<?php

/**

 * Locale API: WP_Locale_Switcher class

 *

 * @package WordPress

 * @subpackage i18n

 * @since 4.7.0

 */

/**

 * Core class used for switching locales.

 *

 * @since 4.7.0

 */

class WP_Locale_Switcher {

	/**

	 * Locale stack.

	 *

	 * @since 4.7.0

	 * @var string[]

	 */

	private $locales = array();

	/**

	 * Original locale.

	 *

	 * @since 4.7.0

	 * @var string

	 */

	private $original_locale;

	/**

	 * Holds all available languages.

	 *

	 * @since 4.7.0

	 * @var array An array of language codes (file names without the .mo extension).

	 */

	private $available_languages = array();

	/**

	 * Constructor.

	 *

	 * Stores the original locale as well as a list of all available languages.

	 *

	 * @since 4.7.0

	 */

	public function __construct() {

		$this->original_locale     = determine_locale();

		$this->available_languages = array_merge( array( 'en_US' ), get_available_languages() );

	}

	/**

	 * Initializes the locale switcher.

	 *

	 * Hooks into the {@see 'locale'} filter to change the locale on the fly.

	 *

	 * @since 4.7.0

	 */

	public function init() {

		add_filter( 'locale', array( $this, 'filter_locale' ) );

	}

	/**

	 * Switches the translations according to the given locale.

	 *

	 * @since 4.7.0

	 *

	 * @param string $locale The locale to switch to.

	 * @return bool True on success, false on failure.

	 */

	public function switch_to_locale( $locale ) {

		$current_locale = determine_locale();

		if ( $current_locale === $locale ) {

			return false;

		}

		if ( ! in_array( $locale, $this->available_languages, true ) ) {

			return false;

		}

		$this->locales[] = $locale;

		$this->change_locale( $locale );

		/**

		 * Fires when the locale is switched.

		 *

		 * @since 4.7.0

		 *

		 * @param string $locale The new locale.

		 */

		do_action( 'switch_locale', $locale );

		return true;

	}

	/**

	 * Restores the translations according to the previous locale.

	 *

	 * @since 4.7.0

	 *

	 * @return string|false Locale on success, false on failure.

	 */

	public function restore_previous_locale() {

		$previous_locale = array_pop( $this->locales );

		if ( null === $previous_locale ) {

			// The stack is empty, bail.

			return false;

		}

		$locale = end( $this->locales );

		if ( ! $locale ) {

			// There's nothing left in the stack: go back to the original locale.

			$locale = $this->original_locale;

		}

		$this->change_locale( $locale );

		/**

		 * Fires when the locale is restored to the previous one.

		 *

		 * @since 4.7.0

		 *

		 * @param string $locale          The new locale.

		 * @param string $previous_locale The previous locale.

		 */

		do_action( 'restore_previous_locale', $locale, $previous_locale );

		return $locale;

	}

	/**

	 * Restores the translations according to the original locale.

	 *

	 * @since 4.7.0

	 *

	 * @return string|false Locale on success, false on failure.

	 */

	public function restore_current_locale() {

		if ( empty( $this->locales ) ) {

			return false;

		}

		$this->locales = array( $this->original_locale );

		return $this->restore_previous_locale();

	}

	/**

	 * Whether switch_to_locale() is in effect.

	 *

	 * @since 4.7.0

	 *

	 * @return bool True if the locale has been switched, false otherwise.

	 */

	public function is_switched() {

		return ! empty( $this->locales );

	}

	/**

	 * Filters the locale of the WordPress installation.

	 *

	 * @since 4.7.0

	 *

	 * @param string $locale The locale of the WordPress installation.

	 * @return string The locale currently being switched to.

	 */

	public function filter_locale( $locale ) {

		$switched_locale = end( $this->locales );

		if ( $switched_locale ) {

			return $switched_locale;

		}

		return $locale;

	}

	/**

	 * Load translations for a given locale.

	 *

	 * When switching to a locale, translations for this locale must be loaded from scratch.

	 *

	 * @since 4.7.0

	 *

	 * @global Mo[] $l10n An array of all currently loaded text domains.

	 *

	 * @param string $locale The locale to load translations for.

	 */

	private function load_translations( $locale ) {

		global $l10n;

		$domains = $l10n ? array_keys( $l10n ) : array();

		load_default_textdomain( $locale );

		foreach ( $domains as $domain ) {

			if ( 'default' === $domain ) {

				continue;

			}

			unload_textdomain( $domain );

			get_translations_for_domain( $domain );

		}

	}

	/**

	 * Changes the site's locale to the given one.

	 *

	 * Loads the translations, changes the global `$wp_locale` object and updates

	 * all post type labels.

	 *

	 * @since 4.7.0

	 *

	 * @global WP_Locale $wp_locale WordPress date and time locale object.

	 *

	 * @param string $locale The locale to change to.

	 */

	private function change_locale( $locale ) {

		// Reset translation availability information.

		_get_path_to_translation( null, true );

		$this->load_translations( $locale );

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

		/**

		 * Fires when the locale is switched to or restored.

		 *

		 * @since 4.7.0

		 *

		 * @param string $locale The new locale.

		 */

		do_action( 'change_locale', $locale );

	}

}