<?php

namespace app\util;

/**
 * 多语言翻译类
 * 支持：中文(zh)、英文(en)、俄语(ru)、西语(es)、法语(fr)
 */
class Lang
{
    private static ?array $translations = null;
    private static string $locale = 'zh';
    private static string $fallbackLocale = 'zh';

    /**
     * 支持的语言列表
     */
    public const SUPPORTED_LOCALES = ['zh', 'en', 'ru', 'es', 'fr'];

    /**
     * 语言名称映射
     */
    public const LOCALE_NAMES = [
        'zh' => '简体中文',
        'en' => 'English',
        'ru' => 'Русский',
        'es' => 'Español',
        'fr' => 'Français',
    ];

    /**
     * 初始化翻译
     */
    private static function loadTranslations(): void
    {
        if (self::$translations !== null) {
            return;
        }

        self::$translations = [];
        foreach (self::SUPPORTED_LOCALES as $locale) {
            $file = base_path() . "/lang/{$locale}.php";
            if (file_exists($file)) {
                self::$translations[$locale] = require $file;
            }
        }
    }

    /**
     * 设置当前语言
     */
    public static function setLocale(string $locale): void
    {
        if (in_array($locale, self::SUPPORTED_LOCALES)) {
            self::$locale = $locale;
        }
    }

    /**
     * 获取当前语言
     */
    public static function getLocale(): string
    {
        return self::$locale;
    }

    /**
     * 从请求中获取语言
     */
    public static function detectFromRequest(): string
    {
        // 从请求头获取语言
        $request = \request();
        $acceptLanguage = $request->header('Accept-Language');

        if ($acceptLanguage) {
            // 解析 Accept-Language 头
            $locales = explode(',', $acceptLanguage);
            foreach ($locales as $locale) {
                $locale = trim(strstr($locale, ';', true));
                $locale = substr($locale, 0, 2);
                if (in_array($locale, self::SUPPORTED_LOCALES)) {
                    return $locale;
                }
            }
        }

        // 从查询参数获取
        $lang = $request->input('lang');
        if ($lang && in_array($lang, self::SUPPORTED_LOCALES)) {
            return $lang;
        }

        return self::$fallbackLocale;
    }

    /**
     * 翻译文本
     *
     * @param string $key 翻译键，使用点号分隔，如 'common.confirm'
     * @param array $params 替换参数
     * @param string|null $locale 指定语言，null 则使用当前语言
     * @return string 翻译后的文本
     */
    public static function get(string $key, array $params = [], ?string $locale = null): string
    {
        self::loadTranslations();

        $locale = $locale ?? self::$locale;

        // 获取翻译值
        $value = self::getTranslationValue($key, $locale);

        // 替换参数
        if (!empty($params)) {
            foreach ($params as $search => $replace) {
                $value = str_replace(':' . $search, $replace, $value);
                $value = str_replace('{' . $search . '}', $replace, $value);
            }
        }

        return $value;
    }

    /**
     * 获取翻译值
     */
    private static function getTranslationValue(string $key, string $locale): string
    {
        $keys = explode('.', $key);
        $value = self::$translations[$locale] ?? [];

        foreach ($keys as $k) {
            if (isset($value[$k])) {
                $value = $value[$k];
            } else {
                // 尝试使用回退语言
                if ($locale !== self::$fallbackLocale) {
                    return self::getTranslationValue($key, self::$fallbackLocale);
                }
                return $key;
            }
        }

        return is_string($value) ? $value : $key;
    }

    /**
     * 判断翻译是否存在
     */
    public static function has(string $key, ?string $locale = null): bool
    {
        self::loadTranslations();

        $locale = $locale ?? self::$locale;

        $keys = explode('.', $key);
        $value = self::$translations[$locale] ?? [];

        foreach ($keys as $k) {
            if (isset($value[$k])) {
                $value = $value[$k];
            } else {
                return false;
            }
        }

        return true;
    }
}