Hooks.php

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<?php
class MWHookException extends MWException {}

class Hooks {

        protected static $handlers = array();

        public static function register( $name, $callback ) {
                if( !isset( self::$handlers[$name] ) ) {
                        self::$handlers[$name] = array();
                }

                self::$handlers[$name][] = $callback;
        }

        public static function isRegistered( $name ) {
                if( !isset( self::$handlers[$name] ) ) {
                        self::$handlers[$name] = array();
                }

                return ( count( self::$handlers[$name] ) != 0 );
        }

        public static function getHandlers( $name ) {
                if( !isset( self::$handlers[$name] ) ) {
                        return array();
                }

                return self::$handlers[$name];
        }

        public static function run( $event, $args = array() ) {
                global $wgHooks;

                // Return quickly in the most common case
                if ( !isset( self::$handlers[$event] ) && !isset( $wgHooks[$event] ) ) {
                        return true;
                }

                if ( !is_array( self::$handlers ) ) {
                        throw new MWException( "Local hooks array is not an array!\n" );
                }

                if ( !is_array( $wgHooks ) ) {
                        throw new MWException( "Global hooks array is not an array!\n" );
                }

                $new_handlers = (array) self::$handlers;
                $old_handlers = (array) $wgHooks;

                $hook_array = array_merge( $new_handlers, $old_handlers );

                if ( !is_array( $hook_array[$event] ) ) {
                        throw new MWException( "Hooks array for event '$event' is not an array!\n" );
                }

                foreach ( $hook_array[$event] as $index => $hook ) {
                        $object = null;
                        $method = null;
                        $func = null;
                        $data = null;
                        $have_data = false;
                        $closure = false;
                        $badhookmsg = false;

                        if ( is_array( $hook ) ) {
                                if ( count( $hook ) < 1 ) {
                                        throw new MWException( 'Empty array in hooks for ' . $event . "\n" );
                                } elseif ( is_object( $hook[0] ) ) {
                                        $object = $hook_array[$event][$index][0];
                                        if ( $object instanceof Closure ) {
                                                $closure = true;
                                                if ( count( $hook ) > 1 ) {
                                                        $data = $hook[1];
                                                        $have_data = true;
                                                }
                                        } else {
                                                if ( count( $hook ) < 2 ) {
                                                        $method = 'on' . $event;
                                                } else {
                                                        $method = $hook[1];
                                                        if ( count( $hook ) > 2 ) {
                                                                $data = $hook[2];
                                                                $have_data = true;
                                                        }
                                                }
                                        }
                                } elseif ( is_string( $hook[0] ) ) {
                                        $func = $hook[0];
                                        if ( count( $hook ) > 1) {
                                                $data = $hook[1];
                                                $have_data = true;
                                        }
                                } else {
                                        throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
                                }
                        } elseif ( is_string( $hook ) ) { # functions look like strings, too
                                $func = $hook;
                        } elseif ( is_object( $hook ) ) {
                                $object = $hook_array[$event][$index];
                                if ( $object instanceof Closure ) {
                                        $closure = true;
                                } else {
                                        $method = "on" . $event;
                                }
                        } else {
                                throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
                        }

                        /* We put the first data element on, if needed. */
                        if ( $have_data ) {
                                $hook_args = array_merge( array( $data ), $args );
                        } else {
                                $hook_args = $args;
                        }

                        if ( $closure ) {
                                $callback = $object;
                                $func = "hook-$event-closure";
                        } elseif ( isset( $object ) ) {
                                $func = get_class( $object ) . '::' . $method;
                                $callback = array( $object, $method );
                        } else {
                                $callback = $func;
                        }

                        // Run autoloader (workaround for call_user_func_array bug)
                        is_callable( $callback );

                        $retval = null;
                        set_error_handler( 'Hooks::hookErrorHandler' );
                        wfProfileIn( $func );
                        try {
                                $retval = call_user_func_array( $callback, $hook_args );
                        } catch ( MWHookException $e ) {
                                $badhookmsg = $e->getMessage();
                        }
                        wfProfileOut( $func );
                        restore_error_handler();

                        /* String return is an error; false return means stop processing. */
                        if ( is_string( $retval ) ) {
                                throw new FatalError( $retval );
                        } elseif( $retval === null ) {
                                if ( $closure ) {
                                        $prettyFunc = "$event closure";
                                } elseif( is_array( $callback ) ) {
                                        if( is_object( $callback[0] ) ) {
                                                $prettyClass = get_class( $callback[0] );
                                        } else {
                                                $prettyClass = strval( $callback[0] );
                                        }
                                        $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
                                } else {
                                        $prettyFunc = strval( $callback );
                                }
                                if ( $badhookmsg ) {
                                        throw new MWException(
                                                'Detected bug in an extension! ' .
                                                "Hook $prettyFunc has invalid call signature; " . $badhookmsg
                                        );
                                } else {
                                        throw new MWException(
                                                'Detected bug in an extension! ' .
                                                "Hook $prettyFunc failed to return a value; " .
                                                'should return true to continue hook processing or false to abort.'
                                        );
                                }
                        } elseif ( !$retval ) {
                                return false;
                        }
                }

                return true;
        }

        public static function hookErrorHandler( $errno, $errstr ) {
                if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
                        throw new MWHookException( $errstr );
                }
                return false;
        }
}