using System;
using System.Diagnostics;
using System.Timers;
using Timer = System.Timers.Timer;
using leak_test_project.Infrastructure;
using leak_test_project.Utils;

namespace leak_test_project.Services
{
    /// <summary>
    /// Sentinel C28 기기와의 통신 프로토콜을 관리하는 서비스.
    /// 자동 재연결(Auto-Reconnect) 및 예외 처리 포함.
    /// </summary>
    public class SentinelC28Service : IDisposable
    {
        private readonly ICommunication _communication;
        private int _sequence = 1;
        private Timer _reconnectTimer;
        private bool _shouldBeConnected = false;

        public event EventHandler<string> RawDataReceived;
        public event EventHandler<string> ResultReceived; 
        public event EventHandler<string> StreamingReceived; 
        public event EventHandler<bool> ConnectionChanged;
        
        /// <summary> 파싱된 최종 검사 결과 알림 </summary>
        public event EventHandler<Models.ParsedData> OnFinalResultParsed;
        
        /// <summary> 파싱된 실시간 스트리밍 데이터 알림 </summary>
        public event EventHandler<Models.ParsedData> OnStreamingParsed;

        public SentinelC28Service(ICommunication communication)
        {
            _communication = communication;
            _communication.DataReceived += OnDataReceived;
            _communication.ConnectionStatusChanged += OnConnectionStatusChanged;

            // 1초(1000ms)마다 연결 상태를 확인하고 재연결 시도
            _reconnectTimer = new Timer(1000);
            _reconnectTimer.AutoReset = false; // 재진입 방지
            _reconnectTimer.Elapsed += (s, e) => {
                if (_shouldBeConnected && !_communication.IsOpen)
                {
                    Debug.WriteLine($"[SentinelC28 Service] Attempting to reconnect to {_communication.Name}...");
                    Console.WriteLine($"[Service] Attempting to reconnect to {_communication.Name}...");
                    if (!_communication.Open())
                    {
                        // 실패 시 다시 타이머 시작
                        if (_shouldBeConnected) _reconnectTimer.Start();
                    }
                }
                else if (_shouldBeConnected)
                {
                    _reconnectTimer.Start();
                }
            };
        }

        private void OnConnectionStatusChanged(object sender, bool isConnected)
        {
            ConnectionChanged?.Invoke(this, isConnected);
            if (!isConnected && _shouldBeConnected) StartReconnectTimer();
        }

        public bool Connect() 
        {
            _shouldBeConnected = true;
            bool opened = _communication.Open();
            if (!opened) StartReconnectTimer();
            return opened;
        }

        public void Disconnect() 
        {
            _shouldBeConnected = false;
            _reconnectTimer.Stop();
            _communication.Close();
        }

        private void StartReconnectTimer()
        {
            if (!_reconnectTimer.Enabled) _reconnectTimer.Start();
        }

        public void SendCommand(string command, string dataTypeCode)
        {
            if (!_communication.IsOpen) return;

            try {
                string sequenceHex = _sequence.ToString("X2");
                string lengthHex = command.Length.ToString("X3");
                string payload = $"{sequenceHex}{lengthHex} {dataTypeCode}\t{command}";
                string crc = SentinelCrc8.CalculateHex(payload);
                
                string fullCommand = $"{crc}{payload}\r\n";
                Debug.WriteLine($"[SentinelC28 Service] Sending Command: {fullCommand.TrimEnd()}");
                
                if (!_communication.Write(fullCommand))
                {
                    FileLogger.Log("ERROR", "[SentinelC28] Failed to send command: Communication channel closed.");
                }
                
                _sequence = (_sequence >= 255) ? 1 : _sequence + 1;
            } catch (Exception ex) {
                FileLogger.Log("ERROR", $"[SentinelC28] Error sending command: {ex.Message}");
            }
        }

        private readonly System.Text.StringBuilder _receiveBuffer = new System.Text.StringBuilder(8192);
        private const int MaxBufferSize = 65536; // 64KB

        private void OnDataReceived(object sender, string rawData)
        {
            try {
                Debug.WriteLine($"[SentinelC28 Service] Raw Data Received: {rawData.Replace("\r", "\\r").Replace("\n", "\\n").Replace("\t", "\\t")}");
                RawDataReceived?.Invoke(this, rawData);
                
                if (string.IsNullOrEmpty(rawData)) return;

                lock (_receiveBuffer)
                {
                    if (_receiveBuffer.Length + rawData.Length > MaxBufferSize)
                    {
                        _receiveBuffer.Clear();
                        FileLogger.Log("WARNING", "[SentinelC28] Buffer size limit exceeded. Buffer cleared to prevent OOM.");
                    }

                    _receiveBuffer.Append(rawData);
                    string content = _receiveBuffer.ToString();

                    int splitIndex;
                    while ((splitIndex = GetFirstDelimiterIndex(content)) >= 0)
                    {
                        string frame = content.Substring(0, splitIndex);
                        content = content.Substring(splitIndex + 1);

                        // 버퍼 갱신 (처리한 데이터 잘라냄)
                        _receiveBuffer.Clear();
                        _receiveBuffer.Append(content);

                        if (string.IsNullOrWhiteSpace(frame)) continue;

                        // 헤더 분석 및 본문 추출
                        string body = SentinelParser.ExtractBody(frame, out char typeCode);

                        switch (typeCode)
                        {
                            case 'R': // 최종 결과 (Result Value)
                                ResultReceived?.Invoke(this, frame);
                                var finalParsed = SentinelParser.ParseFinalResult(frame);
                                OnFinalResultParsed?.Invoke(this, finalParsed);
                                break;

                            case 'S': // 스트리밍 데이터 (Streaming Value)
                                StreamingReceived?.Invoke(this, frame);
                                var streamParsed = SentinelParser.ParseStreamingValue(frame);
                                OnStreamingParsed?.Invoke(this, streamParsed);
                                break;

                            case 'M': // 일반 메시지
                                FileLogger.Log("INFO", $"[SentinelC28 Message] {body}");
                                break;
                        }
                    }
                }
            } catch (Exception ex) {
                FileLogger.Log("ERROR", $"[SentinelC28] Error parsing received data: {ex.Message}");
            }
        }

        private int GetFirstDelimiterIndex(string text)
        {
            int indexN = text.IndexOf('\n');
            int indexR = text.IndexOf('\r');
            if (indexN >= 0 && indexR >= 0) return Math.Min(indexN, indexR);
            return indexN >= 0 ? indexN : indexR;
        }

        public void Dispose()
        {
            Disconnect();
            
            // [Memory Leak 방지] 이벤트 핸들러 명시적 구독 해제
            if (_communication != null)
            {
                _communication.DataReceived -= OnDataReceived;
                _communication.ConnectionStatusChanged -= OnConnectionStatusChanged;
            }

            _reconnectTimer?.Stop();
            _reconnectTimer?.Dispose();
            _reconnectTimer = null;
        }
    }
}