<?php
/*
Plugin Name: Global Terms
Plugin URI: http://wordpress.org/extend/plugins/global-terms/
Description: Global terms for your Network, but not in core!
Author: wordpressdotorg
Author URI: http://wordpress.org/
Version: 1.0
*/

register_activation_hook( __FILE__, 'install_global_terms' );

if ( ! function_exists( 'install_global_terms' ) ) {
	/**
	 * Create global terms table if it doesn't exist
	 * 
	 * @global type $wpdb
	 * @global type $charset_collate
	 * @uses dbDelta
	 * 
	 */
	function install_global_terms() {
		global $wpdb, $charset_collate;

		update_site_option( 'global_terms_enabled', 1 );

		$create_table = "CREATE TABLE IF NOT EXISTS {$wpdb->base_prefix}sitecategories (
			cat_ID bigint(20) NOT NULL auto_increment,
			cat_name varchar(55) NOT NULL default '',
			category_nicename varchar(200) NOT NULL default '',
			last_updated timestamp NOT NULL,
			PRIMARY KEY  (cat_ID),
			KEY category_nicename (category_nicename),
			KEY last_updated (last_updated)
		  ) $charset_collate;";

		dbDelta( $create_table );
	}	
}


class GlobalTerms {
	/**
	 * Table name were global terms are held
	 * 
	 * @var string
	 */
	var $table;
	
	/**
	 * Singleton instance
	 * 
	 * @var GlobalTerms
	 */
	private $instance;
	
	/**
	 * Singleton accessor
	 * 
	 * @return GlobalTerms $instance
	 */
	public static function get_instance() {
		if ( ! isset( self::$instance ) )
			self::$instance = new GlobalTerms;
		
		return self::$instance;
	}
	
	private function __construct() {
		global $wpdb;
		$this->table = $wpdb->base_prefix . 'sitecategories';
		
		add_filter( 'term_id_filter', array( $this, 'global_terms' ), 10, 2 );
		
		add_filter( 'get_term',	array( $this, 'sync_term_slugs' ), 10, 2 );
	}	

	/**
	 * Maintains a canonical list of terms by syncing terms created for each blog with the global terms table.
	 *
	 * @since (was) WP 3.0.0
	 *
	 * @see term_id_filter
	 *
	 * @param int $term_id An ID for a term on the current blog.
	 * @return int An ID from the global terms table mapped from $term_id.
	 */
	function global_terms( $term_id ) {
		global $wpdb;
		static $global_terms_recurse = null;

		if ( ! get_site_option( 'global_terms_enabled' ) )
			return $term_id;

		// prevent a race condition
		$recurse_start = false;
		if ( $global_terms_recurse === null ) {
			$recurse_start = true;
			$global_terms_recurse = 1;
		} elseif ( 10 < $global_terms_recurse++ ) {
			return $term_id;
		}

		$term_id = intval( $term_id );
		$c = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->terms WHERE term_id = %d", $term_id ) );

		$global_id = $wpdb->get_var( $wpdb->prepare( "SELECT cat_ID FROM $this->table WHERE category_nicename = %s", $c->slug ) );
		
		if ( $global_id == null ) {
			$used_global_id = $wpdb->get_var( $wpdb->prepare( "SELECT cat_ID FROM $this->table WHERE cat_ID = %d", $c->term_id ) );
			
			if ( null == $used_global_id ) {
				
				$wpdb->insert( $this->table, array( 'cat_ID' => $term_id, 'cat_name' => $c->name, 'category_nicename' => $c->slug ) );
				
				$global_id = $wpdb->insert_id;
				
				if ( empty( $global_id ) )
					return $term_id;
				
			} else {
				
				$max_global_id = $wpdb->get_var( "SELECT MAX(cat_ID) FROM $this->table" );
				$max_local_id = $wpdb->get_var( "SELECT MAX(term_id) FROM $wpdb->terms" );
				
				$new_global_id = max( $max_global_id, $max_local_id ) + mt_rand( 100, 400 );
				
				$wpdb->insert( $this->table, array( 'cat_ID' => $new_global_id, 'cat_name' => $c->name, 'category_nicename' => $c->slug ) );
				
				$global_id = $wpdb->insert_id;
				
			}
			
		} elseif ( $global_id != $term_id ) {
			
			$local_id = $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->terms WHERE term_id = %d", $global_id ) );
			
			if ( null != $local_id )
				$local_id = global_terms( $local_id );
				if ( 10 < $global_terms_recurse )
					$global_id = $term_id;
		}

		if ( $global_id != $term_id ) {
			
			if ( $term_id == get_option( 'default_category' ) )
				update_option( 'default_category', $global_id );

			$wpdb->update( $wpdb->terms, array( 'term_id' => $global_id ), array( 'term_id' => $term_id ) );
			$wpdb->update( $wpdb->term_taxonomy, array( 'term_id' => $global_id ), array( 'term_id' => $term_id ) );
			$wpdb->update( $wpdb->term_taxonomy, array( 'parent' => $global_id ), array( 'parent' => $term_id ) );

			clean_term_cache( $term_id );
		}
		
		if ( $recurse_start )
			$global_terms_recurse = null;

		return $global_id;
	}

	/**
	 * 
	 * @param object $term
	 * @param string $taxonomy
	 * @return object Term
	 */
	function sync_term_slugs( $term, $taxonomy ) {
		if ( ! get_site_option( 'global_terms_enabled' ) || ! in_array( $taxonomy, array( 'category', 'post_tag' ) ) )
			return $term;

		if ( is_object( $term ) ) {
			$term->slug = sanitize_title( $term->name );
		} else {
			$term['slug'] = sanitize_title( $term['name'] );
		}
		return $term;
	}
}	
GlobalTerms::get_instance();


if ( ! function_exists( 'global_terms_enabled' ) ) {
	/**
	 * Whether global terms are enabled.
	 *
	 * @since WP 3.0.0
	 *
	 * @return bool True if multisite and global terms enabled
	 */
	function global_terms_enabled() {
		if ( ! is_multisite() )
			return false;

		static $global_terms = null;
		if ( is_null( $global_terms ) ) {
			$filter = apply_filters( 'global_terms_enabled', null );
			if ( ! is_null( $filter ) )
				$global_terms = (bool) $filter;
			else
				$global_terms = (bool) get_site_option( 'global_terms_enabled', false );
		}
		return $global_terms;
	}	
}