using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using BITKit;
using Cysharp.Threading.Tasks;
using Microsoft.Extensions.Logging;

namespace Net.BITKit.Localization
{
    /// <summary>
    /// 本地化
    /// </summary>
    public interface ILocalizationService
    {
        public string Prefix { get; }
        /// <summary>
        /// 当前语言
        /// </summary>
        public string CurrentLanguage { get; }
        /// <summary>
        /// 更改回调,通常在此检查并下载语言包
        /// </summary>
        public event Func<string,string,UniTask> OnLanguageChangeAsync;
        /// <summary>
        /// 语言更改完成回调,UI和World执行更新 
        /// </summary>
        public event Action<string,string> OnLanguageChanged;
        /// <summary>
        /// 获取翻译文本,返回无复制的引用
        /// </summary>
        /// <param name="key"></param>
        /// <param name="language">语言,默认为当前CultureInfo.Name</param>
        /// <returns></returns>
        public string GetLocalizedString(string key,string language=null);
        public UniTask ChangeLanguageAsync(string newLanguage);
        public IDictionary<string, IDictionary<string, string>> LocalizedStrings { get; }
    }

    public class LocalizationService : ILocalizationService,IDisposable
    {
        private static LocalizationService _singleton;
        public string Prefix => "#";
        private char _prefix = '#';
        public string CurrentLanguage { get; private set; }

        public event Func<string, string, UniTask> OnLanguageChangeAsync;
        public event Action<string, string> OnLanguageChanged;

        private readonly ILogger<LocalizationService> _logger;
    
        public IDictionary<string, IDictionary<string, string>> LocalizedStrings { get; } =
            new Dictionary<string, IDictionary<string, string>>();

        private readonly ValidHandle _isBusy = new();
        
        private readonly HashSet<string> _untranslatedKeys = new();

        public LocalizationService(ILogger<LocalizationService> logger)
        {
            if (_singleton is not null)
            {
                logger.LogError("LocalizationService can only be one singleton");
                return;
            }
            _logger = logger;
        }


        public string GetLocalizedString(string key, string language = null)
        {
            language ??= CurrentLanguage; // 默认使用当前语言

            if (key[0] != _prefix)
            {
                key = _prefix + key;
            }
            if (LocalizedStrings.TryGetValue(language, out var langDict) && langDict.TryGetValue(key, out var value))
            {
                return value;
            }
            _untranslatedKeys.Add(key);
            return key.Replace(Prefix,string.Empty).Replace("_"," "); // 如果找不到翻译，就返回 key 本身（常见策略）
        }
        public async UniTask ChangeLanguageAsync(string newLanguage)
        {
            if (CurrentLanguage == newLanguage) return;
            var oldLanguage = CurrentLanguage;
            CurrentLanguage = newLanguage;
            
            await _isBusy;
            using var _ = _isBusy.GetHandle();

            await UniTask.SwitchToMainThread();

                await OnLanguageChangeAsync.UniTaskFunc(oldLanguage, newLanguage);

            // 触发同步事件（例如更新 UI）
            OnLanguageChanged?.Invoke(oldLanguage, newLanguage);
        }

        public void Dispose()
        {
            _isBusy?.Dispose();
            _singleton = null;
            _logger.LogInformation("Untranslated keys:\n"+string.Join("\n", _untranslatedKeys));
            _untranslatedKeys.Clear();
        }
    }

}