Proof of Concept for per-post roles and capabilities

poc.php

<?php

/**
 * Proof of concept for per-post roles and capabilities
 *
 * The meta is stored for a page under _post_capabilities postmeta as an array having ->
 *      [<user_id>] => array(
 *          'user_id' => ID of the user
 *          'role' => <name of the role>
 *          'capabilities' => (array) <list of custom capabilities an admin might want to assign>
 *      )
 *
 * @author Shitiz "Dragooon" Garg <mail@dragooon.net>
 */

/**
 * Plugin Name: Dragooon's Proof of Concept
 * Description: POC for per-post roles and capabilities
 * Author:      Shitiz Garg (Dragooon)
 * Author URI:  http://smf-media.cmm
 * Version:     0.0.1
 * Text Domain: poc
 * Domain Path: /languages/
 */

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

$postmeta = array(
    2 => array(
        'user_id' => 2,
        'role' => 'bbp_moderator',
        'capabilities' => array(),
    ),
);
//var_dump(serialize($postmeta));

/**
 * @todo: make sure that $args[2] is actually a post and not an user or something
 * @todo: Allow hierarchical permissions, so that we can assign a permission to a forum and carry it over to topics and replies
 *
 * @param array $allcaps Current user's capabilities
 * @param array $caps Capabilities being tested against
 * @param array $args Additional arguments passed to has_cap. Key [1] always contains the user ID
 * @return array
 */
function poc_user_has_cap ( $allcaps, $caps, $args) {
    global $post, $wp_roles;

    if ( empty( $args[2] ) && is_null( $post ) )
        return $allcaps;

    $check_post = empty( $args[2] ) ? $post : get_post( $args[2] );

    if ( empty( $check_post ) ) {
        return $allcaps;
    }

    $postmeta = get_post_meta($check_post->ID, '_post_capabilities');

    if ( empty( $postmeta ) || empty( $postmeta[0][$args[1]] ) ) {
        return $allcaps;
    }

    $usercaps = $postmeta[0][$args[1]];
    $allcaps = array_merge( $allcaps, !empty( $usercaps['capabilities'] ) ? $usercaps['capabilities'] : array() );

    if ( !empty( $usercaps['role'] ) ) {
        $role = $wp_roles->get_role( $usercaps['role'] );

        if ( empty( $role ) ) {
            return $allcaps;
        }

        $allcaps = array_merge( $allcaps, $role->capabilities );
    }

    return $allcaps;
}