using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Transactions;
using WebLib;

namespace 報到系統
{
    /// <summary>
    /// 簡訊發送服務
    /// 單例類，用於定時發送待發送簡訊
    /// </summary>
    public sealed class SMSSendingService
    {
        private static SMSSendingService _instance;
        private static readonly object _lockObject = new object();
        private bool _busy = false;

        /// <summary>
        /// 取得單一實例
        /// </summary>
        public static SMSSendingService Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (_lockObject)
                    {
                        if (_instance == null)
                        {
                            _instance = new SMSSendingService();
                        }
                    }
                }
                return _instance;
            }
        }

        private SMSSendingService()
        {
        }

        /// <summary>
        /// 是否正在忙碌中
        /// </summary>
        public bool IsBusy
        {
            get { return _busy; }
        }

        /// <summary>
        /// 啟動發送服務，發送所有待發送的簡訊
        /// </summary>
        public void Start()
        {
            // 若已在忙碌中，則不重複啟動
            if (_busy)
            {
                return;
            }

            try
            {
                _busy = true;

                using (var conn = DAC.NewConnection())
                {
                    // 查詢待發送簡訊（Status 為 PENDING 或 SENDING 的）
                    var dacQueue = new DAC_MessageQueue(conn);
                    var messagesToSend = dacQueue.SelectAllPendingOrSending();

                    // 如果沒有待發送簡訊，直接返回
                    if (messagesToSend.Count == 0)
                    {
                        _busy = false;
                        return;
                    }

                    // 查詢簡訊發送帳號密碼併填入 messagesToSend 的項目裡
                    var dacClasses = new DAC_Classes(conn);
                    var classes = dacClasses.SelectAll();

                    // 查詢簡訊平台的主帳號密碼
                    var dacMessagePlatforms = new DAC_MMSPlatform(conn);
                    var currentMMSPlatformAccount = dacMessagePlatforms.SelectByCode(PublicVariable.CurrentMMSPlatform);

                    // 查詢專案的簡訊帳號密碼
                    var dacMessageAccount = new DAC_ProjectMMSAccount(conn);
                    var messageAccounts = dacMessageAccount.SelectAll();

                    foreach (var message in messagesToSend)
                    {
                        var cls = classes.FirstOrDefault(p => p.ID == message.CourseID);
                        // 沒有設定計畫的，使用預設平台的主要帳號密碼
                        if (cls == null || string.IsNullOrEmpty(cls.ProjectID))
                        {
                            message.PlatformCode = PublicVariable.CurrentMMSPlatform;
                            message.MMSAccount = currentMMSPlatformAccount?.Account;
                            message.MMSPassword = currentMMSPlatformAccount?.Password;
                            continue;
                        }

                        var acc = messageAccounts.FirstOrDefault(p => p.ProjectID == cls.ProjectID && p.PlatformCode == PublicVariable.CurrentMMSPlatform);
                        // 沒有設定計畫簡訊帳號密碼的，使用預設平台的主要帳號密碼
                        if (acc == null || string.IsNullOrEmpty(acc.MMSAccount) || string.IsNullOrEmpty(acc.MMSPassword))
                        {
                            message.PlatformCode = PublicVariable.CurrentMMSPlatform;
                            message.MMSAccount = currentMMSPlatformAccount?.Account;
                            message.MMSPassword = currentMMSPlatformAccount?.Password;
                            continue;
                        }

                        // 使用計畫指定的帳號密碼
                        message.MMSAccount = acc.MMSAccount;
                        message.MMSPassword = acc.MMSPassword;
                        message.PlatformCode = PublicVariable.CurrentMMSPlatform;
                    }

                    // 發送
                    var dacLog = new DAC_MessageLog(conn);
                    foreach (var message in messagesToSend)
                    {
                        SendMessage(message, dacQueue, dacLog);
                        Thread.Sleep(500);
                    }
                }
            }
            catch (Exception ex)
            {
                // 記錄錯誤日誌
                LogError("SMSSendingService.Start", ex);
            }
            finally
            {
                _busy = false;
            }
        }

        /// <summary>
        /// 發送單條簡訊
        /// </summary>
        private void SendMessage(MessageQueueItem message, DAC_MessageQueue dacQueue, DAC_MessageLog dacLog)
        {
            using (TransactionScope ts = DAC.NewTransactionScope())
            {
                try
                {
                    // 1. 更新簡訊狀態為 SENDING
                    message.Status = "SENDING";
                    dacQueue.UpdateOne(message);
                    message.DB_APPNO++;

                    // 2. 呼叫簡訊服務商 API 發送
                    bool sendSuccess = false;
                    string failMessage = "";

                    try
                    {
                        switch (message.PlatformCode)
                        {
                            case "EVERY8D":
                                sendSuccess = EVERY8DSMSProvider.SendMMS(message, out failMessage);
                                break;
                            case "MITAKE":
                            default:
                                sendSuccess = MITAKESMSProvider.SendMMS(message, out failMessage);
                                break;
                        }
                    }
                    catch (Exception ex)
                    {
                        sendSuccess = false;
                        failMessage = ex.Message;
                    }

                    // 3. 記錄發送結果到 MessageLog
                    MessageLogItem logItem = new MessageLogItem
                    {
                        CourseID = message.CourseID,
                        Status = sendSuccess ? "SENT" : "FAILED",
                        Name = message.Name,
                        Mobile = message.Mobile,
                        Subject = message.Subject,
                        Content = message.Content,
                        DB_APPNO = 1,
                        DB_CRDAT = DateTime.Now,
                        DB_CRUSR = "SYSTEM",
                        DB_TRDAT = DateTime.MinValue,
                        DB_TRUSR = ""
                    };

                    // 如果失敗，記錄失敗訊息
                    if (!sendSuccess && !string.IsNullOrEmpty(failMessage))
                    {
                        logItem.FailMessage = failMessage;
                    }

                    dacLog.InsertOne(logItem);

                    // 4. 刪除 MessageQueue 紀錄
                    dacQueue.DeleteOne(message);

                    ts.Complete();
                }
                catch (Exception ex)
                {
                    LogError("SendMessage", ex, message.ID.ToString());
                    ts.Dispose();
                }
            }
        }

        /// <summary>
        /// 記錄錯誤日誌
        /// </summary>
        private void LogError(string source, Exception ex, string details = "")
        {
            try
            {
                string logPath = System.Web.HttpContext.Current?.Server.MapPath("~/Log") ?? "~/Log";
                if (!System.IO.Directory.Exists(logPath))
                {
                    System.IO.Directory.CreateDirectory(logPath);
                }

                string fileName = DateTime.Now.ToString("yyyyMMdd_HHmmss_fff");
                string message = string.Format(
                    "[{0}] {1}\r\nSource: {2}\r\nException: {3}\r\nDetails: {4}\r\nStackTrace: {5}\r\n",
                    DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"),
                    "SMS Sending Error",
                    source,
                    ex.Message,
                    details,
                    ex.StackTrace
                );

                System.IO.File.AppendAllText(
                    System.IO.Path.Combine(logPath, string.Format("SMSError_{0}.txt", DateTime.Now.ToString("yyyyMMdd"))),
                    message
                );
            }
            catch
            {
                // 忽略日誌記錄的錯誤
            }
        }
    }
}