<?php
/**
 * Structure version of each knowledge base.
 *
 * @package KarmaDocs
 */

namespace KarmaDocs;

defined( 'ABSPATH' ) || exit;

/**
 * A counter per knowledge base that changes whenever its structure changes
 * (articles or categories added, removed, moved or reordered).
 *
 * The builder sends the version it loaded with every save. A different version
 * means another editor changed the structure in the meantime, and the save is
 * refused with a 409 instead of silently overwriting their work.
 *
 * Content edits (title, body) don't change the version: they can't conflict with
 * a move.
 */
class TreeVersion {

	/**
	 * Term meta key on the KB.
	 */
	const META = 'kdocs_tree_version';

	/**
	 * Hooks.
	 */
	public function register() {
		add_action( 'set_object_terms', array( $this, 'on_set_terms' ), 10, 6 );
		add_action( 'post_updated', array( $this, 'on_post_updated' ), 10, 3 );
		add_action( 'wp_trash_post', array( $this, 'on_post' ) );
		add_action( 'untrashed_post', array( $this, 'on_post' ) );
		add_action( 'before_delete_post', array( $this, 'on_post' ) );
		add_action( 'created_' . Taxonomies::CATEGORY, array( $this, 'on_category' ) );
		add_action( 'edited_' . Taxonomies::CATEGORY, array( $this, 'on_category' ) );
		add_action( 'pre_delete_term', array( $this, 'on_delete_term' ), 10, 2 );
		add_action( 'added_term_meta', array( $this, 'on_term_meta' ), 10, 4 );
		add_action( 'updated_term_meta', array( $this, 'on_term_meta' ), 10, 4 );
		add_action( 'kdocs_tree_saved', array( __CLASS__, 'bump' ) );
	}

	/**
	 * Current version.
	 *
	 * @param int $kb_id KB.
	 * @return int
	 */
	public static function get( $kb_id ) {
		return (int) get_term_meta( (int) $kb_id, self::META, true );
	}

	/**
	 * Marks a knowledge base structure as changed.
	 *
	 * @param int $kb_id KB.
	 */
	public static function bump( $kb_id ) {
		$kb_id = (int) $kb_id;
		if ( $kb_id > 0 ) {
			update_term_meta( $kb_id, self::META, self::get( $kb_id ) + 1 );
		}
	}

	/**
	 * Refuses a save based on a stale version.
	 *
	 * @param int      $kb_id    KB.
	 * @param int|null $expected Version the client loaded (null = not sent, skip check).
	 * @return true|\WP_Error
	 */
	public static function check( $kb_id, $expected ) {
		if ( null === $expected || self::get( $kb_id ) === (int) $expected ) {
			return true;
		}
		return new \WP_Error(
			'kdocs_tree_conflict',
			__( 'Someone else changed this knowledge base while you were editing. Reload to see their changes.', 'karma-docs' ),
			array(
				'status'  => 409,
				'version' => self::get( $kb_id ),
			)
		);
	}

	/**
	 * Article KB / category assignments (new articles, moves between categories and KBs).
	 *
	 * @param int    $object_id  Object.
	 * @param array  $terms      Terms.
	 * @param array  $tt_ids     New term taxonomy ids.
	 * @param string $taxonomy   Taxonomy.
	 * @param bool   $append     Append.
	 * @param array  $old_tt_ids Previous term taxonomy ids.
	 */
	public function on_set_terms( $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids ) {
		if ( ! in_array( $taxonomy, array( Taxonomies::KB, Taxonomies::CATEGORY ), true ) ) {
			return;
		}
		sort( $tt_ids );
		sort( $old_tt_ids );
		if ( array_map( 'intval', $tt_ids ) === array_map( 'intval', $old_tt_ids ) ) {
			return;
		}
		if ( Taxonomies::KB === $taxonomy ) {
			foreach ( array_unique( array_merge( $tt_ids, $old_tt_ids ) ) as $tt_id ) {
				$term = get_term_by( 'term_taxonomy_id', (int) $tt_id, Taxonomies::KB );
				if ( $term ) {
					self::bump( $term->term_id );
				}
			}
			return;
		}
		$kb = Taxonomies::article_kb( $object_id );
		if ( $kb ) {
			self::bump( $kb->term_id );
		}
	}

	/**
	 * Parent or order changed in the editor.
	 *
	 * @param int      $post_id Post.
	 * @param \WP_Post $after   After.
	 * @param \WP_Post $before  Before.
	 */
	public function on_post_updated( $post_id, $after, $before ) {
		if ( PostTypes::ARTICLE !== $after->post_type ) {
			return;
		}
		if ( (int) $after->post_parent !== (int) $before->post_parent || (int) $after->menu_order !== (int) $before->menu_order ) {
			$this->on_post( $post_id );
		}
	}

	/**
	 * Article trashed, restored or deleted.
	 *
	 * @param int $post_id Post.
	 */
	public function on_post( $post_id ) {
		if ( PostTypes::ARTICLE !== get_post_type( $post_id ) ) {
			return;
		}
		$kb = Taxonomies::article_kb( $post_id );
		if ( $kb ) {
			self::bump( $kb->term_id );
		}
	}

	/**
	 * Category created or edited (name, parent).
	 *
	 * @param int $term_id Term.
	 */
	public function on_category( $term_id ) {
		self::bump( Taxonomies::category_kb( $term_id ) );
	}

	/**
	 * Category assigned to a knowledge base (new categories get it right after creation).
	 *
	 * @param int    $meta_id    Meta id.
	 * @param int    $term_id    Term.
	 * @param string $meta_key   Key.
	 * @param mixed  $meta_value Value.
	 */
	public function on_term_meta( $meta_id, $term_id, $meta_key, $meta_value ) {
		if ( 'kdocs_kb' === $meta_key ) {
			self::bump( (int) $meta_value );
		}
	}

	/**
	 * Category about to be deleted (its KB meta is still readable).
	 *
	 * @param int    $term_id  Term.
	 * @param string $taxonomy Taxonomy.
	 */
	public function on_delete_term( $term_id, $taxonomy ) {
		if ( Taxonomies::CATEGORY === $taxonomy ) {
			self::bump( Taxonomies::category_kb( $term_id ) );
		}
	}
}