<?php
/**
 * Language of the current front-end request, detected once from the URL.
 *
 * One object per request (request-scoped state), shared by everything that
 * asks "which language is this page in". '' in admin, REST, cron and CLI.
 */

declare( strict_types = 1 );

namespace AddBlack\Lang\Routing;

defined( 'ABSPATH' ) || exit;

use AddBlack\Lang\Settings\SettingsRepository;

final class CurrentLanguage {

	/** Detected language; null = not detected yet. */
	private ?string $code = null;

	/** Language whose prefix is in the URL ('' = none). */
	private string $prefix_lang = '';

	/** REQUEST_URI the language was detected from. */
	private ?string $detected_uri = null;

	/** REQUEST_URI before Router cut the prefix (null = not cut). */
	private ?string $original_uri = null;

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

	public function get(): string {
		$uri_now = Urls::request_uri();
		// Cached for this request; detected again if the URL changed (other than our own prefix cut).
		if ( null !== $this->code && ( null !== $this->original_uri || $uri_now === $this->detected_uri ) ) {
			return $this->code;
		}
		$this->detected_uri = $uri_now;
		$this->prefix_lang  = '';
		if ( is_admin() || wp_doing_cron() || ( defined( 'WP_CLI' ) && WP_CLI ) || isset( $_GET['rest_route'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification -- presence check only.
			$this->code = '';
			return $this->code;
		}
		$uri   = '' !== $uri_now ? $uri_now : '/';
		$parts = explode( '/', $this->urls->request_path( $uri ) );
		$lang  = $this->urls->lang_by_slug( $parts[0] );
		$rest  = $lang ? ( $parts[1] ?? '' ) : $parts[0];

		if ( function_exists( 'rest_get_url_prefix' ) && rest_get_url_prefix() === $rest ) {
			$this->code = '';
			return $this->code;
		}
		$this->prefix_lang = $lang;
		$this->code        = $lang ? $lang : $this->settings->get()->default_code();
		return $this->code;
	}

	/** Is this a front-end request in a language other than the default one? */
	public function is_other_than_default(): bool {
		$code = $this->get();
		return '' !== $code && $this->settings->get()->default_code() !== $code;
	}

	/** Language whose prefix was in the URL ('' if none). */
	public function prefix_in_url(): string {
		$this->get();
		return $this->prefix_lang;
	}

	/** Router cut the prefix from REQUEST_URI; remember the original. */
	public function mark_prefix_cut( string $original_uri ): void {
		$this->original_uri = $original_uri;
	}

	/** The original REQUEST_URI if the prefix is cut right now, and forget it. */
	public function take_original_uri(): ?string {
		$uri                = $this->original_uri;
		$this->original_uri = null;
		return $uri;
	}

	/** Tests: forget everything detected for the current request. */
	public function reset(): void {
		$this->code         = null;
		$this->prefix_lang  = '';
		$this->detected_uri = null;
		$this->original_uri = null;
	}
}