<?php
/**
 * Elgg cache
 * Cache file interface for caching data.
 *
 * @package    Elgg.Core
 * @subpackage Cache
 */

/* Filepath Cache */

/**
 * Returns an ElggCache object suitable for caching system information
 *
 * @todo Can this be done in a cleaner way?
 * @todo Swap to memcache etc?
 *
 * @return ElggFileCache
 */
function elgg_get_system_cache() {
	global $CONFIG;

	/**
	 * A default filestore cache using the dataroot.
	 */
	static $FILE_PATH_CACHE;

	if (!$FILE_PATH_CACHE) {
		$FILE_PATH_CACHE = new ElggFileCache($CONFIG->dataroot . 'system_cache/');
	}

	return $FILE_PATH_CACHE;
}

/**
 * Reset the system cache by deleting the caches
 *
 * @return bool
 */
function elgg_reset_system_cache() {
	$cache = elgg_get_system_cache();

	$result = true;
	$cache_types = array('view_paths', 'view_types');
	foreach ($cache_types as $type) {
		$result = $result && $cache->delete($type);
	}
	return $result;
}

/**
 * Saves a system cache.
 *
 * @param string $type The type or identifier of the cache
 * @param string $data The data to be saved
 * @return bool
 */
function elgg_save_system_cache($type, $data) {
	global $CONFIG;

	if ($CONFIG->system_cache_enabled) {
		$cache = elgg_get_system_cache();
		return $cache->save($type, $data);
	}

	return false;
}

/**
 * Retrieve the contents of a system cache.
 *
 * @param string $type The type of cache to load
 * @return string
 */
function elgg_load_system_cache($type) {
	global $CONFIG;

	if ($CONFIG->system_cache_enabled) {
		$cache = elgg_get_system_cache();
		$cached_data = $cache->load($type);

		if ($cached_data) {
			return $cached_data;
		}
	}

	return NULL;
}

/**
 * Enables the system disk cache.
 *
 * Uses the 'system_cache_enabled' datalist with a boolean value.
 * Resets the system cache.
 *
 * @return void
 */
function elgg_enable_system_cache() {
	global $CONFIG;

	datalist_set('system_cache_enabled', 1);
	$CONFIG->system_cache_enabled = 1;
	elgg_reset_system_cache();
}

/**
 * Disables the system disk cache.
 *
 * Uses the 'system_cache_enabled' datalist with a boolean value.
 * Resets the system cache.
 *
 * @return void
 */
function elgg_disable_system_cache() {
	global $CONFIG;

	datalist_set('system_cache_enabled', 0);
	$CONFIG->system_cache_enabled = 0;
	elgg_reset_system_cache();
}

/** @todo deprecate in Elgg 1.9 **/

/**
 * @access private
 */
function elgg_get_filepath_cache() {
	return elgg_get_system_cache();
}
/**
 * @access private
 */
function elgg_filepath_cache_reset() {
	return elgg_reset_system_cache();
}
/**
 * @access private
 */
function elgg_filepath_cache_save($type, $data) {
	return elgg_save_system_cache($type, $data);
}
/**
 * @access private
 */
function elgg_filepath_cache_load($type) {
	return elgg_load_system_cache($type);
}
/**
 * @access private
 */
function elgg_enable_filepath_cache() {
	return elgg_enable_system_cache();
}
/**
 * @access private
 */
function elgg_disable_filepath_cache() {
	return elgg_disable_system_cache();
}

/* Simplecache */

/**
 * Registers a view to simple cache.
 *
 * Simple cache is a caching mechanism that saves the output of
 * views and its extensions into a file.  If the view is called
 * by the {@link simplecache/view.php} file, the Elgg framework will
 * not be loaded and the contents of the view will returned
 * from file.
 *
 * @warning Simple cached views must take no parameters and return
 * the same content no matter who is logged in.
 *
 * @example
 * 		$blog_js = elgg_get_simplecache_url('js', 'blog/save_draft');
 *		elgg_register_simplecache_view('js/blog/save_draft');
 *		elgg_register_js('elgg.blog', $blog_js);
 *		elgg_load_js('elgg.blog');
 *
 * @param string $viewname View name
 *
 * @return void
 * @link http://docs.elgg.org/Views/Simplecache
 * @see elgg_regenerate_simplecache()
 * @since 1.8.0
 */
function elgg_register_simplecache_view($viewname) {
	global $CONFIG;

	if (!isset($CONFIG->views)) {
		$CONFIG->views = new stdClass;
	}

	if (!isset($CONFIG->views->simplecache)) {
		$CONFIG->views->simplecache = array();
	}

	$CONFIG->views->simplecache[] = $viewname;
}

/**
 * Get the URL for the cached file
 *
 * @warning You must register the view with elgg_register_simplecache_view()
 * for caching to work. See elgg_register_simplecache_view() for a full example.
 *
 * @param string $type The file type: css or js
 * @param string $view The view name
 * @return string
 * @since 1.8.0
 */
function elgg_get_simplecache_url($type, $view) {
	global $CONFIG;
	$lastcache = (int)$CONFIG->lastcache;
	$viewtype = elgg_get_viewtype();
	if (elgg_is_simplecache_enabled()) {
		$url = elgg_get_site_url() . "cache/$type/$viewtype/$view.$lastcache.$type";
	} else {
		$url = elgg_get_site_url() . "$type/$view.$lastcache.$type";
		$elements = array("view" => $viewtype);
		$url = elgg_http_add_url_query_elements($url, $elements);
	}
	
	return $url;
}

/**
 * Regenerates the simple cache.
 *
 * @warning This does not invalidate the cache, but actively resets it.
 *
 * @param string $viewtype Optional viewtype to regenerate. Defaults to all valid viewtypes.
 *
 * @return void
 * @see elgg_register_simplecache_view()
 * @since 1.8.0
 */
function elgg_regenerate_simplecache($viewtype = NULL) {
	global $CONFIG;

	if (!isset($CONFIG->views->simplecache) || !is_array($CONFIG->views->simplecache)) {
		return;
	}

	$lastcached = time();

	// @todo elgg_view() checks if the page set is done (isset($CONFIG->pagesetupdone)) and
	// triggers an event if it's not. Calling elgg_view() here breaks submenus
	// (at least) because the page setup hook is called before any
	// contexts can be correctly set (since this is called before page_handler()).
	// To avoid this, lie about $CONFIG->pagehandlerdone to force
	// the trigger correctly when the first view is actually being output.
	$CONFIG->pagesetupdone = TRUE;

	if (!file_exists($CONFIG->dataroot . 'views_simplecache')) {
		mkdir($CONFIG->dataroot . 'views_simplecache');
	}

	if (isset($viewtype)) {
		$viewtypes = array($viewtype);
	} else {
		$viewtypes = $CONFIG->view_types;
	}

	$original_viewtype = elgg_get_viewtype();

	// disable error reporting so we don't cache problems
	$old_debug = elgg_get_config('debug');
	elgg_set_config('debug', null);

	foreach ($viewtypes as $viewtype) {
		elgg_set_viewtype($viewtype);
		foreach ($CONFIG->views->simplecache as $view) {
			$viewcontents = elgg_view($view);
			$viewname = md5(elgg_get_viewtype() . $view);
			if ($handle = fopen($CONFIG->dataroot . 'views_simplecache/' . $viewname, 'w')) {
				fwrite($handle, $viewcontents);
				fclose($handle);
			}
		}

		datalist_set("simplecache_lastupdate_$viewtype", $lastcached);
		datalist_set("simplecache_lastcached_$viewtype", $lastcached);
	}

	elgg_set_config('debug', $old_debug);
	elgg_set_viewtype($original_viewtype);

	// needs to be set for links in html head
	$CONFIG->lastcache = $lastcached;

	unset($CONFIG->pagesetupdone);
}

/**
 * Is simple cache enabled
 *
 * @return bool
 * @since 1.8.0
 */
function elgg_is_simplecache_enabled() {
	if (elgg_get_config('simplecache_enabled')) {
		return true;
	}

	return false;
}

/**
 * Enables the simple cache.
 *
 * @access private
 * @see elgg_register_simplecache_view()
 * @return void
 * @since 1.8.0
 */
function elgg_enable_simplecache() {
	global $CONFIG;

	datalist_set('simplecache_enabled', 1);
	$CONFIG->simplecache_enabled = 1;
	elgg_regenerate_simplecache();
}

/**
 * Disables the simple cache.
 *
 * @warning Simplecache is also purged when disabled.
 *
 * @access private
 * @see elgg_register_simplecache_view()
 * @return void
 * @since 1.8.0
 */
function elgg_disable_simplecache() {
	global $CONFIG;
	if ($CONFIG->simplecache_enabled) {
		datalist_set('simplecache_enabled', 0);
		$CONFIG->simplecache_enabled = 0;

		// purge simple cache
		if ($handle = opendir($CONFIG->dataroot . 'views_simplecache')) {
			while (false !== ($file = readdir($handle))) {
				if ($file != "." && $file != "..") {
					unlink($CONFIG->dataroot . 'views_simplecache/' . $file);
				}
			}
			closedir($handle);
		}
	}
}

/**
 * Deletes all cached views in the simplecache and sets the lastcache and
 * lastupdate time to 0 for every valid viewtype.
 *
 * @return bool
 * @since 1.7.4
 */
function elgg_invalidate_simplecache() {
	global $CONFIG;

	if (!isset($CONFIG->views->simplecache) || !is_array($CONFIG->views->simplecache)) {
		return false;
	}

	$handle = opendir($CONFIG->dataroot . 'views_simplecache');

	if (!$handle) {
		return false;
	}

	// remove files.
	$return = true;
	while (false !== ($file = readdir($handle))) {
		if ($file != "." && $file != "..") {
			$return = $return && unlink($CONFIG->dataroot . 'views_simplecache/' . $file);
		}
	}
	closedir($handle);

	// reset cache times
	$viewtypes = $CONFIG->view_types;

	if (!is_array($viewtypes)) {
		return false;
	}

	foreach ($viewtypes as $viewtype) {
		$return = $return && datalist_set("simplecache_lastupdate_$viewtype", 0);
		$return = $return && datalist_set("simplecache_lastcached_$viewtype", 0);
	}

	return $return;
}

/**
 * @see elgg_reset_system_cache()
 * @access private
 */
function _elgg_load_cache() {
	global $CONFIG;
	
	$result = true;
	$cache_types = array(
		'view_paths' => 'views',
		'view_types' => 'view_types',
	);
	$data = array();
	foreach ($cache_types as $type => $var_name) {
		$data[$var_name] = elgg_load_system_cache($type);
		$result = $result && is_string($data[$var_name]);
	}

	if ($result) {
		$CONFIG->system_cache_loaded = true;
		foreach ($data as $name => $value) {
			$CONFIG->$name = unserialize($value);
		}
	} else {
		$CONFIG->system_cache_loaded = false;
	}
}

/**
 * @access private
 */
function _elgg_cache_init() {
	global $CONFIG;

	$viewtype = elgg_get_viewtype();

	// Regenerate the simple cache if expired.
	// Don't do it on upgrade because upgrade does it itself.
	// @todo - move into function and perhaps run off init system event
	if (!defined('UPGRADING')) {
		$lastupdate = datalist_get("simplecache_lastupdate_$viewtype");
		$lastcached = datalist_get("simplecache_lastcached_$viewtype");
		if ($lastupdate == 0 || $lastcached < $lastupdate) {
			elgg_regenerate_simplecache($viewtype);
			$lastcached = datalist_get("simplecache_lastcached_$viewtype");
		}
		$CONFIG->lastcache = $lastcached;
	}

	// cache system data if enabled and not loaded
	if ($CONFIG->system_cache_enabled && !$CONFIG->system_cache_loaded) {
		$cache_types = array(
			'view_paths' => 'views',
			'view_types' => 'view_types',
		);
		$data = array();
		foreach ($cache_types as $type => $var_name) {
			elgg_save_system_cache($type, serialize($CONFIG->$var_name));
		}
	}

	if ($CONFIG->system_cache_enabled && !$CONFIG->i18n_loaded_from_cache) {
		foreach ($CONFIG->translations as $lang => $map) {
			elgg_save_system_cache("$lang.php", serialize($map));
		}
	}
}

elgg_register_event_handler('ready', 'system', '_elgg_cache_init');