<?php

/**
 * keywords.plugin.php
 *
 * Auto generates meta keywords for the page based on the frequency of words.
 * If there are keywords already the nothing is added.
 *
 * @author   Svetoslav Marinov <hide@address.com>
 * @version  1.0
 * @package  keywords
 * @todo Remove, append to existing keyword list.
 */

class seofilter_plugin_keywords extends seofilter_plugin {
	var $version = 1.0;

	/**
     * $event can be executed
     * PRE, POST, INPUT, OUTPUT Filter
     *
     * @param   constant
     * @access  public
     * @return  bool
     */
	function execute($event)
	{
		$keyword_cache_array = array();
		static $meta_keyword_tag = "\n<meta name=\"keywords\" content=\"%s\" />";

		if ($event == SEOFILTER_EVENT_POST) {
			$params = $this->params();
			$buffer = $this->content();

			$partial_buff = '';
			$req_url = empty($_SERVER['REQUEST_URI']) ? '/' : $_SERVER['REQUEST_URI'];
			
			// Remove query params.
			if (($pos = strpos($req_url, "?")) !== false) {
            	$req_url = substr($req_url, 0, $pos);
        	}
        	
        	$refresh_cache = 0;
        	$keyword_str = '';
        	
        	$cache_file = SEOFILTER_TMP_DIR . 'keywords.cache.php';
			
			if (file_exists($cache_file)) {
				$keyword_cache_array = (array) unserialize(seofilter_safe_read($cache_file));
				
				$cache_last_modified = @filemtime($cache_file);
				
				// if the cache file is older than 2 days schedule update.
				if (abs(time() - $cache_last_modified) > 172800) {
					$refresh_cache = 1;
				}
			} else {
				$refresh_cache = 1;
			}
        	
        	if (array_key_exists($req_url, $keyword_cache_array)) {
        		$keyword_str = $keyword_cache_array[$req_url];
        	} else {
        		$refresh_cache = 1;
			
				// Assumming that the header will fit in 2k
				$partial_buff = substr($buffer, 0, 2048);
				
				if (!empty($partial_buff) && !preg_match('#<meta[^>]*keywords#si', $partial_buff)) {
					$keywords = seofilter_util::extract_keywords($buffer, 15);
					$keyword_str = join(',', $keywords);
				}
        	}
        	
			// Are there keywords ? if No we proceed.
			if (!empty($keyword_str)) {
				$buffer = preg_replace('#(<\s*head[^>]*>)#si', '\\1' . sprintf($meta_keyword_tag, $keyword_str), $buffer);

				// inform the main module that the content has been modified
				$this->status(SEOFILTER_STATUS_CONTENT_CHANGED);
				$this->content($buffer);
			}
			
			if ($refresh_cache) {
				$keyword_cache_array[$req_url] = $keyword_str;
				seofilter_safe_write($cache_file, serialize($keyword_cache_array));
				
				/*
				// I have tried to make the updating of the file to be done after the processing but
				// it is NOT possible because shutdown function is already executed when we reach seofilter_handler which calls this plugin
				$inst = seofilter_get_instance('stdClass');
				$inst->listeners = array();
				$inst->listeners[] = array(
					'seofilter_safe_write', $cache_file, serialize($keyword_cache_array)
				);
				*/
				// Scheduling the cache update after the script is done so the user don't have to wait.
//		        register_shutdown_function('seofilter_safe_write', $cache_file, serialize($keyword_cache_array));
			}
		}

		return true;
	}
}
?>