using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using FinlyticCore.Dtos.TechnicalAnalysis;
using FinlyticCore.Services.TradeRepublic;
using FinlyticTechnicalAnalysis.Database;
using FinlyticTechnicalAnalysis.Entities;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace FinlyticTechnicalAnalysis.Services;

public interface ITechnicalAnalysisDbService
{
    Task<TechnicalAnalysisDto?> GetAnalysisAsync(string isin, bool forceRefresh = false, CancellationToken cancellationToken = default);
    Task<LivePriceDto?> GetLivePriceAsync(string isin, CancellationToken cancellationToken = default);
}

public class TechnicalAnalysisDbService : ITechnicalAnalysisDbService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly IYahooMarketDataScraper _yahooScraper;
    private readonly ITradeRepublicService _trService;
    private readonly ITechnicalAnalysisCalculator _calculator;
    private readonly ILogger<TechnicalAnalysisDbService> _logger;

    // Cache Layer 1: In-Memory Candles Cache (TTL: 15 Minuten)
    private static readonly ConcurrentDictionary<string, (List<MarketCandleEntity> Candles, string Symbol, string Currency, DateTime FetchedAt)> _candleCache = new();
    
    // Per-ISIN Semaphores zur Vermeidung von Cache-Stampedes
    private static readonly ConcurrentDictionary<string, SemaphoreSlim> _perIsinLocks = new();
    private static readonly TimeSpan CandleCacheTtl = TimeSpan.FromMinutes(15);
    private static readonly TimeSpan DbCacheTtl = TimeSpan.FromHours(1);

    public TechnicalAnalysisDbService(
        IServiceScopeFactory scopeFactory,
        IYahooMarketDataScraper yahooScraper,
        ITradeRepublicService trService,
        ITechnicalAnalysisCalculator calculator,
        ILogger<TechnicalAnalysisDbService> logger)
    {
        _scopeFactory = scopeFactory;
        _yahooScraper = yahooScraper;
        _trService = trService;
        _calculator = calculator;
        _logger = logger;
    }

    public async Task<TechnicalAnalysisDto?> GetAnalysisAsync(string isin, bool forceRefresh = false, CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(isin)) return null;
        var cleanIsin = isin.Trim().ToUpperInvariant();

        // 1. Layer-1: Fast-Path aus In-Memory Cache (wenn kein forceRefresh)
        if (!forceRefresh && _candleCache.TryGetValue(cleanIsin, out var ramEntry) && DateTime.UtcNow - ramEntry.FetchedAt < CandleCacheTtl)
        {
            _logger.LogDebug("[{Channel}] RAM-Cache Hit for ISIN {Isin}. Merging live price...", "TechnicalAnalysisChannel", cleanIsin);
            return await BuildAnalysisWithLivePriceAsync(cleanIsin, ramEntry.Candles, ramEntry.Symbol, ramEntry.Currency, cancellationToken);
        }

        // Semaphor für ISIN holen (verhindert doppelte parallele Abfragen der gleichen ISIN)
        var semaphore = _perIsinLocks.GetOrAdd(cleanIsin, _ => new SemaphoreSlim(1, 1));
        await semaphore.WaitAsync(cancellationToken);

        try
        {
            // Re-Check nach Lock-Erhalt
            if (!forceRefresh && _candleCache.TryGetValue(cleanIsin, out ramEntry) && DateTime.UtcNow - ramEntry.FetchedAt < CandleCacheTtl)
            {
                return await BuildAnalysisWithLivePriceAsync(cleanIsin, ramEntry.Candles, ramEntry.Symbol, ramEntry.Currency, cancellationToken);
            }

            // 2. Layer-2: Prüfen ob frische Daten in der Datenbank liegen
            if (!forceRefresh)
            {
                var dbDto = await GetFromDbCacheAsync(cleanIsin, cancellationToken);
                if (dbDto != null)
                {
                    _logger.LogDebug("[{Channel}] DB-Cache Hit for ISIN {Isin}.", "TechnicalAnalysisChannel", cleanIsin);
                    return dbDto;
                }
            }

            // 3. Cache Miss / ForceRefresh: Vollständige Neuberechnung
            return await FullRefreshAsync(cleanIsin, cancellationToken);
        }
        finally
        {
            semaphore.Release();
            // Speicher aufräumen, falls Lock nicht mehr genutzt wird
            if (semaphore.CurrentCount == 1)
            {
                _perIsinLocks.TryRemove(cleanIsin, out _);
            }
        }
    }

    public async Task<LivePriceDto?> GetLivePriceAsync(string isin, CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(isin)) return null;
        var cleanIsin = isin.Trim().ToUpperInvariant();

        var (livePrice, liveBid, liveAsk) = await FetchLivePriceAsync(cleanIsin, cancellationToken);
        if (!livePrice.HasValue) return null;

        return new LivePriceDto(
            cleanIsin,
            Math.Round(livePrice.Value, 2),
            0m, // Percent change optional
            liveBid.HasValue ? Math.Round(liveBid.Value, 2) : null,
            liveAsk.HasValue ? Math.Round(liveAsk.Value, 2) : null
        );
    }

    private async Task<TechnicalAnalysisDto?> FullRefreshAsync(string cleanIsin, CancellationToken cancellationToken)
    {
        _logger.LogInformation("[{Channel}] Full refresh for ISIN {Isin}", "TechnicalAnalysisChannel", cleanIsin);

        var tickerTask = _yahooScraper.ResolveTickerFromIsinAsync(cleanIsin, cancellationToken);
        var macroTask = FetchMacroDataAsync(cancellationToken);

        await Task.WhenAll(tickerTask, macroTask);

        var ticker = await tickerTask;
        var querySymbol = !string.IsNullOrEmpty(ticker) ? ticker : cleanIsin;
        var (vix, gspc, dxy) = await macroTask;

        var yahooResult = await _yahooScraper.FetchHistoricalCandlesWithCurrencyAsync(querySymbol, "1y", "1d", cancellationToken);
        var candles = yahooResult.Candles;
        var currency = yahooResult.Currency;

        if (candles.Count == 0 && querySymbol != cleanIsin)
        {
            yahooResult = await _yahooScraper.FetchHistoricalCandlesWithCurrencyAsync(cleanIsin, "1y", "1d", cancellationToken);
            candles = yahooResult.Candles;
            currency = yahooResult.Currency;
        }

        if (candles.Count == 0)
        {
            _logger.LogWarning("[{Channel}] No candles retrieved for {Symbol}", "TechnicalAnalysisChannel", querySymbol);
            return null;
        }

        // In RAM-Cache sichern
        _candleCache[cleanIsin] = (candles.Select(CloneCandle).ToList(), querySymbol, currency, DateTime.UtcNow);

        // Live-Preis einpflegen
        await MergeLivePriceAsync(cleanIsin, candles, querySymbol, cancellationToken);

        var resultDto = BuildDto(cleanIsin, querySymbol, currency, candles, vix, gspc, dxy);

        // Synchron und sicher in DB persistieren
        await PersistToDbCacheAsync(cleanIsin, querySymbol, resultDto, cancellationToken);

        return resultDto;
    }

    private async Task<TechnicalAnalysisDto> BuildAnalysisWithLivePriceAsync(
        string cleanIsin, List<MarketCandleEntity> cachedCandles, string querySymbol, string currency, CancellationToken cancellationToken)
    {
        var candles = cachedCandles.Select(CloneCandle).ToList();

        var livePriceTask = FetchLivePriceAsync(cleanIsin, cancellationToken);
        var macroTask = FetchMacroDataAsync(cancellationToken);
        await Task.WhenAll(livePriceTask, macroTask);

        var (livePrice, liveBid, liveAsk) = await livePriceTask;
        var (vix, gspc, dxy) = await macroTask;

        if (livePrice.HasValue && livePrice.Value > 0m)
        {
            var today = DateTime.UtcNow.Date;
            var lastCandle = candles.LastOrDefault(c => c.Timestamp.Date == today);
            if (lastCandle != null)
            {
                lastCandle.Close = livePrice.Value;
                lastCandle.High = Math.Max(lastCandle.High, livePrice.Value);
                lastCandle.Low = Math.Min(lastCandle.Low, livePrice.Value);
                if (liveBid.HasValue) lastCandle.Bid = liveBid.Value;
                if (liveAsk.HasValue) lastCandle.Ask = liveAsk.Value;
            }
            else
            {
                var prevClose = candles.LastOrDefault()?.Close ?? livePrice.Value;
                candles.Add(new MarketCandleEntity
                {
                    Symbol = querySymbol, Interval = "1d", Timestamp = today,
                    Open = prevClose, High = Math.Max(prevClose, livePrice.Value),
                    Low = Math.Min(prevClose, livePrice.Value), Close = livePrice.Value,
                    Volume = 1000, Bid = liveBid, Ask = liveAsk
                });
            }
        }

        return BuildDto(cleanIsin, querySymbol, currency, candles, vix, gspc, dxy);
    }

    private async Task MergeLivePriceAsync(string cleanIsin, List<MarketCandleEntity> candles, string querySymbol, CancellationToken cancellationToken)
    {
        var (livePrice, liveBid, liveAsk) = await FetchLivePriceAsync(cleanIsin, cancellationToken);
        if (!livePrice.HasValue || livePrice.Value <= 0m) return;

        var today = DateTime.UtcNow.Date;
        var lastCandle = candles.LastOrDefault(c => c.Timestamp.Date == today);
        if (lastCandle != null)
        {
            lastCandle.Close = livePrice.Value;
            lastCandle.High = Math.Max(lastCandle.High, livePrice.Value);
            lastCandle.Low = Math.Min(lastCandle.Low, livePrice.Value);
            if (liveBid.HasValue) lastCandle.Bid = liveBid.Value;
            if (liveAsk.HasValue) lastCandle.Ask = liveAsk.Value;
        }
        else
        {
            var prevClose = candles.LastOrDefault()?.Close ?? livePrice.Value;
            candles.Add(new MarketCandleEntity
            {
                Symbol = querySymbol, Interval = "1d", Timestamp = today,
                Open = prevClose, High = Math.Max(prevClose, livePrice.Value),
                Low = Math.Min(prevClose, livePrice.Value), Close = livePrice.Value,
                Volume = 1000, Bid = liveBid, Ask = liveAsk
            });
        }
    }

    private async Task<(decimal? livePrice, decimal? liveBid, decimal? liveAsk)> FetchLivePriceAsync(string cleanIsin, CancellationToken cancellationToken)
    {
        decimal? livePrice = null;
        decimal? liveBid = null;
        decimal? liveAsk = null;
        
        try
        {
            using var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            cts.CancelAfter(1500); // Maximal 1.5 Sekunden Wartezeit auf Ticker

            var trTask = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
            
            int? subId = await _trService.SubscribeRealtimeTickerAsync(cleanIsin, tick =>
            {
                if (tick.Last != null && tick.Last.PriceValue > 0m)
                {
                    livePrice = tick.Last.PriceValue;
                    liveBid = tick.Bid?.PriceValue;
                    liveAsk = tick.Ask?.PriceValue;
                    trTask.TrySetResult(true);
                }
            }, cts.Token);

            if (subId.HasValue)
            {
                try
                {
                    await trTask.Task.WaitAsync(cts.Token);
                }
                catch (OperationCanceledException) { }
                
                await _trService.UnsubscribeRealtimeTickerAsync(subId.Value);
            }
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "[{Channel}] Real-time price fetch skipped for ISIN {Isin}", "TechnicalAnalysisChannel", cleanIsin);
        }

        return (livePrice, liveBid, liveAsk);
    }

    private async Task<(MacroDataEntity vix, MacroDataEntity gspc, MacroDataEntity dxy)> FetchMacroDataAsync(CancellationToken cancellationToken)
    {
        var vixTask = _yahooScraper.FetchMacroTickerAsync("^VIX", cancellationToken);
        var gspcTask = _yahooScraper.FetchMacroTickerAsync("^GSPC", cancellationToken);
        var dxyTask = _yahooScraper.FetchMacroTickerAsync("DX-Y.NY", cancellationToken);

        await Task.WhenAll(vixTask, gspcTask, dxyTask);

        var vix = await vixTask ?? new MacroDataEntity { Symbol = "^VIX", Value = 18.5m, TrendState = "Moderate" };
        var gspc = await gspcTask ?? new MacroDataEntity { Symbol = "^GSPC", Value = 5500m, TrendState = "Bullish" };
        var dxy = await dxyTask ?? new MacroDataEntity { Symbol = "DX-Y.NY", Value = 104.2m, TrendState = "Neutral" };

        return (vix, gspc, dxy);
    }

    private TechnicalAnalysisDto BuildDto(string cleanIsin, string querySymbol, string currency, List<MarketCandleEntity> candles, MacroDataEntity vix, MacroDataEntity gspc, MacroDataEntity dxy)
    {
        var vixRegime = vix.Value > 25m ? "HighVolatility" : (vix.Value > 18m ? "Moderate" : "LowVolatility");
        var summaryText = $"Markt-Vola (VIX: {vix.Value:F1}) ist {vixRegime}. S&P 500 Trend ist {gspc.TrendState}. DXY: {dxy.Value:F1}.";

        var marketRegime = new MarketRegimeDto(
            VixValue: vix.Value, VixRegime: vixRegime,
            MarketTrend: gspc.TrendState, DxyValue: dxy.Value,
            DxyState: dxy.TrendState == "Bullish" ? "DollarStrengthening" : "DollarWeakening",
            SummaryText: summaryText);

        var (indicators, patterns, signals) = _calculator.CalculateAnalysis(candles, currency);

        var candleDtos = candles.Select(c => new CandleDto(
            Timestamp: c.Timestamp, Open: c.Open, High: c.High,
            Low: c.Low, Close: c.Close, Volume: c.Volume,
            Bid: c.Bid, Ask: c.Ask)).ToList();

        return new TechnicalAnalysisDto(
            Isin: cleanIsin, Ticker: querySymbol, CompanyName: querySymbol,
            LastUpdated: DateTime.UtcNow, Candles: candleDtos,
            Indicators: indicators, Patterns: patterns, Signals: signals,
            MarketRegime: marketRegime, Currency: currency);
    }

    private async Task<TechnicalAnalysisDto?> GetFromDbCacheAsync(string cleanIsin, CancellationToken cancellationToken)
    {
        try
        {
            using var scope = _scopeFactory.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<TechnicalAnalysisDbContext>();
            var cached = await db.CachedAnalyses
                .AsNoTracking()
                .FirstOrDefaultAsync(c => c.Isin == cleanIsin, cancellationToken);

            if (cached != null && DateTime.UtcNow - cached.CalculatedAt < DbCacheTtl)
            {
                return JsonSerializer.Deserialize<TechnicalAnalysisDto>(cached.AnalysisJson);
            }
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "[{Channel}] Failed to read DB cache for ISIN {Isin}", "TechnicalAnalysisChannel", cleanIsin);
        }

        return null;
    }

    private async Task PersistToDbCacheAsync(string cleanIsin, string querySymbol, TechnicalAnalysisDto dto, CancellationToken cancellationToken)
    {
        try
        {
            using var scope = _scopeFactory.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<TechnicalAnalysisDbContext>();
            var json = JsonSerializer.Serialize(dto);

            var existing = await db.CachedAnalyses.FirstOrDefaultAsync(c => c.Isin == cleanIsin, cancellationToken);
            if (existing != null)
            {
                existing.Ticker = querySymbol;
                existing.AnalysisJson = json;
                existing.CalculatedAt = DateTime.UtcNow;
            }
            else
            {
                db.CachedAnalyses.Add(new CachedAnalysisEntity
                {
                    Isin = cleanIsin,
                    Ticker = querySymbol,
                    AnalysisJson = json,
                    CalculatedAt = DateTime.UtcNow
                });
            }

            await db.SaveChangesAsync(cancellationToken);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "[{Channel}] Failed to persist TA DB cache for ISIN {Isin}", "TechnicalAnalysisChannel", cleanIsin);
        }
    }

    private static MarketCandleEntity CloneCandle(MarketCandleEntity c) => new()
    {
        Symbol = c.Symbol, Interval = c.Interval, Timestamp = c.Timestamp,
        Open = c.Open, High = c.High, Low = c.Low, Close = c.Close,
        Volume = c.Volume, Bid = c.Bid, Ask = c.Ask
    };
}