using System;
using MongoDB.Driver;
using PolyTraderSharp.Extensions;
using System.Linq;
using System.Net.WebSockets;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using PolyTraderSharp.Models;

namespace PolyTraderSharp.Services
{
    public class AlchemyWebsocketService : BackgroundService
    {
        private const string CtfContractAddress = "0x4D97DCd97eC945f40cF65F87097ACe5EA0476045";
        private const string TransferSingleTopic = "0xc3d58168c5ae7397731d063d5bbf3d657854427343f4c083240f7aacaa2d0f62";
        private const string TransferBatchTopic = "0x4a39dc06d4c0dbc64b70af90fd698a233a518aa5d07e595d983b8c0526c8f7ce";

        private readonly TradingState _state;
        private readonly CopyTradingState _copyState;
        private readonly ServerSettings _settings;
        private readonly TraderMonitorService _traderMonitor;
        private readonly TerminalLogger _logger;

        public AlchemyWebsocketService(
            TradingState state,
            CopyTradingState copyState,
            ServerSettings settings,
            TraderMonitorService traderMonitor,
            TerminalLogger logger)
        {
            _state = state;
            _copyState = copyState;
            _settings = settings;
            _traderMonitor = traderMonitor;
            _logger = logger;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            if (!_settings.EnableBlockchainListener || string.IsNullOrEmpty(_settings.PolygonRpcUrl))
            {
                _logger.Info("Blockchain Listener is disabled in settings. Using raw polling.");
                _state.IsAlchemyHealthy = false;
                return;
            }

            _logger.Info("Alchemy WSS Service starting up...");

            while (!stoppingToken.IsCancellationRequested)
            {
                if (_state.GlobalTradingPaused || 
                   (_state.LiveTradingMode == TradingMode.Inactive && _state.DemoTradingMode == TradingMode.Inactive))
                {
                    _state.IsAlchemyHealthy = false;
                    await Task.Delay(5000, stoppingToken);
                    continue;
                }

                try
                {
                    await ConnectAndListenAsync(stoppingToken);
                }
                catch (WebSocketException ex)
                {
                    // Usually indicates a connection drop or 429
                    _logger.Warning($"Alchemy WSS drop: {ex.Message}. Falling back to API polling for 5 minutes.");
                    _state.IsAlchemyHealthy = false;
                    await Task.Delay(TimeSpan.FromMinutes(5), stoppingToken);
                }
                catch (Exception ex)
                {
                    if (ex.Message.Contains("429") || ex.Message.Contains("Too Many Requests"))
                    {
                        _logger.Error($"Alchemy HTTP 429 Limit reached. Suspending WSS for 5 minutes.");
                        _state.IsAlchemyHealthy = false;
                        await Task.Delay(TimeSpan.FromMinutes(5), stoppingToken);
                    }
                    else
                    {
                        _logger.Error($"Alchemy WSS Error: {ex.Message}. Retrying in 10s...");
                        _state.IsAlchemyHealthy = false;
                        await Task.Delay(10000, stoppingToken);
                    }
                }
            }
        }

        private async Task ConnectAndListenAsync(CancellationToken stoppingToken)
        {
            using var ws = new ClientWebSocket();
            var wssUrl = _settings.PolygonRpcUrl.Replace("https://", "wss://").Replace("http://", "ws://");

            _logger.Info($"Connecting to Alchemy WebSocket: {wssUrl.Substring(0, Math.Min(35, wssUrl.Length))}...");
            
            await ws.ConnectAsync(new Uri(wssUrl), stoppingToken);
            _state.IsAlchemyHealthy = true;
            _logger.Info("✅ Alchemy WSS Connected. Dynamic API-Throttling activated.");

            var activeTraders = _copyState.Traders.Values.Where(t => t.IsActive).ToList();
            var activeStateHash = string.Join(",", activeTraders.OrderBy(t => t.Id).Select(t => t.WalletAddress.ToLowerInvariant()));

            if (activeTraders.Count > 0)
            {
                var paddedAddresses = activeTraders.Select(t => PadAddress(t.WalletAddress)).ToList();
                int batchSize = 3; // Alchemy limits Topic arrays to a max of 3/4 entries
                int reqId = 1;

                for (int i = 0; i < paddedAddresses.Count; i += batchSize)
                {
                    var chunk = paddedAddresses.Skip(i).Take(batchSize).ToList();
                    var addrJson = JsonSerializer.Serialize(chunk);

                    // Buys: Master Trader is the receiver (Topic 3)
                    var subscribeBuysStr = $@"{{
                        ""jsonrpc"": ""2.0"",
                        ""id"": {reqId++},
                        ""method"": ""eth_subscribe"",
                        ""params"": [
                            ""logs"",
                            {{
                                ""address"": ""{CtfContractAddress}"",
                                ""topics"": [
                                    [""{TransferSingleTopic}"", ""{TransferBatchTopic}""],
                                    null,
                                    null,
                                    {addrJson}
                                ]
                            }}
                        ]
                    }}";

                    // Sells: Master Trader is the sender (Topic 2)
                    var subscribeSellsStr = $@"{{
                        ""jsonrpc"": ""2.0"",
                        ""id"": {reqId++},
                        ""method"": ""eth_subscribe"",
                        ""params"": [
                            ""logs"",
                            {{
                                ""address"": ""{CtfContractAddress}"",
                                ""topics"": [
                                    [""{TransferSingleTopic}"", ""{TransferBatchTopic}""],
                                    null,
                                    {addrJson}
                                ]
                            }}
                        ]
                    }}";

                    await ws.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes(subscribeBuysStr)), WebSocketMessageType.Text, true, stoppingToken);
                    await ws.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes(subscribeSellsStr)), WebSocketMessageType.Text, true, stoppingToken);
                }
            }
            else
            {
                _logger.Info("Keine aktiven Master-Trader. Socket läuft im Standby...");
            }

            var buffer = new byte[1024 * 64];

            var loopCts = CancellationTokenSource.CreateLinkedTokenSource(stoppingToken);
            
            var monitorTask = Task.Run(async () => 
            {
                while (!loopCts.IsCancellationRequested)
                {
                    await Task.Delay(5000, loopCts.Token);
                    var currentTraders = _copyState.Traders.Values.Where(t => t.IsActive).ToList();
                    var currentHash = string.Join(",", currentTraders.OrderBy(t => t.Id).Select(t => t.WalletAddress.ToLowerInvariant()));
                    if (currentHash != activeStateHash)
                    {
                        _logger.Info("🔄 Master-Trader Liste hat sich geändert. Starte Alchemy WSS mit neuen Filtern neu...");
                        loopCts.Cancel();
                        break;
                    }
                }
            });

            try
            {
                while (ws.State == WebSocketState.Open && !loopCts.IsCancellationRequested)
                {
                    var result = await ws.ReceiveAsync(new ArraySegment<byte>(buffer), loopCts.Token);
                    if (result.MessageType == WebSocketMessageType.Close)
                    {
                        break;
                    }

                    var message = Encoding.UTF8.GetString(buffer, 0, result.Count);
                    
                    try
                    {
                        ProcessMessage(message);
                    }
                    catch (Exception ex)
                    {
                        _logger.Error($"Error parsing WSS msg: {ex.Message}");
                    }
                }
            }
            catch (OperationCanceledException)
            {
                // Expected when reconnecting due to trader list change
            }
            finally
            {
                if (!loopCts.IsCancellationRequested) loopCts.Cancel();
            }
        }

        private void ProcessMessage(string jsonStr)
        {
            using var doc = JsonDocument.Parse(jsonStr);
            var root = doc.RootElement;

            if (!root.TryGetProperty("params", out var paramsEl)) return;
            if (!paramsEl.TryGetProperty("result", out var resultEl)) return;
            if (!resultEl.TryGetProperty("topics", out var topicsEl) || topicsEl.GetArrayLength() < 4) return;

            var topics = topicsEl.EnumerateArray().Select(t => t.GetString()).ToList();
            var fromTopic = topics[2]?.ToLowerInvariant();
            var toTopic = topics[3]?.ToLowerInvariant();

            if (fromTopic == null || toTopic == null) return;

            var activeTraders = _copyState.Traders.Values.Where(t => t.IsActive).ToList();
            string? triggeredAddress = null;

            foreach (var trader in activeTraders)
            {
                var padded = PadAddress(trader.WalletAddress);
                if (fromTopic == padded || toTopic == padded)
                {
                    triggeredAddress = trader.WalletAddress;
                    break;
                }
            }

            if (!string.IsNullOrEmpty(triggeredAddress))
            {
                string txHash = resultEl.TryGetProperty("transactionHash", out var th) ? th.GetString() ?? "unknown" : "unknown";
                _traderMonitor.TriggerFastBlockchainPoll(txHash, _settings.PolygonRpcUrl, triggeredAddress);
            }
        }

        private string PadAddress(string address)
        {
            string stripped = address.Replace("0x", "", StringComparison.OrdinalIgnoreCase).ToLowerInvariant();
            return "0x" + stripped.PadLeft(64, '0');
        }
    }
}