function bbp_untrash_forum_topics( $forum_id = 0 ) {

	// Validate forum ID
	$forum_id = bbp_get_forum_id( $forum_id );

	if ( empty( $forum_id ) ) {
		return;
	}

	// Get the topics that were not previously trashed
	$pre_trashed_topics = get_post_meta( $forum_id, '_bbp_pre_trashed_topics', true );

	// There are topics to untrash
	if ( ! empty( $pre_trashed_topics ) ) {

		// Maybe reverse the trashed topics array
		if ( is_array( $pre_trashed_topics ) ) {
			$pre_trashed_topics = array_reverse( $pre_trashed_topics );
		}

		// Loop through topics
		foreach ( (array) $pre_trashed_topics as $topic ) {
			wp_untrash_post( $topic );
		}
	}
}