<?php // phpcs:ignore
/**
 * JWT Authentication implementation.
 *
 * @package WordPress_MCP
 * @subpackage Auth
 */

declare(strict_types=1);
namespace AtlasAiDev\Awfah\Auth;

use Firebase\JWT\JWT;
use Firebase\JWT\Key;
use WP_Error;
use WP_REST_Request;
use WP_REST_Response;
use Exception;

/**
 * Class JwtAuth
 *
 * Handles JWT authentication for WordPress REST API.
 */
class JwtAuth {
	/**
	 * Option name for storing JWT secret key.
	 *
	 * @var string
	 */
	private const JWT_SECRET_KEY_OPTION = 'awfah_jwt_secret_key';

	/**
	 * Default access token expiration time in seconds.
	 *
	 * @var int
	 */
	private const JWT_ACCESS_EXP_DEFAULT = 3600; // 1 hour.

	/**
	 * Minimum access token expiration time in seconds.
	 *
	 * @var int
	 */
	private const JWT_ACCESS_EXP_MIN = 3600; // 1 hour.

	/**
	 * Default maximum access token expiration time in seconds.
	 *
	 * @var int
	 */
	private const JWT_ACCESS_EXP_MAX_DEFAULT = 2592000; // 30 days.

	/**
	 * Option name for storing active tokens.
	 *
	 * @var string
	 */
	private const TOKEN_REGISTRY_OPTION = 'jwt_token_registry';

	/**
	 * MCP endpoint path pattern for authentication.
	 *
	 * @var string
	 */
	private const MCP_ENDPOINT_PATTERN = '/mcp';

	/**
	 * Basic authentication pattern.
	 *
	 * @var string
	 */
	private const BASIC_AUTH_PATTERN = '/^Basic\s/';

	/**
	 * Bearer token pattern.
	 *
	 * @var string
	 */
	private const BEARER_TOKEN_PATTERN = '/Bearer\s(\S+)/';

	/**
	 * Get JWT secret key from options or generate a new one if not exists.
	 *
	 * @return string
	 */
	private function get_jwt_secret_key(): string {
		$key = get_option( self::JWT_SECRET_KEY_OPTION );

		if ( empty( $key ) ) {
			// Generate a new random key if none exists.
			$key = wp_generate_password( 64, true, true );
			update_option( self::JWT_SECRET_KEY_OPTION, $key );
		}

		return $key;
	}

	/**
	 * Get the maximum allowed expiration time for JWT tokens.
	 *
	 * @return int Maximum expiration time in seconds.
	 */
	private function get_max_expiration_time(): int {
		/**
		 * Filter the maximum JWT token expiration time.
		 *
		 * @since 1.0.0
		 *
		 * @param int $max_expiration Maximum expiration time in seconds. Default 30 days.
		 */
		return (int) apply_filters( 'awfah_jwt_max_expiration_time', self::JWT_ACCESS_EXP_MAX_DEFAULT );
	}

	/**
	 * Initialize the JWT authentication.
	 */
	public function __construct() {
		add_action( 'rest_api_init', array( $this, 'register_routes' ) );
		add_filter( 'rest_authentication_errors', array( $this, 'authenticate_request' ) );
		// Also hook into MCP-specific authentication filter.
		add_filter( 'awfah_authenticate_request', array( $this, 'authenticate_mcp_request' ), 5, 2 );
	}

	/**
	 * Register REST API routes for JWT authentication.
	 */
	public function register_routes(): void {
		$max_expiration = $this->get_max_expiration_time();
		register_rest_route(
			'jwt-auth/v1',
			'/token',
			array(
				'methods'             => 'POST',
				'callback'            => array( $this, 'generate_jwt_token' ),
				'permission_callback' => '__return_true',
				'args'                => array(
					'username'   => array(
						'type'        => 'string',
						'description' => 'Username for authentication',
						'required'    => false,
					),
					'password'   => array(
						'type'        => 'string',
						'description' => 'Password for authentication',
						'required'    => false,
					),
					'expires_in' => array(
						'type'        => 'integer',
						'description' => sprintf( 'Token expiration time in seconds (%d-%d)', self::JWT_ACCESS_EXP_MIN, $max_expiration ),
						'required'    => false,
						'minimum'     => self::JWT_ACCESS_EXP_MIN,
						'maximum'     => $max_expiration,
						'default'     => self::JWT_ACCESS_EXP_DEFAULT,
					),
				),
			)
		);

		register_rest_route(
			'jwt-auth/v1',
			'/revoke',
			array(
				'methods'             => 'POST',
				'callback'            => array( $this, 'revoke_token' ),
				'permission_callback' => array( $this, 'check_revoke_permission' ),
			)
		);

		register_rest_route(
			'jwt-auth/v1',
			'/tokens',
			array(
				'methods'             => 'GET',
				'callback'            => array( $this, 'list_tokens' ),
				'permission_callback' => array( $this, 'check_revoke_permission' ),
			)
		);
	}

	/**
	 * Check if the current user has permission to manage tokens.
	 *
	 * @return bool
	 */
	public function check_revoke_permission(): bool {
		return current_user_can( 'manage_options' );
	}

	/**
	 * Generate JWT token for authenticated user.
	 *
	 * @param WP_REST_Request $request The request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function generate_jwt_token( WP_REST_Request $request ) {
		$params         = $request->get_json_params();
		$expires_in     = isset( $params['expires_in'] ) ? intval( $params['expires_in'] ) : self::JWT_ACCESS_EXP_DEFAULT;
		$max_expiration = $this->get_max_expiration_time();

		// Validate expiration time.
		if ( $expires_in < self::JWT_ACCESS_EXP_MIN || $expires_in > $max_expiration ) {
			$max_days = floor( $max_expiration / 86400 );
			return new WP_Error(
				'invalid_expiration',
				sprintf(
					'Token expiration must be between %d seconds (1 hour) and %d seconds (%d days)',
					self::JWT_ACCESS_EXP_MIN,
					$max_expiration,
					$max_days
				),
				array( 'status' => 400 )
			);
		}

		// If user is already authenticated, use their ID.
		if ( is_user_logged_in() ) {
			return rest_ensure_response( $this->generate_token( get_current_user_id(), $expires_in ) );
		}

		// Otherwise, try to authenticate with provided credentials.
		$username = isset( $params['username'] ) ? sanitize_text_field( $params['username'] ) : '';
		$password = isset( $params['password'] ) ? $params['password'] : '';

		$user = wp_authenticate( $username, $password );
		if ( is_wp_error( $user ) ) {
			return new WP_Error(
				'invalid_credentials',
				'Invalid username or password',
				array( 'status' => 403 )
			);
		}

		return rest_ensure_response( $this->generate_token( $user->ID, $expires_in ) );
	}

	/**
	 * Generate access token.
	 *
	 * @param int $user_id The user ID.
	 * @param int $expires_in Token expiration time in seconds.
	 * @return array
	 */
	private function generate_token( int $user_id, int $expires_in = self::JWT_ACCESS_EXP_DEFAULT ): array {
		$issued_at  = time();
		$expires_at = $issued_at + $expires_in;
		$jti        = wp_generate_password( 32, false );

		$payload = array(
			'iss'     => get_bloginfo( 'url' ),
			'iat'     => $issued_at,
			'exp'     => $expires_at,
			'user_id' => $user_id,
			'jti'     => $jti,
		);

		$token = JWT::encode( $payload, $this->get_jwt_secret_key(), 'HS256' );

		// Register the token.
		$this->register_token( $jti, $user_id, $issued_at, $expires_at );

		return array(
			'token'      => $token,
			'user_id'    => $user_id,
			'expires_in' => $expires_in,
			'expires_at' => $expires_at,
		);
	}

	/**
	 * Register a new token in the registry.
	 *
	 * @param string $jti Token ID.
	 * @param int    $user_id User ID.
	 * @param int    $issued_at Token issued timestamp.
	 * @param int    $expires_at Token expiration timestamp.
	 */
	private function register_token( string $jti, int $user_id, int $issued_at, int $expires_at ): void {
		$registry = get_option( self::TOKEN_REGISTRY_OPTION, array() );

		$registry[ $jti ] = array(
			'user_id'    => $user_id,
			'issued_at'  => $issued_at,
			'expires_at' => $expires_at,
			'revoked'    => false,
		);

		update_option( self::TOKEN_REGISTRY_OPTION, $registry );
	}

	/**
	 * Revoke a JWT token.
	 *
	 * @param WP_REST_Request $request The request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function revoke_token( WP_REST_Request $request ) {
		$params = $request->get_json_params();
		$jti    = isset( $params['jti'] ) ? $params['jti'] : '';

		if ( empty( $jti ) ) {
			return new WP_Error(
				'missing_jti',
				'Token ID is required.',
				array( 'status' => 400 )
			);
		}

		$registry = get_option( self::TOKEN_REGISTRY_OPTION, array() );

		if ( ! isset( $registry[ $jti ] ) ) {
			return new WP_Error(
				'token_not_found',
				'Token not found in registry.',
				array( 'status' => 404 )
			);
		}

		$registry[ $jti ]['revoked'] = true;
		update_option( self::TOKEN_REGISTRY_OPTION, $registry );

		return rest_ensure_response(
			array(
				'message' => 'Token revoked successfully.',
			)
		);
	}

	/**
	 * List all active tokens.
	 *
	 * @return WP_REST_Response|WP_Error
	 */
	public function list_tokens() {
		$registry     = get_option( self::TOKEN_REGISTRY_OPTION, array() );
		$tokens       = array();
		$current_time = time();
		$has_changes  = false;

		foreach ( $registry as $jti => $token_data ) {
			// Skip and remove expired tokens.
			if ( $current_time > $token_data['expires_at'] ) {
				unset( $registry[ $jti ] );
				$has_changes = true;
				continue;
			}

			$user = get_user_by( 'id', $token_data['user_id'] );
			if ( ! $user ) {
				unset( $registry[ $jti ] );
				$has_changes = true;
				continue;
			}

			$tokens[] = array(
				'jti'        => $jti,
				'user'       => array(
					'id'           => $user->ID,
					'username'     => $user->user_login,
					'display_name' => $user->display_name,
				),
				'issued_at'  => $token_data['issued_at'],
				'expires_at' => $token_data['expires_at'],
				'revoked'    => $token_data['revoked'],
				'is_expired' => false,
			);
		}

		// Update the registry if we removed any tokens.
		if ( $has_changes ) {
			update_option( self::TOKEN_REGISTRY_OPTION, $registry );
		}

		$response_data = array(
			'tokens'         => $tokens,
			'max_expiration' => $this->get_max_expiration_time(),
			'max_days'       => floor( $this->get_max_expiration_time() / 86400 ),
		);

		return rest_ensure_response( $response_data );
	}

	/**
	 * Check if a token is valid.
	 *
	 * @param string $jti The token ID.
	 * @return bool
	 */
	private function is_token_valid( string $jti ): bool {
		$registry = get_option( self::TOKEN_REGISTRY_OPTION, array() );

		if ( ! isset( $registry[ $jti ] ) ) {
			return false;
		}

		$token_data = $registry[ $jti ];

		// Check if token is revoked or expired.
		if ( $token_data['revoked'] || time() > $token_data['expires_at'] ) {
			return false;
		}

		return true;
	}

	/**
	 * Check if the current request is for an MCP endpoint.
	 *
	 * @return bool
	 */
	private function is_mcp_endpoint(): bool {
		$request_uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
		return str_contains( $request_uri, self::MCP_ENDPOINT_PATTERN );
	}

    /**
     * Get Authorization header from request.
     *
     * @return string
     */
    private function get_authorization_header(): string {
        if ( isset( $_SERVER['HTTP_AUTHORIZATION'] ) ) {
            return sanitize_text_field( wp_unslash( $_SERVER['HTTP_AUTHORIZATION'] ) );
        }

        if ( isset( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) ) {
            return sanitize_text_field( wp_unslash( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) );
        }

        $headers = [];
        if ( function_exists( 'getallheaders' ) ) {
            $headers = getallheaders();
        } elseif ( function_exists( 'apache_request_headers' ) ) {
            $headers = apache_request_headers();
        }

        if ( ! empty( $headers ) ) {
            foreach ( $headers as $name => $value ) {
                if ( 0 === strcasecmp( (string) $name, 'Authorization' ) ) {
                    return sanitize_text_field( wp_unslash( (string) $value ) );
                }
            }
        }

        return '';
    }

	/**
	 * Check if the authorization header contains Basic authentication.
	 *
	 * @param string $auth Authorization header value.
	 * @return bool
	 */
	private function is_basic_auth( string $auth ): bool {
		return ! empty( $auth ) && preg_match( self::BASIC_AUTH_PATTERN, $auth );
	}

	/**
	 * Extract Bearer token from authorization header.
	 *
	 * @param string $auth Authorization header value.
	 * @return string|null Token if found, null otherwise.
	 */
	private function extract_bearer_token( string $auth ): ?string {
		if ( preg_match( self::BEARER_TOKEN_PATTERN, $auth, $matches ) ) {
			return $matches[1];
		}
		return null;
	}

	/**
	 * Check if cookie-based authentication is valid for MCP endpoints.
	 *
	 * @return bool
	 */
	private function is_valid_cookie_auth(): bool {
		// Only allow cookie auth for logged-in users with manage_options capability.
		// This provides a secure fallback for admin users.
		return is_user_logged_in() && current_user_can( 'manage_options' );
	}

	/**
	 * Log authentication events for security monitoring.
	 *
	 * @param string $event Event type.
	 * @param string $details Event details.
	 */
	private function log_auth_event( string $event, string $details ): void {
		// Only log if WP_DEBUG is enabled to avoid filling logs in production.
		if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
			// Use error_log for better performance than custom logging.
			$log_message = sprintf(
				'[AWFAH JWT Auth] %s: %s (IP: %s, URI: %s)',
				$event,
				$details,
				isset( $_SERVER['REMOTE_ADDR'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REMOTE_ADDR'] ) ) : 'unknown',
				isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : 'unknown'
			);
			error_log( $log_message ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
		}
	}

	/**
	 * Authenticate REST API request using JWT token.
	 *
	 * @param mixed $result The authentication result.
	 * @return mixed
	 * @throws Exception When token validation fails.
	 */
	public function authenticate_request( $result ) {
		// If already authenticated, return early.
		if ( ! empty( $result ) ) {
			return $result;
		}

		// Only apply JWT authentication to MCP endpoints.
		if ( ! $this->is_mcp_endpoint() ) {
			return $result;
		}

		$auth = $this->get_authorization_header();

		// Handle Basic authentication - let it pass through to WordPress core handlers.
		if ( $this->is_basic_auth( $auth ) ) {
			$this->log_auth_event( 'BASIC_AUTH_DETECTED', 'Deferring to Basic auth handler' );
			return $result;
		}

		// Handle missing Authorization header.
		if ( empty( $auth ) ) {
			return $this->handle_missing_authorization();
		}

		// Handle Bearer token authentication.
		return $this->handle_bearer_token( $auth );
	}

	/**
	 * Handle authentication when no Authorization header is present.
	 *
	 * @return mixed Authentication result.
	 */
	private function handle_missing_authorization() {
		// Fallback to cookie authentication for admin users.
		if ( $this->is_valid_cookie_auth() ) {
			$this->log_auth_event( 'COOKIE_AUTH_SUCCESS', 'Admin user authenticated via cookies' );
			return true;
		}

		$this->log_auth_event( 'AUTH_REQUIRED', 'No valid authentication method found' );
		return new WP_Error(
			'unauthorized',
			'Authentication required. Please provide a Bearer token or log in as an administrator.',
			array( 'status' => 401 )
		);
	}

	/**
	 * Handle Bearer token authentication.
	 *
	 * @param string $auth Authorization header value.
	 * @return mixed Authentication result.
	 */
	private function handle_bearer_token( string $auth ) {
		$token = $this->extract_bearer_token( $auth );

		if ( null === $token ) {
			// Not a Bearer token — pass through so other authenticators can handle it.
			$this->log_auth_event( 'AUTH_PASSTHROUGH', 'Authorization header present but not Bearer format, passing through' );
			return null;
		}

		return $this->validate_jwt_token( $token );
	}

	/**
	 * Validate JWT token and authenticate user.
	 *
	 * @param string $token JWT token.
	 * @return mixed Authentication result.
	 */
	private function validate_jwt_token( string $token ) {
		// Skip OAuth tokens (they typically start with specific prefixes).
		if ( str_starts_with( $token, 'access_' ) || str_starts_with( $token, 'oauth_' ) ) {
			// Not a JWT token, let OAuth handle it.
			return null;
		}

		// Check if it looks like a JWT token (has dots for header.payload.signature).
		if ( ! str_contains( $token, '.' ) ) {
			// Not a JWT format — pass through so other authenticators can handle it.
			$this->log_auth_event( 'JWT_FORMAT_INVALID', 'Token does not match JWT format, passing through' );
			return null;
		}

		try {
			$decoded = JWT::decode( $token, new Key( $this->get_jwt_secret_key(), 'HS256' ) );

			// Validate token ID.
			if ( ! isset( $decoded->jti ) || ! $this->is_token_valid( $decoded->jti ) ) {
				$this->log_auth_event( 'TOKEN_INVALID', 'Token is invalid, expired, or revoked' );
				return new WP_Error(
					'token_invalid',
					'Token is invalid, expired, or has been revoked.',
					array( 'status' => 401 )
				);
			}

			// Validate user.
			if ( ! isset( $decoded->user_id ) ) {
				$this->log_auth_event( 'TOKEN_MALFORMED', 'Token missing user_id claim' );
				return new WP_Error(
					'invalid_token',
					'Token is malformed: missing user_id.',
					array( 'status' => 403 )
				);
			}

			$user = get_user_by( 'id', $decoded->user_id );
			if ( ! $user ) {
				$this->log_auth_event( 'USER_NOT_FOUND', "User ID {$decoded->user_id} not found" );
				return new WP_Error(
					'invalid_token',
					'User associated with token no longer exists.',
					array( 'status' => 403 )
				);
			}

			// Set current user.
			wp_set_current_user( $user->ID );
			$this->log_auth_event( 'JWT_AUTH_SUCCESS', "User {$user->user_login} authenticated via JWT" );

			return true;
		} catch ( Exception $e ) {
			// Token looks like JWT but failed to decode (wrong signature, different issuer, etc.).
			// Pass through so other authenticators (Basic Auth, cookie, etc.) can handle the request.
			$this->log_auth_event( 'JWT_PASSTHROUGH', 'Bearer token is not a valid AWFAH JWT, passing through' );
			return null;
		}
	}

	/**
	 * Authenticate MCP-specific requests.
	 *
	 * @param mixed                $result Current authentication result.
	 * @param WP_REST_Request|null $request The request object.
	 * @return mixed Authentication result.
	 */
	public function authenticate_mcp_request( $result, ?WP_REST_Request $request ) {
		// If already authenticated, return early.
		if ( ! empty( $result ) ) {
			return $result;
		}

		// If no request object, we can't authenticate via JWT.
		if ( null === $request ) {
			return $result;
		}

		$auth = $request->get_header( 'authorization' );
		if ( empty( $auth ) ) {
			return $result;
		}

		// Extract Bearer token.
		if ( ! preg_match( '/Bearer\s+(.+)/i', $auth, $matches ) ) {
			return $result;
		}

		$token = $matches[1];

		// Skip OAuth tokens (they typically start with specific prefixes).
		if ( str_starts_with( $token, 'access_' ) || str_starts_with( $token, 'oauth_' ) ) {
			// Not a JWT token, let OAuth handle it.
			return $result;
		}

		// Check if it looks like a JWT token (has dots for header.payload.signature).
		if ( ! str_contains( $token, '.' ) ) {
			// Not a JWT format, but we're in MCP context so we should try to validate.
			return $result;
		}

		// Try to validate as JWT.
		try {
			$decoded = JWT::decode( $token, new Key( $this->get_jwt_secret_key(), 'HS256' ) );

			// Validate token ID.
			if ( ! isset( $decoded->jti ) || ! $this->is_token_valid( $decoded->jti ) ) {
				return $result;
			}

			// Validate user.
			if ( ! isset( $decoded->user_id ) ) {
				return $result;
			}

			$user = get_user_by( 'id', $decoded->user_id );
			if ( ! $user ) {
				return $result;
			}

			// Set current user.
			wp_set_current_user( $user->ID );
			return true;
		} catch ( Exception $e ) {
			// Not a valid JWT, let other authenticators try.
			return $result;
		}
	}
}
