<?php
/**
 * WordPress language packs for every site language.
 *
 * The front end switches the WP locale per language, so core, theme and
 * plugin strings come from the official translation files - once they are on
 * the server. This installs them and keeps them updated through WordPress' own
 * translation updates.
 */

declare( strict_types = 1 );

namespace AddBlack\Lang\LanguagePacks;

defined( 'ABSPATH' ) || exit;

use AddBlack\Lang\Hookable;
use AddBlack\Lang\Hooks;
use AddBlack\Lang\Settings\SettingsRepository;
use WP_Error;

final class LanguagePackInstaller implements Hookable {

	public function __construct( private readonly SettingsRepository $settings ) {}

	public function register(): void {
		// WordPress asks for translation updates only in installed locales; add ours.
		Hooks::filter( 'plugins_update_check_locales', array( $this, 'add_locales' ) );
		Hooks::filter( 'themes_update_check_locales', array( $this, 'add_locales' ) );
	}

	/** @return string[] WP locales of the site languages, without the built-in en_US. */
	public function locales(): array {
		$out = array();
		foreach ( $this->settings->get()->languages() as $lang ) {
			if ( '' !== $lang->locale && 'en_US' !== $lang->locale ) {
				$out[] = $lang->locale;
			}
		}
		return array_values( array_unique( $out ) );
	}

	/** @return string[] */
	public function add_locales( mixed $locales ): array {
		return array_values( array_unique( array_merge( (array) $locales, $this->locales() ) ) );
	}

	/** @return string[] Locales whose core pack is not on the server yet. */
	public function missing(): array {
		return array_values( array_diff( $this->locales(), get_available_languages() ) );
	}

	/**
	 * Install core packs for the locales, then theme and plugin packs.
	 *
	 * @param string[]|null $locales Default: all site locales.
	 * @return array{core: string[], failed: string[], unreachable?: string[], packs: int}|WP_Error
	 */
	public function install( ?array $locales = null ): array|WP_Error {
		$locales = null === $locales ? $this->locales() : array_values( array_diff( $locales, array( 'en_US', '' ) ) );
		if ( ! $locales ) {
			return array(
				'core'   => array(),
				'failed' => array(),
				'packs'  => 0,
			);
		}

		require_once ABSPATH . 'wp-admin/includes/file.php';
		require_once ABSPATH . 'wp-admin/includes/translation-install.php';
		require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
		require_once ABSPATH . 'wp-includes/update.php';

		if ( ! wp_can_install_language_pack() ) {
			return new WP_Error( 'blocklingo_langpack_fs', __( 'WordPress cannot write to wp-content/languages here (file permissions or FTP credentials needed). Install the languages in Settings > General > Site Language instead.', 'blocklingo' ) );
		}

		// The list of WordPress translations comes from wordpress.org. Empty = it could not be reached
		// (wp_download_language_pack() would then fail for every locale as if none existed).
		$have      = get_available_languages();
		$available = array_diff( $locales, $have ) ? wp_get_available_translations() : array();
		if ( array_diff( $locales, $have ) && ! $available ) {
			return new WP_Error( 'blocklingo_langpack_offline', __( 'Could not connect to wordpress.org to download translation files. The site may be offline or a firewall may block outgoing connections. Try again later with "Save and install", or install the languages in Settings > General > Site Language.', 'blocklingo' ) );
		}

		$core        = array();
		$failed      = array();
		$unreachable = array();
		foreach ( $locales as $locale ) {
			if ( in_array( $locale, $have, true ) ) {
				continue;
			}
			if ( wp_download_language_pack( $locale ) ) {
				$core[] = $locale;
			} elseif ( isset( $available[ $locale ] ) ) {
				$unreachable[] = $locale; // Listed on wordpress.org, but the download failed (SSL, firewall, timeout).
			} else {
				$failed[] = $locale;
			}
		}

		// Ask wordpress.org again (our locales are added by the filters above).
		delete_site_transient( 'update_plugins' );
		delete_site_transient( 'update_themes' );
		wp_update_plugins();
		wp_update_themes();

		$updates = array_values(
			array_filter(
				wp_get_translation_updates(),
				static fn( $u ): bool => isset( $u->language ) && in_array( $u->language, $locales, true )
			)
		);
		$packs   = 0;
		if ( $updates ) {
			$upgrader = new \Language_Pack_Upgrader( new \Automatic_Upgrader_Skin() );
			$result   = $upgrader->bulk_upgrade( $updates, array( 'clear_update_cache' => true ) );
			if ( is_array( $result ) ) {
				$packs = count( array_filter( $result, static fn( $r ): bool => $r && ! is_wp_error( $r ) ) );
			}
		}

		return array(
			'core'        => $core,
			'failed'      => $failed,
			'unreachable' => $unreachable,
			'packs'       => $packs,
		);
	}

	/**
	 * One-line summary for an admin notice.
	 *
	 * @param array{core: string[], failed: string[], unreachable?: string[], packs: int}|WP_Error $result
	 */
	public static function summary( array|WP_Error $result ): string {
		if ( is_wp_error( $result ) ) {
			return $result->get_error_message();
		}
		$parts = array();
		if ( $result['core'] ) {
			$parts[] = sprintf( /* translators: %s: list of locales. */ __( 'WordPress translations installed: %s.', 'blocklingo' ), implode( ', ', $result['core'] ) );
		}
		if ( $result['packs'] > 0 || ( ! $result['core'] && ! $result['failed'] && empty( $result['unreachable'] ) ) ) {
			$parts[] = sprintf( /* translators: %d: number of files. */ __( 'Theme and plugin translation files installed or updated: %d.', 'blocklingo' ), $result['packs'] );
		}
		if ( ! empty( $result['unreachable'] ) ) {
			$parts[] = sprintf( /* translators: %s: list of locales. */ __( 'Could not download from wordpress.org: %s. The server may block outgoing connections or fail the SSL check. Try "Save and install" again later.', 'blocklingo' ), implode( ', ', $result['unreachable'] ) );
		}
		if ( $result['failed'] ) {
			$parts[] = sprintf( /* translators: %s: list of locales. */ __( 'Not available on wordpress.org: %s.', 'blocklingo' ), implode( ', ', $result['failed'] ) );
		}
		return implode( ' ', $parts );
	}
}