using System;
using System.Threading;
using System.Threading.Channels;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using PolyTraderSharp.Models;
using System.Collections.Concurrent;
using System.Linq;

namespace PolyTraderSharp.Services
{
    public class CopyTradingEngine : BackgroundService
    {
        private readonly TradingState _state;
        private readonly ChannelReader<CopySignal> _signalReader;
        private readonly ChannelWriter<ClosedTrade> _closedTradeWriter;
        private readonly TerminalLogger _logger;
        private readonly PolymarketClobClient _clob;
        private readonly PolymarketApiService _api;
        private readonly LiteDB.ILiteDatabase _db;
        private static readonly ConcurrentDictionary<string, MarketData> _marketCache = new(StringComparer.OrdinalIgnoreCase);

        public CopyTradingEngine(
            TradingState state,
            ChannelReader<CopySignal> signalReader,
            ChannelWriter<ClosedTrade> closedTradeWriter,
            TerminalLogger logger,
            PolymarketClobClient clob,
            PolymarketApiService api,
            LiteDB.ILiteDatabase db = null)
        {
            _state = state;
            _signalReader = signalReader;
            _closedTradeWriter = closedTradeWriter;
            _logger = logger;
            _clob = clob;
            _api = api;
            _db = db;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            _logger.Info("CopyTradingEngine Channel Listener started (Concurrent).");
            var semaphore = new SemaphoreSlim(15, 15);

            await foreach (var signal in _signalReader.ReadAllAsync(stoppingToken))
            {
                await semaphore.WaitAsync(stoppingToken);
                
                _ = Task.Run(async () =>
                {
                    try
                    {
                        await ProcessSignalAsync(signal);
                    }
                    catch (Exception ex)
                    {
                        _logger.Error($"Absturz im SignalProcessor: {ex.Message}");
                    }
                    finally
                    {
                        semaphore.Release();
                    }
                }, stoppingToken);
            }
        }

        private async Task ProcessSignalAsync(CopySignal signal)
        {
            if (_state.GlobalTradingPaused)
            {
                return;
            }

            // Internal System Signal (e.g. Demo Auto-Close)
            if (signal.TraderId == 0)
            {
                var sysaccountTasks = new List<Task>();
                foreach (var account in _state.Accounts.Values.Where(a => a.IsDemo && a.IsActive))
                {
                    if (account.OpenPositions.ContainsKey(signal.TokenId))
                    {
                        sysaccountTasks.Add(ProcessAccountOrderAsync(account, null, signal));
                    }
                }
                await Task.WhenAll(sysaccountTasks);
                return;
            }

            if (!_state.Traders.TryGetValue(signal.TraderId, out var trader) || !trader.IsActive)
                return;

            var accountTasks = new List<Task>();

            foreach (var accountId in trader.AssignedAccountIds)
            {
                if (!_state.Accounts.TryGetValue(accountId, out var account) || !account.IsActive)
                    continue;

                accountTasks.Add(ProcessAccountOrderAsync(account, trader, signal));
            }

            await Task.WhenAll(accountTasks);
        }

        private async Task ProcessAccountOrderAsync(AccountState account, TrackedTrader trader, CopySignal signal)
        {
            var mode = account.IsDemo ? _state.DemoTradingMode : _state.LiveTradingMode;
            if (mode == TradingMode.Inactive)
                return;

            // Restrict BUY operations if mode is SellOnly
            if (mode == TradingMode.SellOnly && signal.Side == "BUY")
                return;

            string shareType = string.IsNullOrEmpty(signal.Outcome) ? signal.Side : signal.Outcome;

            // ==========================================
            // PRE-FLIGHT RISK CHECKS (Before DB/API!)
            // ==========================================
            decimal exactShares = 0m;
            decimal exactUsdc = 0m;
            decimal orderPrice = signal.Price;
            
            if (signal.Side == "BUY")
            {
                if (signal.Price > account.MaxBuyPrice && account.TotalBalance >= 500m)
                {
                    _logger.TradeReasoning($"❌ Trade BUY [{signal.MarketQuestion}] [{shareType}] verworfen:\n" +
                                           $"   Konto:      {account.Name}\n" +
                                           $"   Begründung: Preis (${signal.Price:F3}) übersteigt das MaxBuy Limit (${account.MaxBuyPrice:F3})");
                    return;
                }

                decimal investedInMarket = account.OpenPositions.TryGetValue(signal.TokenId, out var ep) ? ep.AmountUsd : 0m;
                decimal minTrade = 1.0m;
                decimal maxAllowed = account.TotalBalance * (account.MaxTradePercent / 100.0m);
                
                // Low Balance Bypass (Stufen-System)
                // Erhöht auf 1.20m um Puffer für das API Min-Limit von $1.00 zu gewährleisten
                if (account.TotalBalance < 150m) maxAllowed = Math.Min(1.20m, Math.Max(account.AvailableBalance, 0m));
                else if (account.TotalBalance < 500m) maxAllowed = Math.Min(3.0m, Math.Max(account.AvailableBalance, 0m));

                decimal maxAmountToBuy = maxAllowed - investedInMarket;
                decimal investedInMaster = account.OpenPositions.Values.Where(p => p.SourceTraderId == trader.Id).Sum(p => (decimal)p.AmountUsd);
                decimal maxAllowedPerMaster = account.TotalBalance * (account.PerMasterLimit / 100.0m);

                if ((investedInMaster + maxAmountToBuy) > maxAllowedPerMaster)
                {
                    decimal pctInvested = account.TotalBalance > 0 ? (investedInMaster / account.TotalBalance) * 100m : 0m;
                    _logger.TradeReasoning($"❌ Trade BUY [{signal.MarketQuestion}] [{shareType}] verworfen:\n" +
                                           $"   Konto:      {account.Name}\n" +
                                           $"   Begründung: PerMasterLimit ({account.PerMasterLimit:F1}%) erreicht. Bisher investiert in '{trader.DisplayName}': ${investedInMaster:F2} ({pctInvested:F1}%).");
                    return;
                }

                if (maxAmountToBuy < minTrade)
                {
                    _logger.TradeReasoning($"❌ Trade BUY [{signal.MarketQuestion}] [{shareType}] verworfen:\n" +
                                           $"   Konto:      {account.Name}\n" +
                                           $"   Begründung: Kauflimit (${maxAllowed:F2}) bereits in Markt investiert (${investedInMarket:F2}). Rest: ${maxAmountToBuy:F2} < MinTrade (${minTrade:F2})");
                    return;
                }

                if (maxAmountToBuy > account.AvailableBalance)
                {
                    _logger.TradeReasoning($"❌ Trade BUY [{signal.MarketQuestion}] [{shareType}] verworfen:\n" +
                                           $"   Konto:      {account.Name}\n" +
                                           $"   Begründung: Kontostand (${account.AvailableBalance:F2}) nicht ausreichend für errechnetes Size (${maxAmountToBuy:F2})");
                    return;
                }

                decimal desiredLimit = signal.Price * 1.05m;
                orderPrice = Math.Min(desiredLimit, account.MaxBuyPrice);
                if (orderPrice > 0.99m) orderPrice = 0.99m;

                var exact = PolymarketClobClient.CalculateExactOrderAmounts(maxAmountToBuy, orderPrice, orderPrice, "BUY");
                if (exact.shares <= 0 || exact.usdc > account.AvailableBalance)
                {
                    _logger.TradeReasoning($"❌ Trade BUY [{signal.MarketQuestion}] [{shareType}] gestoppt:\n" +
                                           $"   Begründung: Mathematisch unmöglicher Trade ({exact.shares} Shares für ${exact.usdc:F2}). Kontostand (${account.AvailableBalance:F2}) reicht für Minimum nicht aus.");
                    return;
                }
                exactShares = exact.shares;
                exactUsdc = exact.usdc;
            }
            else if (signal.Side == "SELL")
            {
                // PRE-FLIGHT SELL Check: Exists in portfolio?
                // Allow fallback matching by slug and outcome if tokenId is slightly off or missing
                var inPortfolio = account.OpenPositions.Values.FirstOrDefault(p => p.TokenId == signal.TokenId || (p.MarketSlug == signal.MarketSlug && p.Outcome == signal.Outcome));
                if (inPortfolio == null)
                {
                    _logger.Info($"❌ Trade SELL [{signal.MarketQuestion}] [{shareType}] ignoriert:\n" +
                                 $"   Konto:      {account.Name}\n" +
                                 $"   Begründung: Position nicht im Portfolio gefunden (möglicherweise zuvor gefiltert).");
                    return;
                }
            }

            // ==========================================
            // EXPENSIVE DB/API MARKET LOOKUP
            // ==========================================
            bool isNegRisk = false;
            
            if (_marketCache.TryGetValue(signal.TokenId, out var cachedData))
            {
                if (!string.IsNullOrEmpty(cachedData.Slug)) signal.MarketSlug = cachedData.Slug;
                if (!string.IsNullOrEmpty(cachedData.Question)) signal.MarketQuestion = cachedData.Question;
                if (cachedData.EndDate.HasValue) signal.EndDate = cachedData.EndDate;
                isNegRisk = cachedData.NegRisk;
            }
            else if (_db != null)
            {
                try
                {
                    var marketColl = _db.GetCollection<MarketData>("markets");
                    var marketData = marketColl.Find(x => x.ClobTokenIds != null && x.ClobTokenIds.Contains(signal.TokenId)).FirstOrDefault();
                    
                    if (marketData == null && !string.IsNullOrEmpty(signal.TokenId))
                    {
                        var fetchedMarket = await _api.GetMarketByTokenIdAsync(signal.TokenId);
                        if (fetchedMarket != null) { marketColl.Upsert(fetchedMarket); marketData = fetchedMarket; }
                    }

                    if (marketData == null && !string.IsNullOrEmpty(signal.MarketSlug) && !signal.MarketSlug.StartsWith("0x"))
                    {
                        var fetchedMarkets = await _api.GetMarketsByEventSlugAsync(signal.MarketSlug);
                        foreach (var fetched in fetchedMarkets) {
                            marketColl.Upsert(fetched);
                            if (fetched.ClobTokenIds != null && fetched.ClobTokenIds.Contains(signal.TokenId)) marketData = fetched;
                        }
                    }

                    if (marketData != null)
                    {
                        if (!string.IsNullOrEmpty(marketData.Slug)) signal.MarketSlug = marketData.Slug;
                        if (!string.IsNullOrEmpty(marketData.Question)) signal.MarketQuestion = marketData.Question;
                        if (marketData.EndDate.HasValue) signal.EndDate = marketData.EndDate;
                        isNegRisk = marketData.NegRisk;
                        
                        // Add to Cache for fast lookup
                        _marketCache[signal.TokenId] = marketData;
                    }
                }
                catch (Exception ex)
                {
                    _logger.Warning($"Fehler beim Abrufen von MarketData für Token {signal.TokenId}: {ex.Message}");
                }
            }

            // If BUY -> Invest
            if (signal.Side == "BUY")
            {
                    if (account.IsDemo)
                    {
                        var pos = new Position
                        {
                            TokenId = signal.TokenId,
                            MarketSlug = signal.MarketSlug,
                            SourceTraderId = trader.Id,
                            SourceTraderName = trader.DisplayName,
                            SourceTraderAddress = trader.WalletAddress,
                            MarketQuestion = signal.MarketQuestion,
                            Outcome = signal.Outcome,
                            Side = "BUY",
                            EntryPrice = orderPrice,
                            Size = exactShares,
                            AmountUsd = exactUsdc,
                            ExpiryDate = signal.EndDate ?? DateTime.UtcNow.AddDays(14)
                        };

                        _state.TotalCopyTrades++;
                        
                        var finalPos = account.OpenPositions.AddOrUpdate(signal.TokenId, pos, (k, old) =>
                        {
                            old.Size += pos.Size;
                            old.AmountUsd += pos.AmountUsd;
                            old.EntryPrice = old.AmountUsd / old.Size; // weighted average
                            return old;
                        });

                        if (_db != null) _db.GetCollection<Position>($"demo_positions_{account.AccountId}").Upsert(finalPos);

                        account.UpdateBalance(account.AvailableBalance - exactUsdc);
                        if (_db != null) _db.GetCollection<AccountState>("accounts").Upsert(account);
                        _logger.Trade($"✅ [DEMO AUSGEFÜHRT]\n" +
                                      $"   Konto: {account.Name}\n" +
                                      $"   Markt: {signal.MarketQuestion}\n" +
                                      $"   BUY:   {exactShares:F4} Shares [{shareType}] @ ${orderPrice:F3} (Gesamt: ${exactUsdc:F2})");
                    }
                    else
                    {
                        _logger.Info($"🌐 [LIVE-EXECUTION] Sende MARKET BUY an Polymarket CTF-Router...\n" +
                                     $"   Account: {account.Name}\n" +
                                     $"   Limit:   ${orderPrice:F3} (Target: {signal.Price:F3} + 5%)");
                        
                        var result = await _clob.PlaceOrderAsync(account, signal.TokenId, signal.Side, exactUsdc, orderPrice, "MARKET", _state.DebugOrderPayloadLog, isNegRisk);

                        if (result == "OK")
                        {
                            var pos = new Position
                            {
                                TokenId = signal.TokenId,
                                MarketSlug = signal.MarketSlug,
                                SourceTraderId = trader.Id,
                                SourceTraderName = trader.DisplayName,
                                SourceTraderAddress = trader.WalletAddress,
                                MarketQuestion = signal.MarketQuestion,
                                Outcome = signal.Outcome,
                                Side = "BUY",
                                EntryPrice = orderPrice, // Real execution price will update on next SyncOpenPositions poll
                                Size = exactShares,
                                AmountUsd = exactUsdc,
                                ExpiryDate = signal.EndDate ?? DateTime.UtcNow.AddDays(14)
                            };

                            _state.TotalCopyTrades++;
                            account.OpenPositions.AddOrUpdate(signal.TokenId, pos, (k, old) =>
                            {
                                old.Size += pos.Size;
                                old.AmountUsd += pos.AmountUsd;
                                old.EntryPrice = old.AmountUsd / old.Size;
                                return old;
                            });

                            account.UpdateBalance(account.AvailableBalance - exactUsdc);
                            if (_db != null) _db.GetCollection<AccountState>("accounts").Upsert(account);

                            if (_db != null)
                            {
                                var liveCol = _db.GetCollection<Position>($"open_positions_{account.AccountId}");
                                if (account.OpenPositions.TryGetValue(signal.TokenId, out var savedPos))
                                {
                                    liveCol.Upsert(savedPos);
                                }
                            }
                        }
                    }
                }
                // If SELL -> Divest
                else if (signal.Side == "SELL")
                {
                    bool removed = account.OpenPositions.TryRemove(signal.TokenId, out var openPos);
                    
                    if (!removed && !string.IsNullOrEmpty(signal.MarketSlug))
                    {
                        var altPos = account.OpenPositions.Values.FirstOrDefault(p => p.MarketSlug == signal.MarketSlug && p.Outcome == signal.Outcome);
                        if (altPos != null)
                        {
                            removed = account.OpenPositions.TryRemove(altPos.TokenId, out openPos);
                            if (removed)
                            {
                                _logger.Info($"Fallback: Position für SELL über Slug+Outcome gefunden ({altPos.TokenId}) statt TokenId ({signal.TokenId})");
                                signal.TokenId = altPos.TokenId; // Fix for further processing
                            }
                        }
                    }

                    if (removed)
                    {
                        if (account.IsDemo)
                        {
                            if (_db != null) _db.GetCollection<Position>($"demo_positions_{account.AccountId}").Delete(signal.TokenId);
                            
                            decimal exitUsd = openPos.Size * signal.Price;
                            decimal realizedPnl = exitUsd - openPos.AmountUsd;
                            
                            _state.GlobalPnl += realizedPnl;
                            account.UpdateBalance(account.AvailableBalance + exitUsd);
                            if (_db != null) _db.GetCollection<AccountState>("accounts").Upsert(account);

                            var ct = new ClosedTrade
                            {
                                TradeId = _state.TotalCopyTrades,
                                AccountId = account.AccountId,
                                SourceTraderId = signal.TraderId,
                                IsDemo = account.IsDemo,
                                MarketSlug = signal.MarketSlug,
                                MarketQuestion = signal.MarketQuestion,
                                Outcome = signal.Outcome,
                                Side = signal.Side,
                                EntryPrice = openPos.EntryPrice,
                                ExitPrice = signal.Price,
                                Size = openPos.Size,
                                RealizedPnl = realizedPnl,
                                PnlPercent = openPos.AmountUsd > 0 ? (realizedPnl / openPos.AmountUsd * 100m) : 0m,
                                OpenedAt = openPos.OpenedAt,
                                ClosedAt = DateTime.UtcNow,
                                ExitReason = signal.Reason
                            };
                            
                            _closedTradeWriter.TryWrite(ct);
                            _logger.Trade($"✅ [DEMO GESCHLOSSEN]\n" +
                                          $"   Konto: {account.Name}\n" +
                                          $"   Markt: {signal.MarketQuestion}\n" +
                                          $"   SELL:  {openPos.Size:F2} Shares [{shareType}] @ ${signal.Price:F3} (Gewinn: ${realizedPnl:F2})");
                        }
                        else
                        {
                            decimal sellLimit = 0.01m; // Slippage Limit (Min $0.01/share)
                            decimal maxInvest = openPos.Size * sellLimit;

                            var exact = PolymarketClobClient.CalculateExactOrderAmounts(maxInvest, sellLimit, sellLimit, "SELL", "MARKET");

                            if (exact.shares <= 0)
                            {
                                _logger.TradeReasoning($"❌ Trade SELL [{signal.MarketQuestion}] [{shareType}] fehlgeschlagen!\n" +
                                                       $"   Konto:      {account.Name}\n" +
                                                       $"   Grund:      Mathematical Order Size Error (Dust Token).");
                                account.OpenPositions.TryAdd(signal.TokenId, openPos);
                                return;
                            }

                            _logger.Info($"🌐 [LIVE-EXECUTION] Sende MARKET SELL an Polymarket CTF-Router...\n" +
                                         $"   Account: {account.Name}\n" +
                                         $"   Typ:     MARKET Order");

                            var result = await _clob.PlaceOrderAsync(account, signal.TokenId, signal.Side, maxInvest, sellLimit, "MARKET", _state.DebugOrderPayloadLog, isNegRisk);

                            if (result == "OK")
                            {
                                // Simulate fill at expected price for immediate UI accuracy 
                                // (Exact executed amounts will auto-correct on next SyncOpenPositions poll)
                                decimal exitUsd = exact.shares * signal.Price;
                                decimal realizedPnl = exitUsd - openPos.AmountUsd;
                                
                                _state.GlobalPnl += realizedPnl;
                                account.UpdateBalance(account.AvailableBalance + exitUsd);
                                if (_db != null) _db.GetCollection<AccountState>("accounts").Upsert(account);

                                var ct = new ClosedTrade
                                {
                                    TradeId = _state.TotalCopyTrades,
                                    AccountId = account.AccountId,
                                    SourceTraderId = signal.TraderId,
                                    IsDemo = false,
                                    MarketSlug = signal.MarketSlug,
                                    MarketQuestion = signal.MarketQuestion,
                                    Outcome = signal.Outcome,
                                    Side = signal.Side,
                                    EntryPrice = openPos.EntryPrice,
                                    ExitPrice = signal.Price,
                                    Size = openPos.Size,
                                    RealizedPnl = realizedPnl,
                                    PnlPercent = openPos.AmountUsd > 0 ? (realizedPnl / openPos.AmountUsd * 100m) : 0m,
                                    OpenedAt = openPos.OpenedAt,
                                    ClosedAt = DateTime.UtcNow,
                                    ExitReason = signal.Reason
                                };
                                
                                _closedTradeWriter.TryWrite(ct);
                                _logger.Trade($"✅ [LIVE GESCHLOSSEN] - {account.Name} - Gewinne/Verluste in Kürze im API Sync sichtbar.");
                            }
                            else
                            {
                                // Call failed, log it so the user knows Sells are being attempted but failing.
                                _logger.TradeReasoning($"❌ Trade SELL [{signal.MarketQuestion}] [{shareType}] fehlgeschlagen!\n" +
                                                       $"   Konto:      {account.Name}\n" +
                                                       $"   Grund:      {result}\n" +
                                                       $"   Aktion:     Position bleibt vorerst im Portfolio erhalten.");

                                // Reverse the TryRemove if it failed, so the next poll can try again
                                account.OpenPositions.TryAdd(signal.TokenId, openPos);
                            }
                        }
                    }
                    else
                    {
                        _logger.Info($"❌ Trade SELL [{signal.MarketQuestion}] [{shareType}] ignoriert:\n" +
                                     $"   Konto:      {account.Name}\n" +
                                     $"   Begründung: Position nicht im Portfolio gefunden (möglicherweise zuvor gefiltert).");
                    }
                }
            }

    }
}