Ticket #26511: switch_to_locale.php

<?php

/**
 * Switches the translations to the given language.
 *
 * @param string $locale The slug of the language: en, fr, ja, etc.
 * @param   bool $pop    Wether to push or pop the stack of switched languages.
 * @see restore_current_locale()
 *
 * @return bool|string False on failure, language slug on success
 */
function switch_to_locale( $locale, $pop = false ) {
        global $l10n, $wp_locale;
        static $stack = false,           // Numeric array: The stack of languages we've switched to.  Does not include the original language.
               $translations = false,    // Associative array: References to the translations.  Keyed by language slug.
               $filters = false,         // Associative array: Functions used to filter
               $original_locale = false; // String

        if ( false === $stack ) {
                $stack = $translations = $filters = array();
                $original_locale = get_locale();
        }

        // We're restoring to the previous language via wpcom_restore_current_locale()
        if ( $pop ) {
                // The stack is empty, bail
                if ( !array_pop( $stack ) ) {
                        return false;
                }

                // Remove all filters
                foreach ( $filters as $filter ) {
                        remove_filter( 'locale', $filter );
                }

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

                // Hack the correct translations in.
                foreach ( array_keys( $l10n ) as $textdomain ) {
                        $l10n[$textdomain] =& $translations[$locale][$textdomain];
                }

                // Set up date and number formatting globals
                $wp_locale = new WP_Locale();

                return $locale;
        }

        $current_locale = get_locale();

        // We don't have a reference to the current translations stored here.  This must be the first time this function was called.
        // Store it.
        if ( ! isset( $translations[$current_locale] ) ) {
                foreach ( array_keys( $l10n ) as $textdomain ) {
                        $translations[$current_locale][$textdomain] = get_translations_for_domain( $textdomain );
                }
        }

        // No change needed.  Still push to the stack so that a future wpcom_restore_current_locale() call won't break anything.
        if ( $current_locale == $locale ) {
                $stack[] = $locale;
                return $locale;
        }

        // Push to the stack
        $stack[] = $locale;

        // Remove any filters we have attached
        foreach ( $filters as $filter ) {
                remove_filter( 'locale', $filter );
        }

        // Generate the required filter...
        if ( ! isset( $filters[$locale] ) ) {
                $filters[$locale] = function() use( $locale ) {
                        return $locale;
                };
        }

        // ... and add it
        add_filter( 'locale', $filters[$locale] );

        if ( isset( $translations[$locale] ) ) {
                // We already have a reference - use it
                foreach ( array_keys( $l10n ) as $textdomain ) {
                        $l10n[$textdomain] =& $translations[$locale][$textdomain];
                }
        } else {
                // We don't have a reference to the new translations stored here.  They must not have been generated yet.
                // Create the translations and store a reference.
                foreach ( array_keys( $l10n ) as $textdomain ) {

                        unload_textdomain( $textdomain );
                        if( $textdomain == 'default' ) {
                                load_default_textdomain();
                        } else {
                                //BLOCKER: how do we get the MO file now?
                                load_textdomain( $textdomain, $mo);
                                $translations[$locale][$textdomain] = get_translations_for_domain( $textdomain );
                        }
                }
        }

        // Set up date and number formatting globals
        $wp_locale = new WP_Locale();

        return $locale;
}

/**
 * Restores the translation language to the previous language in the stack.
 * @uses switch_to_locale()
 *
 * @return bool|string False on failure, language slug on success.
 */
function restore_current_locale() {
        return switch_to_locale( null, true );
}