<?php
namespace AccessNow\SimpleLMS;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

class I18n {

	const META_KEY         = '_slms_course_language';
	const DEFAULT_LANGUAGE = 'en_AU';

	private static $current_language = '';
	private static $switched         = false;

	public static function init() {
		add_action( 'template_redirect', array( __CLASS__, 'detect_and_switch_locale' ), 5 );
		add_action( 'pre_get_posts', array( __CLASS__, 'filter_courses_by_language' ) );
		add_action( 'wp_footer', array( __CLASS__, 'restore_locale' ), 999 );
	}

	public static function get_supported_languages() {
		return array(
			'en_AU' => array(
				'label' => 'English',
				'badge' => 'EN',
			),
			'ja'    => array(
				'label' => '日本語',
				'badge' => 'JA',
			),
		);
	}

	public static function detect_and_switch_locale() {
		if ( is_admin() ) {
			return;
		}

		$post_type = get_post_type();
		if ( ! in_array( $post_type, array( 'slms_course', 'slms_lesson', 'slms_quiz' ), true ) ) {
			return;
		}

		$post_id   = get_the_ID();
		$course_id = Access_Control::get_course_id_from_content( $post_id, $post_type );
		if ( ! $course_id ) {
			return;
		}

		$language               = self::get_course_language( $course_id );
		self::$current_language = $language;

		// The course's language pack from translate.wordpress.org, when the site has it installed;
		// otherwise the page stays in the site's language.
		$mo_file = WP_LANG_DIR . '/plugins/accessnow-lms-' . $language . '.mo';
		if ( self::DEFAULT_LANGUAGE !== $language && ( is_readable( $mo_file ) || is_readable( substr( $mo_file, 0, -3 ) . '.l10n.php' ) ) ) {
			unload_textdomain( 'accessnow-lms', true );
			if ( load_textdomain( 'accessnow-lms', $mo_file ) ) {
				self::$switched = true;
			}
		}
	}

	public static function restore_locale() {
		if ( self::$switched ) {
			// Reloadable, so the site language's translations load again just in time.
			unload_textdomain( 'accessnow-lms', true );
			self::$switched = false;
		}
	}

	public static function filter_courses_by_language( $query ) {
		if ( is_admin() || ! $query->is_main_query() ) {
			return;
		}

		if ( ! $query->is_post_type_archive( 'slms_course' ) ) {
			return;
		}

		$lang = self::get_requested_language();
		if ( $lang ) {
			$existing   = $query->get( 'meta_query' ) ?: array();
			$existing[] = array(
				'key'   => self::META_KEY,
				'value' => $lang,
			);
			$query->set( 'meta_query', $existing );
		}
	}

	public static function get_requested_language() {
		// Read-only catalogue filter from a public link: no nonce needed.
		if ( ! isset( $_GET['lang'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
			return '';
		}
		$lang = sanitize_text_field( wp_unslash( $_GET['lang'] ) ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended
		return isset( self::get_supported_languages()[ $lang ] ) ? $lang : '';
	}

	/**
	 * The languages the site's published courses are in, in the supported-languages order. The
	 * catalogue's language filter only appears when there are two or more.
	 *
	 * @return string[] Language codes.
	 */
	public static function languages_in_use() {
		$used = array();
		foreach ( get_posts( array( 'post_type' => 'slms_course', 'post_status' => 'publish', 'posts_per_page' => -1, 'fields' => 'ids' ) ) as $course_id ) {
			$used[ self::get_course_language( $course_id ) ] = true;
		}
		$codes = array_values( array_filter( array_keys( self::get_supported_languages() ), function ( $code ) use ( $used ) {
			return isset( $used[ $code ] );
		} ) );
		/**
		 * The languages offered by the catalogue's language filter (shown when there are two or more).
		 *
		 * @param string[] $codes Language codes in use by published courses.
		 */
		return (array) apply_filters( 'accessnow_slms_catalogue_languages', $codes );
	}

	public static function get_course_language( $course_id ) {
		return Course_Meta::get( $course_id, self::META_KEY, self::DEFAULT_LANGUAGE );
	}

	public static function get_current_language() {
		return self::$current_language ?: self::DEFAULT_LANGUAGE;
	}
}