Ticket #26511: switch_to_locale__revisited.php

<?php

/**
 * Simple single value storage with a getter.
 */
class WP_Locale_Storage {

        /**
         * @var string
         */
        private $locale;

        /**
         * Constructor. Stores the given locale.
         *
         * @param string $locale The locale.
         */
        public function __construct( $locale ) {

                $this->locale = (string) $locale;
        }

        /**
         * Returns the stored locale.
         *
         * @return string The stored locale.
         */
        public function get() {

                return $this->locale;
        }
}

/**
 * Handles switching locales.
 */
class WP_Locale_Switcher {

        /**
         * @var callback[]
         */
        private $filters = array();

        /**
         * @var string[]
         */
        private $locales = array();

        /**
         * @var string
         */
        private $original_locale;

        /**
         * @var NOOP_Translations[][]
         */
        private $translations = array();

        /**
         * Constructor. Stores the original locale.
         */
        public function __construct() {

                $this->original_locale = get_locale();
        }

        /**
         * Switches the translations according to the given locale.
         *
         * @param string $locale The locale.
         */
        public function switch_to_locale( $locale ) {

                $this->locales[] = $locale;

                $current_locale = get_locale();
                if ( $current_locale === $locale ) {
                        return;
                }

                global $l10n;

                $textdomains = array_keys( $l10n );

                if ( ! $this->has_translations_for_locale( $current_locale ) ) {
                        foreach ( $textdomains as $textdomain ) {
                                $this->translations[ $current_locale ][ $textdomain ] = get_translations_for_domain( $textdomain );
                        }
                }

                $this->remove_filters();

                $this->add_filter_for_locale( $locale );

                if ( $this->has_translations_for_locale( $locale ) ) {
                        foreach ( $textdomains as $textdomain ) {
                                if ( isset( $this->translations[ $locale ][ $textdomain ] ) ) {
                                        $l10n[ $textdomain ] = $this->translations[ $locale ][ $textdomain ];
                                }
                        }
                } else {
                        foreach ( $textdomains as $textdomain ) {
                                if ( 'default' === $textdomain ) {
                                        load_default_textdomain();

                                        continue;
                                }

                                unload_textdomain( $textdomain );

                                /**
                                 * TODO: Retrieve the MO file for the current textdomain.
                                 *
                                 * The current problem is, as yoavf said already, that the textdomain (string) alone doesn't carry
                                 * enough information to determine if we have to call `load_plugin_textdomain()`, or something else.
                                 * This could be easily fixed if we were to store the file in `MO::import_from_file()`.
                                 */
                                load_textdomain( $textdomain, $mofile );

                                $this->translations[ $locale ][ $textdomain ] = get_translations_for_domain( $textdomain );
                        }
                }

                $GLOBALS['wp_locale'] = new WP_Locale();
        }

        /**
         * Restores the translations according to the previous locale.
         *
         * @return string|false Locale on success, false on error.
         */
        public function restore_locale() {

                if ( ! array_pop( $this->locales ) ) {
                        // The stack is empty, bail.
                        return false;
                }

                $this->remove_filters();

                if ( $locale = end( $this->locales ) ) {
                        if ( isset( $filters[ $locale ] ) ) {
                                add_filter( 'locale', $filters[ $locale ] );
                        }
                } else {
                        // There's nothing left in the stack: go back to the original locale.
                        $locale = $this->original_locale;
                }

                global $l10n;

                foreach ( array_keys( $l10n ) as $textdomain ) {
                        if ( isset( $this->translations[ $locale ][ $textdomain ] ) ) {
                                $l10n[ $textdomain ] = $this->translations[ $locale ][ $textdomain ];
                        }
                }

                $GLOBALS['wp_locale'] = new WP_Locale();

                return $locale;
        }

        /**
         * Checks if there are cached translations for the given locale.
         *
         * @param string $locale The locale.
         *
         * @return bool True if there are cached translations for the given locale, false otherwise.
         */
        private function has_translations_for_locale( $locale ) {

                return ! empty( $this->translations[ $locale ] );
        }

        /**
         * Removes all filter callbacks added before.
         */
        private function remove_filters() {

                foreach ( $this->filters as $filter ) {
                        remove_filter( 'locale', $filter );
                }
        }

        /**
         * Adds a filter callback returning the given locale.
         *
         * @param string $locale The locale.
         */
        private function add_filter_for_locale( $locale ) {

                if ( ! isset( $this->filters[ $locale ] ) ) {
                        // This really should be a closure, but ... well ... you know.
                        $this->filters[ $locale ] = array( new WP_Locale_Storage( $locale ), 'get' );
                }

                add_filter( 'locale', $this->filters[ $locale ] );
        }
}

$GLOBALS['wp_locale_switcher'] = new WP_Locale_Switcher();

/**
 * Switches the translations according to the given locale.
 *
 * @see WP_Locale_Switcher::switch_to_locale()
 *
 * @param string $locale The locale.
 */
function switch_to_locale( $locale ) {

        /**
         * @global WP_Locale_Switcher $wp_locale_switcher
         */
        global $wp_locale_switcher;

        $wp_locale_switcher->switch_to_locale( $locale );
}

/**
 * Restores the translations according to the previous locale.
 *
 * @see WP_Locale_Switcher::restore_locale()
 *
 * @return string|false Locale on success, false on error.
 */
function restore_locale() {

        /**
         * @global WP_Locale_Switcher $wp_locale_switcher
         */
        global $wp_locale_switcher;

        return $wp_locale_switcher->restore_locale();
}