using Newtonsoft.Json;
using System;
using System.IO;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using 報到系統客戶端.Models;

namespace 報到系統客戶端.Services
{
    /// <summary>
    /// API 服務基礎類別
    /// 處理 HTTP 請求、Session cookie、錯誤處理
    /// </summary>
    public class ApiService
    {
        private static ApiService _instance;
        private static readonly object _lockObject = new object();

        private string _baseUrl;
        private CookieContainer _cookieContainer;

        // 用於儲存 cookie 的檔案路徑
        private string _cookiePath;

        public static JsonSerializerSettings jsonConvertSettings = new JsonSerializerSettings { DateTimeZoneHandling = DateTimeZoneHandling.Local };

        public static object DeserializeObject(string value)
        {
            return JsonConvert.DeserializeObject(value, jsonConvertSettings);
        }
        public static T DeserializeObject<T>(string value)
        {
            return (T)JsonConvert.DeserializeObject(value, typeof(T), jsonConvertSettings);
        }

        /// <summary>
        /// 取得單例實例
        /// </summary>
        public static ApiService Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (_lockObject)
                    {
                        if (_instance == null)
                        {
                            _instance = new ApiService();
                        }
                    }
                }
                return _instance;
            }
        }

        private ApiService()
        {
            // 從設定檔讀取基底 URL
            _baseUrl = ConfigService.Instance.GetApiBaseUrl();
            if (string.IsNullOrWhiteSpace(_baseUrl))
            {
                _baseUrl = "http://localhost:58792";
            }

            // 初始化 Cookie 容器
            _cookieContainer = new CookieContainer();
            _cookiePath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
                "報到系統客戶端",
                "cookies.txt"
            );

            // 嘗試載入已儲存的 Cookie
            LoadCookies();
        }

        /// <summary>
        /// 設定基底 URL
        /// </summary>
        public string BaseUrl
        {
            set
            {
                _baseUrl = value;
            }
            get 
            {
                return _baseUrl;
            }
        }

        /// <summary>
        /// 執行 POST 請求
        /// </summary>
        public async Task<BaseResponse> PostAsync(string servicePath, string methodName, object parameters)
        {
            try
            {
                string url = $"{_baseUrl}{servicePath}/{methodName}";
                
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.Method = "POST";
                request.ContentType = "application/json; charset=utf-8";
                request.CookieContainer = _cookieContainer;
                request.KeepAlive = true;

                // 序列化參數
                string jsonData = JsonConvert.SerializeObject(parameters ?? new { });

                // 寫入請求體
                byte[] data = Encoding.UTF8.GetBytes(jsonData);
                request.ContentLength = data.Length;

                using (Stream requestStream = request.GetRequestStream())
                {
                    await requestStream.WriteAsync(data, 0, data.Length);
                }

                // 取得回應
                using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())
                {
                    // 更新 Cookie（用於 Session 管理）
                    _cookieContainer.Add(response.ResponseUri, response.Cookies);
                    SaveCookies();

                    using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                    {
                        string responseJson = await reader.ReadToEndAsync();
                        
                        // 解析回應
                        dynamic result = DeserializeObject(responseJson);
                        
                        // ASP.NET Web Service 會將結果包在 "d" 屬性中
                        if (result.d != null)
                        {
                            string dataJson = JsonConvert.SerializeObject(result.d);
                            return DeserializeObject<BaseResponse>(dataJson);
                        }
                        else
                        {
                            return DeserializeObject<BaseResponse>(responseJson);
                        }
                    }
                }
            }
            catch (WebException ex)
            {
                return new BaseResponse
                {
                    Success = false,
                    Message = $"網路錯誤: {ex.Message}"
                };
            }
            catch (Exception ex)
            {
                return new BaseResponse
                {
                    Success = false,
                    Message = $"錯誤: {ex.Message}"
                };
            }
        }

        /// <summary>
        /// 同步版本的 POST 請求（用於向後相容）
        /// </summary>
        public BaseResponse Post(string servicePath, string methodName, object parameters)
        {
            try
            {
                string url = $"{_baseUrl}{servicePath}/{methodName}";

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.Method = "POST";
                request.ContentType = "application/json; charset=utf-8";
                request.CookieContainer = _cookieContainer;
                request.KeepAlive = true;

                // 序列化參數
                string jsonData = JsonConvert.SerializeObject(parameters ?? new { });

                // 寫入請求體
                byte[] data = Encoding.UTF8.GetBytes(jsonData);
                request.ContentLength = data.Length;

                using (Stream requestStream = request.GetRequestStream())
                {
                    requestStream.Write(data, 0, data.Length);
                }

                // 取得回應
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {
                    // 更新 Cookie（用於 Session 管理）
                    _cookieContainer.Add(response.ResponseUri, response.Cookies);
                    SaveCookies();

                    using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                    {
                        string responseJson = reader.ReadToEnd();

                        // 解析回應
                        dynamic result = DeserializeObject(responseJson);

                        // ASP.NET Web Service 會將結果包在 "d" 屬性中
                        if (result.d != null)
                        {
                            string dataJson = JsonConvert.SerializeObject(result.d);
                            return DeserializeObject<BaseResponse>(dataJson);
                        }
                        else
                        {
                            return DeserializeObject<BaseResponse>(responseJson);
                        }
                    }
                }
            }
            catch (WebException ex)
            {
                return new BaseResponse
                {
                    Success = false,
                    Message = $"網路錯誤: {ex.Message}"
                };
            }
            catch (Exception ex)
            {
                return new BaseResponse
                {
                    Success = false,
                    Message = $"錯誤: {ex.Message}"
                };
            }
        }

        /// <summary>
        /// 清除所有 Session cookie
        /// </summary>
        public void ClearSession()
        {
            _cookieContainer = new CookieContainer();
            DeleteCookies();
        }

        /// <summary>
        /// 儲存 Cookie 到檔案
        /// </summary>
        private void SaveCookies()
        {
            try
            {
                string directory = Path.GetDirectoryName(_cookiePath);
                if (!Directory.Exists(directory))
                {
                    Directory.CreateDirectory(directory);
                }

                using (StreamWriter sw = new StreamWriter(_cookiePath, false, Encoding.UTF8))
                {
                    foreach (Cookie cookie in _cookieContainer.GetCookies(new Uri(_baseUrl)))
                    {
                        sw.WriteLine($"{cookie.Name}={cookie.Value}");
                    }
                }
            }
            catch
            {
                // 忽略儲存錯誤
            }
        }

        /// <summary>
        /// 從檔案載入 Cookie
        /// </summary>
        private void LoadCookies()
        {
            try
            {
                if (File.Exists(_cookiePath))
                {
                    using (StreamReader sr = new StreamReader(_cookiePath, Encoding.UTF8))
                    {
                        string line;
                        while ((line = sr.ReadLine()) != null)
                        {
                            if (string.IsNullOrWhiteSpace(line)) continue;

                            string[] parts = line.Split(new[] { '=' }, 2);
                            if (parts.Length == 2)
                            {
                                Cookie cookie = new Cookie(parts[0], parts[1])
                                {
                                    Path = "/",
                                    HttpOnly = true
                                };
                                _cookieContainer.Add(new Uri(_baseUrl), cookie);
                            }
                        }
                    }
                }
            }
            catch
            {
                // 忽略載入錯誤
            }
        }

        /// <summary>
        /// 刪除儲存的 Cookie 檔案
        /// </summary>
        private void DeleteCookies()
        {
            try
            {
                if (File.Exists(_cookiePath))
                {
                    File.Delete(_cookiePath);
                }
            }
            catch
            {
                // 忽略刪除錯誤
            }
        }
    }
}