wpml-rest-api.php

<?php

/*
Plugin Name: WPML REST API
Version: 1.1.1
Description: Adds links to posts in other languages into the results of a WP REST API query for sites running the WPML plugin.
Author: Shawn Hooper
Author URI: https://profiles.wordpress.org/shooper
*/

namespace ShawnHooper\WPML;

class WPML_REST_API {

	public function wordpress_hooks() {
		add_action( 'rest_api_init', array($this, 'init'), 1000 );
	}

	public function init() {
		// Check if WPML is installed
		include_once( ABSPATH . 'wp-admin/includes/plugin.php' );

		if (!is_plugin_active('sitepress-multilingual-cms/sitepress.php')) {
			return;
		}

		$available_langs = wpml_get_active_languages_filter('', array('skip_missing' => false, ) );

		if ( ! empty( $available_langs ) && ! isset( $GLOBALS['icl_language_switched'] ) || ! $GLOBALS['icl_language_switched'] ) {
			if ( isset( $_REQUEST['wpml_lang'] ) ) {
				$lang = $_REQUEST['wpml_lang'];
			} else if ( isset( $_REQUEST['lang'] ) ) {
				$lang = $_REQUEST['lang'];
			}

			if ( isset( $lang ) && in_array( $lang, array_keys( $available_langs ) ) ) {
				do_action( 'wpml_switch_language', $lang );
			}
		}

		// Add WPML fields to all post types
		// Thanks to Roy Sivan for this trick.
		// http://www.roysivan.com/wp-api-v2-adding-fields-to-all-post-types/#.VsH0e5MrLcM

		$post_types = get_post_types( array( 'public' => true, 'exclude_from_search' => false ), 'names' );
		foreach( $post_types as $post_type ) {
			$this->register_api_field($post_type);
		}
	}

	public function register_api_field($post_type) {
		register_rest_field( $post_type,
			'wpml_current_locale',
			array(
				'get_callback'    => array($this, 'get_current_locale'),
				'update_callback' => null,
				'schema'          => null,
			)
		);

		register_rest_field( $post_type,
			'wpml_translations',
			array(
				'get_callback'    => array($this, 'get_translations'),
				'update_callback' => null,
				'schema'          => null,
			)
		);
	}

	/**
	 * Calculate the relative path for this post, supports also nested pages
	 *
	 * @param WP_Post $thisPost
	 * @return string the relative path for this page e.g. `root-page/child-page`
	 */
	public function calculate_rel_path(WP_Post $thisPost): string
	{
		$post_name = $thisPost->post_name;
		if ($thisPost->post_parent > 0) {
			$cur_post = get_post($thisPost->post_parent);
			if (isset($cur_post)) {
				$rel_path = $this->calculate_rel_path($cur_post);
				return $rel_path . "/" . $post_name;
			}
		}
		return $post_name;
	}

	/**
	 * Retrieve available translations
	 *
	 * @param array $object Details of current post.
	 * @param string $field_name Name of field.
	 * @param WP_REST_Request $request Current request
	 *
	 * @return mixed
	 */
	public function get_translations( $object, $field_name, $request ) {
		global $sitepress;
		$languages = apply_filters('wpml_active_languages', null);
		$translations = [];
		$show_on_front = get_option( 'show_on_front' );
		$page_on_front = get_option( 'page_on_front' );

		foreach ($languages as $language) {
			$post_id = apply_filters( 'wpml_object_id', $object['id'], 'post', false, $language['language_code'] );
			if ($post_id === null || $post_id == $object['id']) continue;
			$thisPost = get_post($post_id);

			// Only show published posts
			if ( 'publish' !== $thisPost->post_status) {
				continue;
			}

			$href = apply_filters( 'wpmlrestapi_translations_href', $language['url'], $thisPost );

			if ( 'page' == $show_on_front && $object['id'] == $page_on_front ) {
				$href = trailingslashit( $href );
			} else {
				if (strpos($href, '?') !== false) {
					$href = str_replace('?', '/' . $thisPost->post_name . '/?', $href);
				} else {
					if (substr($href, -1) !== '/') {
						$href .= '/';
					}

					$href .= $thisPost->post_name . '/';
				}
			}

			$translations[] = array('locale' => $language['default_locale'], 'id' => $thisPost->ID, 'post_title' => $thisPost->post_title, 'href' => $href);
		}

		return $translations;
	}

	/**
	 * Retrieve the current locale
	 *
	 * @param array $object Details of current post.
	 * @param string $field_name Name of field.
	 * @param WP_REST_Request $request Current request
	 *
	 * @return mixed
	 */
	public function get_current_locale( $object, $field_name, $request ) {
		$langInfo = wpml_get_language_information($object);
		if (!is_wp_error($langInfo)) {
			return $langInfo['locale'];
		}
	}
}

$GLOBALS['WPML_REST_API'] = new WPML_REST_API();
$GLOBALS['WPML_REST_API']->wordpress_hooks();