<?php
/**
 * Hooks.php -- a tool for running hook functions
 * Copyright 2004, 2005 Evan Prodromou <evan@wikitravel.org>.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 *
 * @author Evan Prodromou <evan@wikitravel.org>
 * @see hooks.txt
 * @file
 */

/* Private */
function _wfInvokeInternalGoop( $event, $hook ) {
	$object = NULL;
	$method = NULL;
	$func = NULL;
	$data = NULL;
	$have_data = false;

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

	if ( isset( $object ) ) {
		$func = get_class( $object ) . '::' . $method;
		$callback = array( $object, $method );
	} elseif ( false !== ( $pos = strpos( $func, '::' ) ) ) {
		$callback = array( substr( $func, 0, $pos ), substr( $func, $pos + 2 ) );
	} else {
		$callback = $func;
	}
	
	return array($callback, $func, $data);
}

/* Return a string describing the hook for debugging purposes. */
function wfFormatInvocation( $event, $hook, $args = array() ) {
	list( $callback, $func, $data ) = _wfInvokeInternalGoop( $event, $hook, $args );
	
	if( 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 );
	}
	return $prettyFunc;
}


/*
 * Invoke a function dynamically.
 * $event is the name of the invocation; this is used if the hook specifies
 * an object but no method name; 'on$event' is then invoked on the object.
 * $hook can be: a function, an object, an array of $function and $data,
 * an array of just a function, an array of object and method, or an
 * array of object, method, and data.
 * If arguments are provided both as part of the hook itself, and when
 * calling wfCallFancyCallback, the two arrays are merged.
 */
function wfInvoke( $event, $hook, $args = array() ) {
	list( $callback, $func, $data ) = _wfInvokeInternalGoop( $event, $hook, $args );
	
	/* We put the first data element on, if needed. */
	if ( $data ) {
		$hook_args = array_merge( array( $data ), $args );
	} else {
		$hook_args = $args;
	}

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

	/* Call the hook. */
	wfProfileIn( $func );
	$retval = call_user_func_array( $callback, $hook_args );
	wfProfileOut( $func );
	return $retval;
}


/**
 * Because programmers assign to $wgHooks, we need to be very
 * careful about its contents. So, there's a lot more error-checking
 * in here than would normally be necessary.
 */
function wfRunHooks( $event, $args = array() ) {

	global $wgHooks;

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

	if (!array_key_exists( $event, $wgHooks ) ) {
		return true;
	}

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

	foreach ( $wgHooks[$event] as $index => $hook ) {

		$retval = wfInvoke( $event, $hook, $args );

		/* String return is an error; false return means stop processing. */

		if ( is_string( $retval ) ) {
			global $wgOut;
			$wgOut->showFatalError( $retval );
			return false;
		} elseif( $retval === null ) {
			$prettyFunc = wfFormatInvocation( $event, $hook, $args );
			throw new MWException( "Detected bug in an extension! " .
				"Hook $prettyFunc failed to return a value; " .
				"should return true to continue hook processing or false to abort." );
		} else if ( !$retval ) {
			return false;
		}
	}

	return true;
}