TranslationsPress_Updater.php

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<?php
/**
 * @license GPL-2.0-or-later
 *
 * Modified by gravityview on 13-January-2023 using Strauss.
 * @see https://github.com/BrianHenryIE/strauss
 */

namespace GravityKit\GravityView\Foundation\Translations;

use Exception;
use WP_Filesystem;
use GravityKit\GravityView\Foundation\ThirdParty\Gettext\Translation;
use GravityKit\GravityView\Foundation\ThirdParty\Gettext\Translations;
use GravityKit\GravityView\Foundation\Helpers\Arr;
use GravityKit\GravityView\Foundation\Logger\Framework as LoggerFramework;

/**
 * Allows downloading and installing translations from TranslationsPress.
 *
 * This is a modified version of the Gravity Forms' TranslationsPress_Updater class, which is based on the T15S library.
 *
 * @since 1.0.0
 *
 * @see   https://github.com/WP-Translations/t15s-registry
 * @see   gravityforms/includes/class-translationspress-updater.php
 */
class TranslationsPress_Updater {
    const T15S_TRANSIENT_KEY = 't15s-registry-gravitykit';

    const T15S_TRANSIENT_EXPIRY = 12 * HOUR_IN_SECONDS;

    const T15S_API_PACKAGES_URL = 'https://packages.translationspress.com/gravitykit/packages.json';

    const T15S_API_EXPORT_URL = 'https://translationspress.com/app/gravitykit/{plugin_slug}/{language_slug}/default/export-translations';

    /**
     * The plugin slug.
     *
     * @since 1.0.0
     *
     * @var string
     */
    private $_slug = '';

    /**
     * Translations storage path.
     *
     * @since 1.0.0
     *
     * @var string
     */
    private $_translations_path = WP_LANG_DIR . '/plugins/';

    /**
     * Cached TranslationsPress data for all GravityKit plugins.
     *
     * @var null|object
     */
    private $_all_translations;

    /**
     * The current instances of this class keyed by plugin slugs.
     *
     * @var TranslationsPress_Updater[]
     */
    private static $_instances = [];

    /**
     * Class constructor.
     *
     * @since 1.0.0
     *
     * @param string $slug              The plugin slug.
     * @param string $translations_path Translations storage path.
     *
     */
    private function __construct( $slug, $translations_path = '' ) {
        $this->_slug = $slug;

        if ( $translations_path ) {
            $this->_translations_path = $translations_path;
        }

        add_action( 'upgrader_process_complete', [ $this, 'on_upgrader_process_complete' ], 10, 2 );

        add_filter( 'translations_api', [ $this, 'translations_api' ], 10, 3 );

        add_filter( 'pre_set_site_transient_update_plugins', [ $this, 'site_transient_update_plugins' ] );
    }

    /**
     * Returns an instance of this class for the given slug.
     *
     * @since 1.0.0
     *
     * @param string $slug              The plugin slug.
     * @param string $translations_path Translations storage path.
     *
     * @return TranslationsPress_Updater
     */
    public static function get_instance( $slug, $translations_path = '' ) {
        if ( empty( self::$_instances[ $slug ] ) ) {
            self::$_instances[ $slug ] = new self( $slug, $translations_path );
        }

        return self::$_instances[ $slug ];
    }

    /**
     * Short-circuits translations API requests for private projects.
     *
     * @since 1.0.0
     *
     * @param bool|array $result         The result object (default: false).
     * @param string     $requested_type The type of translations being requested.
     * @param object     $args           Translation API arguments.
     *
     * @throws Exception
     *
     * @return bool|array
     */
    public function translations_api( $result, $requested_type, $args ) {
        if ( 'plugins' !== $requested_type || $this->_slug !== $args['slug'] ) {
            return $result;
        }

        return $this->get_plugin_translations();
    }

    /**
     * Gets the TranslationsPress data for the current plugin.
     *
     * @since 1.0.0
     *
     * @throws Exception
     *
     * @return array
     */
    public function get_plugin_translations() {
        $this->set_all_translations();

        return isset( $this->_all_translations->projects[ $this->_slug ] ) ? $this->_all_translations->projects[ $this->_slug ] : [];
    }

    /**
     * Filters the translations transients to include the current plugin.
     *
     * @since 1.0.0
     *
     * @see   wp_get_translation_updates()
     *
     * @param mixed $value The transient value.
     *
     * @throws Exception
     *
     * @return object
     */
    public function site_transient_update_plugins( $value ) {
        if ( ! $value ) {
            $value = new \stdClass();
        }

        if ( ! isset( $value->translations ) ) {
            $value->translations = [];
        }

        $translations = $this->get_plugin_translations();

        if ( empty( $translations['translations'] ) ) {
            return $value;
        }

        foreach ( $translations['translations'] as $translation ) {
            if ( ! $this->should_install( $translation ) ) {
                continue;
            }

            $translation['type'] = 'plugin';
            $translation['slug'] = $this->_slug;

            $value->translations[] = $translation;
        }

        return $value;
    }

    /**
     * Refreshes the cached TranslationsPress data, if expired.
     *
     * @since 1.0.0
     *
     * @throws Exception
     *
     * @return void
     */
    public function refresh_all_translations() {
        static $done;

        if ( $done ) {
            return;
        }

        $this->_all_translations = null;

        $this->set_all_translations();

        $done = true;
    }

    /**
     * Determines if the cached TranslationsPress data needs refreshing.
     *
     * @since 1.0.0
     *
     * @return bool
     */
    public function is_transient_expired() {
        $cache_lifespan = self::T15S_TRANSIENT_EXPIRY;

        return ! isset( $this->_all_translations->_last_checked ) || ( time() - $this->_all_translations->_last_checked ) > $cache_lifespan;
    }

    /**
     * Gets the translation data from the TranslationsPress API.
     *
     * @since 1.0.0
     *
     * @throws Exception
     *
     * @return array
     */
    public function get_remote_translations_data() {
        $request = wp_remote_get( self::T15S_API_PACKAGES_URL, [
            'timeout' => 3
        ] );

        if ( is_wp_error( $request ) ) {
            throw new Exception(
                $this->get_exception( 'Unable to reach TranslationsPress API: %s.', __METHOD__, $request->get_error_message() )
            );
        }

        if ( 200 !== wp_remote_retrieve_response_code( $request ) ) {
            throw new Exception(
                $this->get_exception( 'TranslationsPress API returned an invalid response: %s.', __METHOD__, $request['response']['message'] )
            );
        }

        try {
            $result = json_decode( wp_remote_retrieve_body( $request ), true );

            if ( ! is_array( $result ) ) {
                throw new Exception();
            }
        } catch ( Exception $e ) {
            throw new Exception(
                $this->get_exception( 'Could not decode the response received from TranslationsPress API: $s.', __METHOD__, wp_remote_retrieve_body( $request ) )
            );
        }

        return $result;
    }

    /**
     * Caches the TranslationsPress data, if not already cached.
     *
     * @since 1.0.0
     *
     * @throws Exception
     *
     * @return void
     */
    public function set_all_translations() {
        if ( is_object( $this->_all_translations ) ) {
            return;
        }

        $this->_all_translations = get_site_transient( self::T15S_TRANSIENT_KEY );

        if ( is_object( $this->_all_translations ) && ! $this->is_transient_expired() ) {
            return;
        }

        $this->_all_translations                = new \stdClass();
        $this->_all_translations->projects      = $this->get_remote_translations_data();
        $this->_all_translations->_last_checked = time();

        set_site_transient( self::T15S_TRANSIENT_KEY, $this->_all_translations );
    }

    /**
     * Downloads and installs the translations package for the specified plugin.
     *
     * @since 1.0.0
     *
     * @param string $slug   The plugin slug.
     * @param string $locale The locale when the site locale is changed or an empty string to install all the user available locales.
     *
     * @throws Exception
     *
     * @return void
     */
    public function download_package( $slug, $locale = '' ) {
        self::get_instance( $slug )->install( $locale );
    }

    /**
     * Installs translations for a given locale.
     *
     * @since 1.0.0
     *
     * @param string $locale Locale for which to install the translation.
     *
     * @throws Exception
     *
     * @return void
     */
    public function install( $locale = '' ) {
        $translations = $this->get_plugin_translations();

        if ( empty( $translations['translations'] ) ) {
            throw new Exception(
                $this->get_exception( 'No translations found for %s.', __METHOD__, $this->_slug )
            );
        }

        foreach ( $translations['translations'] as $translation ) {
            if ( ! $this->should_install( $translation, $locale ) ) {
                continue;
            }

            $this->install_translation( $translation );

            if ( $locale ) {
                return;
            }
        }
    }

    /**
     * Downloads and installs the given translation.
     *
     * @since 1.0.0
     * @since 1.0.1 Download an extra file from the T15S API.
     *
     * @param array $translation The translation data.
     *
     * @throws Exception
     *
     * @return void
     */
    public function install_translation( $translation ) {
        global $wp_filesystem;

        if ( ! $wp_filesystem ) {
            require_once ABSPATH . '/wp-admin/includes/admin.php';

            if ( ! WP_Filesystem() ) {
                throw new Exception(
                    $this->get_exception( 'Aborting translation package installation; unable to init WP_Filesystem.', __METHOD__ )
                );
            }
        }

        if ( ! $wp_filesystem->is_dir( $this->_translations_path ) ) {
            $wp_filesystem->mkdir( $this->_translations_path, FS_CHMOD_DIR );
        }

        $temp_package_file = download_url( $translation['package'] );

        if ( is_wp_error( $temp_package_file ) ) {
            throw new Exception(
                $this->get_exception( 'Error downloading translation package. Code: %s; Message %s.', __METHOD__, $temp_package_file->get_error_code(), $temp_package_file->get_error_message() )
            );
        }

        $_get_file_name = function ( $extension, $language ) {
            return sprintf(
                '%s/%s-%s.%s',
                untrailingslashit( $this->_translations_path ),
                $this->_slug,
                $language,
                $extension
            );
        };

        $zip_file = $_get_file_name( 'zip', $translation['language'] );

        $copy_result = $wp_filesystem->copy( $temp_package_file, $zip_file, true, FS_CHMOD_FILE );

        $wp_filesystem->delete( $temp_package_file );

        if ( ! $copy_result ) {
            throw new Exception(
                $this->get_exception( 'Unable to move translation package to %s.', __METHOD__, $this->_translations_path )
            );
        }

        $result = unzip_file( $zip_file, $this->_translations_path );

        $wp_filesystem->delete( $zip_file );

        if ( is_wp_error( $result ) ) {
            throw new Exception(
                $this->get_exception( 'Error extracting translation package. Code: %s; Message %s.', __METHOD__, $temp_package_file->get_error_code(), $temp_package_file->get_error_message() )
            );
        }

        // Follows is a workaround for T15S purging JS translations from the .po file included in the translation package.
        // This is typically what happens when WP CLI's `i18n make-json` command is used to generate JS translation files (.json).
        // The filenames contain a hash of the source JS file, which in many of our cases is not the actual file that we end up loading since we tend to bundle UI assets.
        // As a result, WP is unable to automatically load JS translations and what we do instead is manually create (and later load) a single .json file with all JS translations by extracting them from a .po file.
        // Since the .po file in the translation package is missing some JS translations, we need to download an unprocessed .po file that's provided by T15S via an API endpoint.
        $T15S_language_slug = $this->get_slug_from_locale( $translation['language'] );

        if ( ! $T15S_language_slug ) {
            LoggerFramework::get_instance()->warn( 'Unable to get the T15S language slug for ' . $translation['language'] . ' locale.' );

            return;
        }

        $temp_po_file = download_url( strtr(
            self::T15S_API_EXPORT_URL,
            [
                '{plugin_slug}'   => $this->_slug,
                '{language_slug}' => $T15S_language_slug
            ]
        ) );

        if ( is_wp_error( $temp_po_file ) ) {
            throw new Exception(
                $this->get_exception( 'Error downloading translation PO file. Code: %s; Message %s.', __METHOD__, $temp_package_file->get_error_code(), $temp_package_file->get_error_message() )
            );
        }

        $json_file = $_get_file_name( 'json', $translation['language'] );

        $this->convert_po_to_json( $temp_po_file, $json_file );

        $wp_filesystem->delete( $temp_po_file );
    }

    /**
     * Converts the PO file to JSON file by extracting only JavaScript translations.
     *
     * @since 1.0.0
     * @since 1.0.1 New $json_file parameter and Exception when the PO file cannot be read/JSON file cannot be saved.
     *
     * @param string $po_file   File with path to the PO file.
     * @param string $json_file File with path where the JSON file will be saved.
     *
     * @throws Exception
     *
     * @return void
     */
    function convert_po_to_json( $po_file, $json_file ) {
        if ( ! file_exists( $po_file ) ) {
            throw new Exception(
                $this->get_exception( 'PO file %s does not exist. Code: %s; Message %s.', __METHOD__, $po_file )
            );
        }

        $original_translations = Translations::fromPoFile( $po_file );

        $filtered_translations = [];

        foreach ( $original_translations as $original_translation ) {
            // Get translations only for files with .js (or .js.php) extensions and only where translated data exists.
            if ( strpos( json_encode( $original_translation->getReferences() ), '.js' ) === false || ! $original_translation->getTranslation() ) {
                continue;
            }

            // We need to re-create the translation without context or else it will be joined with the source string (see https://github.com/php-gettext/Gettext/blob/3f7bc5ef23302a9059e64934f3d59e454516bec0/src/Generators/Jed.php#L51).
            $filtered_translation = new Translation( '', $original_translation->getOriginal(), $original_translation->getPlural() );
            $filtered_translation->setTranslation( $original_translation->getTranslation() );

            $filtered_translations[] = $filtered_translation;
        }

        if ( empty( $filtered_translations ) ) {
            return;
        }

        $converted_translations = new Translations( $filtered_translations );

        foreach ( $original_translations->getHeaders() as $key => $header ) {
            $converted_translations->setHeader( $key, $header );
        }

        $converted_translations = [
            'translation-revision-date' => $converted_translations->getHeader( 'PO-Revision-Date' ),
            'generator'                 => 'GravityKit Translations',
            'locale_data'               => json_decode( $converted_translations->toJedString(), true )
        ];

        if ( ! file_put_contents( $json_file, json_encode( $converted_translations ) ) ) {
            throw new Exception(
                $this->get_exception( 'Unable to save JSON file %s.', __METHOD__, $json_file )
            );
        }
    }

    /**
     * Determines if a translation should be installed.
     *
     * @since 1.0.0
     *
     * @param array  $translation The translation data.
     * @param string $locale      The locale when the site locale is changed or an empty string to check all the user available locales.
     *
     * @return bool
     */
    public function should_install( $translation, $locale = '' ) {
        if ( ( $locale !== $translation['language'] ) || ! in_array( $translation['language'], $this->get_available_languages(), true ) ) {
            return false;
        }

        if ( empty( $translation['updated'] ) ) {
            return true;
        }

        $installed = $this->get_installed_translations_data();

        if ( ! isset( $installed[ $translation['language'] ] ) ) {
            return true;
        }

        $local  = date_create( $installed[ $translation['language'] ]['PO-Revision-Date'] );
        $remote = date_create( $translation['updated'] );

        return $remote > $local;
    }

    /**
     * Returns an array of locales the site has installed.
     *
     * @since 1.0.0
     *
     * @return array
     */
    public function get_available_languages() {
        static $languages = [];

        if ( empty( $languages ) ) {
            $languages = get_available_languages();
        }

        return $languages;
    }

    /**
     * Returns header data from the installed translations for the current plugin.
     *
     * @since 1.0.0
     *
     * @return array
     */
    public function get_installed_translations_data() {
        static $data = [];

        if ( isset( $data[ $this->_slug ] ) ) {
            return $data[ $this->_slug ];
        }

        $data[ $this->_slug ] = [];
        $translations         = $this->get_installed_translations( true );

        foreach ( $translations as $locale => $mo_file ) {
            $po_file = str_replace( '.mo', '.po', $mo_file );
            if ( ! file_exists( $po_file ) ) {
                continue;
            }

            $data[ $this->_slug ][ $locale ] = wp_get_pomo_file_data( $po_file );
        }

        return $data[ $this->_slug ];
    }

    /**
     * Returns an array of locales or .mo translation files found in the translations folder.
     *
     * @since 1.0.0
     *
     * @param bool $return_files Indicates if the object should be keyed by locale (e.g., 'en_EN').
     *
     * @return array
     */
    public function get_installed_translations( $return_files = false ) {
        $files = glob( sprintf(
            '%s/%s-*.mo',
            $this->_translations_path,
            $this->_slug
        ) );

        if ( empty( $files ) ) {
            return [];
        }

        $translations = [];

        foreach ( $files as $file ) {
            $translations[ str_replace( $this->_slug . '-', '', basename( $file, '.mo' ) ) ] = $file;
        }

        return $return_files ? $translations : array_keys( $translations );
    }

    /**
     * Formats and returns an exception message.
     *
     * @since 1.0.0
     *
     * @param string $message  Exception message with placeholders for sprintf() replacement.
     * @param string $method   Method throwing the exception.
     * @param mixed  $args,... Variable-length argument lists for sprintf() replacement.
     *
     * @return string
     */
    public function get_exception( $message, $method, ...$args ) {
        $message = "%s(): ${message}";

        return sprintf(
            $message,
            $method,
            ...$args
        );
    }

    /**
     * Returns T15S slug for the language based on the WP locale.
     * This is used to access the export URL (e.g., https://translationspress.com/app/gravitykit/gk-gravitycalendar/<slug>/default/export-translations/)
     *
     * @since 1.0.1
     *
     * @param string $locale WP language locale.
     *
     * @return string|null T15S slug.
     */
    public function get_slug_from_locale( $locale ) {
        // Taken from GlotPress that powers T15S: https://github.com/GlotPress/GlotPress/blob/a4436a6169d9f6cba5bc0ed62abe31e4f3ef15b4/locales/locales.php
        $slug_to_locale_map = [
            'az'          => 'az',
            'azb'         => 'azb',
            'az_TR'       => 'az-tr',
            'ba'          => 'ba',
            'bal'         => 'bal',
            'bcc'         => 'bcc',
            'bel'         => 'bel',
            'bg_BG'       => 'bg',
            'bgn'         => 'bgn',
            'bho'         => 'bho',
            'bn_BD'       => 'bn',
            'bn_IN'       => 'bn-in',
            'bo'          => 'bo',
            'bre'         => 'br',
            'brx'         => 'brx',
            'bs_BA'       => 'bs',
            'ca'          => 'ca',
            'ca_valencia' => 'ca-valencia',
            'ceb'         => 'ceb',
            'ckb'         => 'ckb',
            'co'          => 'co',
            'cor'         => 'cor',
            'cs_CZ'       => 'cs',
            'cy'          => 'cy',
            'da_DK'       => 'da',
            'de_DE'       => 'de',
            'de_AT'       => 'de-at',
            'de_CH'       => 'de-ch',
            'dsb'         => 'dsb',
            'dv'          => 'dv',
            'dzo'         => 'dzo',
            'ewe'         => 'ee',
            'el'          => 'el',
            'art_xemoji'  => 'art-xemoji',
            'en_US'       => 'en',
            'en_AU'       => 'en-au',
            'en_CA'       => 'en-ca',
            'en_GB'       => 'en-gb',
            'en_NZ'       => 'en-nz',
            'en_ZA'       => 'en-za',
            'eo'          => 'eo',
            'es_ES'       => 'es',
            'es_AR'       => 'es-ar',
            'es_CL'       => 'es-cl',
            'es_CO'       => 'es-co',
            'es_CR'       => 'es-cr',
            'es_DO'       => 'es-do',
            'es_EC'       => 'es-ec',
            'es_GT'       => 'es-gt',
            'es_HN'       => 'es-hn',
            'es_MX'       => 'es-mx',
            'es_PE'       => 'es-pe',
            'es_PR'       => 'es-pr',
            'es_UY'       => 'es-uy',
            'es_VE'       => 'es-ve',
            'et'          => 'et',
            'eu'          => 'eu',
            'fa_IR'       => 'fa',
            'fa_AF'       => 'fa-af',
            'fuc'         => 'fuc',
            'fi'          => 'fi',
            'fo'          => 'fo',
            'fon'         => 'fon',
            'fr_FR'       => 'fr',
            'fr_BE'       => 'fr-be',
            'fr_CA'       => 'fr-ca',
            'frp'         => 'frp',
            'fur'         => 'fur',
            'fy'          => 'fy',
            'ga'          => 'ga',
            'gax'         => 'gax',
            'gd'          => 'gd',
            'gl_ES'       => 'gl',
            'gu'          => 'gu',
            'hat'         => 'hat',
            'hau'         => 'hau',
            'haw_US'      => 'haw',
            'haz'         => 'haz',
            'he_IL'       => 'he',
            'hi_IN'       => 'hi',
            'hr'          => 'hr',
            'hsb'         => 'hsb',
            'hu_HU'       => 'hu',
            'hy'          => 'hy',
            'ibo'         => 'ibo',
            'id_ID'       => 'id',
            'ido'         => 'ido',
            'is_IS'       => 'is',
            'it_IT'       => 'it',
            'ja'          => 'ja',
            'jv_ID'       => 'jv',
            'ka_GE'       => 'ka',
            'kaa'         => 'kaa',
            'kab'         => 'kab',
            'kal'         => 'kal',
            'kin'         => 'kin',
            'kk'          => 'kk',
            'km'          => 'km',
            'kmr'         => 'kmr',
            'kn'          => 'kn',
            'ko_KR'       => 'ko',
            'kir'         => 'kir',
            'lb_LU'       => 'lb',
            'li'          => 'li',
            'lij'         => 'lij',
            'lin'         => 'lin',
            'lmo'         => 'lmo',
            'lo'          => 'lo',
            'lt_LT'       => 'lt',
            'lug'         => 'lug',
            'lv'          => 'lv',
            'mai'         => 'mai',
            'me_ME'       => 'me',
            'mfe'         => 'mfe',
            'mg_MG'       => 'mg',
            'mk_MK'       => 'mk',
            'ml_IN'       => 'ml',
            'mlt'         => 'mlt',
            'mn'          => 'mn',
            'mr'          => 'mr',
            'mri'         => 'mri',
            'ms_MY'       => 'ms',
            'my_MM'       => 'mya',
            'ne_NP'       => 'ne',
            'nb_NO'       => 'nb',
            'nl_NL'       => 'nl',
            'nl_BE'       => 'nl-be',
            'nn_NO'       => 'nn',
            'nqo'         => 'nqo',
            'oci'         => 'oci',
            'ory'         => 'ory',
            'os'          => 'os',
            'pa_IN'       => 'pa',
            'pa_PK'       => 'pa-pk',
            'pap_CW'      => 'pap-cw',
            'pap_AW'      => 'pap-aw',
            'pcd'         => 'pcd',
            'pcm'         => 'pcm',
            'art_xpirate' => 'pirate',
            'pl_PL'       => 'pl',
            'pt_PT'       => 'pt',
            'pt_PT_ao90'  => 'pt-ao90',
            'pt_AO'       => 'pt-ao',
            'pt_BR'       => 'pt-br',
            'ps'          => 'ps',
            'rhg'         => 'rhg',
            'ro_RO'       => 'ro',
            'roh'         => 'roh',
            'ru_RU'       => 'ru',
            'sah'         => 'sah',
            'sa_IN'       => 'sa-in',
            'scn'         => 'scn',
            'si_LK'       => 'si',
            'sk_SK'       => 'sk',
            'skr'         => 'skr',
            'sl_SI'       => 'sl',
            'sna'         => 'sna',
            'snd'         => 'snd',
            'so_SO'       => 'so',
            'sq'          => 'sq',
            'sq_XK'       => 'sq-xk',
            'sr_RS'       => 'sr',
            'srd'         => 'srd',
            'ssw'         => 'ssw',
            'su_ID'       => 'su',
            'sv_SE'       => 'sv',
            'sw'          => 'sw',
            'syr'         => 'syr',
            'szl'         => 'szl',
            'ta_IN'       => 'ta',
            'ta_LK'       => 'ta-lk',
            'tah'         => 'tah',
            'te'          => 'te',
            'tg'          => 'tg',
            'th'          => 'th',
            'tir'         => 'tir',
            'tl'          => 'tl',
            'tr_TR'       => 'tr',
            'tt_RU'       => 'tt',
            'tuk'         => 'tuk',
            'twd'         => 'twd',
            'tzm'         => 'tzm',
            'ug_CN'       => 'ug',
            'uk'          => 'uk',
            'ur'          => 'ur',
            'uz_UZ'       => 'uz',
            'vec'         => 'vec',
            'vi'          => 'vi',
            'wol'         => 'wol',
            'xho'         => 'xho',
            'yor'         => 'yor',
            'zgh'         => 'zgh',
            'zh_CN'       => 'zh-cn',
            'zh_HK'       => 'zh-hk',
            'zh_SG'       => 'zh-sg',
            'zh_TW'       => 'zh-tw',
            'zul'         => 'zul'
        ];

        return Arr::get( $slug_to_locale_map, $locale, null );
    }
}