------------
        // give up. log the 404.
        if (@$options['capture_404'] == '1') {
            // get the existing redirect before adding a new one.
            $redirect = $this->dao->getExistingRedirectForURL($requestedURL);
            if (!isset($redirect['id']) || $redirect['id'] == 0) {
                $this->dao->setupRedirect($requestedURL, ABJ404_STATUS_CAPTURED, ABJ404_TYPE_404_DISPLAYED, ABJ404_TYPE_404_DISPLAYED, $options['default_redirect'], 0);
            }
        } else {
            $this->logger->debugMessage("No permalink found to redirect to. capture_404 is off. Requested URL: " . $requestedURL .
                    " | Redirect: (none)" . " | is_single(): " . is_single() . " | " .
                    "is_page(): " . is_page() . " | is_feed(): " . is_feed() . " | is_trackback(): " .
                    is_trackback() . " | is_preview(): " . is_preview() . " | options: " . wp_kses_post(json_encode($options)));
        }
    }
    
    /** Returns true if there is a custom 404 page. */
    function thereIsAUserSpecified404Page($dest404page) {
    	if ($dest404page == null) {
    		return false;
    	}
    	$check1 = ($dest404page !== (ABJ404_TYPE_404_DISPLAYED . '|' . ABJ404_TYPE_404_DISPLAYED));
    	$check2 = ($dest404page !== ABJ404_TYPE_404_DISPLAYED);
    	return $check1 && $check2;
    }
    
    /** 
     * @param bool $skip_db_check
     * @return array
     */
    function getOptions($skip_db_check = false) {
    	if ($this->options == null) {
        	$this->options = get_option('abj404_settings');
    	}
    	$options = $this->options;

        if (!is_array($options)) {
            add_option('abj404_settings', '', '', 'no');
            $options = array();
        }

        // Check to make sure we aren't missing any new options.
        $defaults = $this->getDefaultOptions();
        $missing = false;
        foreach ($defaults as $key => $value) {
            if (!isset($options) || $options == '' ||
                    !isset($options[$key]) || '' == $options[$key]) {
                $options[$key] = $value;
                $missing = true;
            }
        }

        if ($missing) {
            $this->updateOptions($options);
        }

        if ($skip_db_check == false) {
            if (!array_key_exists('DB_VERSION', $options) || $options['DB_VERSION'] != ABJ404_VERSION) {
                $options = $this->updateToNewVersion($options);
            }
        }

        return $options;
    }
    
    function updateOptions($options) {
    	$old_options = $this->options;
    	update_option('abj404_settings', $options);
    	$this->options = $options;
    }

    /** Do any maintenance when upgrading to a new version.
     * @global type $abj404logging
     * @param array $options
     * @return array
     */
    function updateToNewVersion($options) {
        $syncUtils = ABJ_404_Solution_SynchronizationUtils::getInstance();

        $synchronizedKeyFromUser = "update_db_version";
        $uniqueID = $syncUtils->synchronizerAcquireLockTry($synchronizedKeyFromUser);

        if ($uniqueID == '' || $uniqueID == null) {
        	$this->logger->debugMessage("Avoiding infinite loop on database update.");
            return $options;
        }

        $returnValue = $options;

        // Fixed: Use finally block to ensure lock is ALWAYS released, even on fatal errors
        try {
            $returnValue = $this->updateToNewVersionAction($options);

        } catch (Throwable $e) {  // Fixed: Catch Throwable (Exception + Error) instead of just Exception
            $this->logger->errorMessage("Error updating to new version. ", $e);
            throw $e;  // Re-throw to propagate the error
        } finally {
            // This ALWAYS executes, even on fatal errors or exceptions
            $syncUtils->synchronizerReleaseLock($uniqueID, $synchronizedKeyFromUser);
        }

        // update the permalink cache because updating the plugin version may affect it.
        $permalinkCache = ABJ_404_Solution_PermalinkCache::getInstance();
        $permalinkCache->updatePermalinkCache(1);

        return $returnValue;
    }
    
    /** Do any maintenance when upgrading to a new version.
     * @global type $abj404logic
     * @global type $abj404logging
     * @global type $wpdb
     * @param array $options
     * @return array
     */
    function updateToNewVersionAction($options) {
    	global $wpdb;

        $currentDBVersion = "(unknown)";
        if (array_key_exists('DB_VERSION', $options)) {
            $currentDBVersion = $options['DB_VERSION'];
        }
        $this->logger->infoMessage(self::$uniqID . ": Updating database version from " . 
        	$currentDBVersion . " to " . ABJ404_VERSION . " (begin).");
        
        // remove old log files. added in 2.28.0
        $fileUtils = ABJ_404_Solution_Functions::getInstance();
        $fileUtils->deleteDirectoryRecursively(ABJ404_PATH . 'temp/');

        // wp_abj404_logsv2 exists since 1.7.
        $upgradesEtc = ABJ_404_Solution_DatabaseUpgradesEtc::getInstance();
        $upgradesEtc->createDatabaseTables(true);

        // abj404_duplicateCronAction is no longer needed as of 1.7.
        wp_clear_scheduled_hook('abj404_duplicateCronAction');

        ABJ_404_Solution_PluginLogic::doUnregisterCrons();
        // added in 1.8.2
        ABJ_404_Solution_PluginLogic::doRegisterCrons();

        // since 1.9.0. ignore_doprocess add SeznamBot, Pinterestbot, UptimeRobot and "Slurp" -> "Yahoo! Slurp"
        if (version_compare($currentDBVersion, '1.9.0') < 0) {
            $userAgents = $this->f->explodeNewline($options['ignore_doprocess']);
            
            $uasForSearch = $this->f->explodeNewline($options['ignore_doprocess']);
            
            foreach ($userAgents as &$str) {
                if ($this->f->strtolower(trim($str)) == "slurp") {
                    $str = "Yahoo! Slurp";
                    $this->logger->infoMessage('Changed user agent "Slurp" to "Yahoo! Slurp" in the do not log list.');
                }
            }

            if (!in_array("seznambot", $uasForSearch)) {
                $userAgents[] = 'SeznamBot';
                $this->logger->infoMessage('Added user agent "SeznamBot" to do not log list."');
            }
            if (!in_array("pinterestbot", $uasForSearch)) {
                $userAgents[] = 'Pinterestbot';
                $this->logger->infoMessage('Added user agent "Pinterestbot" to do not log list."');
            }
            if (!in_array("uptimerobot", $uasForSearch)) {
                $userAgents[] = 'UptimeRobot';
                $this->logger->infoMessage('Added user agent "UptimeRobot" to do not log list."');
            }

            $options['ignore_doprocess'] = implode("\n",$userAgents);
            $this->updateOptions($options);
        }

        // move to the new log table
        if (version_compare($currentDBVersion, '1.8.0') < 0) {
            $query = "SHOW TABLES LIKE '{wp_abj404_logs}'";
            $result = $this->dao->queryAndGetResults($query);
            $rows = $result['rows'];
            
            // make sure empty() only sees a variable and not a function for older PHP versions, due to
            // https://stackoverflow.com/a/2173318 and 
            // https://wordpress.org/support/topic/fatal-error-will-latest-release/
            $filteredRows = array_filter($rows);
            if (!empty($filteredRows)) {
                $query = ABJ_404_Solution_Functions::readFileContents(__DIR__ . "/sql/migrateToNewLogsTable.sql");
                $query = $this->dao->doTableNameReplacements($query);
                $result = $this->dao->queryAndGetResults($query);

                // if anything was successfully imported then delete the old table.
                if ($result['rows_affected'] > 0) {
                    $this->logger->infoMessage($result['rows_affected'] . 
                            ' log rows were migrated to the new table structre.');
                    // log the rows inserted/migrated.
                    $wpdb->query('drop table ' . $this->dao->getLowercasePrefix() . 'abj404_logs');
                }
            }
        }
        
        if (version_compare($currentDBVersion, '2.18.0') < 0) {
            // add .well-known/acme-challenge/*, wp-content/themes/*, wp-content/plugins/* to folders_files_ignore
            $originalItems = $this->f->explodeNewline($options['folders_files_ignore']);

            $newItems = array("wp-content/plugins/*", "wp-content/themes/*", ".well-known/acme-challenge/*");
            foreach ($newItems as $newItem) {
                if (array_search($newItem, $originalItems) === false) {
                    $originalItems[] = $newItem;
                    $this->logger->infoMessage('Added ' . $newItem . ' to the list of folders to ignore."');
                }
            }

            $options['folders_files_ignore'] = implode("\n",$originalItems);
            $this->updateOptions($options);
        }        

        // add the second part of the default destination page.
        $dest404page = $options['dest404page'];
        if ($this->f->strpos($dest404page, '|') === false) {
            // not found
            if ($dest404page == '0') {
                $dest404page .= "|" . ABJ404_TYPE_404_DISPLAYED;
            } else {
                $dest404page .= '|' . ABJ404_TYPE_POST;
            }
            $options['dest404page'] = $dest404page;
            $this->updateOptions($options);
        }

        // Since 3.0.7: Mark existing users as having completed setup wizard
        // This prevents the wizard from showing to users upgrading from earlier versions
        // Important: Skip this for NEW installs (where DB_VERSION is 0.0.0) so they see the wizard
        if ($currentDBVersion !== '0.0.0' && version_compare($currentDBVersion, '3.0.7') < 0) {
            update_option('abj404_setup_completed', gmdate('Y-m-d'));
            $this->logger->infoMessage('Marked setup wizard as completed for existing user.');
        }

        // Since 3.0.9: Migrate suggest_minscore to suggest_minscore_enabled checkbox
        // If user had suggest_minscore set from an older version, enable the checkbox to preserve their behavior
        if (!isset($options['suggest_minscore_enabled'])) {
            if (isset($options['suggest_minscore']) && intval($options['suggest_minscore']) >= 25) {
                $options['suggest_minscore_enabled'] = '1';
                $this->logger->infoMessage('Enabled minimum score filtering based on existing suggest_minscore setting.');
            } else {
                $options['suggest_minscore_enabled'] = '0';
            }
            $this->updateOptions($options);
        }

        $options = $this->doUpdateDBVersionOption($options);
        $this->logger->infoMessage(self::$uniqID . ": Updating database version to " . 
        	ABJ404_VERSION . " (end).");
        
        return $options;
    }

    /** 
     * @return array
     */
    function getDefaultOptions() {
        $options = array(
            'default_redirect' => '301',
            'send_error_logs' => '0',
            'capture_404' => '1',
            'capture_deletion' => 1095,
            'manual_deletion' => '0',
            'log_deletion' => '365',
            'admin_notification' => '0',
            'remove_matches' => '1',
            'suggest_max' => '5',
            'suggest_title' => '<h3>{suggest_title_text}</h3>',
            'suggest_before' => '<ol>',
            'suggest_after' => '</ol>',
            'suggest_entrybefore' => '<li>',
            'suggest_entryafter' => '</li>',
            'suggest_noresults' => '<p>{suggest_noresults_text}</p>',
            'suggest_cats' => '1',
            'suggest_tags' => '1',
            'suggest_minscore' => '25',
            'suggest_minscore_enabled' => '0',
            'update_suggest_url' => '0',
            'auto_redirects' => '1',
            'auto_slugs' => '1',
            'auto_score' => '90',
            'template_redirect_priority' => '9',
            'auto_deletion' => '1095',
            'auto_cats' => '1',
            'auto_tags' => '1',
            'dest404page' => '0|' . ABJ404_TYPE_404_DISPLAYED,
            'maximum_log_disk_usage' => '10',
            'ignore_dontprocess' => 'zemanta aggregator',
            'ignore_doprocess' => "Googlebot\nMediapartners-Google\nAdsBot-Google\ndevelopers.google.com\n"
            . "Bingbot\nYahoo! Slurp\nDuckDuckBot\nBaiduspider\nYandexBot\nwww.sogou.com\nSogou-Test-Spider\n"
            . "Exabot\nfacebot\nfacebookexternalhit\nia_archiver\nSeznamBot\nPinterestbot\nUptimeRobot\nMJ12bot",
            'recognized_post_types' => "page\npost\nproduct",
            'recognized_categories' => "",
            'folders_files_ignore' => implode("\n", array("wp-content/plugins/*", "wp-content/themes/*", 
                ".well-known/acme-challenge/*")),
            'folders_files_ignore_usable' => "",
            'suggest_regex_exclusions' => "",
            'suggest_regex_exclusions_usable' => "",
        	'plugin_admin_users' => "",
        	'debug_mode' => 0,
            'days_wait_before_major_update' => 30,
            'DB_VERSION' => '0.0.0',
            'menuLocation' => 'underSettings',
            'admin_theme' => 'default',
            'plugin_language_override' => '',
            'disable_auto_dark_mode' => '0',
            'admin_notification_email' => '',
            'page_redirects_order_by' => 'url',
            'page_redirects_order' => 'ASC',
            'captured_order_by' => 'logshits',
            'captured_order' => 'DESC',
        	'excludePages[]' => '',
        );
        
        return $options;
    }

    function doUpdateDBVersionOption($options = null) {
        if ($options == null) {
        	$options = $this->getOptions(true);
        }

        $options['DB_VERSION'] = ABJ404_VERSION;

        $this->updateOptions($options);

        return $options;
    }

    /** Remove cron jobs. */
    static function doUnregisterCrons() {
        $crons = array('abj404_cleanupCronAction', 'abj404_duplicateCronAction', 'removeDuplicatesCron', 'deleteOldRedirectsCron');
        for ($i = 0; $i < count($crons); $i++) {
            $cron_name = $crons[$i];
            $timestamp1 = wp_next_scheduled($cron_name);
            while ($timestamp1 != False) {
                wp_unschedule_event($timestamp1, $cron_name);
                $timestamp1 = wp_next_scheduled($cron_name);
            }

            $timestamp2 = wp_next_scheduled($cron_name, '');
            while ($timestamp2 != False) {
                wp_unschedule_event($timestamp2, $cron_name, '');
                $timestamp2 = wp_next_scheduled($cron_name, '');
            }

            wp_clear_scheduled_hook($cron_name);
        }
    }

    /** Create database tables. Register crons. etc.
     * Handles both single-site and multisite activations.
     *
     * For network activations, sites are activated asynchronously in the background
     * to prevent timeouts on large networks.
     *
     * @param bool $network_wide Whether this is a network-wide activation
     * @global type $abj404logic
     * @global type $abj404dao
     */
    static function runOnPluginActivation($network_wide = false) {
        if (is_multisite() && $network_wide) {
            // Network activation: Schedule background activation to prevent timeouts
            $sites = get_sites(array('fields' => 'ids', 'number' => 0));

            // Store list of pending site IDs in network option
            update_site_option('abj404_pending_network_activation', $sites);
            update_site_option('abj404_network_activation_total', count($sites));

            // Schedule first batch immediately
            wp_schedule_single_event(time(), 'abj404_network_activation_hook');

            // Show admin notice that activation is happening in background
            add_action('network_admin_notices', function() {
                $pending = get_site_option('abj404_pending_network_activation', array());
                $total = get_site_option('abj404_network_activation_total', 0);
                $completed = $total - count($pending);

                if (!empty($pending)) {
                    echo '<div class="notice notice-info"><p><strong>404 Solution:</strong> Network activation in progress... ' .
                         esc_html($completed) . ' of ' . esc_html($total) . ' sites activated. ' .
                         'This will complete in the background.</p></div>';
                }
            });
        } else {
            // Single site activation (or individual subsite activation)
            self::activateSingleSite();
        }
    }

    /**
     * Activate plugin for a single site.
     * This contains the actual activation logic that was previously in runOnPluginActivation.
     *
     * @global type $abj404logic
     * @global type $abj404dao
     * @global type $abj404logging
     */
    private static function activateSingleSite() {
        $abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
        add_option('abj404_settings', '', '', 'no');

        if (!isset($abj404logging)) {
        }
        if (!isset($abj404dao)) {
        }
        if (!isset($abj404logic)) {
            $abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
        }

        $upgradesEtc = ABJ_404_Solution_DatabaseUpgradesEtc::getInstance();
        $upgradesEtc->createDatabaseTables();

        ABJ_404_Solution_PluginLogic::doRegisterCrons();

        $abj404logic->doUpdateDBVersionOption();
    }

    /**
     * Background cron handler for network activation.
     * Processes one site at a time to prevent timeouts.
     * Reschedules itself if more sites remain.
     */
    static function networkActivationCronHandler() {
        // Get list of pending sites
        $pending = get_site_option('abj404_pending_network_activation', array());

        if (empty($pending)) {
            // All done! Clean up network options
            delete_site_option('abj404_pending_network_activation');
            delete_site_option('abj404_network_activation_total');
            return;
        }

        // Process one site
        $blog_id = array_shift($pending);

        try {
            switch_to_blog($blog_id);
            self::activateSingleSite();
            restore_current_blog();
        } catch (Exception $e) {
            // Log error but continue with other sites
            error_log('404 Solution: Network activation failed for site ' . $blog_id . ': ' . $e->getMessage());
            restore_current_blog();
        }

        // Update pending list
        update_site_option('abj404_pending_network_activation', $pending);

        // Schedule next site (10 seconds delay to spread load)
        if (!empty($pending)) {
            wp_schedule_single_event(time() + 10, 'abj404_network_activation_hook');
        } else {
            // All done! Clean up network options
            delete_site_option('abj404_pending_network_activation');
            delete_site_option('abj404_network_activation_total');
        }
    }

    /**
     * Handle new blog creation in multisite (WordPress < 5.1).
     * This is triggered by the wpmu_new_blog action.
     *
     * @param int $blog_id Blog ID of the new blog
     * @param int $user_id User ID of the user creating the blog
     * @param string $domain Domain of the new blog
     * @param string $path Path of the new blog
     * @param int $site_id Site ID (network ID)
     * @param array $meta Additional meta information
     */
    static function activateNewSite($blog_id, $user_id, $domain, $path, $site_id, $meta) {
        // Only activate if the plugin is network-activated
        if (is_plugin_active_for_network(plugin_basename(ABJ404_FILE))) {
            switch_to_blog($blog_id);
            self::activateSingleSite();
            restore_current_blog();
        }
    }

    /**
     * Handle new blog creation in multisite (WordPress >= 5.1).
     * This is triggered by the wp_initialize_site action.
     *
     * @param WP_Site $site The site object for the new site
     * @param array $args Additional arguments passed to the hook
     */
    static function activateNewSiteModern($site, $args) {
        // Only activate if the plugin is network-activated
        if (is_plugin_active_for_network(plugin_basename(ABJ404_FILE))) {
            switch_to_blog($site->blog_id);
            self::activateSingleSite();
            restore_current_blog();
        }
    }

    /**
     * Handle plugin deactivation for both single-site and multisite.
     *
     * @param bool $network_wide Whether this is a network-wide deactivation
     */
    static function runOnPluginDeactivation($network_wide = false) {
        if (is_multisite() && $network_wide) {
            // Network deactivation: deactivate for all sites
            $sites = get_sites(array('fields' => 'ids', 'number' => 0));

            foreach ($sites as $blog_id) {
                switch_to_blog($blog_id);
                self::deactivateSingleSite();
                restore_current_blog();
            }
        } else {
            // Single site deactivation
            self::deactivateSingleSite();
        }
    }

    /**
     * Deactivate plugin for a single site.
     * Unregisters cron jobs.
     */
    private static function deactivateSingleSite() {
        self::doUnregisterCrons();
    }

    /**
     * Clean up when a blog is deleted in multisite.
     * This is triggered by the delete_blog action.
     *
     * @global wpdb $wpdb WordPress database object
     * @param int $blog_id Blog ID being deleted
     * @param bool $drop Whether to drop the tables (true) or just deactivate (false)
     */
    static function deleteBlogData($blog_id, $drop = false) {
        if ($drop) {
            switch_to_blog($blog_id);

            global $wpdb;
            $dao = ABJ_404_Solution_DataAccess::getInstance();
            $prefix = $dao->getLowercasePrefix();

            // Remove ALL custom database tables
            // Core tables
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_redirects");
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_logsv2");
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_lookup");

            // Cache tables
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_permalink_cache");
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_ngram_cache");
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_spelling_cache");

            // Temporary tables
            $wpdb->query("DROP TABLE IF EXISTS {$prefix}abj404_logs_hits_temp");

            // Remove ALL plugin options
            $plugin_options = array(
                'abj404_settings',
                'abj404_db_version',
                'abj404_migrated_to_relative_paths',
                'abj404_migration_results',
                'abj404_ngram_cache_initialized',
                'abj404_ngram_rebuild_offset',
                'abj404_ngram_usage_stats',
                'abj404_installed_time',
                'abj404_user_feedback',
                'abj404_uninstall_preferences'
            );

            foreach ($plugin_options as $option) {
                delete_option($option);
            }

            // Delete dynamic sync options (using LIKE pattern)
            $wpdb->query(
                $wpdb->prepare(
                    "DELETE FROM {$wpdb->options} WHERE option_name LIKE %s",
                    $wpdb->esc_like('abj404_sync_') . '%'
                )
            );

            // Clear ALL scheduled cron jobs for this blog
            $cron_hooks = array(
                'abj404_cleanupCronAction',
                'abj404_updateLogsHitsTableAction',
                'abj404_updatePermalinkCacheAction',
                'abj404_rebuild_ngram_cache_hook'
            );

            foreach ($cron_hooks as $hook) {
                wp_clear_scheduled_hook($hook);
            }

            // Also clear legacy cron hooks
            $legacy_hooks = array(
                'abj404_duplicateCronAction',
                'abj404_updatePermalinkCache',
                'abj404_cleanupCron'
            );

            foreach ($legacy_hooks as $hook) {
                wp_clear_scheduled_hook($hook);
            }

            restore_current_blog();
        }
    }

    static function doRegisterCrons() {
        if (!wp_next_scheduled('abj404_cleanupCronAction')) {
            // we randomize this so that when the geo2ip file is downloaded, there aren't a whole
            // lot of users that request the file at the same time.
            $timeForEvent = '0' . rand(0, 5) . ':' . rand(10, 59) . ':' . rand(10, 59);
            wp_schedule_event(strtotime($timeForEvent), 'daily', 'abj404_cleanupCronAction');
        }
    }
    
    function getDebugLogFileLink() {
        return "?page=" . ABJ404_PP . "&subpage=abj404_debugfile";
    }

    /** Do the passed in action and return the associated message. 
     * @global type $abj404logic
     * @param string $action
     * @param string $sub
     * @return string
     */
    function handlePluginAction($action, &$sub) {
        $abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
        
        $message = "";
        $message = array_key_exists('display-this-message', $_POST) ? 
        	sanitize_text_field($_POST['display-this-message']) : '';
        
        if ($action == "updateOptions") {
        	if (wp_verify_nonce($_POST['nonce'], 'abj404UpdateOptions') && is_admin()) {
                // delete the debug file and lose all changes, or
                if (array_key_exists('deleteDebugFile', $_POST) && $_POST['deleteDebugFile']) {
                    $filepath = $this->logger->getDebugFilePath();
                    if (!file_exists($filepath)) {
                        $message = sprintf(__("Debug file not found. (%s)", '404-solution'), $filepath);
                    } else if ($this->logger->deleteDebugFile()) {
                        $message = sprintf(__("Debug file(s) deleted. (%s)", '404-solution'), $filepath);
                    } else {
                        $message = sprintf(__("Issue deleting debug file. (%s)", '404-solution'), $filepath);
                    }
                    return $message;
                }
                
                // save all changes. saveOptions, saveSettings
                $sub = "abj404_options";
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "addRedirect") {
            if (check_admin_referer('abj404addRedirect') && is_admin()) {
                $message = $this->addAdminRedirect();
                if ($message == "") {
                    $message = __('New Redirect Added Successfully!', '404-solution');
                } else {
                    $message .= __('Error: unable to add new redirect.', '404-solution');
                }
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "emptyRedirectTrash") {
            if (check_admin_referer('abj404_bulkProcess') && is_admin()) {
                $abj404logic->doEmptyTrash('abj404_redirects');
                $message = __('All trashed URLs have been deleted!', '404-solution');
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "emptyCapturedTrash") {
            if (check_admin_referer('abj404_bulkProcess') && is_admin()) {
                $abj404logic->doEmptyTrash('abj404_captured');
                $message = __('All trashed URLs have been deleted!', '404-solution');
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "purgeRedirects") {
            if (check_admin_referer('abj404_purgeRedirects') && is_admin()) {
                $message = $this->dao->deleteSpecifiedRedirects();
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "runMaintenance") {
            if (check_admin_referer('abj404_runMaintenance') && is_admin()) {
                $message = $this->dao->deleteOldRedirectsCron();
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " .
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "rebuildNgramCache") {
            if (check_admin_referer('abj404_rebuildNgramCache') && is_admin()) {
                // Server-side request deduplication to prevent race conditions
                $userId = get_current_user_id();
                $transientKey = 'abj404_ngram_rebuild_request_' . $userId;
                $recentRequest = get_transient($transientKey);

                if ($recentRequest) {
                    // Duplicate request within 10 seconds - likely from rapid button clicks
                    $message = __('N-gram cache rebuild is already scheduled or in progress. Please wait for it to complete.', '404-solution');
                } else {
                    // Set transient to prevent duplicate requests for 10 seconds
                    set_transient($transientKey, time(), 10);

                    $dbUpgrades = ABJ_404_Solution_DatabaseUpgradesEtc::getInstance();

                    // Use async rebuild to avoid timeouts on large sites
                    $scheduled = $dbUpgrades->scheduleNGramCacheRebuild();

                    if ($scheduled) {
                        $message = __('N-gram cache rebuild has been scheduled and will run in the background. This may take several minutes on large sites. You can continue using the plugin normally.', '404-solution');
                    } else {
                        // Check if already running
                        $nextScheduled = wp_next_scheduled('abj404_rebuild_ngram_cache_hook');
                        if ($nextScheduled) {
                            $message = __('N-gram cache rebuild is already scheduled or in progress. Please wait for it to complete.', '404-solution');
                        } else {
                            $message = __('Failed to schedule N-gram cache rebuild. Please try again or check your WordPress cron configuration.', '404-solution');
                        }
                    }
                }
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " .
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($action == "clearSpellingCache") {
            if (check_admin_referer('abj404_clearSpellingCache') && is_admin()) {
                $this->dao->deleteSpellingCache();
                $message = __('Spelling cache cleared successfully.', '404-solution');
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " .
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        } else if ($this->f->substr($action . '', 0, 4) == "bulk") {
            if (check_admin_referer('abj404_bulkProcess') && is_admin()) {
                if (!isset($_POST['idnum'])) {
                    $this->logger->debugMessage("No ID(s) specified for bulk action: " . esc_html($action));
                    echo sprintf(__("Error: No ID(s) specified for bulk action. (%s)", '404-solution'), 
                        esc_html($action), false);
                    return;
                }
                $message = $abj404logic->doBulkAction($action, array_map('absint', $_POST['idnum']));
            } else {
                $this->logger->debugMessage("Unexpected result. How did we get here? is_admin: " . 
                        is_admin() . ", Action: " . $action . ", Sub: " . $sub);
            }
        }
                
        return $message;
    }

    /** Move redirects to trash. 
     * @return string
     */
    function hanldeTrashAction() {
        
        $message = "";
        // Handle Trash Functionality
        if (isset($_GET['trash'])) {
            if (is_admin() && $this->verifyLinkNonce('abj404_trashRedirect')) {
                $trash = "";
                if ($_GET['trash'] == 0) {
                    $trash = 0;
                } else if ($_GET['trash'] == 1) {
                    $trash = 1;
                } else {
                    $this->logger->errorMessage("Unexpected trash operation: " . 
                            esc_html($_GET['trash']));
                    $message = __('Error: Bad trash operation specified.', '404-solution');
                    return $message;
                }
                
                $id = absint($_GET['id']);
                $message = $this->dao->moveRedirectsToTrash($id, $trash);
                if ($message == "") {
                    // Captured URLs: restoring from the Captured->Trash view should return to Captured (not Ignored/Later).
                    $subpage = isset($_GET['subpage']) ? sanitize_text_field(wp_unslash($_GET['subpage'])) : '';
                    $filter = isset($_GET['filter']) ? intval($_GET['filter']) : 0;
                    if ($trash == 0 && $subpage === 'abj404_captured' && $filter === ABJ404_TRASH_FILTER) {
                        $this->dao->updateRedirectTypeStatus($id, ABJ404_STATUS_CAPTURED);
                    }
                    if ($trash == 1) {
                        $message = __('Redirect moved to trash successfully!', '404-solution');
                    } else {
                        $message = __('Redirect restored from trash successfully!', '404-solution');
                    }
                } else {
                    if ($trash == 1) {
                        $message = __('Error: Unable to move redirect to trash.', '404-solution');
                    } else {
                        $message = __('Error: Unable to move redirect from trash.', '404-solution');
                    }
                }
                
            }
        }
        
        return $message;
    }
    
    function handleActionChangeItemsPerRow() {

        if ($this->dao->getPostOrGetSanitize('action') == 'changeItemsPerRow' && $this->userIsPluginAdmin()) {
            check_admin_referer('abj404_changeItemsPerRow'); // verify nonce for CSRF protection
            $this->updatePerPageOption(absint($this->dao->getPostOrGetSanitize('perpage')));
        }
    }
    
    function handleActionExport() {
        
        if (($this->dao->getPostOrGetSanitize('action') == 'exportRedirects') && $this->userIsPluginAdmin()) {
            check_admin_referer('abj404_exportRedirects'); // this verifies the nonce
            $this->doExport();
        }
    }
    
    function handleActionImportFile() {

        if (($this->dao->getPostOrGetSanitize('action') == 'importRedirectsFile') && $this->userIsPluginAdmin()) {
            check_admin_referer('abj404_importRedirectsFile'); // this verifies the nonce (must match View.php form nonce)
            $result = $this->doImportFile();
            return $result;
        }
    }
    
    function getExportFilename() {
    	$tempFile = abj404_getUploadsDir() . 'export.csv';
    	return $tempFile;
    }
    
    function doExport() {
    	
    	$tempFile = $this->getExportFilename();
    	
    	$this->dao->doRedirectsExport($tempFile);
    	
    	if (file_exists($tempFile)) {
	    	header('Content-Description: File Transfer');
	    	header('Content-Disposition: attachment; filename=' . basename($tempFile));
	    	header('Expires: 0');
	    	header('Cache-Control: must-revalidate');
	    	header('Pragma: public');
	    	header('Content-Length: ' . filesize($tempFile));
	    	header("Content-Type: text/plain");
	    	readfile($tempFile);
            exit(); // avoid headers already sent error. avoid other things executing afterwards.
	    	
    	} else {
    		$this->logger->infoMessage("I don't see any data to export.");
    	}
    }
    
    /** Expected formats are 
     * from_url,status,type,to_url,wp_type
     * from_url,to_url 
     */
    function doImportFile() {
        $anyIssuesToNote = array();
        if (isset($_FILES['import_file']) && $_FILES['import_file']['error'] == UPLOAD_ERR_OK) {
            // Validate file extension to prevent malicious file uploads
            $allowed_extensions = array('csv', 'txt');
            $file_ext = strtolower(pathinfo($_FILES['import_file']['name'], PATHINFO_EXTENSION));
            if (!in_array($file_ext, $allowed_extensions)) {
                return "Error: Invalid file type. Only CSV/TXT files are allowed.";
            }

            // Validate file size (max 5MB to prevent DoS)
            $max_file_size = 5 * 1024 * 1024; // 5MB in bytes
            if ($_FILES['import_file']['size'] > $max_file_size) {
                return "Error: File too large. Maximum size is 5MB.";
            }

            // Validate MIME type
            $allowed_mime_types = array('text/csv', 'text/plain', 'application/csv', 'text/comma-separated-values', 'application/vnd.ms-excel');
            $finfo = finfo_open(FILEINFO_MIME_TYPE);
            $mime_type = finfo_file($finfo, $_FILES['import_file']['tmp_name']);
            finfo_close($finfo);
            if (!in_array($mime_type, $allowed_mime_types)) {
                return "Error: Invalid file type. Only CSV files are allowed.";
            }

            // Open the uploaded file for reading
            $file_handle = fopen($_FILES['import_file']['tmp_name'], 'r');
            if (!$file_handle) {
                return "Error opening the file.";
            }
            
            while (($line = fgets($file_handle)) !== false) {
                $dataArray = $this->splitCsvLine($line);
                if (isset($dataArray['error'])) {
                    return $dataArray['error'];
                }
                
                $anyIssuesToNote = array_merge($anyIssuesToNote, 
                    $this->loadDataArrayFromFile($dataArray));
            }
            fclose($file_handle);
            
        } else {
            return "File upload error.";
        }
        
        if (count($anyIssuesToNote) > 0) {
            return 'Error: ' . implode(", <BR/>\n", $anyIssuesToNote);
        }

        $msg = __("The file seems to have loaded okay. Please check the redirects page.", 
            '404-solution');
        return $msg;
    }

    function loadDataArrayFromFile($dataArray) {
        if ($dataArray['from_url'] == 'from_url' || $dataArray['from_url'] == 'request') {
            return array();
        }
        
        $fromURL = $dataArray['from_url'];
        $status = ABJ404_STATUS_MANUAL;
        $final_dest = $dataArray['to_url'];
        $anyIssuesToNote = array();
        
        // avoid duplicates - verify that the from URL doesn't already exist as a redirect.
        $maybeExisting2 = $this->dao->getExistingRedirectForURL($fromURL);
        
        if ((count($maybeExisting2) > 0 && $maybeExisting2['id'] != 0)) {
            $msg = "Ignored importing redirect because a redirect with the same " .
                "from URL already exists. URL: " . $fromURL;
            $this->logger->warn($msg);
            array_push($anyIssuesToNote, $msg);
            return $anyIssuesToNote;
        }
        
        // Determine $type based on $final_dest
        if (empty($final_dest)) {
            $type = ABJ404_TYPE_404_DISPLAYED; // "404"
        } else if ($final_dest == '5') {
            $type = ABJ404_TYPE_HOME; // "homepage"
        } else if (strpos($final_dest, 'http') !== false) {
            $type = ABJ404_TYPE_EXTERNAL; // "external"
            
            // if there's any kind of regular expression character that is NOT a valid
            // URL character then we'll assume it's a regular expression.
            $urlPattern = '/[!#$&\'()*+,;=]/';
            if (preg_match($urlPattern, $fromURL)) {
                $status = ABJ404_STATUS_REGEX;
            }
            
            
        } else if (strpos($final_dest, '/') === 0) {
            $type = ABJ404_TYPE_POST; // Initially set to "page/post"
        } else {
            // Some default or error handling in case $final_dest does not match any expected format
            $msg = "Unrecognized destination type while importing file. " .
                "Destination: " . $final_dest;
            $this->logger->warn($msg);
            array_push($anyIssuesToNote, $msg);
            return $anyIssuesToNote;
        }
        
        // If the type is set to ABJ404_TYPE_404_DISPLAYED
        if ($type == ABJ404_TYPE_404_DISPLAYED) {
            $final_dest = ABJ404_TYPE_404_DISPLAYED;
        } else if (strpos($final_dest, 'http') !== false) {
            // Check if $final_dest contains "http"
            $type = ABJ404_TYPE_EXTERNAL;
            // $final_dest remains unchanged
        } else if ($type == ABJ404_TYPE_HOME) {
            // If the type is set to ABJ404_TYPE_HOME
            $final_dest = ABJ404_TYPE_HOME;
        } else {
            // If the type is post, further refine the type and set the ID
            // Trim slashes for slug compatibility
            $slug = trim($final_dest, '/');
            
            // Check if slug corresponds to a post
            $postsFromSlugRows = $this->dao->getPublishedPagesAndPostsIDs($slug);
            $postsFromCategoryRows = $this->dao->getPublishedCategories(null, $slug);
            $postsFromTagRows = $this->dao->getPublishedTags($slug);
            
            $postFromSlug = isset($postsFromSlugRows[0]) ? $postsFromSlugRows[0] : null;
            $postFromCategory = isset($postsFromCategoryRows[0]) ? $postsFromCategoryRows[0] : null;
            $postFromTag = isset($postsFromTagRows[0]) ? $postsFromTagRows[0] : null;
            
            if ($postFromSlug) {
                $type = ABJ404_TYPE_POST;
                $final_dest = $postFromSlug->id; // Set to post ID
            } else if ($postFromCategory) {
                // Check if slug corresponds to a category
                $type = ABJ404_TYPE_CAT;
                $final_dest = $postFromCategory->term_id; // Set to category ID
            } else if ($postFromTag) {
                // Check if slug corresponds to a tag
                $type = ABJ404_TYPE_TAG;
                $final_dest = $postFromTag->term_id; // Set to tag ID
            } else {
                $this->logger->warn("Couldn't find post from slug. slug: " .
                    $slug);
            }
        }
        $this->dao->setupRedirect($fromURL, $status, $type, $final_dest, 301);
        
        return $anyIssuesToNote;
    }
    
    function splitCsvLine($line) {
        // Split the CSV line into an array
        // Specify delimiter/enclosure/escape explicitly to avoid PHP 8.4 deprecation about default escape.
        $data = array_map('trim', str_getcsv($line, ',', '"', '\\'));  // Trim each value in the array
        
        // Check the format based on the number of columns
        if (count($data) === 5) {
            // Format: from_url,status,type,to_url,wp_type
            return [
                'from_url' => $data[0],
                'status'   => $data[1],
                'type'     => $data[2],
                'to_url'   => $data[3],
                'wp_type'  => $data[4]
            ];
        } else if (count($data) === 2) {
            // Format: from_url,to_url
            return [
                'from_url' => $data[0],
                'to_url'   => $data[1]
            ];
        } else {
            // Invalid format or unexpected number of columns
            return ["error" => "Invalid CSV format. " . count($data) . " found but 2 or 5 expected."];
        }
    }
    
    function updatePerPageOption($rows) {
        $showRows = max($rows, ABJ404_OPTION_MIN_PERPAGE);
        $showRows = min($showRows, ABJ404_OPTION_MAX_PERPAGE);

        $options = $this->getOptions();
        $options['perpage'] = $showRows;
        $this->updateOptions($options);
    }
    
    /** 
     * 
     * @global type $abj404dao
     * @global type $abj404logging
     * @return string
     */
    function handleActionImportRedirects() {
        $message = "";
        
        
        if ($this->dao->getPostOrGetSanitize('action') == 'importRedirects') {
            if ($this->dao->getPostOrGetSanitize('sanity_404redirected') != '1') {
                $message = __("Error: You didn't check the I understand checkbox. No importing for you!", '404-solution');
                return $message;
            }

            check_admin_referer('abj404_importRedirects');
            
            try {
                $result = $this->dao->importDataFromPluginRedirectioner();
                if ($result['last_error'] != '') {
                    $message = sprintf(__("Error: No records were imported. SQL result: %s", '404-solution'), 
                            wp_kses_post(json_encode($result['last_error'])));
                } else {
                    $message = sprintf(__("Records imported: %s", '404-solution'), esc_html($result['rows_affected']));
                }
                
            } catch (Exception $e) {
                $message = "Error: Importing failed. Message: " . $e->getMessage();
                $this->logger->errorMessage('Error importing redirects.', $e);
            }
        }
        
        return $message;
    }
    
    /** Delete redirects.
     * @global type $abj404dao
     * @return string
     */
    function handleDeleteAction() {
        $message = "";
        
        //Handle Delete Functionality
        if (array_key_exists('remove', $_GET) && @$_GET['remove'] == 1) {
            if (is_admin() && $this->verifyLinkNonce('abj404_removeRedirect')) {
                if ($this->f->regexMatch('[0-9]+', $_GET['id'])) {
                    $this->dao->deleteRedirect(absint($_GET['id']));
                    $message = __('Redirect Removed Successfully!', '404-solution');
                }
            }
        }
        
        return $message;
    }
    
    /**
     * Generic handler for updating redirect status based on URL parameters.
     * Eliminates duplication between handleIgnoreAction and handleLaterAction.
     *
     * @param string $paramName The $_GET parameter name ('ignore' or 'later')
     * @param string $nonceAction The nonce action name for security verification
     * @param int $activeStatus The status constant to use when action=1
     * @param string $errorActionName Action name for error messages ('ignore' or 'organize later')
     * @param string $successActionName Action name for success messages ('ignored' or 'organize later')
     * @return string Success/error message or empty string
     */
    private function handleStatusUpdate($paramName, $nonceAction, $activeStatus, $errorActionName, $successActionName) {
        $message = "";

        if (isset($_GET[$paramName])) {
            if (is_admin() && $this->verifyLinkNonce($nonceAction)) {
                if ($_GET[$paramName] != 0 && $_GET[$paramName] != 1) {
                    $this->logger->debugMessage("Unexpected {$errorActionName} operation: " .
                            esc_html($_GET[$paramName]));
                    $message = sprintf(__('Error: Bad %s operation specified.', '404-solution'), $errorActionName);
                    return $message;
                }

                if ($this->f->regexMatch('[0-9]+', $_GET['id'])) {
                    if ($_GET[$paramName] == 1) {
                        $newstatus = $activeStatus;
                    } else {
                        $newstatus = ABJ404_STATUS_CAPTURED;
                    }

                    $message = $this->dao->updateRedirectTypeStatus(absint($_GET['id']), $newstatus);
                    if ($message == "") {
                        if ($newstatus == ABJ404_STATUS_CAPTURED) {
                            $message = sprintf(__('Removed 404 URL from %s list successfully!', '404-solution'), $successActionName);
                        } else {
                            $message = sprintf(__('404 URL marked as %s successfully!', '404-solution'), $successActionName);
                        }
                    } else {
                        if ($newstatus == ABJ404_STATUS_CAPTURED) {
                            $message = sprintf(__('Error: unable to remove URL from %s list', '404-solution'), $successActionName);
                        } else {
                            $message = sprintf(__('Error: unable to mark URL as %s', '404-solution'), $successActionName);
                        }
                    }
                }
            }
        }

        return $message;
    }

    /** Set a redirect as ignored.
     * @return string
     */
    function handleIgnoreAction() {
        return $this->handleStatusUpdate('ignore', 'abj404_ignore404', ABJ404_STATUS_IGNORED, 'ignore', 'ignored');
    }

    /** Set a redirect as "organize later".
     * @return string
     */
    function handleLaterAction() {
        return $this->handleStatusUpdate('later', 'abj404_organizeLater', ABJ404_STATUS_LATER, 'organize later', 'organize later');
    }

    /** Edit redirect data.
     * @global type $abj404dao
     * @param string $sub
     * @param string $action
     * @return string
     */
    function handleActionEdit(&$sub, &$action) {
        $message = "";
        
        //Handle edit posts
        if (array_key_exists('action', $_POST) && $_POST['action'] == "editRedirect") {
            $id = $this->dao->getPostOrGetSanitize('id');
            $ids = $this->dao->getPostOrGetSanitize('ids_multiple');
            if (!($id === null && $ids === null) && ($this->f->regexMatch('[0-9]+', '' . $id) || $this->f->regexMatch('[0-9]+', '' . $ids))) {
                if (is_admin() && $this->verifyLinkNonce('abj404editRedirect')) {
                    $message = $this->updateRedirectData();
                    if ($message == "") {
                        // Return user to the page they came from instead of always going to redirects page
                        $source_page = $this->dao->getPostOrGetSanitize('source_page');

                        // Validate source_page is a known tab
                        $valid_tabs = array('abj404_redirects', 'abj404_captured', 'abj404_logs',
                                          'abj404_stats', 'abj404_tools', 'abj404_options');
                        if ($source_page === null || !in_array($source_page, $valid_tabs)) {
                            // Default to redirects page if source_page is missing or invalid
                            $source_page = 'abj404_redirects';
                        }

                        // Build redirect URL with source page and preserved table options
                        $redirect_url = "?page=" . ABJ404_PP . "&subpage=" . $source_page;
                        $redirect_url .= "&updated=1"; // Add flag to show success message

                        // Preserve table options
                        $source_filter = $this->dao->getPostOrGetSanitize('source_filter');
                        if ($source_filter !== null && $source_filter != 0) {
                            $redirect_url .= "&filter=" . urlencode($source_filter);
                        }

                        $source_orderby = $this->dao->getPostOrGetSanitize('source_orderby');
                        $source_order = $this->dao->getPostOrGetSanitize('source_order');
                        if ($source_orderby !== null && $source_order !== null) {
                            if (!($source_orderby == "url" && $source_order == "ASC")) {
                                $redirect_url .= "&orderby=" . urlencode($source_orderby);
                                $redirect_url .= "&order=" . urlencode($source_order);
                            }
                        }

                        $source_paged = $this->dao->getPostOrGetSanitize('source_paged');
                        if ($source_paged !== null && $source_paged > 1) {
                            $redirect_url .= "&paged=" . urlencode($source_paged);
                        }

                        // Perform redirect using Post/Redirect/Get pattern
                        wp_safe_redirect(admin_url('admin.php' . $redirect_url));
                        // Note: Intentionally not calling exit() to allow for testability
                        // WordPress will handle the redirect on next page load
                        return "";
                    } else {
                        $message .= __('Error: Unable to update redirect data.', '404-solution');
                    }
                }
            }
        }

        return $message;
    }
    
    /**
     * @global type $abj404dao
     * @param string $action
     * @param array $ids
     * @return string
     */
    function doBulkAction($action, $ids) {
        $message = "";

        // nonce already verified.
        
        $this->logger->debugMessage("In doBulkAction. Action: " . 
                esc_html($action == '' ? '(none)' : $action)) . ", ids: " . wp_kses_post(json_encode($ids));

        if ($action == "bulkignore" || $action == "bulkcaptured" || $action == "bulklater" || 
                $action == "bulk_trash_restore") {
            
            if ($action == "bulkignore") {
                $status = ABJ404_STATUS_IGNORED;
                
            } else if ($action == "bulkcaptured") {
                $status = ABJ404_STATUS_CAPTURED;
                
            } else if ($action == "bulklater") {
                $status = ABJ404_STATUS_LATER;
                
            } else if ($action == "bulk_trash_restore") {
                // don't change the status for this case.
                
            } else {
                $this->logger->errorMessage("Unrecognized bulk action: " . esc_html($action));
                echo sprintf(__("Error: Unrecognized bulk action. (%s)", '404-solution'), esc_html($action));
                return;
            }
            $count = 0;
            foreach ($ids as $id) {
                $s = $this->dao->moveRedirectsToTrash($id, 0);
                if ($action != "bulk_trash_restore") {
                    $s = $this->dao->updateRedirectTypeStatus($id, $status);
                }
                if ($s == "") {
                    $count++;
                }
            }
            if ($action == "bulkignore") {
                $message = $count . " " . __('URL(s) marked as Ignored.', '404-solution');
            } else if ($action == "bulkcaptured") {
                $message = $count . " " . __('URL(s) marked as Captured.', '404-solution');
            } else if ($action == "bulklater") {
                $message = $count . " " . __('URL(s) marked as Later.', '404-solution');
            } else if ($action == "bulk_trash_restore") {
                $message = $count . " " . __('URL(s) restored.', '404-solution');
            } else {
                $this->logger->errorMessage("Unrecognized bulk action: " . esc_html($action));
                echo sprintf(__("Error: Unrecognized bulk action. (%s)", '404-solution'), esc_html($action));
            }
            
        } else if ($action == "bulk_trash_delete_permanently") {
            $count = 0;
            foreach ($ids as $id) {
                $this->dao->deleteRedirect(absint($id));
                $count ++;
            }
            $message = $count . " " . __('URL(s) deleted', '404-solution');

        } else if ($action == "bulktrash") {
            $count = 0;
            foreach ($ids as $id) {
                $s = $this->dao->moveRedirectsToTrash($id, 1);
                if ($s == "") {
                    $count ++;
                }
            }
            $message = $count . " " . __('URL(s) moved to trash', '404-solution');

        } else {
            $this->logger->errorMessage("Unrecognized bulk action: " . esc_html($action));
            echo sprintf(__("Error: Unrecognized bulk action. (%s)", '404-solution'), esc_html($action));
        }
        return $message;
    }

    /** 
     * This is for both empty trash buttons (page redirects and captured 404 URLs).
     * @param string $sub
     */
    function doEmptyTrash($sub) {
        global $wpdb;
        global $abj404_redirect_types;
        global $abj404_captured_types;
        
        $query = "";
        if ($sub == "abj404_captured") {
            $query = "delete FROM {wp_abj404_redirects} \n" .
                    "where disabled = 1 \n" .
                    "      and status in (" . implode(", ", $abj404_captured_types) . ")";
            
        } else if ($sub == "abj404_redirects") {
            $query = "delete FROM {wp_abj404_redirects} \n" .
                    "where disabled = 1 \n" .
                    "      and status in (" . implode(", ", $abj404_redirect_types) . ")";
            
        } else {
            $this->logger->errorMessage("Unrecognized type in doEmptyTrash(" . $sub . ")");
        }

        $result = $this->dao->queryAndGetResults($query);
        $this->logger->debugMessage("doEmptyTrash deleted " . $result['rows_affected'] . " rows total. (" . $sub . ")");

        // Invalidate status counts cache after bulk delete
        $this->dao->invalidateStatusCountsCache();

        $this->dao->queryAndGetResults("optimize table {wp_abj404_redirects}");
    }
    
    /** 
     * @global type $abj404dao
     * @return string
     */
    function updateRedirectData() {
        $message = "";
        $fromURL = "";
        $ids_multiple = "";
        
        if (
        	(!array_key_exists('url', $_POST) || $_POST['url'] == "") && 
        	(array_key_exists('ids_multiple', $_POST) && $_POST['ids_multiple'] != "")) {
            $ids_multiple = array_map('absint', explode(',', $_POST['ids_multiple']));
            
        } else if (array_key_exists('url', $_POST) && $_POST['url'] != "" && 
        	(!array_key_exists('ids_multiple', $_POST) || $_POST['ids_multiple'] == "")) {
        		
        	$fromURL = stripslashes($_POST['url']);
        } else {
            $message .= __('Error: URL is a required field.', '404-solution') . "<BR/>";
        }

        if ($fromURL != "" && $this->f->substr($_POST['url'], 0, 1) != "/") {
            $message .= __('Error: URL must start with /', '404-solution') . "<BR/>";
        }

        $typeAndDest = $this->getRedirectTypeAndDest();

        if ($typeAndDest['message'] != "") {
            return $typeAndDest['message'];
        }

        if ($typeAndDest['type'] != "" && $typeAndDest['dest'] !== "") {
            $statusType = ABJ404_STATUS_MANUAL;
            if (isset($_POST['is_regex_url']) &&
                $_POST['is_regex_url'] != '0') {
                
                $statusType = ABJ404_STATUS_REGEX;
            }
            
            // decide whether we're updating one or multiple redirects.
            if ($fromURL != "") {
                $id = isset($_POST['id']) ? $_POST['id'] : 0;
                $code = isset($_POST['code']) ? $_POST['code'] : '';
                $this->dao->updateRedirect($typeAndDest['type'], $typeAndDest['dest'],
                        $fromURL, $id, $code, $statusType);

            } else if ($ids_multiple != "") {
                // get the redirect data for each ID.
                $redirects_multiple = $this->dao->getRedirectsByIDs($ids_multiple);
                $code = isset($_POST['code']) ? $_POST['code'] : '';
                foreach ($redirects_multiple as $redirect) {
                    $this->dao->updateRedirect($typeAndDest['type'], $typeAndDest['dest'],
                            $redirect['url'], $redirect['id'], $code, $statusType);
                }

            } else {
                $this->logger->errorMessage("Issue determining which redirect(s) to update. " . 
                    "fromURL: " . $fromURL . ", ids_multiple: " . 
                	(is_array($ids_multiple) ? implode(',', $ids_multiple) : ''));
            }

        } else {
            $message .= __('Error: Data not formatted properly.', '404-solution') . "<BR/>";
            $this->logger->errorMessage("Update redirect data issue. Type: " . esc_html($typeAndDest['type']) . 
                    ", dest: " . esc_html($typeAndDest['dest']));
        }

        return $message;
    }
    
    function getRedirectTypeAndDest() {

        $response = array();
        $response['type'] = "";
        $response['dest'] = "";
        $response['message'] = "";

        if (!isset($_POST['redirect_to_data_field_id'])) {
            $response['message'] = __('Error: Redirect destination is required.', '404-solution') . "<BR/>";
            return $response;
        }

        if ($_POST['redirect_to_data_field_id'] == ABJ404_TYPE_EXTERNAL . '|' . ABJ404_TYPE_EXTERNAL) {
            $userEnteredURL = esc_url($this->dao->getPostOrGetSanitize('redirect_to_user_field'), array('http', 'https'));
            if ($userEnteredURL == "") {
                $response['message'] = __('Error: You selected external URL but did not enter a URL.', '404-solution') . "<BR/>";

            } else if ($this->f->strlen($userEnteredURL) < 8) {
                $response['message'] = __('Error: External URL is too short.', '404-solution') . "<BR/>";

            } else if ($this->f->strpos($userEnteredURL, "://") === false) {
                $response['message'] = __("Error: External URL doesn't contain ://", '404-solution') . "<BR/>";

            } else {
                // Validate that URL uses safe protocol (http/https only)
                $parsed_url = parse_url($userEnteredURL);
                if (!isset($parsed_url['scheme']) || !in_array(strtolower($parsed_url['scheme']), array('http', 'https'))) {
                    $response['message'] = __('Error: External URL must use http:// or https:// protocol only.', '404-solution') . "<BR/>";
                }

                // Allow filtering of external redirect URLs for additional validation
                // Usage: add_filter('abj404_validate_external_redirect', function($url) { /* validation */ return $url; });
                $validated_url = apply_filters('abj404_validate_external_redirect', $userEnteredURL);
                if ($validated_url === false) {
                    $response['message'] = __('Error: External redirect URL failed validation.', '404-solution') . "<BR/>";
                } else {
                    $userEnteredURL = $validated_url;
                }
            }
        }

        if ($response['message'] != "") {
            return $response;
        }
        $info = explode("|", sanitize_text_field($_POST['redirect_to_data_field_id']));

        if ($_POST['redirect_to_data_field_id'] == ABJ404_TYPE_EXTERNAL . '|' . ABJ404_TYPE_EXTERNAL) {
            $response['type'] = ABJ404_TYPE_EXTERNAL;
            // Use the sanitized $userEnteredURL (created at line 1932) instead of raw POST
            $response['dest'] = $userEnteredURL;
        } else {
            if (count($info) == 2) {
                $response['dest'] = absint($info[0]);
                $response['type'] = $info[1];
            } else {
                $this->logger->errorMessage("Unexpected info while updating redirect: " . 
                        wp_kses_post(json_encode($info)));
            }
        }
        
        return $response;
    }
    
    /**
     * @global type $abj404dao
     * @return string
     */
    function addAdminRedirect() {
        $message = "";

        if (!isset($_POST['manual_redirect_url']) || $_POST['manual_redirect_url'] == "") {
            $message .= __('Error: URL is a required field.', '404-solution') . "<BR/>";
            return $message;
        }

        $manualURL = isset($_POST['manual_redirect_url']) ? $_POST['manual_redirect_url'] : '';
        if ($this->f->substr($manualURL, 0, 1) != "/") {
            $message .= __('Error: URL must start with /', '404-solution') . "<BR/>";
            return $message;
        }

        $typeAndDest = $this->getRedirectTypeAndDest();

        if ($typeAndDest['message'] != "") {
            return $typeAndDest['message'];
        }

        if ($typeAndDest['type'] != "" && $typeAndDest['dest'] !== "") {
            // url match type. regex or normal exact match.
            $statusType = ABJ404_STATUS_MANUAL;
            if (isset($_POST['is_regex_url']) &&
                $_POST['is_regex_url'] != '0') {
                
                $statusType = ABJ404_STATUS_REGEX;
            }
            
            $code = isset($_POST['code']) && !empty($_POST['code']) ? $_POST['code'] : ABJ404_STATUS_MANUAL;

            $this->dao->setupRedirect(esc_url($_POST['manual_redirect_url']), $statusType,
                    $typeAndDest['type'], $typeAndDest['dest'],
                    sanitize_text_field($code), 0);
            
        } else {
            $message .= __('Error: Data not formatted properly.', '404-solution') . "<BR/>";
            $this->logger->errorMessage("Add redirect data issue. Type: " . esc_html($typeAndDest['type']) . ", dest: " .
                    esc_html($typeAndDest['dest']));
        }

        return $message;
    }

    /** 
     * @param string $pageBeingViewed
     * @return array
     */
    function getTableOptions($pageBeingViewed) {
        $tableOptions = array();
        $options = $this->getOptions(true);

        $translationArray = array(
            '{ABJ404_STATUS_MANUAL_text}' => __('Man', '404-solution'),
            '{ABJ404_STATUS_AUTO_text}' => __('Auto', '404-solution'),
            '{ABJ404_STATUS_REGEX_text}' => __('RegEx', '404-solution'),
            '{ABJ404_TYPE_EXTERNAL_text}' => __('External', '404-solution'),
            '{ABJ404_TYPE_CAT_text}' => __('Category', '404-solution'),
            '{ABJ404_TYPE_TAG_text}' => __('Tag', '404-solution'),
       		'{ABJ404_TYPE_HOME_text}' => __('Home Page', '404-solution'),
       		'{ABJ404_TYPE_404_DISPLAYED_text}' => __('(Default 404 Page)', '404-solution'),
       		'{ABJ404_TYPE_SPECIAL_text}' => __('(Special)', '404-solution'),
        );
        
        $tableOptions['translations'] = $translationArray;
        
        $tableOptions['filter'] = intval($this->dao->getPostOrGetSanitize("filter", ""));
        if ($tableOptions['filter'] == "") {
            if ($this->dao->getPostOrGetSanitize('subpage') == 'abj404_captured') {
                $tableOptions['filter'] = ABJ404_STATUS_CAPTURED;
            } else {
                $tableOptions['filter'] = '0';
            }
        }
        
        $tableOptions['filterText'] = trim($this->dao->getPostOrGetSanitize("filterText", ""));
        // Remove comment markers early to prevent filterText from breaking SQL comments.
        $tableOptions['filterText'] = $this->f->str_replace(array('*', '/', '$'), '', $tableOptions['filterText']);

        $orderbyInput = $this->dao->getPostOrGetSanitize('orderby', "");
        if ($orderbyInput != "" && in_array($orderbyInput, self::$allowedOrderbyColumns, true)) {
            $tableOptions['orderby'] = $orderbyInput;

            if ($pageBeingViewed == 'abj404_redirects') {
                $options['page_redirects_order_by'] = $tableOptions['orderby'];
                $this->updateOptions($options);

            } else if ($pageBeingViewed == 'abj404_captured') {
                $options['captured_order_by'] = $tableOptions['orderby'];
                $this->updateOptions($options);
            }

        } else if ($pageBeingViewed == "abj404_logs") {
            $tableOptions['orderby'] = "timestamp";
        } else if ($pageBeingViewed == 'abj404_redirects') {
            $tableOptions['orderby'] = $options['page_redirects_order_by'];
        } else if ($pageBeingViewed == 'abj404_captured') {
            $tableOptions['orderby'] = $options['captured_order_by'];
        } else {
            $tableOptions['orderby'] = 'url';
        }

        $orderInput = strtoupper($this->dao->getPostOrGetSanitize('order', ''));
        if ($orderInput != '' && in_array($orderInput, self::$allowedOrderValues, true)) {
            $tableOptions['order'] = $orderInput;

            if ($pageBeingViewed == 'abj404_redirects') {
                $options['page_redirects_order'] = $tableOptions['order'];
                $this->updateOptions($options);

            } else if ($pageBeingViewed == 'abj404_captured') {
                $options['captured_order'] = $tableOptions['order'];
                $this->updateOptions($options);
            }

        } else if ($tableOptions['orderby'] == "created" || $tableOptions['orderby'] == "lastused" || $tableOptions['orderby'] == "timestamp") {
            $tableOptions['order'] = "DESC";

        } else if ($pageBeingViewed == 'abj404_redirects') {
            $tableOptions['order'] = $options['page_redirects_order'];

        } else if ($pageBeingViewed == 'abj404_captured') {
            $tableOptions['order'] = $options['captured_order'];

        } else {
            $tableOptions['order'] = "ASC";
        }

        $tableOptions['paged'] = $this->dao->getPostOrGetSanitize("paged", 1);

        $perPageOption = ABJ404_OPTION_DEFAULT_PERPAGE;
        if (isset($options['perpage'])) {
            $perPageOption = max(absint($options['perpage']), ABJ404_OPTION_MIN_PERPAGE);
        }
        $tableOptions['perpage'] = $this->dao->getPostOrGetSanitize("perpage", $perPageOption);

        $tableOptions['logsid'] = 0;
        if ($this->dao->getPostOrGetSanitize('subpage') == "abj404_logs") {
            if (isset($_GET['id']) && $this->f->regexMatch('[0-9]+', $_GET['id'])) {                
                $tableOptions['logsid'] = absint($_GET['id']);
                
            } else if (array_key_exists('redirect_to_data_field_id', $_GET) && 
                    isset($_GET['redirect_to_data_field_id']) && 
                    $this->f->regexMatch('[0-9]+', $_GET['redirect_to_data_field_id'])) {
                $tableOptions['logsid'] = absint($_GET['redirect_to_data_field_id']);
            }
        }

        // sanitize all values.
        $sanitizedTableOptions = $this->sanitizePostData($tableOptions);

        return $sanitizedTableOptions;
    }
    
    /** 
     * @param array $postData
     * @param boolean $restoreNewlines
     * @return array
     */
    function sanitizePostData($postData, $restoreNewlines = false) {
        $newData = array();
        foreach ($postData as $key => $value) {
            $key = wp_kses_post($key);
            if (is_array($value)) {
                $newData[$key] = $this->sanitizePostData($value, $restoreNewlines);
            } else {
                // Handle null values (PHP 8.1+ deprecation fix)
                if ($value === null) {
                    $newData[$key] = '';
                } else {
                    $newData[$key] = wp_kses_post($value);
                    $newData[$key] = esc_sql($newData[$key]);
                    if ($restoreNewlines) {
                        $newData[$key] = str_replace('\n', "\n", $newData[$key]);
                    }
                }
            }
        }
        return $newData;
    }
    
    /** Remove non a-zA-Z0-9 or _ characters. 
     * @param string $str
     * @return string
     */
    function sanitizeForSQL($str) {
        if ($str == null || $str == '') {
            return $str;
        }
        $re = '/[^\w_]/';
        
        $result = preg_replace($re, '', $str);
        return $result;
    }
    
    /** 
     * @return string
     */
    function updateOptionsFromPOST() {

        $message = "";
        $options = $this->getOptions();

        // get the submitted settings
        if (!isset($_POST['encodedData'])) {
            $this->logger->errorMessage('Missing encodedData in POST');
            return;
        }
        $encodedData = $_POST['encodedData'];
        $postData = $this->f->decodeComplicatedData($encodedData);

        // to return after handling the ajax call.
        $returnData = array();
        $returnData['newURL'] = admin_url() . "options-general.php?page=" . ABJ404_PP . '&subpage=abj404_options';

        // verify nonce
        if (!wp_verify_nonce($postData['nonce'], 'abj404UpdateOptions') || !is_admin()) {
        	$returnData['message'] = 'Task failed successfully.';
        	echo json_encode($returnData);
        	exit(1);
        }

        $_POST = $postData;

        // delete the debug file if requested.
        if (array_key_exists('deleteDebugFile', $_POST) && $_POST['deleteDebugFile'] == true) {
        	$sub = '';
        	$returnData['error'] = '';
        	$returnData['message'] = $this->handlePluginAction('updateOptions', $sub);

        } else {
        	// save all options - grouped by related functionality
	        $message .= $this->updateRedirectSettings($options, $_POST);
	        $message .= $this->updateWordPressSettings($options, $_POST);
	        $message .= $this->updateNotificationSettings($options, $_POST);
	        $message .= $this->updateDeletionSettings($options, $_POST);
	        $message .= $this->updateSuggestionSettings($options, $_POST);
	        $message .= $this->updateBooleanToggles($options, $_POST);
	        $message .= $this->updateSuggestionHTMLOptions($options, $_POST);
	        $message .= $this->updateRegexPatternSettings($options, $_POST);
	        $message .= $this->updateAdminUsers($options, $_POST);
	        $message .= $this->updateExcludedPages($options, $_POST);

	        // save this for later to sanitize it ourselves.
	        $excludedPages = $options['excludePages[]'];

	        /** Sanitize all data. */
	        $new_options = array();
	        // when sanitizing data we keep the newlines (\n) because some data
	        // is entered that way and it shouldn't allow any kind of sql
	        // injection or any other security issues that I foresee at this point.
	        $new_options = $this->sanitizePostData($options, true);

	        // only some characters in the string.
	        $excludedPages = $excludedPages == null ? '' : trim($excludedPages);
	        $excludedPages = preg_replace('/[^\[\",\]a-zA-Z\d\|\\\\ ]/', '', $excludedPages);
            $new_options['excludePages[]'] = $excludedPages;

	        $this->updateOptions($new_options);

	        // update the permalink cache because the post types included may have changed.
	        $permalinkCache = ABJ_404_Solution_PermalinkCache::getInstance();
	        $permalinkCache->updatePermalinkCache(2);

	        $returnData['error'] = $message;
	        if ($message == "") {
	        	$returnData['message'] = __('Options Saved Successfully!', '404-solution');
	        } else {
	        	$returnData['message'] = __('Some options were not saved successfully.', '404-solution') .
	        		'		' . $message;
	        }
        }

        echo json_encode($returnData);
        exit();
    }

    /** Update redirect-related settings.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateRedirectSettings(&$options, $postData) {
        $message = "";

        if (isset($postData['default_redirect'])) {
            if ($postData['default_redirect'] == "301" || $postData['default_redirect'] == "302") {
                $options['default_redirect'] = intval($postData['default_redirect']);
            } else {
                $message .= __('Error: Invalid value specified for default redirect type', '404-solution') . ".<BR/>";
            }
        }

        if (isset($postData['redirect_to_data_field_id'])) {
            $options['dest404page'] = sanitize_text_field($postData['redirect_to_data_field_id']);
        }
        if (isset($postData['redirect_to_data_field_title'])) {
            $options['dest404pageURL'] = sanitize_text_field($postData['redirect_to_data_field_title']);
            if ($options['dest404page'] == ABJ404_TYPE_EXTERNAL . '|' . ABJ404_TYPE_EXTERNAL) {
            	$options['dest404page'] = $options['dest404pageURL'] . '|' . ABJ404_TYPE_EXTERNAL;
            }
        }

        if (isset($postData['template_redirect_priority'])) {
            if (is_numeric($postData['template_redirect_priority']) && $postData['template_redirect_priority'] >= 0 && $postData['template_redirect_priority'] <= 999) {
                $options['template_redirect_priority'] = absint($postData['template_redirect_priority']);
            } else {
                $message .= __('Error: Template redirect priority value must be a number between 0 and 999', '404-solution') . ".<BR/>";
            }
        }

        return $message;
    }

    /** Update WordPress-specific settings.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateWordPressSettings(&$options, $postData) {
        $message = "";

        if (isset($postData['ignore_dontprocess'])) {
        	$options['ignore_dontprocess'] = wp_kses_post($postData['ignore_dontprocess']);
        }
        if (isset($postData['ignore_doprocess'])) {
        	$options['ignore_doprocess'] = wp_kses_post($postData['ignore_doprocess']);
        }
        if (isset($postData['recognized_post_types'])) {
        	$options['recognized_post_types'] = wp_kses_post($postData['recognized_post_types']);
        }
        if (isset($postData['recognized_categories'])) {
        	$options['recognized_categories'] = wp_kses_post($postData['recognized_categories']);
        }
        if (isset($postData['menuLocation'])) {
        	$options['menuLocation'] = wp_kses_post($postData['menuLocation']);
        }

        if (isset($postData['admin_theme'])) {
            // Only allow specific theme values
            $allowed_themes = array('default', 'calm', 'mono', 'neon', 'obsidian');
            $theme = sanitize_text_field($postData['admin_theme']);
            if (in_array($theme, $allowed_themes)) {
                $options['admin_theme'] = $theme;
            } else {
                $message .= __('Error: Invalid theme selected', '404-solution') . ".<BR/>";
            }
        }

        if (isset($postData['plugin_language_override'])) {
            // Only allow specific locale values
            $allowed_locales = array('', 'en_US', 'de_DE', 'es_ES', 'fr_FR', 'it_IT', 'pt_BR', 'nl_NL', 'ru_RU', 'ja', 'zh_CN', 'id_ID', 'sv_SE');
            $locale = sanitize_text_field($postData['plugin_language_override']);
            if (in_array($locale, $allowed_locales)) {
                $options['plugin_language_override'] = $locale;
            } else {
                $message .= __('Error: Invalid language selected', '404-solution') . ".<BR/>";
            }
        }

        // Handle disable_auto_dark_mode checkbox (unchecked = not in postData)
        if (isset($postData['disable_auto_dark_mode']) && $postData['disable_auto_dark_mode'] == '1') {
            $options['disable_auto_dark_mode'] = '1';
        } else {
            $options['disable_auto_dark_mode'] = '0';
        }

        if (isset($postData['days_wait_before_major_update'])) {
            if (is_numeric($postData['days_wait_before_major_update'])) {
                $options['days_wait_before_major_update'] = absint($postData['days_wait_before_major_update']);
            } else {
                $message .= sprintf(__('Error: The time to wait before an automatic update must be a number between 0 and something around %d.', '404-solution'), PHP_INT_MAX) . "<BR/>";
            }
        }

        return $message;
    }

    /** Update notification settings.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateNotificationSettings(&$options, $postData) {
        $message = "";

        if (isset($postData['admin_notification'])) {
            if (is_numeric($postData['admin_notification'])) {
                $options['admin_notification'] = absint($postData['admin_notification']);
            }
        }

        if (isset($postData['admin_notification_email'])) {
            $options['admin_notification_email'] = trim(wp_kses_post($postData['admin_notification_email']));
        }

        return $message;
    }

    /**
     * Validate and set a numeric field value from POST data.
     * Eliminates duplication in settings update methods.
     *
     * @param array $options Reference to options array to update
     * @param array $postData POST data containing field value
     * @param string $fieldName Name of the field to validate
     * @param string $errorMessage Error message to display on validation failure
     * @param int $minValue Minimum allowed value (default: 0)
     * @param bool $useAbsintForCheck Whether to use absint() before comparison (default: false)
     * @return string Error message if validation fails, empty string otherwise
     */
    private function validateAndSetNumericField(&$options, $postData, $fieldName, $errorMessage, $minValue = 0, $useAbsintForCheck = false) {
        if (isset($postData[$fieldName])) {
            $value = $postData[$fieldName];
            $passesValidation = false;

            if ($useAbsintForCheck) {
                // For maximum_log_disk_usage: check absint(value) > minValue
                $passesValidation = is_numeric($value) && absint($value) > $minValue;
            } else {
                // For other fields: check value >= minValue
                $passesValidation = is_numeric($value) && $value >= $minValue;
            }

            if ($passesValidation) {
                $options[$fieldName] = absint($value);
                return "";
            } else {
                return __($errorMessage, '404-solution') . ".<BR/>";
            }
        }
        return "";
    }

    /** Update deletion-related settings.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateDeletionSettings(&$options, $postData) {
        $message = "";

        $message .= $this->validateAndSetNumericField($options, $postData, 'capture_deletion',
            'Error: Collected URL deletion value must be a number greater than or equal to zero');

        $message .= $this->validateAndSetNumericField($options, $postData, 'manual_deletion',
            'Error: Manual redirect deletion value must be a number greater than or equal to zero');

        $message .= $this->validateAndSetNumericField($options, $postData, 'log_deletion',
            'Error: Log deletion value must be a number greater than or equal to zero');

        $message .= $this->validateAndSetNumericField($options, $postData, 'auto_deletion',
            'Error: Auto redirect deletion value must be a number greater than or equal to zero');

        $message .= $this->validateAndSetNumericField($options, $postData, 'maximum_log_disk_usage',
            'Error: Maximum log disk usage must be a number greater than zero', 0, true);

        return $message;
    }

    /** Update suggestion/spelling settings.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateSuggestionSettings(&$options, $postData) {
        $message = "";

        if (isset($postData['suggest_max'])) {
            if (is_numeric($postData['suggest_max']) && $postData['suggest_max'] >= 1) {
                if ($options['suggest_max'] != absint($postData['suggest_max'])) {
                    $this->logger->debugMessage(__CLASS__ . "/" . __FUNCTION__ .
                            ": Truncating spelling cache because the max suggestions # changed from " .
                            $options['suggest_max'] . ' to ' . absint($postData['suggest_max']));

                    // the spelling cache only stores up to X entries. X is based on suggest_max
                    // so the spelling cache has to be reset when this number changes.
                    $this->dao->deleteSpellingCache();
                }

                $options['suggest_max'] = absint($postData['suggest_max']);
            } else {
                $message .= __('Error: Maximum number of suggest value must be a number greater than or equal to 1', '404-solution') . ".<BR/>";
            }
        }

        if (isset($postData['auto_score'])) {
            if (is_numeric($postData['auto_score']) && $postData['auto_score'] >= 0 && $postData['auto_score'] <= 99) {
                $options['auto_score'] = absint($postData['auto_score']);
            } else {
                $message .= __('Error: Auto match score value must be a number between 0 and 99', '404-solution') . ".<BR/>";
            }
        }

        return $message;
    }

    /** Update boolean toggle options (checkboxes).
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateBooleanToggles(&$options, $postData) {
        $message = "";

        // Check if we're in simple or advanced settings mode
        $settingsMode = $this->getSettingsMode();

        // All boolean options that could be in forms
        $allBooleanOptions = array('remove_matches', 'debug_mode', 'suggest_cats', 'suggest_tags',
            'auto_redirects', 'auto_slugs', 'auto_cats', 'auto_tags', 'capture_404', 'send_error_logs', 'log_raw_ips',
        	'redirect_all_requests', 'update_suggest_url', 'suggest_minscore_enabled'
        );

        // Options that appear in Simple Mode form
        $simpleModeOptions = array('auto_redirects', 'capture_404');

        // Determine which options to process from POST data
        if ($settingsMode === 'simple') {
            // Simple mode: only process options that are actually in the form
            $optionsToProcess = $simpleModeOptions;
        } else {
            // Advanced mode: process all options (existing behavior)
            $optionsToProcess = $allBooleanOptions;
        }

        foreach ($optionsToProcess as $optionName) {
        	$newVal = (array_key_exists($optionName, $postData) && $postData[$optionName] == "1") ? 1 : 0;

        	// in case the suggest_cats or suggest_tags is changed.
        	if (!array_key_exists($optionName, $options) ||
        		$options[$optionName] != $newVal) {

        		$this->dao->deleteSpellingCache();
        	}
            $options[$optionName] = $newVal;
        }

        // In Simple Mode, sync auto_cats and auto_tags with auto_redirects
        if ($settingsMode === 'simple') {
            $autoRedirectsValue = isset($options['auto_redirects']) ? $options['auto_redirects'] : 0;
            $options['auto_cats'] = $autoRedirectsValue;
            $options['auto_tags'] = $autoRedirectsValue;
        }

        return $message;
    }

    /** Update suggestion HTML display options.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateSuggestionHTMLOptions(&$options, $postData) {
        $message = "";

        // the suggest_.* options have html in them.
        $optionsListSuggest = array('suggest_title', 'suggest_before', 'suggest_after', 'suggest_entrybefore',
            'suggest_entryafter', 'suggest_noresults');
        foreach ($optionsListSuggest as $optionName) {
            // Only update if the option was posted (Simple Mode doesn't include these)
            if (isset($postData[$optionName])) {
                $options[$optionName] = wp_kses_post($postData[$optionName]);
            }
        }

        return $message;
    }

    /** Update regex pattern settings for ignoring files/folders and suggestion exclusions.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateRegexPatternSettings(&$options, $postData) {
        $message = "";

        if (isset($postData['folders_files_ignore'])) {
            $options['folders_files_ignore'] = wp_unslash(wp_kses_post($postData['folders_files_ignore']));

            // make the regular expressions usable.
            $patternsToIgnore = $this->f->explodeNewline($options['folders_files_ignore']);
            $usableFilePatterns = array();
            foreach ($patternsToIgnore as $patternToIgnore) {
                $newPattern = '^' . preg_quote(trim($patternToIgnore), '/') . '$';
                $newPattern = $this->f->str_replace("\*",".*", $newPattern);
                $usableFilePatterns[] = $newPattern;
            }
            $options['folders_files_ignore_usable'] = $usableFilePatterns;
        }

        if ( isset( $postData['suggest_regex_exclusions'] ) ) {
            // 1. Sanitize the raw input using the appropriate function for multi-line text without HTML.
            $sanitized_exclusions = sanitize_textarea_field( wp_unslash( $postData['suggest_regex_exclusions'] ) );
            $options['suggest_regex_exclusions'] = $sanitized_exclusions;

            // 2. Generate the usable regex patterns *from the sanitized input*.
            $patternsToIgnore = $this->f->explodeNewline( $sanitized_exclusions );
            $usableFilePatterns = array();
            foreach ( $patternsToIgnore as $patternToIgnore ) {
                $trimmedPattern = trim( $patternToIgnore );
                // Only process non-empty lines
                if ( ! empty( $trimmedPattern ) ) {
                    // Escape regex special characters, then convert literal '*' into '.*' for wildcard matching.
                    $newPattern = '^' . preg_quote( $trimmedPattern, '/' ) . '$';
                    // Use standard str_replace; $this->f->str_replace is likely unnecessary here unless it provides specific multibyte handling not needed for '\*'.
                    $newPattern = str_replace( '\*', '.*', $newPattern );
                    $usableFilePatterns[] = $newPattern;
                }
            }
            $options['suggest_regex_exclusions_usable'] = $usableFilePatterns;
        }

        return $message;
    }

    /** Update plugin admin users list.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateAdminUsers(&$options, $postData) {
        $message = "";

        if (isset($postData['plugin_admin_users'])) {
        	$pluginAdminUsers = $postData['plugin_admin_users'];
        	if (is_array($pluginAdminUsers)) {
        		$pluginAdminUsers = array_filter($pluginAdminUsers,
        			array($this->f, 'removeEmptyCustom'));
        	}

        	$options['plugin_admin_users'] = $pluginAdminUsers;
        }

        return $message;
    }

    /** Update excluded pages list.
     * @param array $options The options array to update
     * @param array $postData The POST data
     * @return string Any error messages
     */
    private function updateExcludedPages(&$options, $postData) {
        $message = "";

        if (is_array($options['excludePages[]'])) {
            $this->logger->warn("Exclude pages settings lost.");
            $options['excludePages[]'] = '';
        }
        if (isset($postData['excludePages[]'])) {
        	$oldExcludePages = json_decode($options['excludePages[]']);
        	if (!is_array($postData['excludePages[]'])) {
        		$postData['excludePages[]'] = array($postData['excludePages[]']);
        	}
        	$options['excludePages[]'] = json_encode($postData['excludePages[]']);
        	$newExcludePages = json_decode($options['excludePages[]']);
        	if ($newExcludePages !== $oldExcludePages) {
        		// if any excluded pages changed or if the number of excluded pages changed
        		// then the spelling cache has to be reset.
        		$this->dao->deleteSpellingCache();
        	}
        } else {
        	$oldExcludePages = json_decode($options['excludePages[]']);
        	if (null !== $oldExcludePages) {
        		// if any excluded pages changed or if the number of excluded pages changed
        		// then the spelling cache has to be reset.
        		$this->dao->deleteSpellingCache();
        	}
        	$options['excludePages[]'] = null;
        }

        return $message;
    }
    
    /** Get the "/commentpage" and the "?query=part" of the URL. 
     * @return string */
    function getCommentPartAndQueryPartOfRequest() {
    	$userRequest = ABJ_404_Solution_UserRequest::getInstance();
    	$queryParts = $this->f->removePageIDFromQueryString($userRequest->getQueryString());
    	$queryParts = ($queryParts == '') ? '' : '?' . $queryParts;
    	$commentPart = $userRequest->getCommentPagePart();
    	return $commentPart . $queryParts;
    }
    
    /** First try a wp_redirect. Then try a redirect with JavaScript. The wp_redirect usually works, but doesn't 
     * if some other plugin has already output any kind of data. 
     * @param string $location
     * @param number $status
     * @param number $type only 0 for sending to a 404 page
     * @param string $requestedURL
     * @return boolean true if the user is sent to the default 404 page.
     */
    function forceRedirect($location, $status = 302, $type = -1, $requestedURL = '', $isCustom404 = false) {

        $commentPartAndQueryPart = $this->getCommentPartAndQueryPartOfRequest();
        // Sanitize and encode the base location and query parts
        $sanitizedLocation = esc_url_raw($location); // Ensure the base URL is safe
        $sanitizedQueryPart = esc_html($commentPartAndQueryPart); // Encode the query part for safe output
        $finalDestination = $sanitizedLocation . $sanitizedQueryPart;

        // Append _ref LAST for custom 404 redirects (prevents user override via query string)
        // This is a fallback for when cookies don't survive 301 redirects
        if ($isCustom404 && !empty($requestedURL)) {
            $refUrl = preg_replace('/\?.*/', '', $requestedURL); // Strip query string from ref
            $separator = (strpos($finalDestination, '?') === false) ? '?' : '&';
            $finalDestination .= $separator . ABJ404_PP . '_ref=' . urlencode($refUrl);
        }

    	$previousRequest = $this->readCookieWithPreviousRqeuestShort();
    	$finalDestNoHome = $this->f->substr($finalDestination, $this->f->strpos($finalDestination, '://') + 3);
    	$finalDestNoHome = $this->f->substr($finalDestNoHome, $this->f->strpos($finalDestNoHome, '/'));
    	$locationNoHome = $this->f->substr($location, $this->f->strpos($location, '://') + 3);
    	$locationNoHome = $this->f->substr($locationNoHome, $this->f->strpos($locationNoHome, '/'));
    	// maybe avoid infinite redirects.
    	if (!empty($previousRequest)) {
    		if ($previousRequest == $finalDestNoHome && $previousRequest != $locationNoHome) {
    			$this->logger->infoMessage("Maybe avoided infite redirects to/from: " .
    				$previousRequest);
    			$finalDestination = $location;
    			
    		} else if ($previousRequest == $finalDestination) {
    			$this->logger->infoMessage("Avoided infite redirects to/from: " .
    				$previousRequest);
    			return false;
    		}
    	}
    	
    	// if the destination is the default 404 page then send the user there.
    	if ($type == ABJ404_TYPE_404_DISPLAYED) {
    		$abj404logic = ABJ_404_Solution_PluginLogic::getInstance();
    		$abj404logic->sendTo404Page($requestedURL, '', false);
    		
    		return true;
    	}
    	
    	// try a normal redirect using a header.
    	$this->setCookieWithPreviousRequest();
        wp_redirect($finalDestination, $status, ABJ404_NAME);

        // TODO add an ajax request here that fires after 5 seconds.
        // upon getting the request the server will log the error. the plugin could then notify an admin.

        // This javascript redirect will only appear if the header redirect did not work for some reason.
        // Use wp_json_encode to safely encode URL for JavaScript to prevent XSS
        $c = '<script>' . 'function doRedirect() {' . "\n" .
                '   window.location.replace(' . wp_json_encode($finalDestination) . ');' . "\n" .
                '}' . "\n" .
                'setTimeout(doRedirect, 1);' . "\n" .
                '</script>' . "\n" .
                'Page moved: <a href="' . esc_url($finalDestination) . '">' .
        			esc_html($location) . '</a>';
        echo $c;
        exit;
    }

    /** Order pages and set the page depth for child pages.
     * Move the children to be underneath the parents.
     * @param array $pages
     */    
    function orderPageResults($pages, $includeMissingParentPages = false) {
        
        // sort by type then title.
        usort($pages, array($this, "sortByTypeThenTitle"));
        // run this to see if there are any child pages left.
        $orderedPages = $this->setDepthAndAddChildren($pages);
        
        // The pages are now sorted. We now apply the depth AND we make sure the child pages
        // always immediately follow the parent pages.

        // -------------
        if ($includeMissingParentPages && (count($orderedPages) != count($pages))) {
            $iterations = 0;
            
            do {
                $idsOfMissingParentPages = $this->getMissingParentPageIDs($pages);
                $pageCountBefore = count($pages);
                $iterations = $iterations + 1;
                
                // get the parents of the unused pages.
                foreach ($idsOfMissingParentPages as $pageID) {
                    $postParent = get_post($pageID);
                    if ($postParent == null) {
                        continue;
                    }
                    $parentPageSlug = $postParent->post_name;
                    $parentPage = $this->dao->getPublishedPagesAndPostsIDs($parentPageSlug);
                    if (count($parentPage) != 0) {
                        $pages[] = $parentPage[0];
                    }
                }
                
                if ($iterations > 30) {
                    break;
                }
                
                $idsOfMissingParentPages = $this->getMissingParentPageIDs($pages);
                
                // loop until we can't find any more parents. This may happen if a sub-page is published
                // and the parent page is not published.
            } while ($pageCountBefore != count($pages));
            
            // sort everything again
            usort($pages, array($this, "sortByTypeThenTitle"));
            $orderedPages = $this->setDepthAndAddChildren($pages);
        }
        
        // if there are child pages left over then there's an issue. it means there's a child page that was
        // returned but the parent for that child was not returned. so we don't have any place to display
        // the child page. this could be because the parent page is not "published"
        if (count($orderedPages) != count($pages)) {
            $unusedPages = array_udiff($pages, $orderedPages, array($this, 'compareByID'));
            $this->logger->debugMessage("There was an issue finding the parent pages for some child pages. " .
                    "These pages' parents may not have a 'published' status. Pages: " . 
                    wp_kses_post(json_encode($unusedPages)));
        }
        
        return $orderedPages;
    }
    
    /** For custom categories we create a Map<String, List> where the key is the name 
     * of the taxonomy and the list holds the rows that have the category info.
     * @param array $categoryRows
     * @return array
     */
    function getMapOfCustomCategories($categoryRows) {
        $customTagsEtc = array();
        
        foreach ($categoryRows as $cat) {
            $taxonomy = $cat->taxonomy;
            if ($taxonomy == 'category') {
                continue;
            }
            // for custom categories we create a Map<String, List> where the key is the name
            // of the taxonomy and the list holds the rows that have the category info.
            if (!array_key_exists($taxonomy, $customTagsEtc) || $customTagsEtc[$taxonomy] == null) {
                $customTagsEtc[$taxonomy] = array($cat);
            } else {
                array_push($customTagsEtc[$taxonomy], $cat);
            }
            
        }
        return $customTagsEtc;
    }
    
    /** Returns a list of parent IDs that can't be found in the passed in pages.
     * @param array $pages
     */
    function getMissingParentPageIDs($pages) {
        $listOfIDs = array();
        $missingParentPageIDs = array();
        
        foreach ($pages as $page) {
            $listOfIDs[] = $page->id;
        }
        
        foreach ($pages as $page) {
            if ($page->post_parent == 0) {
                continue;
            }
            if (in_array($page->post_parent, $listOfIDs)) {
                continue;
            }
            
            $missingParentPageIDs[] = $page->post_parent;
        }

        $missingParentPageIDs = array_merge(
        	array_unique($missingParentPageIDs, SORT_REGULAR), array());
        return $missingParentPageIDs;
    }

    /** Compare pages based on their ID. */
    function compareByID($a, $b) {
        if ($a->id < $b->id) {
            return -1;
        }
        if ($b->id < $a->id) {
            return 1;
        }
        return 0;
    }
    
    /** Set the depth of each page and add pages under their parents by rebuilding the list
     * every time we iterate through it and adding the child pages at the right moment every time
     * the list is built.
     * @param array $pages
     * @return array
     */
    function setDepthAndAddChildren($pages) {
        // find all child pages (pages that have parents).
        $childPages = $this->findChildPages($pages);
        
        // find all pages with no parents.
        $mainPages = $this->findAllMainPages($pages);
        
        $oldChildPageCount = -1;
        
        // this do{} loop is here because some child pages have children.
        do {
            // add every page to a new list, while looking for parents.
            $orderedPages = array();
            foreach ($mainPages as $page) {
                // always add the main page.
                $orderedPages[] = $page;
                
                // if this page is the parent of any children then add the children.
                $removeThese = array();
                foreach ($childPages as $child) {
                    if ($child->post_parent == $page->id) {
                        // set the page depth based on the parent's page depth.
                        $child->depth = $page->depth + 1;

                        $removeThese[] = $child;
                        $orderedPages[] = $child;
                    }
                }
                
                // remove any child pages that have been placed already
                $childPages = $this->removeUsedChildPages($childPages, $removeThese);
            }
            
            // the new list becomes the list that we will iterate over next time. 
            // this prepares us for the next iteration and for child pages with a depth greater than 1.
            // (for child pages that have children).
            $mainPages = $orderedPages;
            
            // if the count has not changed then there's no point in looping again.
            if (count($childPages) == $oldChildPageCount) {
                break;
            }
            $oldChildPageCount = count($childPages);
            // stop the loop once there are no more children to add.
        } while (count($childPages) > 0);
        
        return $orderedPages;
    }
    
    /** 
     * @param array $pages
     * @return array
     */
    function findAllMainPages($pages) {
        $mainPages = array();
        foreach ($pages as $page) {
            // if there's no parent then just add the page.
            if ($page->post_parent == 0) {
                $mainPages[] = $page;
            }
        }
        
        return $mainPages;
    }
    
    /** 
     * @param array $childPages
     * @param array $removeThese
     * @return array
     */
    function removeUsedChildPages($childPages, $removeThese) {
        // if any children were added then remove them from the list.
        foreach ($removeThese as $removeThis) {
            $key = array_search($removeThis, $childPages);
            if ($key !== false) {
                $childPages[$key] = null;
                unset($childPages[$key]);
            }
        }
        
        return $childPages;
    }
    
    /** Return pages that have a non-0 parent.
     * @param array $pages
     * @return array
     */
    function findChildPages($pages) {
        $childPages = array();
        foreach ($pages as $page) {
            if ($page->post_parent != 0) {
                $childPages[] = $page;
            }
        }
        return $childPages;
    }

    /** 
     * @param array $a
     * @param array $b
     * @return int
     */
    function sortByTypeThenTitle($a, $b) {
        // first sort by type
        $result = strcmp($a->post_type, $b->post_type);
        if ($result != 0) {
            return $result;
        }
        
        // then by title.
        return strcmp($a->post_title, $b->post_title);
    }

    /** Send an email if a notification should be displayed. Return true if an email is sent, or false otherwise.
     * @return string
     */
    function emailCaptured404Notification() {
        
        $options = $this->getOptions(true);
        
        $captured404Count = $this->dao->getCapturedCountForNotification();
        if (!$this->shouldNotifyAboutCaptured404s($captured404Count)) {
            return "Not enough 404s found to send an admin notification email (" . $captured404Count . ").";
        }
        
        $captured404URLSettings = admin_url() . "options-general.php?page=" . ABJ404_PP . '&subpage=abj404_captured';
        $generalSettings = admin_url() . "options-general.php?page=" . ABJ404_PP . '&subpage=abj404_options';
        $to = $options['admin_notification_email'];
        $subject = '404 Solution: Captured 404 Notification';
        $body = "There are currently " . $captured404Count . " captured 404s to look at. <BR/><BR/>\n\n";
        $body .= 'Visit <a href="' . $captured404URLSettings . '">' . $captured404URLSettings . 
                '</a> to see them.<BR/><BR/>' . "\n";
        $body .= 'To stop getting these emails, update the settings at <a href="' . $generalSettings . '">' . 
                $generalSettings . '</a>, or contact the site administrator.' . "<BR/>\n";
        $body .= "<BR/><BR/>\n\nSent " . date('Y/m/d h:i:s T') . "<BR/>\n" . "PHP version: " . PHP_VERSION . 
                ", <BR/>\nPlugin version: " . ABJ404_VERSION;
        $headers = array('Content-Type: text/html; charset=UTF-8');
        $headers[] = 'From: ' . get_option('admin_email') . '<' . get_option('admin_email') . '>';
        
        // send the email
        $this->logger->debugMessage("Sending captured 404 notification email to: " . $options['admin_notification_email']);
        wp_mail($to, $subject, $body, $headers);
        $this->logger->debugMessage("Captured 404 notification email sent.");
        return "Captured 404 notification email sent to: " . trim($options['admin_notification_email']);
    }
    
    /** Return true if a notification should be displayed, or false otherwise.
     * @global type $abj404dao
     * @param number $captured404Count the number of captured 404s
     * @return boolean
     */
    function shouldNotifyAboutCaptured404s($captured404Count) {
        $options = $this->getOptions(true);
        
        if (isset($options['admin_notification']) && $options['admin_notification'] != '0') {
            if ($captured404Count >= $options['admin_notification']) {
                return true;
            }
        }
        
        return false;
    }
    
    /** 0|0 => "(Default 404 Page)"
     * 5|5 => "(Home Page)"
     * 10|1 => "About"
     * @param string $idAndType
     * @param string $externalLinkURL
     * @return string
     */
    function getPageTitleFromIDAndType($idAndType, $externalLinkURL) {
        
        if ($idAndType == '') {
            return '';
        }

        $meta = explode("|", $idAndType);
        $id = $meta[0];
        // Handle malformed data that doesn't contain a pipe separator
        $type = isset($meta[1]) ? $meta[1] : '';

        // Use strict comparison to avoid null/false == 0 issues with type coercion
        // Cast to int for comparison since ABJ404_TYPE_* constants are integers
        $typeInt = is_numeric($type) ? (int)$type : -1;

        if ($idAndType == ABJ404_TYPE_404_DISPLAYED . '|' . ABJ404_TYPE_404_DISPLAYED) {
            return __('(Default 404 Page)', '404-solution');
        } else if ($idAndType == ABJ404_TYPE_HOME . '|' . ABJ404_TYPE_HOME) {
            return __('(Home Page)', '404-solution');
        } else if ($typeInt === ABJ404_TYPE_EXTERNAL) {
            return $externalLinkURL;
        }

        if ($typeInt === ABJ404_TYPE_POST) {
            return get_the_title($id);

        } else if ($typeInt === ABJ404_TYPE_CAT) {
            $rows = $this->dao->getPublishedCategories($id);
            if (empty($rows)) {
                $this->logger->debugMessage('No TERM (category) found with ID: ' . $id);
                return '';
            }
            $firstRow = $rows[0];
            return $firstRow->name;

        } else if ($typeInt === ABJ404_TYPE_TAG) {
            $tag = get_tag($id);
            return $tag == '' ? '' : $tag->name;
        }

        $this->logger->errorMessage("Couldn't get page title. No matching type found for type: " . esc_html($type));
        return '';
    }
}
