<?php

class WPML_Sync_Custom_Fields {

	/** @var WPML_Translation_Element_Factory $element_factory */
	private $element_factory;

	/** @var array $fields_to_sync */
	private $fields_to_sync;

	/**
	 * WPML_Sync_Custom_Fields constructor.
	 *
	 * @param WPML_Translation_Element_Factory $element_factory
	 * @param array                            $fields_to_sync
	 */
	public function __construct( WPML_Translation_Element_Factory $element_factory, array $fields_to_sync ) {
		$this->element_factory = $element_factory;
		$this->fields_to_sync  = $fields_to_sync;
	}

	/**
	 * @param int    $post_id_from
	 * @param string $meta_key
	 */
	public function sync_to_translations( $post_id_from, $meta_key ) {
		if ( in_array( $meta_key, $this->fields_to_sync, true ) ) {
			$post_element = $this->element_factory->create( $post_id_from, 'post' );
			$translations = $post_element->get_translations();

			foreach ( $translations as $translation ) {
				$translation_id = $translation->get_element_id();
				if ( $translation_id !== $post_id_from ) {
					$this->sync_custom_field( $post_id_from, $translation_id, $meta_key );
				}
			}
		}
	}

	/**
	 * @param int $post_id_from
	 */
	public function sync_all_custom_fields( $post_id_from ) {
		foreach ( $this->fields_to_sync as $meta_key ) {
			$this->sync_to_translations( $post_id_from, $meta_key );
		}
	}

	/**
	 * @param int    $post_id_from
	 * @param int    $post_id_to
	 * @param string $meta_key
	 */
	public function sync_custom_field( $post_id_from, $post_id_to, $meta_key ) {
		$custom_fields_from = get_post_meta( $post_id_from );
		$custom_fields_to   = get_post_meta( $post_id_to );

		$values_from = isset( $custom_fields_from[ $meta_key ] ) ? $custom_fields_from[ $meta_key ] : [];
		$values_to   = isset( $custom_fields_to[ $meta_key ] ) ? $custom_fields_to[ $meta_key ] : [];

		$removed = array_diff( $values_to, $values_from );
		foreach ( $removed as $v ) {
			delete_post_meta( $post_id_to, $meta_key, maybe_unserialize( $v ) );
		}

		$added = array_diff( $values_from, $values_to );
		foreach ( $added as $v ) {
			$copied_value = maybe_unserialize( $v );

			/**
			 * Filters the $copied_value of $meta_key which will be copied from $post_id_from to $post_id_to
			 *
			 * @param mixed  $copied_value The unserialized and slashed value.
			 * @param int    $post_id_from The ID of the source post.
			 * @param int    $post_id_to   The ID of the destination post.
			 * @param string $meta_key     The key of the post meta being copied.
			 *
			 * @since 4.3.0
			 */
			$copied_value = apply_filters( 'wpml_sync_custom_field_copied_value', $copied_value, $post_id_from, $post_id_to, $meta_key );

			$copied_value = wp_slash( $copied_value );
			add_post_meta( $post_id_to, $meta_key, $copied_value );
		}

		do_action( 'wpml_after_copy_custom_field', $post_id_from, $post_id_to, $meta_key );
	}

}