Added advanced custom column sorting

Added sorting custom columns where the column is a meta value that
refers to a different post, where the column needs to be sorted by the
title of said different post
Added placeholder case statements for columns that lack sorting logic
Improved comments for tax sorting
Added condition to tax sorting whereby no columns in the function would
be sorted by. Otherwise conflicts would arise when sorting by other
columns (potentially in other plugins as well)

lib/admin-tables.class.php

@@ -51,6 +51,9 @@ function __construct( WP_LIBRARIAN $wp_librarian ) {
 		// Adds custom sorting logic to custom taxonomy columns
 		add_filter( 'posts_clauses',								array($this,			'sortCustomTaxColumns'),			10, 2);
 
+		// Adds custom sorting logic to columns that rely on meta-based foreign keys
+		add_filter( 'posts_clauses',								array($this,			'sortCustomForeignMetaColumns'),	10, 2);
+
 		// Adds custom sorting logic to custom post meta columns
 		add_action( 'pre_get_posts',								array($this,			'sortCustomMetaColumns'),			10, 1);
 
@@ -363,7 +366,7 @@ public function fillUsersTableColumns( $value='', $column, $user_id ) {
 	 */
 	public function setSortableItemsTableColumns( Array $columns ) {
 		// Makes array of columns sortable
-		foreach(['taxonomy-wp_lib_media_type','taxonomy-wp_lib_author','item_condition'] as $sortable ) {
+		foreach(['taxonomy-wp_lib_media_type','taxonomy-wp_lib_author','item_status','item_condition'] as $sortable ) {
 			$columns[$sortable] = $sortable;
 		}
 
@@ -377,7 +380,7 @@ public function setSortableItemsTableColumns( Array $columns ) {
 	 */
 	public function setSortableMembersTableColumns( Array $columns ) {
 		// Makes array of columns sortable
-		foreach(['member_name'] as $sortable ) {
+		foreach(['member_name','member_loans','member_fines','member_donated'] as $sortable ) {
 			$columns[$sortable] = $sortable;
 		}
 
@@ -405,7 +408,7 @@ public function setSortableLoansTableColumns( Array $columns ) {
 	 */
 	public function setSortableFinesTableColumns( Array $columns ) {
 		// Makes array of columns sortable
-		foreach(['fine_fine','fine_status','fine_amount'] as $sortable ) {
+		foreach(['fine_fine','fine_item','fine_member','fine_status','fine_amount'] as $sortable ) {
 			$columns[$sortable] = $sortable;
 		}
 
@@ -416,12 +419,11 @@ public function setSortableFinesTableColumns( Array $columns ) {
 	 * Defines custom logic for sorting the Items table's custom taxonomy columns
 	 * Adapted from Mike Schinkel's comment on Scribu's post: 
 	 * @link	http://scribu.net/wordpress/sortable-taxonomy-columns.html#direct-joins
-	 * @param	Array		$clauses	
+	 * @param	Array		$clauses	SQL clauses for fetching posts
 	 * @param	WP_Query	$wp_query	A request to WordPress for posts
+	 * @return	Array					Modified SQL clauses
 	 */
 	public function sortCustomTaxColumns( Array $clauses, WP_Query $wp_query ) {
-		global $wpdb;
-
 		if ( !isset($wp_query->query['orderby']) )
 			return $clauses;
 
@@ -433,8 +435,14 @@ public function sortCustomTaxColumns( Array $clauses, WP_Query $wp_query ) {
 			case 'taxonomy-wp_lib_media_type':
 				$taxonomy = 'wp_lib_media_type';
 			break;
+
+			default:
+				return $clauses;
+			break;
 		}
 
+		global $wpdb;
+
 		$clauses['join'] .= <<<SQL
 LEFT OUTER JOIN {$wpdb->term_relationships} ON {$wpdb->posts}.ID={$wpdb->term_relationships}.object_id
 LEFT OUTER JOIN {$wpdb->term_taxonomy} USING (term_taxonomy_id)
@@ -449,6 +457,57 @@ public function sortCustomTaxColumns( Array $clauses, WP_Query $wp_query ) {
 		return $clauses;
 	}
 
+	/**
+	 * Sorts a custom column by its value, where that value comes a different post type's title
+	 * @todo							Give this function a better name
+	 * @param	Array		$clauses	SQL clauses for fetching posts
+	 * @param	WP_Query	$wp_query	A request to WordPress for posts
+	 * @return	Array					Modified SQL clauses
+	 */
+	public function sortCustomForeignMetaColumns( Array $clauses, WP_Query $wp_query ) {
+		if (!isset($wp_query->query['orderby']))
+			return $clauses;
+
+		switch( $wp_query->query['orderby'] ) {
+			// The item title column of the loans table
+			case 'loan_item':
+				$meta_key	= 'wp_lib_item';
+			break;
+
+			// The member name column of the loans table
+			case 'loan_member':
+				$meta_key	= 'wp_lib_member';
+			break;
+
+			// The item title column of the fines table
+			case 'fine_item':
+				$meta_key	= 'wp_lib_item';
+			break;
+
+			// The member name column of the fines table
+			case 'fine_member':
+				$meta_key	= 'wp_lib_member';
+			break;
+
+			default:
+				return $clauses;
+			break;
+		}
+
+		global $wpdb;
+
+		// Posts table -> Foreign Keys in Meta Table -> Posts table posts that match f. key
+		$clauses['join'] .= <<<SQL
+LEFT OUTER JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID={$wpdb->postmeta}.post_id AND {$wpdb->postmeta}.meta_key='{$meta_key}'
+LEFT OUTER JOIN {$wpdb->posts} AS wp_lib_cpt ON meta_value=wp_lib_cpt.ID
+SQL;
+
+		$clauses['orderby'] = "wp_lib_cpt.post_title ";
+		$clauses['orderby'] .= ( 'ASC' === strtoupper( $wp_query->get('order') ) ) ? 'ASC' : 'DESC';
+
+		return $clauses;
+	}
+
 	/**
 	 * Tells WordPress how to sort the Items table's custom post meta columns
 	 * @param	Array		$vars		Query variables passed to default main SQL query
@@ -459,6 +518,10 @@ public function sortCustomMetaColumns( WP_Query $query ) {
 
 		// Adds sorting logic based on column being sorted
 		switch( $query->get( 'orderby') ) {
+			case 'item_status':
+				// Requires special logic
+			break;
+
 			case 'item_condition':
 				$query->set('meta_key',	'wp_lib_item_condition');
 				$query->set('orderby',	'meta_value_num');
@@ -468,6 +531,22 @@ public function sortCustomMetaColumns( WP_Query $query ) {
 				$query->set('orderby',	'title');	// Member's names are stored as the title of their post
 			break;
 
+			case 'member_loans':
+				// Requires special logic
+			break;
+
+			case 'member_fines':
+				// Requires special logic
+			break;
+
+			case 'member_donated':
+				// Requires special logic
+			break;
+
+			case 'loan_loan':
+				$query->set('orderby',	'ID');
+			break;
+
 			case 'loan_status':
 				$query->set('meta_key',	'wp_lib_status');
 				$query->set('orderby',	'meta_value_num');