<?php
/**
 * Restores trashed articles to where they were.
 *
 * @package KarmaDocs
 */

namespace KarmaDocs;

defined( 'ABSPATH' ) || exit;

/**
 * When an article is trashed its tree position is saved (parent article, category,
 * knowledge base, order and the nested articles that moved up a level). Restoring
 * puts it back in the same place, with its previous status, and re-nests the
 * articles that were under it, as long as nobody moved them in the meantime.
 */
class Trash {

	/**
	 * Post meta holding the position at trash time.
	 */
	const META = '_kdocs_trash_position';

	/**
	 * Hooks.
	 */
	public function register() {
		add_action( 'wp_trash_post', array( $this, 'on_trash' ) );
		add_action( 'untrashed_post', array( $this, 'on_untrash' ) );
		add_filter( 'wp_untrash_post_status', array( $this, 'untrash_status' ), 10, 3 );
	}

	/**
	 * Saves an article's position before it is trashed.
	 *
	 * @param \WP_Post $post     Article.
	 * @param int[]    $children Nested articles that are about to move up a level.
	 */
	public static function remember( $post, array $children = array() ) {
		$category = Taxonomies::article_category( $post );
		$kb       = Taxonomies::article_kb( $post );
		update_post_meta(
			$post->ID,
			self::META,
			array(
				'parent'   => (int) $post->post_parent,
				'category' => $category ? (int) $category->term_id : 0,
				'kb'       => $kb ? (int) $kb->term_id : 0,
				'order'    => (int) $post->menu_order,
				'children' => $children,
			)
		);
	}

	/**
	 * Trashed from anywhere (the WordPress editor included).
	 *
	 * @param int $post_id Post.
	 */
	public function on_trash( $post_id ) {
		$post = get_post( $post_id );
		// The builder already saved the position together with the nested articles.
		if ( $post && PostTypes::ARTICLE === $post->post_type && ! metadata_exists( 'post', $post_id, self::META ) ) {
			self::remember( $post );
		}
	}

	/**
	 * WordPress restores trashed posts as drafts; docs return to their previous status.
	 *
	 * @param string $status          Status WordPress will use.
	 * @param int    $post_id         Post.
	 * @param string $previous_status Status before trashing.
	 * @return string
	 */
	public function untrash_status( $status, $post_id, $previous_status ) {
		if ( PostTypes::ARTICLE === get_post_type( $post_id ) && $previous_status ) {
			return $previous_status;
		}
		return $status;
	}

	/**
	 * Puts a restored article back in its old position.
	 *
	 * @param int $post_id Post.
	 */
	public function on_untrash( $post_id ) {
		$position = get_post_meta( $post_id, self::META, true );
		delete_post_meta( $post_id, self::META );
		if ( ! is_array( $position ) || PostTypes::ARTICLE !== get_post_type( $post_id ) ) {
			return;
		}

		$kb = $position['kb'] && term_exists( (int) $position['kb'], Taxonomies::KB ) ? (int) $position['kb'] : 0;
		if ( $kb ) {
			wp_set_object_terms( $post_id, array( $kb ), Taxonomies::KB );
		}
		$category = (int) $position['category'];
		if ( $category && term_exists( $category, Taxonomies::CATEGORY ) && ( ! $kb || Taxonomies::category_kb( $category ) === $kb ) ) {
			wp_set_object_terms( $post_id, array( $category ), Taxonomies::CATEGORY );
		}

		// The old parent article must still be live and in the same knowledge base.
		$parent    = (int) $position['parent'];
		$parent_kb = $parent ? Taxonomies::article_kb( $parent ) : null;
		if ( ! $parent || ! in_array( get_post_status( $parent ), array( 'publish', 'draft', 'pending', 'private', 'future' ), true ) || ! $parent_kb || (int) $parent_kb->term_id !== $kb ) {
			$parent = 0;
		}
		wp_update_post(
			array(
				'ID'          => $post_id,
				'post_parent' => $parent,
				'menu_order'  => (int) $position['order'],
			)
		);

		// Re-nest the articles that moved up a level, unless they were moved since.
		foreach ( (array) $position['children'] as $child ) {
			$child = get_post( (int) $child );
			if ( $child && PostTypes::ARTICLE === $child->post_type && 'trash' !== $child->post_status && (int) $child->post_parent === (int) $position['parent'] ) {
				wp_update_post(
					array(
						'ID'          => $child->ID,
						'post_parent' => $post_id,
					)
				);
			}
		}
	}
}