map_meta_cap( string $cap, int $user_id )

function map_meta_cap( $cap, $user_id ) {
	$args = array_slice( func_get_args(), 2 );
	$caps = array();

	switch ( $cap ) {
	case 'remove_user':
		// In multisite the user must be a super admin to remove themselves.
		if ( isset( $args[0] ) && $user_id == $args[0] && ! is_super_admin( $user_id ) ) {
			$caps[] = 'do_not_allow';
		} else {
			$caps[] = 'remove_users';
		}
		break;
	case 'promote_user':
	case 'add_users':
		$caps[] = 'promote_users';
		break;
	case 'edit_user':
	case 'edit_users':
		// Allow user to edit itself
		if ( 'edit_user' == $cap && isset( $args[0] ) && $user_id == $args[0] )
			break;

		// In multisite the user must have manage_network_users caps. If editing a super admin, the user must be a super admin.
		if ( is_multisite() && ( ( ! is_super_admin( $user_id ) && 'edit_user' === $cap && is_super_admin( $args[0] ) ) || ! user_can( $user_id, 'manage_network_users' ) ) ) {
			$caps[] = 'do_not_allow';
		} else {
			$caps[] = 'edit_users'; // edit_user maps to edit_users.
		}
		break;
	case 'delete_post':
	case 'delete_page':
		$post = get_post( $args[0] );
		if ( ! $post ) {
			$caps[] = 'do_not_allow';
			break;
		}

		if ( 'revision' == $post->post_type ) {
			$post = get_post( $post->post_parent );
			if ( ! $post ) {
				$caps[] = 'do_not_allow';
				break;
			}
		}

		if ( ( get_option( 'page_for_posts' ) == $post->ID ) || ( get_option( 'page_on_front' ) == $post->ID ) ) {
			$caps[] = 'manage_options';
			break;
		}

		$post_type = get_post_type_object( $post->post_type );
		if ( ! $post_type ) {
			/* translators: 1: post type, 2: capability name */
			_doing_it_wrong( __FUNCTION__, sprintf( __( 'The post type %1$s is not registered, so it may not be reliable to check the capability "%2$s" against a post of that type.' ), $post->post_type, $cap ), 'WP-4.4.0' );
			$caps[] = 'edit_others_posts';
			break;
		}

		if ( ! $post_type->map_meta_cap ) {
			$caps[] = $post_type->cap->$cap;
			// Prior to WP-3.1 we would re-call map_meta_cap here.
			if ( 'delete_post' == $cap )
				$cap = $post_type->cap->$cap;
			break;
		}

		// If the post author is set and the user is the author...
		if ( $post->post_author && $user_id == $post->post_author ) {
			// If the post is published or scheduled...
			if ( in_array( $post->post_status, array( 'publish', 'future' ), true ) ) {
				$caps[] = $post_type->cap->delete_published_posts;
			} elseif ( 'trash' == $post->post_status ) {
				$status = get_post_meta( $post->ID, '_wp_trash_meta_status', true );
				if ( in_array( $status, array( 'publish', 'future' ), true ) ) {
					$caps[] = $post_type->cap->delete_published_posts;
				} else {
					$caps[] = $post_type->cap->delete_posts;
				}
			} else {
				// If the post is draft...
				$caps[] = $post_type->cap->delete_posts;
			}
		} else {
			// The user is trying to edit someone else's post.
			$caps[] = $post_type->cap->delete_others_posts;
			// The post is published or scheduled, extra cap required.
			if ( in_array( $post->post_status, array( 'publish', 'future' ), true ) ) {
				$caps[] = $post_type->cap->delete_published_posts;
			} elseif ( 'private' == $post->post_status ) {
				$caps[] = $post_type->cap->delete_private_posts;
			}
		}

		/*
		 * Setting the privacy policy page requires `manage_privacy_options`,
		 * so deleting it should require that too.
		 */
		if ( (int) get_option( 'wp_page_for_privacy_policy' ) === $post->ID ) {
			$caps = array_merge( $caps, map_meta_cap( 'manage_privacy_options', $user_id ) );
		}

		break;
		// edit_post breaks down to edit_posts, edit_published_posts, or
		// edit_others_posts
	case 'edit_post':
	case 'edit_page':
		$post = get_post( $args[0] );
		if ( ! $post ) {
			$caps[] = 'do_not_allow';
			break;
		}

		if ( 'revision' == $post->post_type ) {
			$post = get_post( $post->post_parent );
			if ( ! $post ) {
				$caps[] = 'do_not_allow';
				break;
			}
		}

		$post_type = get_post_type_object( $post->post_type );
		if ( ! $post_type ) {
			/* translators: 1: post type, 2: capability name */
			_doing_it_wrong( __FUNCTION__, sprintf( __( 'The post type %1$s is not registered, so it may not be reliable to check the capability "%2$s" against a post of that type.' ), $post->post_type, $cap ), 'WP-4.4.0' );
			$caps[] = 'edit_others_posts';
			break;
		}

		if ( ! $post_type->map_meta_cap ) {
			$caps[] = $post_type->cap->$cap;
			// Prior to WP-3.1 we would re-call map_meta_cap here.
			if ( 'edit_post' == $cap )
				$cap = $post_type->cap->$cap;
			break;
		}

		// If the post author is set and the user is the author...
		if ( $post->post_author && $user_id == $post->post_author ) {
			// If the post is published or scheduled...
			if ( in_array( $post->post_status, array( 'publish', 'future' ), true ) ) {
				$caps[] = $post_type->cap->edit_published_posts;
			} elseif ( 'trash' == $post->post_status ) {
				$status = get_post_meta( $post->ID, '_wp_trash_meta_status', true );
				if ( in_array( $status, array( 'publish', 'future' ), true ) ) {
					$caps[] = $post_type->cap->edit_published_posts;
				} else {
					$caps[] = $post_type->cap->edit_posts;
				}
			} else {
				// If the post is draft...
				$caps[] = $post_type->cap->edit_posts;
			}
		} else {
			// The user is trying to edit someone else's post.
			$caps[] = $post_type->cap->edit_others_posts;
			// The post is published or scheduled, extra cap required.
			if ( in_array( $post->post_status, array( 'publish', 'future' ), true ) ) {
				$caps[] = $post_type->cap->edit_published_posts;
			} elseif ( 'private' == $post->post_status ) {
				$caps[] = $post_type->cap->edit_private_posts;
			}
		}

		/*
		 * Setting the privacy policy page requires `manage_privacy_options`,
		 * so editing it should require that too.
		 */
		if ( (int) get_option( 'wp_page_for_privacy_policy' ) === $post->ID ) {
			$caps = array_merge( $caps, map_meta_cap( 'manage_privacy_options', $user_id ) );
		}

		break;
	case 'read_post':
	case 'read_page':
		$post = get_post( $args[0] );
		if ( ! $post ) {
			$caps[] = 'do_not_allow';
			break;
		}

		if ( 'revision' == $post->post_type ) {
			$post = get_post( $post->post_parent );
			if ( ! $post ) {
				$caps[] = 'do_not_allow';
				break;
			}
		}

		$post_type = get_post_type_object( $post->post_type );
		if ( ! $post_type ) {
			/* translators: 1: post type, 2: capability name */
			_doing_it_wrong( __FUNCTION__, sprintf( __( 'The post type %1$s is not registered, so it may not be reliable to check the capability "%2$s" against a post of that type.' ), $post->post_type, $cap ), 'WP-4.4.0' );
			$caps[] = 'edit_others_posts';
			break;
		}

		if ( ! $post_type->map_meta_cap ) {
			$caps[] = $post_type->cap->$cap;
			// Prior to WP-3.1 we would re-call map_meta_cap here.
			if ( 'read_post' == $cap )
				$cap = $post_type->cap->$cap;
			break;
		}

		$status_obj = get_post_status_object( $post->post_status );
		if ( $status_obj->public ) {
			$caps[] = $post_type->cap->read;
			break;
		}

		if ( $post->post_author && $user_id == $post->post_author ) {
			$caps[] = $post_type->cap->read;
		} elseif ( $status_obj->private ) {
			$caps[] = $post_type->cap->read_private_posts;
		} else {
			$caps = map_meta_cap( 'edit_post', $user_id, $post->ID );
		}
		break;
	case 'publish_post':
		$post = get_post( $args[0] );
		if ( ! $post ) {
			$caps[] = 'do_not_allow';
			break;
		}

		$post_type = get_post_type_object( $post->post_type );
		if ( ! $post_type ) {
			/* translators: 1: post type, 2: capability name */
			_doing_it_wrong( __FUNCTION__, sprintf( __( 'The post type %1$s is not registered, so it may not be reliable to check the capability "%2$s" against a post of that type.' ), $post->post_type, $cap ), 'WP-4.4.0' );
			$caps[] = 'edit_others_posts';
			break;
		}

		$caps[] = $post_type->cap->publish_posts;
		break;
	case 'edit_post_meta':
	case 'delete_post_meta':
	case 'add_post_meta':
	case 'edit_comment_meta':
	case 'delete_comment_meta':
	case 'add_comment_meta':
	case 'edit_term_meta':
	case 'delete_term_meta':
	case 'add_term_meta':
	case 'edit_user_meta':
	case 'delete_user_meta':
	case 'add_user_meta':
		list( $_, $object_type, $_ ) = explode( '_', $cap );
		$object_id = (int) $args[0];
		$object_subtype = get_object_subtype( $object_type, $object_id );

		if ( empty( $object_subtype ) ) {
			$caps[] = 'do_not_allow';
			break;
		}

		$caps = map_meta_cap( "edit_{$object_type}", $user_id, $object_id );

		$meta_key = isset( $args[1] ) ? $args[1] : false;

		if ( $meta_key ) {
			$allowed = ! is_protected_meta( $meta_key, $object_type );

			if ( ! empty( $object_subtype ) && has_filter( "auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}" ) ) {

				/**
				 * Filters whether the user is allowed to edit a specific meta key of a specific object type and subtype.
				 *
				 * The dynamic portions of the hook name, `$object_type`, `$meta_key`,
				 * and `$object_subtype`, refer to the metadata object type (comment, post, term or user),
				 * the meta key value, and the object subtype respectively.
				 *
				 * @since WP-4.9.8
				 *
				 * @param bool     $allowed   Whether the user can add the object meta. Default false.
				 * @param string   $meta_key  The meta key.
				 * @param int      $object_id Object ID.
				 * @param int      $user_id   User ID.
				 * @param string   $cap       Capability name.
				 * @param string[] $caps      Array of the user's capabilities.
				 */
				$allowed = apply_filters( "auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $allowed, $meta_key, $object_id, $user_id, $cap, $caps );
			} else {

				/**
				 * Filters whether the user is allowed to edit a specific meta key of a specific object type.
				 *
				 * Return true to have the mapped meta caps from `edit_{$object_type}` apply.
				 *
				 * The dynamic portion of the hook name, `$object_type` refers to the object type being filtered.
				 * The dynamic portion of the hook name, `$meta_key`, refers to the meta key passed to map_meta_cap().
				 *
				 * @since WP-3.3.0 As `auth_post_meta_{$meta_key}`.
				 * @since WP-4.6.0
				 *
				 * @param bool     $allowed   Whether the user can add the object meta. Default false.
				 * @param string   $meta_key  The meta key.
				 * @param int      $object_id Object ID.
				 * @param int      $user_id   User ID.
				 * @param string   $cap       Capability name.
				 * @param string[] $caps      Array of the user's capabilities.
				 */
				$allowed = apply_filters( "auth_{$object_type}_meta_{$meta_key}", $allowed, $meta_key, $object_id, $user_id, $cap, $caps );
			}

			if ( ! empty( $object_subtype ) ) {

				/**
				 * Filters whether the user is allowed to edit meta for specific object types/subtypes.
				 *
				 * Return true to have the mapped meta caps from `edit_{$object_type}` apply.
				 *
				 * The dynamic portion of the hook name, `$object_type` refers to the object type being filtered.
				 * The dynamic portion of the hook name, `$object_subtype` refers to the object subtype being filtered.
				 * The dynamic portion of the hook name, `$meta_key`, refers to the meta key passed to map_meta_cap().
				 *
				 * @since WP-4.6.0 As `auth_post_{$post_type}_meta_{$meta_key}`.
				 * @since WP-4.7.0
				 * @deprecated WP-4.9.8 Use `auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}`
				 *
				 * @param bool     $allowed   Whether the user can add the object meta. Default false.
				 * @param string   $meta_key  The meta key.
				 * @param int      $object_id Object ID.
				 * @param int      $user_id   User ID.
				 * @param string   $cap       Capability name.
				 * @param string[] $caps      Array of the user's capabilities.
				 */
				$allowed = apply_filters_deprecated( "auth_{$object_type}_{$object_subtype}_meta_{$meta_key}", array( $allowed, $meta_key, $object_id, $user_id, $cap, $caps ), 'WP-4.9.8', "auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}" );
			}

			if ( ! $allowed ) {
				$caps[] = $cap;
			}
		}
		break;
	case 'edit_comment':
		$comment = get_comment( $args[0] );
		if ( ! $comment ) {
			$caps[] = 'do_not_allow';
			break;
		}

		$post = get_post( $comment->comment_post_ID );

		/*
		 * If the post doesn't exist, we have an orphaned comment.
		 * Fall back to the edit_posts capability, instead.
		 */
		if ( $post ) {
			$caps = map_meta_cap( 'edit_post', $user_id, $post->ID );
		} else {
			$caps = map_meta_cap( 'edit_posts', $user_id );
		}
		break;
	case 'unfiltered_upload':
		if ( defined('ALLOW_UNFILTERED_UPLOADS') && ALLOW_UNFILTERED_UPLOADS && ( !is_multisite() || is_super_admin( $user_id ) )  )
			$caps[] = $cap;
		else
			$caps[] = 'do_not_allow';
		break;
	case 'edit_css' :
	case 'unfiltered_html' :
		// Disallow unfiltered_html for all users, even admins and super admins.
		if ( defined( 'DISALLOW_UNFILTERED_HTML' ) && DISALLOW_UNFILTERED_HTML )
			$caps[] = 'do_not_allow';
		elseif ( is_multisite() && ! is_super_admin( $user_id ) )
			$caps[] = 'do_not_allow';
		else
			$caps[] = 'unfiltered_html';
		break;
	case 'edit_files':
	case 'edit_plugins':
	case 'edit_themes':
		// Disallow the file editors.
		if ( defined( 'DISALLOW_FILE_EDIT' ) && DISALLOW_FILE_EDIT )
			$caps[] = 'do_not_allow';
		elseif ( ! wp_is_file_mod_allowed( 'capability_edit_themes' ) )
			$caps[] = 'do_not_allow';
		elseif ( is_multisite() && ! is_super_admin( $user_id ) )
			$caps[] = 'do_not_allow';
		else
			$caps[] = $cap;
		break;
	case 'update_plugins':
	case 'delete_plugins':
	case 'install_plugins':
	case 'upload_plugins':
	case 'update_themes':
	case 'delete_themes':
	case 'install_themes':
	case 'upload_themes':
	case 'update_core':
		// Disallow anything that creates, deletes, or updates core, plugin, or theme files.
		// Files in uploads are excepted.
		if ( ! wp_is_file_mod_allowed( 'capability_update_core' ) ) {
			$caps[] = 'do_not_allow';
		} elseif ( is_multisite() && ! is_super_admin( $user_id ) ) {
			$caps[] = 'do_not_allow';
		} elseif ( 'upload_themes' === $cap ) {
			$caps[] = 'install_themes';
		} elseif ( 'upload_plugins' === $cap ) {
			$caps[] = 'install_plugins';
		} else {
			$caps[] = $cap;
		}
		break;
	case 'install_languages':
	case 'update_languages':
		if ( ! wp_is_file_mod_allowed( 'can_install_language_pack' ) ) {
			$caps[] = 'do_not_allow';
		} elseif ( is_multisite() && ! is_super_admin( $user_id ) ) {
			$caps[] = 'do_not_allow';
		} else {
			$caps[] = 'install_languages';
		}
		break;
	case 'activate_plugins':
	case 'deactivate_plugins':
	case 'activate_plugin':
	case 'deactivate_plugin':
		$caps[] = 'activate_plugins';
		if ( is_multisite() ) {
			// update_, install_, and delete_ are handled above with is_super_admin().
			$menu_perms = get_site_option( 'menu_items', array() );
			if ( empty( $menu_perms['plugins'] ) )
				$caps[] = 'manage_network_plugins';
		}
		break;
	case 'delete_user':
	case 'delete_users':
		// If multisite only super admins can delete users.
		if ( is_multisite() && ! is_super_admin( $user_id ) )
			$caps[] = 'do_not_allow';
		else
			$caps[] = 'delete_users'; // delete_user maps to delete_users.
		break;
	case 'create_users':
		if ( !is_multisite() )
			$caps[] = $cap;
		elseif ( is_super_admin( $user_id ) || get_site_option( 'add_new_users' ) )
			$caps[] = $cap;
		else
			$caps[] = 'do_not_allow';
		break;
	case 'manage_links' :
		if ( get_option( 'link_manager_enabled' ) )
			$caps[] = $cap;
		else
			$caps[] = 'do_not_allow';
		break;
	case 'customize' :
		$caps[] = 'edit_theme_options';
		break;
	case 'delete_site':
		if ( is_multisite() ) {
			$caps[] = 'manage_options';
		} else {
			$caps[] = 'do_not_allow';
		}
		break;
	case 'edit_term':
	case 'delete_term':
	case 'assign_term':
		$term_id = (int) $args[0];
		$term = get_term( $term_id );
		if ( ! $term || is_wp_error( $term ) ) {
			$caps[] = 'do_not_allow';
			break;
		}

		$tax = get_taxonomy( $term->taxonomy );
		if ( ! $tax ) {
			$caps[] = 'do_not_allow';
			break;
		}

		if ( 'delete_term' === $cap && ( $term->term_id == get_option( 'default_' . $term->taxonomy ) ) ) {
			$caps[] = 'do_not_allow';
			break;
		}

		$taxo_cap = $cap . 's';

		$caps = map_meta_cap( $tax->cap->$taxo_cap, $user_id, $term_id );

		break;
	case 'manage_post_tags':
	case 'edit_categories':
	case 'edit_post_tags':
	case 'delete_categories':
	case 'delete_post_tags':
		$caps[] = 'manage_categories';
		break;
	case 'assign_categories':
	case 'assign_post_tags':
		$caps[] = 'edit_posts';
		break;
	case 'create_sites':
	case 'delete_sites':
	case 'manage_network':
	case 'manage_sites':
	case 'manage_network_users':
	case 'manage_network_plugins':
	case 'manage_network_themes':
	case 'manage_network_options':
	case 'upgrade_network':
		$caps[] = $cap;
		break;
	case 'setup_network':
		if ( is_multisite() ) {
			$caps[] = 'manage_network_options';
		} else {
			$caps[] = 'manage_options';
		}
		break;
	case 'export_others_personal_data':
	case 'erase_others_personal_data':
	case 'manage_privacy_options':
		$caps[] = is_multisite() ? 'manage_network' : 'manage_options';
		break;
	default:
		// Handle meta capabilities for custom post types.
		global $post_type_meta_caps;
		if ( isset( $post_type_meta_caps[ $cap ] ) ) {
			$args = array_merge( array( $post_type_meta_caps[ $cap ], $user_id ), $args );
			return call_user_func_array( 'map_meta_cap', $args );
		}

		// If no meta caps match, return the original cap.
		$caps[] = $cap;
	}

	/**
	 * Filters a user's capabilities depending on specific context and/or privilege.
	 *
	 * @since WP-2.8.0
	 *
	 * @param array  $caps    Returns the user's actual capabilities.
	 * @param string $cap     Capability name.
	 * @param int    $user_id The user ID.
	 * @param array  $args    Adds the context to the cap. Typically the object ID.
	 */
	return apply_filters( 'map_meta_cap', $caps, $cap, $user_id, $args );
}