Ticket #32879: switcher.php

<?php
class Language_Switcher {
        /**
         * @var Language_Switcher
         */
        private static $instance;

        /**
         * The array containing all the mofiles
         *
         * @var array
         */
        private $mo_files;

        protected function __construct() {

                /**
                 * Store all the textdomain and files
                 */
                add_filter( 'load_textdomain_mofile', array( $this, 'load_textdomain_mofile' ), 1, 2 );
        }

        /**
         * @return self
         * @author Nicolas Juen
         */
        public static function get_instance() {
                if ( is_null( self::$instance ) ) {
                        self::$instance = new self();
                }

                return self::$instance;
        }

        /**
         * Add the mo file to the class
         *
         * @param string $mo_file : the mo file path
         * @param string $domain : domain
         *
         * @author Nicolas Juen
         * @return string
         */
        public function load_textdomain_mofile( $mo_file, $domain ) {
                $this->mo_files[ $domain ][] = $mo_file;
                return $mo_file;
        }

        /**
         * Unload all registered files
         *
         * @author Nicolas Juen
         */
        private function unload_text_domains() {
                // Unload the files
                foreach ( $this->mo_files as $domain => $file ) {
                        unload_textdomain( $domain );
                }

                unload_textdomain( 'default' );
        }

        /**
         * Load other locale files
         *
         * @param $locale_to : the locale to switch
         *
         * @author Nicolas Juen
         * @return bool
         */
        public function switch_locale( $locale_to ) {
                global $locale;

                /**
                 * Do not switch locale if same
                 * or empty mo files
                 */
                if ( $locale === $locale_to || empty( $this->mo_files ) ) {
                        return false;
                }

                remove_filter( 'load_textdomain_mofile', array( $this, 'load_textdomain_mofile' ), 1, 2 );
                $this->unload_text_domains();

                // Reload the files
                foreach ( $this->mo_files as $domain => $files ) {
                        foreach ( $files as $file ) {
                                load_textdomain( $domain, str_replace( $locale, $locale_to, $file ) );
                        }
                }

                // Load WP text domain
                load_default_textdomain( $locale_to );

                return true;
        }

        /**
         * Restore the original locale
         *
         * @author Nicolas Juen
         */
        public function restore_locale() {
                $this->unload_text_domains();
                $this->switch_locale( get_locale() );
        }
}