<?php
/*
Plugin Name: Fulltext Search
*/

function fulltext_posts_search($search) {
	// Discard the core search clause.
	return '';
}

function fulltext_posts_join($join) {
	global $wpdb, $wp_query;

	if ( is_search() ) {
		$match = $wpdb->prepare("MATCH (object_text) AGAINST (%s)", $wp_query->get('s'));
		$query = "SELECT object_id, object_type, $match AS score FROM {$wpdb->prefix}fulltext WHERE $match";
		$join .= " RIGHT JOIN ($query) AS ft ON (ID=ft.post_id)";

		add_filter('posts_orderby', 'fulltext_posts_orderby_once', 10);
	}

	return $join;
}

function fulltext_posts_orderby_once() {
	remove_filter('posts_orderby', 'fulltext_posts_orderby_once', 10);
	return "score DESC";
}

function fulltext_init() {
	global $fulltext_index;

	$fulltext_index = new fulltext_index();
}

add_action('init', 'fulltext_init');

class fulltext_index {
	// These are populated from the filters of the same names, then used in reconstructing the search query.
	var $posts_fields = '';
	var $posts_join = '';
	var $posts_where = '';
	var $posts_groupby = '';
	var $posts_orderby = '';
	var $post_limits = '';

	function fulltext_index() {
		// Actions that trigger indexing a post or comment:
		add_action( 'delete_post',           array( &$this, 'delete_post' ) );
		add_action( 'save_post',             array( &$this, 'index_post' ) );
		add_action( 'delete_comment',        array( &$this, 'index_comment' ) );
		add_action( 'comment_post',          array( &$this, 'index_comment' ) );
		add_action( 'edit_comment',          array( &$this, 'index_comment' ) );
		add_action( 'wp_set_comment_status', array( &$this, 'index_comment' ) );

		// WP_Query::get_posts filters for modifying:
		add_filter( 'posts_search', array(&$this, 'return_blank') );

		// WP_Query::get_posts filters for saving:
		add_filter( 'posts_fields',  array(&$this, 'set_posts_fields') );
		add_filter( 'posts_join',    array(&$this, 'set_posts_join') );
		add_filter( 'posts_where',   array(&$this, 'set_posts_where') );
		add_filter( 'posts_groupby', array(&$this, 'set_posts_groupby') );
		add_filter( 'posts_orderby', array(&$this, 'set_posts_orderby') );
		add_filter( 'post_limits',  array(&$this, 'set_post_limits') );

		// WP_Query::get_posts filters for reconstructing:
		add_filter( 'posts_request', array(&$this, 'posts_request') );
	}

	function return_blank($v) {
		if ( is_search() )
			return '';
		return $v;
	}

	function set_posts_fields ($v) { $this->posts_fields  = $v; return $v; }
	function set_posts_join   ($v) { $this->posts_join    = $v; return $v; }
	function set_posts_where  ($v) { $this->posts_where   = $v; return $v; }
	function set_posts_groupby($v) { $this->posts_groupby = $v; return $v; }
	function set_posts_orderby($v) { $this->posts_orderby = $v; return $v; }
	function set_post_limits ($v) { $this->post_limits  = $v; return $v; }

	function posts_request($request) {
		global $wpdb, $wp_query;

		if ( !is_search() )
			return $request;

		if ( !empty($this->posts_limits) )
			$found_rows = 'SQL_CALC_FOUND_ROWS';

		$fields = "$wpdb->posts.*, $wpdb->comments.*";
		$match = $wpdb->prepare("MATCH (object_text) AGAINST (%s)", $wp_query->get('s'));
		$subquery = "SELECT object_id, object_type, $match AS score FROM {$wpdb->prefix}fulltext WHERE $match";
		$tables = "($subquery) AS ft LEFT JOIN wp_posts ON (ID=object_id AND object_type='post') LEFT JOIN wp_comments ON (comment_id=object_id AND object_type='comment')";
		$where = "(1=1 $this->posts_where) OR (comment_post_id IS NOT NULL)";
		$orderby = "ORDER BY score DESC";
		$limits = $this->post_limits;

		return "SELECT $found_rows $fields FROM $tables WHERE $where $orderby $limits";
	}

	function delete_post($post_id) {
		global $wpdb;
		$wpdb->query($wpdb->prepare("DELETE FROM {$wpdb->prefix}fulltext WHERE object_id = %d AND object_type='post'", $post_id));
	}

	function index_comment($comment_id) {
		global $wpdb;

		$comment = get_comment($comment_id);
		$post = get_post($comment->comment_post_id);

		$text = $post->post_title;

		$text .= '  ' . $comment->comment_author;
		$text .= '  ' . $comment->comment_content;

		$wpdb->query($wpdb->prepare("INSERT INTO {$wpdb->prefix}fulltext (object_id, object_type, object_text) VALUES (%d, 'comment', %s) ON DUPLICATE KEY UPDATE object_text=VALUES(object_text)", $comment_id, $text));
	}

	function index_post($post_id) {
		global $wpdb;

		$post = get_post($post_id);

		$text = $post->post_title;
		$text .= '  ' . $post->post_content;

		$terms = wp_get_object_terms($post_id, get_object_taxonomies($post));
		foreach ( $terms as $term )
			$text .= '  ' . $term->name;

		if ( $comments = get_approved_comments($post_id) )
			foreach ( $comments as $comment )
				$text .= '  ' . $comment->comment_author . '  ' . $comment->comment_content;

		$wpdb->query($wpdb->prepare("INSERT INTO {$wpdb->prefix}fulltext (object_id, object_type, object_text) VALUES (%d, 'post', %s) ON DUPLICATE KEY UPDATE object_text=VALUES(object_text)", $post_id, $text));
	}

	function create_table() {
		global $wpdb;
		$wpdb->query("
			CREATE TABLE IF NOT EXISTS {$wpdb->prefix}fulltext (
				object_id INT(11) NOT NULL,
				object_type VARCHAR(20) NOT NULL,
				object_text TEXT NOT NULL,
				PRIMARY KEY (object_id, object_type),
				FULLTEXT KEY (object_text)
			) ENGINE=MyISAM
		");

		$this->index_all();
	}

	function index_all() {
		global $wpdb;
		if ( $types = get_post_types( array("exclude_from_search" => false) ) ) {
			$and_type = "AND post_type IN (";
			foreach ( $types as $type )
				$and_type .= $wpdb->prepare("%s", $type) . ',';
			$and_type = substr($and_type, 0, -1) . ')';
		}

		if ( $stati = get_post_stati( array("exclude_from_search" => false) ) ) {
			$and_status = "AND post_status IN (";
			foreach ( $stati as $status )
				$and_status .= $wpdb->prepare("%s", $status) . ',';
			$and_status = substr($and_status, 0, -1) . ')';
		}

		if ( $post_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE 1=1 $and_type $and_status") ) {
			foreach ( $post_ids as $post_id )
				$this->index_post($post_id);
		}
	}		
}

$fulltext_index = new fulltext_index();

register_activation_hook( __FILE__, array(&$fulltext_index, 'create_table') );