class BBP_Walker_Reply extends Walker {

	/**
	 * @see Walker::$tree_type
	 *
	 * @since 2.4.0 bbPress (r4944)
	 *
	 * @var string
	 */
	public $tree_type = 'reply';

	/**
	 * @see Walker::$db_fields
	 *
	 * @since 2.4.0 bbPress (r4944)
	 *
	 * @var array
	 */
	public $db_fields = array(
		'parent' => 'reply_to',
		'id'     => 'ID'
	);

	/**
	 * Confirm the tree_type
	 *
	 * @since 2.6.0 bbPress (r5389)
	 */
	public function __construct() {
		$this->tree_type = bbp_get_reply_post_type();
	}

	/**
	 * @see Walker::start_lvl()
	 *
	 * @since 2.4.0 bbPress (r4944)
	 *
	 * @param string $output Passed by reference. Used to append additional content
	 * @param int $depth Depth of reply
	 * @param array $args Uses 'style' argument for type of HTML list
	 */
	public function start_lvl( &$output = '', $depth = 0, $args = array() ) {
		bbpress()->reply_query->reply_depth = (int) $depth + 1;

		switch ( $args['style'] ) {
			case 'div':
				break;
			case 'ol':
				$output .= "<ol class='bbp-threaded-replies'>\n";
				break;
			case 'ul':
			default:
				$output .= "<ul class='bbp-threaded-replies'>\n";
				break;
		}
	}

	/**
	 * @see Walker::end_lvl()
	 *
	 * @since 2.4.0 bbPress (r4944)
	 *
	 * @param string $output Passed by reference. Used to append additional content
	 * @param int $depth Depth of reply
	 * @param array $args Will only append content if style argument value is 'ol' or 'ul'
	 */
	public function end_lvl( &$output = '', $depth = 0, $args = array() ) {
		bbpress()->reply_query->reply_depth = (int) $depth + 1;

		switch ( $args['style'] ) {
			case 'div':
				break;
			case 'ol':
				$output .= "</ol>\n";
				break;
			case 'ul':
			default:
				$output .= "</ul>\n";
				break;
		}
	}

	/**
	 * @since 2.4.0 bbPress (r4944)
	 */
	public function display_element( $element = false, &$children_elements = array(), $max_depth = 0, $depth = 0, $args = array(), &$output = '' ) {

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

		// Get element's id
		$id_field = $this->db_fields['id'];
		$id       = $element->$id_field;

		// Display element
		parent::display_element( $element, $children_elements, $max_depth, $depth, $args, $output );

		// If we're at the max depth and the current element still has children, loop over those
		// and display them at this level to prevent them being orphaned to the end of the list.
		if ( ( $max_depth <= (int) $depth + 1 ) && isset( $children_elements[ $id ] ) ) {
			foreach ( $children_elements[ $id ] as $child ) {
				$this->display_element( $child, $children_elements, $max_depth, $depth, $args, $output );
			}
			unset( $children_elements[ $id ] );
		}
	}

	/**
	 * @see Walker:start_el()
	 *
	 * @since 2.4.0 bbPress (r4944)
	 */
	public function start_el( &$output, $object, $depth = 0, $args = array(), $current_object_id = 0 ) {

		// Set up reply
		$depth++;
		bbpress()->reply_query->reply_depth = (int) $depth;
		bbpress()->reply_query->post        = $object;
		bbpress()->current_reply_id         = $object->ID;

		// Check for a callback and use it if specified
		if ( ! empty( $args['callback'] ) ) {
			ob_start();
			call_user_func( $args['callback'], $object, $args, $depth );
			$output .= ob_get_clean();
			return;
		}

		// Style for div or list element
		if ( ! empty( $args['style'] ) && ( 'div' === $args['style'] ) ) {
			$output .= "<div>\n";
		} else {
			$output .= "<li>\n";
		}

		$output .= bbp_buffer_template_part( 'loop', 'single-reply', false );
	}

	/**
	 * @since 2.4.0 bbPress (r4944)
	 */
	public function end_el( &$output = '', $object = false, $depth = 0, $args = array() ) {

		// Check for a callback and use it if specified
		if ( ! empty( $args['end-callback'] ) ) {
			ob_start();
			call_user_func( $args['end-callback'], $object, $args, $depth );
			$output .= ob_get_clean();
			return;
		}

		// Style for div or list element
		if ( ! empty( $args['style'] ) && ( 'div' === $args['style'] ) ) {
			$output .= "</div>\n";
		} else {
			$output .= "</li>\n";
		}
	}
}