Proof of Concept for bbPress' per forum moderation

poc.php

<?php

/**
 * Proof of concept for per-forum moderation
 *
 * Place this under wp-content/plugins/poc, activate it via Plugins section of WP Admin
 * Add a row in postmeta table having the post_id of the forum you want to assign the moderator(s) to,
 * meta_key as "_bbp_forum_moderators" and a comma separated list of the user's IDs you want
 * to make moderators for the said forum
 *
 * @author Shitiz "Dragooon" Garg <mail@dragooon.net>
 */

/**
 * Plugin Name: Dragooon's Proof of Concept
 * Description: POC for bbp's per-forum moderation
 * Author:      Shitiz Garg (Dragooon)
 * Author URI:  http://bbpress.org
 * Version:     0.0.1
 * Text Domain: poc
 * Domain Path: /languages/
 */

add_filter( 'user_has_cap', 'poc_user_has_cap', 99, 3 );

/**
 * Very crude proof of concept, grants the moderator role's capabilities
 * to the specified user (see header for instructions)
 * 
 * @todo: Take care of sub-forums
 * @todo: Features?
 *
 * @param array $allcaps Current user's capabilities
 * @param array $caps Capabilities being tested against
 * @param array $args Additional arguments passed to has_cap
 * @return array
 */
function poc_user_has_cap ( $allcaps, $caps, $args ) {
    if ( empty( $args[2] ) )
        return $allcaps;

    $is_forum_check = false;
    foreach ( $caps as $cap) {
        if ( in_array( $cap, array( 'moderate', 'spectate', 'participate' ))
                || strpos( $cap, 'forum') > -1 || strpos( $cap, 'topic' ) > -1 ) {
            $is_forum_check = true;
        }
    }

    if ( !$is_forum_check )
        return false;

    $post = get_post( $args[2] );

    // Make sure this post is either a forum or a topic
    if ( $post->post_type != bbp_get_forum_post_type() && $post->post_type != bbp_get_topic_post_type()
            && $post->post_type != bbp_get_reply_post_type() ) {
        return $allcaps;
    }

    // Find the forum's ID
    if ( $post->post_type != bbp_get_forum_post_type() ) {
        $postmeta = get_post_meta($post->ID);
        if ( !empty( $postmeta['_bbp_forum_id'] ) ) {
            $forum_id = (int) $postmeta['_bbp_forum_id'][0];
        } else {
            return $allcaps;
        }
    } else {
        $forum_id = $post->ID;
    }

    $meta = get_post_meta( $forum_id );

    if ( empty( $meta['_bbp_forum_moderators'] ) || !in_array( $args[1], explode(',', $meta['_bbp_forum_moderators'][0]) ) ) {
        return $allcaps;
    } else {
        // This user is a moderator here, grant the additional permissions
        $allcaps = array_merge( $allcaps, bbp_get_caps_for_role( bbp_get_moderator_role() ) );
        return $allcaps;
    }
}