<?php
/**
 * Buoy Alert
 *
 * A Buoy Alert may also be referred to as an "incident" depending on
 * context.
 *
 * @package WordPress\Plugin\WP_Buoy_Plugin\WP_Buoy_Alert
 *
 * @copyright Copyright (c) 2015-2016 by Meitar "maymay" Moscovitz
 *
 * @license https://www.gnu.org/licenses/gpl-3.0.en.html
 */

if (!defined('ABSPATH')) { exit; } // Disallow direct HTTP access.

/**
 * Class for creating and delegating responses to alerts.
 *
 * Alerts are posts that record some incident information such as the
 * location and attached media recordings of what's going on.
 */
class WP_Buoy_Alert extends WP_Buoy_Plugin {

    /**
     * Alert post.
     *
     * @var WP_Post
     */
    public $wp_post;

    /**
     * The author of the alert.
     *
     * @var WP_User
     */
    private $user;

    /**
     * The teams to which this alert was sent.
     *
     * @var int[]
     */
    private $teams;

    /**
     * The alert's WP_Post data.
     *
     * This holds the initialization data for the alert's WP_Post data
     * and is the same as `wp_insert_post()`'s `$postarr` parameter.
     *
     * @link https://developer.wordpress.org/reference/functions/wp_insert_post/
     *
     * @var array
     */
    private $postarr;

    /**
     * The alert's public identifier.
     *
     * The `$hash` is a randomly generated lookup value that is used
     * instead of a WordPress post ID. This is because a post ID is a
     * sequential number, and would expose the Buoy to attack if a bad
     * (malicious) actor. Using a hash value instead of an integer in
     * this context makes it harder for attackrs to guess quantity and
     * frequency of alerts that this Buoy maintains.
     *
     * @link https://www.owasp.org/index.php/How_to_protect_sensitive_data_in_URL%27s
     *
     * @var string
     */
    private $hash;

    /**
     * The chat room associated with this alert.
     *
     * @var string
     */
    private $chat_room_name;

    /**
     * List of all the HTML Document Object Model hooks (IDs, class names)
     * touched by this module.
     *
     * @var string[]
     */
    private static $dom_hooks = array(
        'chat_room_container' => '#alert-chat-room-container',
        'fit_map_button' => '#fit-map-to-markers-btn',
        'incident_map' => '#buoy-map',
        'incident_media_group' => '#incident-media-group',
        'incident_media_group_item' => '#incident-media-group ul.dropdown-menu li',
        'incident_response_form' => '#incident-response-form',
        'map_container' => '#buoy-map-container',
        'my_location_button' => '#go-to-my-location',
        'page_activate_alert' => '.dashboard_page_buoy_activate_alert',
        'page_chat' => '.dashboard_page_buoy_chat', // TODO: This maybe should be in the chat room's own class?
        'page_review_alert' => '.dashboard_page_buoy_review_alert',
        'safety_info_modal' => '#safety-information-modal',
        'toggle_map_button' => '#toggle-incident-map-btn',
        'upload_media_button' => '#upload-media-btn',
        'vidchat_button' => '#buoy-videochat-btn',
    );

    /**
     * Constructor.
     *
     * Retrieves an alert post as a WP_Buoy_Alert object, or an empty,
     * new such object if no `$lookup` value is provided with which to
     * search for a pre-existing alert.
     *
     * @uses WP_Buoy_Alert::load()
     *
     * @param int|WP_Post|string $lookup Optional lookup value, WP_Post, ID, or hash.
     *
     * @return WP_Buoy_Alert
     */
    public function __construct ($lookup = null) {
        if (null !== $lookup) {
            return $this->load($lookup);
        }
    }

    /**
     * Get an alert from the WordPress database based on lookup value.
     *
     * @param string|int $lookup The lookup value.
     *
     * @return WP_Buoy_Alert
     *
     * @throws Exception If no alert could be found using `$lookup`.
     */
    public function load ($lookup) {
        if (strlen($lookup) > 7) {
            $posts = get_posts(array(
                'post_type' => self::$prefix.'_alert',
                'post_status' => array('publish', 'future'),
                'meta_query' => array(
                    array(
                        'key' => self::$prefix.'_hash',
                        'value' => "^$lookup",
                        'compare' => 'REGEXP'
                    )
                )
            ));
        }

        if (!empty($posts)) {
            $this->wp_post = array_pop($posts);
        } else {
            $this->wp_post = get_post($lookup);
        }

        if ($this->wp_post && self::$prefix.'_alert' === $this->wp_post->post_type) {
            $this->set_hash();
            $this->set_chat_room_name();
            $this->user = get_userdata($this->wp_post->post_author);
            $this->teams = array_map(
                'absint', get_post_meta($this->wp_post->ID, self::$prefix.'_teams', true)
            );
        } else {
            throw new Exception(sprintf(__('No alert with lookup "%s" found.', 'buoy'), $lookup));
        }

        return $this;
    }

    /**
     * Saves the alert (incident) in the WordPress database.
     *
     * @uses wp_insert_post()
     * @uses get_post()
     * @uses WP_Buoy_Alert::set_hash()
     * @uses WP_Buoy_Alert::set_chat_room_name()
     *
     * @return int|WP_Error Result of `wp_insert_post()`.
     */
    public function save () {
        $result = wp_insert_post($this->postarr, true);
        if (is_int($result)) {
            $this->wp_post = get_post($result);
            $this->set_hash();
            $this->set_chat_room_name();
        }
        return $result;
    }

    /**
     * Sets the WP_Post data for this alert.
     *
     * @link https://developer.wordpress.org/reference/functions/wp_insert_post/
     *
     * @uses WP_Buoy_Settings::get()
     *
     * @param array $postarr Same as `wp_insert_post()`'s `$postarr` parameter.
     *
     * @return WP_Buoy_Alert
     */
    public function set ($postarr = array()) {
        // These args are always hardcoded.
        $postarr['post_type']      = self::$prefix.'_alert';
        $postarr['post_content']   = ''; // empty content
        $postarr['ping_status']    = 'closed';
        $postarr['comment_status'] = 'closed'; // always closed, but dynamically opened by filter

        $defaults = array(
            'post_status' => 'publish',
            'post_author' => get_current_user_id()
        );

        $postarr = wp_parse_args($postarr, $defaults);

        $alerter = new WP_Buoy_User($postarr['post_author']);
        $default_meta = array(
            self::$prefix.'_hash' => $this->make_hash(),
            self::$prefix.'_chat_room_name' => $this->make_chat_room_name(),
            self::$prefix.'_teams' => $alerter->get_default_teams(),
            self::$prefix.'_chat_system' => WP_Buoy_Settings::get_instance()->get('chat_system', 'post_comments')
        );

        if (!isset($postarr['meta_input'])) {
            $postarr['meta_input'] = array();
        }
        $postarr['meta_input'] = wp_parse_args($postarr['meta_input'], $default_meta);

        $this->postarr = $postarr;

        return $this;
    }

    /**
     * Gets this alert's lookup hash value.
     *
     * @return string
     */
    public function get_hash () {
        return $this->hash;
    }

    /**
     * Gets the teams to which this alert was sent.
     *
     * @return int[]
     */
    public function get_teams () {
        return $this->teams;
    }

    /**
     * Checks whether a user is allowed to respond to this alert.
     *
     * A user is allowed to respond to an alert if they are listed as
     * a "confirmed" member in one of the teams associated with this
     * alert.
     *
     * @todo
     * Currently, an alert dynamically looks up who is on the
     * teams associated with it. This should be changed so it
     * keeps a snapshotted list of the confirmed team members
     * at the time the alert was created. This will prevent a
     * user from being added to a team (and thus granted access
     * to an alert) *after* the alert has been sent out.
     *
     * @uses WP_Buoy_Team::get_confirmed_members()
     *
     * @param int $user_id
     *
     * @return bool
     */
    public function can_respond ($user_id) {
        foreach ($this->get_teams() as $team_id) {
            $team = new WP_Buoy_Team($team_id);
            if (in_array($user_id, $team->get_confirmed_members())) {
                return true;
            }
        }
        return false;
    }

    /**
     * Loads the alert hash from the database.
     *
     * @return void
     */
    private function set_hash () {
        $prev_hash = sanitize_text_field(get_post_meta($this->wp_post->ID, self::$prefix.'_hash', true));
        if ($prev_hash) {
            $this->hash = $prev_hash;
        }
    }

    /**
     * Loads this alert's chat room name from the database.
     *
     * @return void
     */
    private function set_chat_room_name () {
        $this->chat_room_name = sanitize_text_field(get_post_meta($this->wp_post->ID, self::$prefix.'_chat_room_name', true));
    }

    /**
     * Gets this alert's chat room name.
     *
     * @return string
     */
    public function get_chat_room_name () {
        return $this->chat_room_name;
    }

    /**
     * Gets this alert's chat room system provider.
     *
     * @return string
     */
    public function get_chat_system () {
        $meta_key = self::$prefix.'_chat_system';
        return $this->wp_post->$meta_key;
    }

    /**
     * Retrieves a list of users who have responded to this alert.
     *
     * @return int[]
     */
    public function get_responders () {
        return get_post_meta($this->wp_post->ID, self::$prefix.'_responders');
    }

    /**
     * Determine whether a user has responded to the alert.
     *
     * @param int $user_id
     *
     * @return bool
     */
    public function is_responder ($user_id) {
        return in_array($user_id, $this->get_responders());
    }

    /**
     * Adds a responder to this alert.
     *
     * @uses WP_Buoy_Alert::is_responder()
     * @uses add_post_meta()
     *
     * @param int $user_id
     *
     * @return WP_Buoy_Alert
     */
    public function add_responder ($user_id) {
        if (!$this->is_responder($user_id)) {
            add_post_meta($this->wp_post->ID, self::$prefix.'_responders', $user_id, false);
        }
        return $this;
    }

    /**
     * Saves new geolocation data (lat/lon pair) for a responder.
     *
     * @uses update_post_meta()
     *
     * @param int $user_id
     * @param float[] $geo
     *
     * @return WP_Buoy_Alert
     */
    public function set_responder_geo ($user_id, $geo) {
        update_post_meta($this->wp_post->ID, self::$prefix."_responder_{$user_id}_location", $geo);
        return $this;
    }

    /**
     * Retrieves the current geolocation coords of a given responder.
     *
     * @uses get_post_meta()
     *
     * @param int $user_id
     *
     * @return float[]
     */
    public function get_responder_geo ($user_id) {
        return get_post_meta($this->wp_post->ID, self::$prefix."_responder_{$user_id}_location", true);
    }

    /**
     * Retrieves an array containing information about all responders
     * and the alerter involved in this alert.
     *
     * @uses WP_Buoy_Alert::get_responders()
     * @uses get_avatar_url()
     * @uses WP_Buoy_Alert::get_responder_geo()
     * @uses WP_Buoy_User::get_phone_number()
     *
     * @return array
     */
    public function get_incident_state () {
        $responders = $this->get_responders();
        $incident_state = array();
        foreach ($responders as $id) {
            $responder = new WP_Buoy_User($id);
            $incident_state[] = $responder->get_incident_response_info($this->wp_post->ID);
        }
        $alerter = new WP_Buoy_User($this->wp_post->post_author);
        $incident_state[] = $alerter->get_incident_response_info($this->wp_post->ID);
        return $incident_state;
    }

    /**
     * Makes a random lookup hash for this alert.
     *
     * @uses WP_Buoy_Alert::get_random_seed()
     * @uses hash()
     *
     * @return string
     */
    private function make_hash () {
        return hash('sha256', $this->get_random_seed());
    }

    /**
     * Makes a randomized chat room name for this alert.
     *
     * @uses WP_Buoy_Alert::get_random_seed()
     * @uses hash()
     *
     * @return string
     */
    private function make_chat_room_name () {
        // need to limit the length of this string due to Tlk.io integration for now
        return self::$prefix.'_'.substr(hash('sha1', $this->get_random_seed()), 0, 20);
    }

    /**
     * This function tries to use the best available source of random
     * numbers to create the seed data for a hash that it can find.
     *
     * @uses random_bytes()
     * @uses openssl_random_pseudo_bytes()
     * @uses mt_rand()
     * @uses microtime()
     * @uses getmypid()
     * @uses uniqid()
     *
     * @return string
     */
    private function get_random_seed () {
        $preferred_functions = array(
            // sorted in order of preference, strongest functions 1st
            'random_bytes', 'openssl_random_pseudo_bytes'
        );
        $length = MB_IN_BYTES * mt_rand(1, 4);
        foreach ($preferred_functions as $func) {
            if (function_exists($func)) {
                $seed = $func($length);
                break;
            } else {
                static::debug_log(sprintf(
                    __('WARNING! Your system does not have %s available to generate alert hashes.', 'buoy'),
                    $func.'()'
                ));
            }
        }
        return (isset($seed)) ? $seed : mt_rand().microtime().getmypid().uniqid('', true);
    }

    /**
     * Registers the Buoy Alert post type and hooks.
     *
     * @return void
     */
    public static function register () {
        register_post_type(self::$prefix.'_alert', array(
            'label' => __('Incidents', 'buoy'),
            'description' => __('A call for help.', 'buoy'),
            'supports' => array('title'),
            'has_archive' => false,
            'rewrite' => false,
            'can_export' => false,
            'delete_with_user' => true,
            'show_in_rest' => true
        ));

        add_action('send_headers', array(__CLASS__, 'redirectShortUrl'));

        add_action('wp_before_admin_bar_render', array(__CLASS__, 'addAlertsMenu'));
        add_action('admin_menu', array(__CLASS__, 'registerAdminMenu'));

        add_action('wp_ajax_'.self::$prefix.'_new_alert', array(__CLASS__, 'handleNewAlert'));
        add_action('wp_ajax_'.self::$prefix.'_upload_media', array(__CLASS__, 'handleMediaUpload'));
        add_action('wp_ajax_'.self::$prefix.'_unschedule_alert', array(__CLASS__, 'handleUnscheduleAlert'));
        add_action('wp_ajax_'.self::$prefix.'_update_location', array(__CLASS__, 'handleLocationUpdate'));
        add_action('wp_ajax_'.self::$prefix.'_dismiss_installer', array(__CLASS__, 'handleDismissInstaller'));
        add_action('wp_ajax_'.self::$prefix.'_chat_event_stream', array(__CLASS__, 'chatEventStream'));
        add_action('wp_ajax_'.self::$prefix.'_post_comments_chat', array(__CLASS__, 'renderPostCommentsChatRoom'));

        add_action('publish_'.self::$prefix.'_alert', array('WP_Buoy_Notification', 'publishAlert'), 10, 2);

        /**
         * Fired when the Buoy chat room is printed.
         *
         * Remove the default function and hook your own callback to
         * this hook create custom chat room output.
         *
         * @param WP_Buoy_Alert $alert
         * @param WP_User $curr_user
         */
        add_action(self::$prefix.'_chat_room', array(__CLASS__, 'renderChatRoom'), 10, 2);

        add_filter('comments_open', array(__CLASS__, 'handleNewPostCommentChat'), 1, 2);    // run early
        add_filter('comments_clauses', array(__CLASS__, 'filterCommentsClauses'), 900, 2); // run late
    }

    /**
     * Omit comments used in Buoy Alert chats from comment queries.
     *
     * Comments on Buoy Alerts (posts with the type `buoy_alert`) are
     * actually "chat room" messages. These should not show elsewhere
     * in the WordPress blog, such as in the "Recent comments" widget
     * or other areas where a "show all comments" kind of request is
     * asked for.
     *
     * See also {@link https://github.com/meitar/better-angels/issues/157 issue #157}.
     *
     * @link https://developer.wordpress.org/reference/hooks/comments_clauses/
     *
     * @global wpdb $wpdb
     *
     * @param string[] $clauses
     * @param WP_Comment_Query $wp_comment_query
     *
     * @uses get_current_user_id()
     *
     * @return string[]
     */
    public static function filterCommentsClauses ($clauses, $wp_comment_query) {
        global $wpdb;
        // When querying for "comments on posts" there will be a JOIN clause,
        // but when querying for comments only, there won't be. We only want
        // to modify the WHERE clause when asking for comments associated with
        // some post or another, to remove the Buoy Alert post type from that
        // query. In cases where the comments are queried directly, we don't
        // need to make any change because such cases are, for instance, the
        // comments admin screen or the Buoy Alert chat room itself.
        $w = $wpdb->prepare(" AND {$wpdb->posts}.post_type != %s", self::$prefix.'_alert');
        if ($clauses['join']) {
            $clauses['where'] .= $w;
        } else if (0 === get_current_user_id()) {
            // If there isn't a JOIN clause then the comment query is
            // only quering the comments table itself but the request
            // might still be from an anonymous visitor. If it is, we
            // still need to exlude any comments associated with each
            // Buoy Alet, so we add the JOIN ourselves
            $clauses['join'] = "JOIN {$wpdb->posts} ON {$wpdb->posts}.ID = {$wpdb->comments}.comment_post_ID";
            // and make the same modification to the WHERE clause.
            $clauses['where'] .= $w;
        } else {
            // Finally, if there is no JOIN clause but the request is
            // coming from a logged-in user we need to check that the
            // user has permission to view the given comments. That
            // will be the case if the given user is a "responder" of
            // the Buoy Alert to which the comments are attached.
            $post_ids = array();
            if ($wp_comment_query->query_vars['post_id']) {
                $post_ids[] = $wp_comment_query->query_vars['post_id'];
            }
            if ($wp_comment_query->query_vars['post__in']) {
                $post_ids = array_merge($post_ids, $wp_comment_query->query_vars['post__in']);
            }
            if ($post_ids) {
                foreach ($post_ids as $id) {
                    $post = get_post($id);
                    if (self::$prefix . '_alert' === $post->post_type) {
                        $alert = new self($id);
                        // If they're not a responder for the given post ID,
                        // and are also not the alerter themselves (author),
                        if (!$alert->is_responder(get_current_user_id()) && get_current_user_id() != $post->post_author) {
                            // then we remove that post's ID from the SQL query.
                            $clauses['where'] = preg_replace("/$id,?/", '', $clauses['where']);
                        }
                    }
                }
                // If we removed all post IDs, then we need to fix the SQL statement
                // by adding an empty string inside the parenthesis.
                $clauses['where'] = preg_replace('/AND comment_post_ID IN \(  \)/', "AND comment_post_ID IN ('')", $clauses['where']);
            }
        }
        return $clauses;
    }

    /**
     * Redirects users arriving at Buoy via short url.
     *
     * Detects an alert "short URL," which is an HTTP GET request with
     * a special querystring parameter that matches the first 8 chars
     * of an alert's hash value and, if matched, redirects to the full
     * URL of that particular alert's "review" screen, then `exit()`s.
     *
     * This occurrs during {@see https://developer.wordpress.org/reference/hooks/send_headers/ WordPress's `send_headers` hook}.
     * 
     * @global $_GET
     *
     * @uses WP_Buoy_Alert::get_hash()
     * @uses wp_safe_redirect()
     * @uses admin_url()
     *
     * @param WP $wp
     *
     * @return void
     */
    public static function redirectShortUrl ($wp) {
        $get_param = self::$prefix.'_alert';
        if (isset($_GET[$get_param]) && 8 === strlen($_GET[$get_param])) {
            $alert = new self(sanitize_text_field(urldecode($_GET[$get_param])));
            if ($alert->get_hash()) {
                wp_safe_redirect(admin_url(
                    '?page='.self::$prefix.'_review_alert'
                   .'&'.self::$prefix.'_hash='.urlencode($alert->get_hash())
                ));
                exit();
            }
        }
    }

    /**
     * Alters the redirection URL after a "chat" comment is posted.
     *
     * @param string $location
     * @param WP_Comment $comment
     *
     * @return string
     */
    public static function redirectChatComment ($location, $comment) {
        $fragment = parse_url($location, PHP_URL_FRAGMENT);
        $alert = new WP_Buoy_Alert($comment->comment_post_ID);
        $new_location = admin_url('admin-ajax.php').'?action='.self::$prefix.'_post_comments_chat&hash='.$alert->get_hash().'&reset';
        if ($fragment) {
            $new_location .= "#$fragment";
        }
        return $new_location;
    }

    /**
     * Attaches the "Active Alerts" menu to WordPress's admin toolbar.
     *
     * @global $wp_admin_bar
     *
     * @return void
     */
    public static function addAlertsMenu () {
        global $wp_admin_bar;

        $wp_admin_bar->add_node(array(
            'id' => 'new-'.self::$prefix.'-alert',
            'title' => __('Alert', 'buoy'),
            'parent' => 'new-content',
            'href' => admin_url('index.php?page='.self::$prefix.'_activate_alert')
        ));

        $alerts = array(
            'my_alerts' => array(),
            'my_responses' => array(),
            'my_scheduled_alerts' => array(),
            'my_unanswered_alerts' => array(),
        );

        foreach (self::getActiveAlerts() as $post) {
            $alert = new WP_Buoy_Alert($post->ID);
            if (get_current_user_id() == $post->post_author) {
                $alerts['my_alerts'][] = $post;
            } else if (in_array(get_current_user_id(), $alert->get_responders())) {
                $alerts['my_responses'][] = $post;
            } else {
                $members = array();
                foreach ($alert->teams as $team_id) {
                    $team = new WP_Buoy_Team($team_id);
                    $members = array_merge($members, $team->get_confirmed_members());
                }
                if (in_array(get_current_user_id(), $members)) {
                    $alerts['my_unanswered_alerts'][] = $post;
                }
            }
        }

        foreach (self::getScheduledAlerts(get_current_user_id()) as $post) {
            if (get_current_user_id() == $post->post_author) {
                $alerts['my_scheduled_alerts'][] = $post;
            }
        }

        if (!empty($alerts['my_alerts'])
            || !empty($alerts['my_responses'])
            || !empty($alerts['my_scheduled_alerts'])
            || !empty($alerts['my_unanswered_alerts'])) {
            $wp_admin_bar->add_menu(array(
                'id' => self::$prefix.'-alerts-menu',
                'title' => '<span class="ab-icon"></span><span class="ab-label">'.__('Active alerts', 'buoy').'</span></a>',
            ));
        }

        // TODO: Each of these nodes have similar HTML, reuse some code between these?
        // Add group nodes to WP Toolbar
        foreach ($alerts as $group_name => $posts) {
            $wp_admin_bar->add_group(array(
                'id' => self::$prefix.'_'.$group_name,
                'parent' => self::$prefix.'-alerts-menu'
            ));
        }

        $dtfmt = get_option('date_format').' '.get_option('time_format');
        foreach ($alerts['my_alerts'] as $post) {
            $alert = new WP_Buoy_Alert($post->ID);
            $author = get_userdata($post->post_author);
            $url = wp_nonce_url(
                admin_url('?page='.self::$prefix.'_chat&'.self::$prefix.'_hash='.$alert->get_hash()),
                self::$prefix.'_chat', self::$prefix.'_nonce'
            );
            $wp_admin_bar->add_node(array(
                'id' => self::$prefix.'-alert-'.$alert->get_hash(),
                'title' => sprintf(__('My alert on %2$s', 'buoy'), $author->display_name, date($dtfmt, strtotime($post->post_date))),
                'parent' => self::$prefix.'_my_alerts',
                'href' => $url
            ));
        }

        foreach ($alerts['my_responses'] as $post) {
            $alert = new WP_Buoy_Alert($post->ID);
            $author = get_userdata($post->post_author);
            $url = wp_nonce_url(
                admin_url('?page='.self::$prefix.'_chat&'.self::$prefix.'_hash='.$alert->get_hash()),
                self::$prefix.'_chat', self::$prefix.'_nonce'
            );
            $wp_admin_bar->add_node(array(
                'id' => self::$prefix.'-alert-'.$alert->get_hash(),
                'title' => sprintf(__('Alert issued by %1$s on %2$s', 'buoy'), $author->display_name, date($dtfmt, strtotime($post->post_date))),
                'parent' => self::$prefix.'_my_responses',
                'href' => $url
            ));
        }

        foreach ($alerts['my_scheduled_alerts'] as $post) {
            $alert = new WP_Buoy_Alert($post->ID);
            $url = wp_nonce_url(
                admin_url('admin-ajax.php?action='.self::$prefix.'_unschedule_alert&'.self::$prefix .'_hash='.$alert->get_hash().'&r='.esc_url($_SERVER['REQUEST_URI'])),
                self::$prefix.'_unschedule_alert', self::$prefix.'_nonce'
            );
            $wp_admin_bar->add_node(array(
                'id' => self::$prefix.'-alert-'.$alert->get_hash(),
                'title' => sprintf(__('Cancel scheduled alert for %1$s', 'buoy'), date($dtfmt, strtotime($post->post_date))),
                'meta' => array(
                    'title' => __('Cancel this alert', 'buoy')
                ),
                'parent' => self::$prefix.'_my_scheduled_alerts',
                'href' => $url
            ));
        }

        foreach ($alerts['my_unanswered_alerts'] as $post) {
            $alert = new WP_Buoy_Alert($post->ID);
            $author = get_userdata($post->post_author);
            $url = admin_url('?page='.self::$prefix.'_review_alert&'.self::$prefix .'_hash='.$alert->get_hash());
            $wp_admin_bar->add_node(array(
                'id' => self::$prefix.'-alert-'.$alert->get_hash(),
                'title' => sprintf(__('New alert by %1$s on %2$s', 'buoy'), $author->display_name, date($dtfmt, strtotime($post->post_date))),
                'meta' => array(
                    'title' => __('View alert', 'buoy')
                ),
                'parent' => self::$prefix.'_my_unanswered_alerts',
                'href' => $url
            ));
        }
    }

    /**
     * Registers plugin hooks for the WordPress Dashboard admin menu.
     *
     * @link https://codex.wordpress.org/Administration_Menus
     *
     * @uses add_dashboard_page()
     * @uses add_submenu_page()
     * @uses add_action()
     *
     * @return void
     */
    public static function registerAdminMenu () {
        $hooks = array();

        $hooks[] = $hook = add_dashboard_page(
            __('Activate Alert', 'buoy'),
            __('Activate Alert', 'buoy'),
            'read', // give access to all users including Subscribers role
            self::$prefix.'_activate_alert',
            array(__CLASS__, 'renderActivateAlertPage')
        );
        add_action('load-'.$hook, array(__CLASS__, 'removeScreenOptions'));
        add_action('load-'.$hook, array(__CLASS__, 'addInstallerScripts'));

        $hooks[] = add_submenu_page(
            null,
            __('Respond to Alert', 'buoy'),
            __('Respond to Alert', 'buoy'),
            'read',
            self::$prefix.'_review_alert',
            array(__CLASS__, 'renderReviewAlertPage')
        );

        $hooks[] = add_submenu_page(
            null,
            __('Incident Chat', 'buoy'),
            __('Incident Chat', 'buoy'),
            'read',
            self::$prefix.'_chat',
            array(__CLASS__, 'renderIncidentChatPage')
        );

        foreach ($hooks as $hook) {
            add_action('load-'.$hook, array(__CLASS__, 'enqueueFrontEndScripts'));
            add_action('load-'.$hook, array(__CLASS__, 'enqueueFrameworkScripts'));
        }
    }

    /**
     * Prints HTML for the "activate alert" page.
     *
     * @uses get_current_user_id()
     * @uses WP_Buoy_User::has_responder()
     *
     * @return void
     */
    public static function renderActivateAlertPage () {
        $buoy_user = new WP_Buoy_User(get_current_user_id());
        if (!$buoy_user->has_responder()) {
            require_once plugin_dir_path(dirname(__FILE__)).'pages/no-responders-available.php';
        } else {
            require_once plugin_dir_path(dirname(__FILE__)).'pages/activate-alert.php';
        }
    }

    /**
     * Prints HTML for the "review alert" page.
     *
     * @global $_GET
     *
     * @uses current_user_can()
     * @uses get_current_user_id()
     * @uses WP_Buoy_Alert::can_respond()
     *
     * @return void
     */
    public static function renderReviewAlertPage () {
        if (empty($_GET[self::$prefix.'_hash'])) {
            return;
        }
        try {
            $alert = new WP_Buoy_Alert($_GET[self::$prefix.'_hash']);
        } catch (Exception $e) {
            esc_html_e('You do not have sufficient permissions to access this page.', 'buoy');
            return;
        }
        if (!current_user_can('read') || !$alert->can_respond(get_current_user_id())) {
            esc_html_e('You do not have sufficient permissions to access this page.', 'buoy');
            return;
        }
        require_once plugin_dir_path(dirname(__FILE__)).'pages/review-alert.php';
    }

    /**
     * Prints HTML for the "incident chat" page.
     *
     * @global $_GET
     *
     * @uses current_user_can()
     * @uses wp_verify_nonce()
     * @uses get_current_user_id()
     * @uses WP_Buoy_Alert::add_responder()
     * @uses WP_Buoy_Alert::set_responder_geo()
     *
     * @return void
     */
    public static function renderIncidentChatPage () {
        try {
            $alert = new WP_Buoy_Alert(urldecode($_GET[self::$prefix.'_hash']));
        } catch (Exception $e) {
            esc_html_e('You do not have sufficient permissions to access this page.', 'buoy');
            return;
        }

        if (!$alert->wp_post || !current_user_can('read') || !isset($_GET[self::$prefix.'_nonce']) || !wp_verify_nonce($_GET[self::$prefix.'_nonce'], self::$prefix.'_chat')) {
            esc_html_e('You do not have sufficient permissions to access this page.', 'buoy');
            return;
        }

        if (get_current_user_id() != $alert->wp_post->post_author) {
            $alert->add_responder(get_current_user_id());
            // TODO: Clean this up a bit, maybe the JavaScript should send JSON data?
            if (!empty($_POST[self::$prefix.'_location'])) {
                $p = explode(',', $_POST[self::$prefix.'_location']);
                $geo = array(
                    'latitude' => $p[0],
                    'longitude' => $p[1]
                );
                $alert->set_responder_geo(get_current_user_id(), $geo);
            }
        }

        require_once plugin_dir_path(dirname(__FILE__)).'pages/incident-chat.php';
    }

    /**
     * Hookable action to print out the HTML for the given chat room system.
     *
     * This function is called by the custom `buoy_chat_room` action hook.
     * Plugin developers can replace the Buoy chat room by hooking their
     * own code to the action after removing the default action. This allows
     * plugin developers to develop their own plugins that use custom chat
     * room code for their own Buoys.
     *
     * @param WP_Buoy_Alert $alert
     */
    public static function renderChatRoom ($alert, $curr_user) {
        switch ($alert->get_chat_system()) {
            case 'tlk.io':
                include plugin_dir_path(dirname(__FILE__)).'pages/chat-room-tlk-io.php';
                break;
            default:
                include plugin_dir_path(dirname(__FILE__)).'/pages/chat-room-wordpress-comments.php';
                break;
        }
    }

    /**
     * Shows the built-in post comments chat room.
     *
     * @return void
     */
    public static function renderPostCommentsChatRoom () {
        require_once plugin_dir_path(dirname(__FILE__)).'pages/post-comments-chat.php';
        exit();
    }

    /**
     * A super-simple HTML5 Server-Side Events streaming server.
     *
     * @link https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#Sending_events_from_the_server
     */
    public static function chatEventStream () {
        $post_id = absint($_GET['post_id']);
        $offset  = absint($_GET['offset']);
        // How many comments to return in a single batch.
        $limit   = 5; // arbitrary

        header('Content-Type: text/event-stream');
        header('Cache-Control: no-cache, must-revalidate, max-age=0');
        // Tell nginx not to buffer us!
        // See http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_buffering
        header('X-Accel-Buffering: no');

        $start_time = time();
        while (true) {
            $comments = get_comments(array(
                'post_id' => $post_id,
                'number'  => $limit,
                'offset'  => $offset,
                'order'   => 'ASC'
            ));
            wp_cache_flush();

            if ($comments) {
                $offset += count($comments);
                // Translate a WP_Comment into a WP REST API version of the same.
                // TODO: This should be a helper function. :P
                foreach ($comments as $comment) {
                    $comment->id = $comment->comment_ID;
                    $comment->author_name = $comment->comment_author;
                    $comment->date = $comment->comment_date;
                    $comment->author_avatar_urls = array(
                        '48' => get_avatar_url($comment->comment_author_email, '48')
                    );
                    $comment->content = new stdClass();
                    $comment->content->rendered = $comment->comment_content;
                }
                print self::eventStreamMessage(json_encode($comments), 'updated');
            } else {
                print self::eventStreamMessage(); // Heartbeat.
            }

            @ob_end_flush();
            flush();

            // Prevent server exhaustion by killing this thread eventually.
            if ((time() - $start_time) > (1 * MINUTE_IN_SECONDS)) {
                break;
            }
            sleep(1);
        }

        exit(0);
    }

    /**
     * Utility function to create an HTML5 SSE message.
     *
     * Call without arguments to send a heartbeat.
     *
     * @param string $data
     * @param string $type
     *
     * @return string
     */
    public static function eventStreamMessage ($data = '', $type = '') {
        $msg = '';
        if ($type) {
            $msg .= "event: $type\n";
        }
        if ($data) {
            $msg .= "data: $data\n";
        } else {
            $msg .= ":\n"; // Heartbeat.
        }
        return "$msg\n";
    }

    /**
     * Utility function to remove the WordPress "Screen Options" tab.
     *
     * @todo Move to the main plugin class?
     *
     * @link https://developer.wordpress.org/reference/hooks/screen_options_show_screen/
     *
     * @uses add_filter()
     */
    public static function removeScreenOptions () {
        add_filter('screen_options_show_screen', '__return_false');
    }

    /**
     * Enqueues main alert functionality scripts and styles.
     *
     * @uses get_plugin_data()
     * @uses wp_enqueue_style
     * @uses wp_register_script
     * @uses wp_enqueue_script
     * @uses wp_localize_script
     *
     * @return void
     */
    public static function enqueueFrontEndScripts () {
        $plugin_data = get_plugin_data(plugin_dir_path(dirname(__FILE__)).self::$prefix.'.php');
        wp_enqueue_style(
            self::$prefix.'-alert-style',
            plugins_url('../css/alerts.css', __FILE__),
            array('bootstrap-css'),
            $plugin_data['Version']
        );
        wp_enqueue_style(
            self::$prefix.'-css-hacks',
            plugins_url('../css/hacks.css', __FILE__),
            array(self::$prefix.'-alert-style'),
            $plugin_data['Version']
        );

        // Enqueue main "buoy.js" file
        wp_register_script(
            self::$prefix.'-script',
            plugins_url(self::$prefix.'.js', dirname(__FILE__)),
            array(
                'jquery',
                'underscore',
                'backbone',
            ),
            $plugin_data['Version']
        );
        // Localize it.
        wp_localize_script(self::$prefix.'-script', self::$prefix.'_vars', self::localizeUiText());
        wp_localize_script(self::$prefix.'-script', self::$prefix.'_dom_hooks', self::$dom_hooks);

        wp_enqueue_script(self::$prefix.'-script');

        wp_enqueue_script(
            self::$prefix.'-alert',
            plugins_url('alert.js', __FILE__),
            array(self::$prefix.'-script'),
            $plugin_data['Version']
        );

        wp_enqueue_script(
            self::$prefix.'-map',
            plugins_url(self::$prefix.'-map.js', __FILE__),
            array(
                self::$prefix.'-script',
                'leaflet'
            ),
            $plugin_data['Version']
        );

    }

    /**
     * Enqueues the "webapp/native" installer scripts if the user has
     * not previously dismissed this functionality.
     *
     * @uses get_current_user_id()
     * @uses WP_Buoy_User_Settings::get()
     * @uses wp_enqueue_script
     * @uses wp_enqueue_style
     *
     * @return void
     */
    public static function addInstallerScripts () {
        $usropt = new WP_Buoy_User_Settings(get_current_user_id());
        if (!$usropt->get('installer_dismissed')) {
            wp_enqueue_script(
                self::$prefix.'-install-webapp',
                plugins_url('install-webapp.js', __FILE__),
                array('jquery')
            );
            wp_enqueue_style(
                self::$prefix.'-install-webapp',
                plugins_url('install-webapp.css', __FILE__)
            );
        }
    }

    /**
     * Enqueues the Bootstrap CSS and JavaScript framework resources,
     * along with jQuery and Leaflet library plugins used for Alert UI.
     *
     * @todo Should this kind of utility loader be moved into its own class?
     *
     * @return void
     */
    public static function enqueueFrameworkScripts () {
        // Enqueue jQuery plugins.
        wp_enqueue_style(
            'jquery-datetime-picker',
            plugins_url('jquery.datetimepicker.css', __FILE__)
        );
        wp_enqueue_script(
            'jquery-datetime-picker',
            plugins_url('jquery.datetimepicker.full.min.js', __FILE__),
            array('jquery'),
            null,
            true
        );

        self::enqueueBootstrapFramework();

        wp_enqueue_style(
            'leaflet',
            plugins_url('vendor/leaflet/dist/leaflet.css', dirname(__FILE__))
        );
        wp_enqueue_script(
            'leaflet',
            plugins_url('vendor/leaflet/dist/leaflet.js', dirname(__FILE__)),
            array(),
            null,
            true
        );

        // Enqueue a custom pulse loader CSS animation.
        wp_enqueue_style(
            self::$prefix.'-pulse-loader',
            plugins_url('pulse-loader.css', __FILE__)
        );
    }

    /**
     * Enqueues the Bootstrap framework CSS and JavaScript.
     *
     * @link https://getbootstrap.com/
     *
     * @return void
     */
    public static function enqueueBootstrapFramework () {
        // Enqueue BootstrapCSS/JS framework.
        wp_enqueue_style(
            'bootstrap-css',
            'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css'
        );
        wp_enqueue_script(
            'bootstrap-js',
            'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js',
            array(),
            null,
            true
        );

        if (is_ssl() || WP_Buoy_Settings::get_instance()->get('debug')) {
            add_filter('style_loader_tag', array(__CLASS__, 'addIntegrityAttribute'), 9999, 2);
            add_filter('script_loader_tag', array(__CLASS__, 'addIntegrityAttribute'), 9999, 2);
        }
    }

    /**
     * Sets subresource integrity attributes on elements loaded via CDN.
     *
     * @link https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity
     * @link https://developer.wordpress.org/reference/hooks/style_loader_tag/
     * @link https://developer.wordpress.org/reference/hooks/script_loader_tag/
     *
     * @param string $html
     * @param string $handle
     *
     * @return string
     */
    public static function addIntegrityAttribute ($html, $handle) {
        $integrities = array(
            // sha*-$hash => handle
            'sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u' => 'bootstrap-css',
            'sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa' => 'bootstrap-js'
        );
        if ($integrity = array_search($handle, $integrities)) {
            $sri_att = ' crossorigin="anonymous" integrity="'.$integrity.'"';
            $insertion_pos = strpos($html, '>');
            // account for self-closing tags
            if (0 === strpos($html, '<link ')) {
                $insertion_pos--;
                $sri_att .= ' ';
            }
            return substr($html, 0, $insertion_pos).$sri_att.substr($html, $insertion_pos);
        }
        return $html;
    }

    /**
     * Translate user interface strings used in JavaScript.
     *
     * @return string[] An array of translated strings suitable for wp_localize_script().
     */
    public static function localizeUiText () {
        $locale_parts = explode('_', get_locale());
        return array(
            'ietf_language_tag' => array_shift($locale_parts),
            'i18n_install_btn_title' => __('Install Buoy', 'buoy'),
            'i18n_install_btn_content' => __('Install Buoy by tapping this button, then choosing "Add to home screen" from the menu.', 'buoy'),
            'i18n_dismiss' => __('Dismiss', 'buoy'),
            'i18n_map_title' => __('Incident Map', 'buoy'),
            'i18n_crisis_location' => __('Location of emergency alert signal', 'buoy'),
            'i18n_my_location' => __('My location', 'buoy'),
            'i18n_directions' => __('Directions to here', 'buoy'),
            'i18n_call' => __('Call', 'buoy'),
            'i18n_responding_to_alert' => __('Responding to alert', 'buoy'),
            'i18n_schedule_alert' => __('Schedule alert', 'buoy'),
            'i18n_scheduling_alert' => __('Scheduling alert', 'buoy'),
            'incident_nonce' => wp_create_nonce(self::$prefix.'_incident_nonce')
        );
    }

    /**
     * Responds to requests activated from the main emergency alert button.
     *
     * @link https://developer.wordpress.org/reference/hooks/wp_ajax__requestaction/
     *
     * @global $_POST
     *
     * @uses WP_Buoy_Plugin::$prefix
     * @uses check_ajax_referer()
     * @uses get_current_user_id()
     * @uses WP_Buoy_User_Settings::get()
     * @uses sanitize_text_field()
     * @uses stripslashes_deep()
     * @uses WP_Buoy_Alert::set()
     * @uses WP_Buoy_Alert::save()
     * @uses WP_Buoy_Alert::get_hash()
     * @uses wp_send_json_error()
     * @uses wp_send_json_success()
     * @uses wp_safe_redirect()
     *
     * @return void
     */
    public static function handleNewAlert () {
        check_ajax_referer(self::$prefix.'_new_alert', self::$prefix.'_nonce');

        $postarr    = array();
        $meta_input = array();

        // Collect info from the browser via Ajax request
        $alert_position = (empty($_POST['pos'])) ? false : $_POST['pos']; // TODO: array_map and sanitize this?
        if ($alert_position) {
            $meta_input['geo_latitude'] = $alert_position['latitude'];
            $meta_input['geo_longitude'] = $alert_position['longitude'];
        }
        if (isset($_POST[self::$prefix.'_teams']) && is_array($_POST[self::$prefix.'_teams'])) {
            $my_teams = array_map('absint', $_POST[self::$prefix.'_teams']);
            $valid_teams = array();
            foreach ($my_teams as $team_id) {
                $team = new WP_Buoy_Team($team_id);
                if (get_current_user_id() == $team->wp_post->post_author) {
                    $valid_teams[] = $team_id;
                }
            }
            $meta_input[self::$prefix.'_teams'] = $valid_teams;
        }
        // Create and publish the new alert.
        $buoy_user = new WP_Buoy_User(get_current_user_id());
        $postarr['post_title'] = (empty($_POST['msg']))
            ? $buoy_user->get_crisis_message()
            : sanitize_text_field(stripslashes_deep($_POST['msg']));

        if (!empty($meta_input)) {
            $postarr['meta_input'] = $meta_input;
        }

        $err = new WP_Error();
        if (isset($_POST['scheduled-datetime-utc'])) {
            // TODO: Scheduled alerts should be their own function?
            $old_timezone = date_default_timezone_get();
            date_default_timezone_set('UTC');
            $when_utc = strtotime(stripslashes_deep($_POST['scheduled-datetime-utc']));
            if (!$when_utc) {
                $err->add(
                    'scheduled-datetime-tz',
                    __('Buoy could not understand the date and time you entered.', 'buoy')
                );
            } else {
                $dt = new DateTime("@$when_utc");
                // TODO: This fails to offset the UTC time back to server-local time
                //       correctly if the WP site is manually offset by a 30 minute
                //       offset instead of an hourly offset.
                $dt->setTimeZone(new DateTimeZone(wp_get_timezone_string()));
                $postarr['post_date']     = $dt->format('Y-m-d H:i:s');
                $postarr['post_date_gmt'] = gmdate('Y-m-d H:i:s', $when_utc);
                $postarr['post_status']   = 'future';
            }
            date_default_timezone_set($old_timezone);
        }

        $buoy_alert = new self();
        $post_id = $buoy_alert->set($postarr)->save();

        if (is_wp_error($post_id)) {
            wp_send_json_error($post_id);
        } else if (!empty($err->errors)) {
            wp_send_json_error($err);
        } else if (isset($_POST['scheduled-datetime-utc']) && empty($err->errors)) {
            wp_send_json_success(array(
                'id' => $post_id,
                'message' => __('Your timed alert has been scheduled. Schedule another?', 'buoy')
            ));
        } else {
            // Construct the redirect URL to the alerter's chat room
            $next_url = wp_nonce_url(
                admin_url(
                    '?page='.self::$prefix.'_chat'
                   .'&'.self::$prefix.'_hash='.$buoy_alert->get_hash()
                ),
                self::$prefix.'_chat', self::$prefix.'_nonce'
            );

            if (isset($_SERVER['HTTP_ACCEPT'])) {
                $accepts = explode(',', $_SERVER['HTTP_ACCEPT']);
            }
            if ($accepts && 'application/json' === array_shift($accepts)) {
                wp_send_json_success($next_url);
            } else {
                wp_safe_redirect(html_entity_decode($next_url));
                exit();
            }
        }
    }

    /**
     * Adds a media file as an attachment to the incident post.
     *
     * @link https://developer.wordpress.org/reference/hooks/wp_ajax__requestaction/
     *
     * @global $_GET
     * @global $_FILES
     *
     * @return void
     */
    public static function handleMediaUpload () {
        check_ajax_referer(self::$prefix.'_incident_nonce', self::$prefix.'_nonce');

        $alert = new self($_GET[self::$prefix.'_hash']);
        $keys = array_keys($_FILES);
        $k  = array_shift($keys);
        $id = media_handle_upload($k, $alert->wp_post->ID, array('post_status' => 'private'));
        $m = wp_get_attachment_metadata($id);
        if (is_wp_error($id)) {
            wp_send_json_error($id);
        } else {
            $mime_type = null;
            if (isset($m['mime_type'])) {
                $mime_type = $m['mime_type'];
            } else if (isset($m['image_meta'])) {
                $mime_type = 'image/*';
                if (isset($m['sizes'])) {
                    foreach ($m['sizes'] as $size) {
                        if (isset($size['mime-type'])) {
                            $mime_type = $m['sizes']['thumbnail']['mime-type'];
                            break;
                        }
                    }
                }
            } else {
                $mime_type = 'audio/*';
            }
            $media_type = substr($mime_type, 0, strpos($mime_type, '/'));
            $html = self::getIncidentMediaHtml($media_type, $id);
            $resp = array(
                'id' => $id,
                'media_type' => ('application' === $media_type) ? 'audio' : $media_type,
                'html' => $html
            );
            wp_send_json_success($resp);
        }
    }

    /**
     * Cancels a scheduled alert by deleting it from the database.
     *
     * @global $_GET
     *
     * @return void
     */
    public static function handleUnscheduleAlert () {
        if (isset($_GET[self::$prefix.'_nonce']) && wp_verify_nonce($_GET[self::$prefix.'_nonce'], self::$prefix.'_unschedule_alert')) {
            $alert = new WP_Buoy_Alert($_GET[self::$prefix.'_hash']);
            if ($alert && get_current_user_id() == $alert->wp_post->post_author) {
                wp_delete_post($alert->wp_post->ID, true);
                if (isset($_SERVER['HTTP_ACCEPT']) && false === strpos($_SERVER['HTTP_ACCEPT'], 'application/json')) {
                    wp_safe_redirect(urldecode($_GET['r']));
                    exit();
                } else {
                    wp_send_json_success();
                }
            }
        } else {
            wp_send_json_error();
        }
    }

    /**
     * Responds to Ajax POSTs containing new position information of
     * responders/alerter, sends back the location of all of this
     * alert's responders.
     *
     * @global $_POST
     *
     * @todo Should the WP_Buoy_Alert object be responsible for handling
     *       metadata associated with responder location updates? Right
     *       now, this is all just manually updates of postmeta. Not the
     *       best way to this in the long run, methinks.
     *
     * @return void
     */
    public static function handleLocationUpdate () {
        check_ajax_referer(self::$prefix.'_incident_nonce', self::$prefix.'_nonce');

        try {
            if (isset($_POST['incident_hash'])) {
                $alert = new WP_Buoy_Alert($_POST['incident_hash']);
                if (isset($_POST['pos'])) {
                    $alert->set_responder_geo(get_current_user_id(), $_POST['pos']);
                    wp_send_json_success($alert->get_incident_state());
                }
            }
        } catch (Exception $e) {
            // TODO: Handle exception more gracefully?
            wp_send_json_error();
        }

        wp_send_json_error();
    }

    /**
     * Hooks the new comment routine to allow a "comment" on Alerts.
     *
     * This is used to intercept the {@see https://developer.wordpress.org/reference/functions/wp_handle_comment_submission/ `wp_handle_comment_submission()`}
     * function early in its processing and allow only comments with
     * the required Buoy Alert "chat" nonces to go through.
     *
     * @link https://developer.wordpress.org/reference/functions/comments_open/
     * @link https://developer.wordpress.org/reference/hooks/duplicate_comment_id/
     *
     * @uses $_POST
     * @uses get_post()
     * @uses wp_verify_nonce()
     *
     * @param bool $open
     * @param int $post_id
     *
     * @return bool
     */
    public static function handleNewPostCommentChat ($open, $post_id) {
        $post = get_post($post_id);
        if (self::$prefix.'_alert' !== $post->post_type
            || 'post_comments' !== $post->buoy_chat_system
            || !isset($_POST[self::$prefix.'_chat_comment_nonce'])
        ) { return $open; }

        if (1 === wp_verify_nonce($_POST[self::$prefix.'_chat_comment_nonce'], self::$prefix.'_chat_comment')) {
            add_filter('duplicate_comment_id', '__return_false'); // allow dupes
            add_filter('comment_flood_filter', '__return_false'); // allow floods
            add_filter('pre_comment_approved', '__return_true');  // always approve
            add_filter('comment_notification_recipients', function ($emails) {
                return array(); // don't send chat room email notifications to anyone
            });
            add_filter('comment_post_redirect', array(__CLASS__, 'redirectChatComment'), 10, 2);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Saves a flag in the user's options that tells Buoy not to show
     * the "webapp installer" scripts again.
     *
     * @uses check_ajax_referer()
     * @uses get_current_user_id()
     * @uses WP_Buoy_User_Settings::set()
     * @uses WP_Buoy_User_Settings::save()
     * @uses wp_send_json_success()
     *
     * @return void
     */
    public static function handleDismissInstaller () {
        check_ajax_referer(self::$prefix.'_incident_nonce', self::$prefix.'_nonce');

        $usropt = new WP_Buoy_User_Settings(get_current_user_id());
        $usropt->set('installer_dismissed', true)->save();
        wp_send_json_success();
    }

    /**
     * Gets alert posts with an incident hash.
     *
     * @return WP_Post[]
     */
    public static function getActiveAlerts () {
        return get_posts(array(
            'post_type' => self::$prefix.'_alert',
            'meta_key' => self::$prefix.'_hash',
            'posts_per_page' => -1
        ));
    }

    /**
     * Gets scheduled alert posts.
     *
     * @param int $uid The WordPress user ID of an author's scheduled posts to look up.
     *
     * @return WP_Post[]
     */
    public static function getScheduledAlerts ($uid = false) {
        $args = array(
            'post_type' => self::$prefix.'_alert',
            'post_status' => 'future',
            'posts_per_page' => -1
        );
        if (false !== $uid) {
            $args['author'] = $uid;
        }
        return get_posts($args);
    }

    /**
     * Returns an HTML structure containing nested lists and list items
     * referring to any media attached to the given post ID.
     *
     * @param int $post_id The post ID from which to fetch attached media.
     *
     * @uses WP_Buoy_Alert::getIncidentMediaHtml()
     *
     * @return string HTML ready for insertion into an `<ul>` element.
     */
    private static function getIncidentMediaList ($post_id) {
        $html = '';

        $posts = array(
            'video' => get_attached_media('video', $post_id),
            'image' => get_attached_media('image', $post_id),
            'audio' => get_attached_media('audio', $post_id)
        );

        foreach ($posts as $type => $set) {
            $html .= '<li class="'.esc_attr($type).' list-group">';
            $html .= '<div class="list-group-item">';
            $html .= '<h4 class="list-group-item-heading">';
            switch ($type) {
                case 'video':
                    $html .= esc_html('Video attachments', 'buoy');
                    break;
                case 'image':
                    $html .= esc_html('Image attachments', 'buoy');
                    break;
                case 'audio':
                    $html .= esc_html('Audio attachments', 'buoy');
                    break;
            }
            $html .= ' <span class="badge">'.count($set).'</span>';
            $html .= '</h4>';
            $html .= '<ul>';

            foreach ($set as $post) {
                $html .= '<li id="incident-media-'. $post->ID .'" class="list-group-item">';
                $html .= '<h5 class="list-group-item-header">'.esc_html($post->post_title).'</h5>';
                $html .= self::getIncidentMediaHtml($type, $post->ID);
                $html .= '<p class="list-group-item-text">';
                $html .= sprintf(
                    esc_html_x('uploaded %1$s ago', 'Example: uploaded 5 mins ago', 'buoy'),
                    human_time_diff(strtotime($post->post_date_gmt))
                );
                $u = get_userdata($post->post_author);
                $html .= ' '.sprintf(
                    esc_html_x('by %1$s', 'a byline, like "written by Bob"', 'buoy'),
                    $u->display_name
                );
                $html .= '</p>';
                $html .= '</li>';
            }

            $html .= '</ul>';
            $html .= '</div>';
            $html .= '</li>';
        }

        return $html;
    }

    /**
     * Gets the correct HTML embeds/elements for a given media type.
     *
     * @param string $type One of 'video', 'audio', or 'image'
     * @param int $post_id The WP post ID of the attachment media.
     *
     * @return string
     */
    private static function getIncidentMediaHtml ($type, $post_id) {
        $html = '';
        switch ($type) {
            case 'video':
                $html .= wp_video_shortcode(array(
                    'src' => wp_get_attachment_url($post_id)
                ));;
                break;
            case 'image':
                $html .= '<a href="'.wp_get_attachment_url($post_id).'" target="_blank">';
                $html .= wp_get_attachment_image($post_id);
                $html .= '</a>';
                break;
            case 'audio':
            default:
                $html .= wp_audio_shortcode(array(
                    'src' => wp_get_attachment_url($post_id)
                ));
                break;
        }
        return $html;
    }

}

/**
 * Helpers.
 */
if (!function_exists('wp_get_timezone_string')) {
    /**
    * Get the timezone string for a site.
    *
    * @link https://secure.php.net/manual/en/function.timezone-name-from-abbr.php#89155
    *
    * @link https://github.com/woothemes/woocommerce/blob/5893875b0c03dda7b2d448d1a904ccfad3cdae3f/includes/wc-formatting-functions.php#L441-L485
    *
    * @link http://core.trac.wordpress.org/ticket/24730
    *
    * @return string valid PHP timezone string
    */
    function wp_get_timezone_string() {
        // if site timezone string exists, return it
        if ( $timezone = get_option( 'timezone_string' ) ) {
            return $timezone;
        }
        // get UTC offset, if it isn't set then return UTC
        if ( 0 === ( $utc_offset = get_option( 'gmt_offset', 0 ) ) ) {
            return 'UTC';
        }
        // adjust UTC offset from hours to seconds
        $utc_offset *= 3600;
        // attempt to guess the timezone string from the UTC offset
        $timezone = timezone_name_from_abbr( '', $utc_offset, 0 );
        // last try, guess timezone string manually
        if ( false === $timezone ) {
            $is_dst = date( 'I' );
            foreach ( timezone_abbreviations_list() as $abbr ) {
                foreach ( $abbr as $city ) {
                    if ( $city['dst'] == $is_dst && $city['offset'] == $utc_offset ) {
                        return $city['timezone_id'];
                    }
                }
            }
            // fallback to UTC
            return 'UTC';
        }
        return $timezone;
    }
}
