using System.Threading.Channels;
using MongoDB.Driver;
using PolyTraderSharp.Extensions;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using PolyTraderSharp.Models;

namespace PolyTraderSharp.Services
{
    public class PersistenceService : BackgroundService
    {
        private readonly ChannelReader<ClosedTrade> _tradeReader;
        private readonly IMongoDatabase _db;
        private readonly TerminalLogger _logger;
        private readonly JobStatusRow _jobStatus;

        public PersistenceService(ChannelReader<ClosedTrade> tradeReader, IMongoDatabase db, TerminalLogger logger, JobManager jobManager)
        {
            _tradeReader = tradeReader;
            _db = db;
            _logger = logger;

            _jobStatus = new JobStatusRow
            {
                JobName = "MongoDB Transaction Log",
                Description = "Awaits internal signals to write Closed Trades to the database safely.",
                StatusText = "Pending Initial Delay..."
            };

            _jobStatus.ManualTriggerAction = async () =>
            {
                _jobStatus.StatusText = "Manual trigger not supported for Channel Reader";
                await Task.Delay(2000);
                _jobStatus.StatusText = "Listening (Channel)...";
            };

            jobManager.RegisterJob(_jobStatus);
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            _logger.Info("PersistenceService started writing background DB logs.");
            _jobStatus.StatusText = "Listening (Channel)...";

            // One-time index setup (moved out of hot loop)
            var col = _db.GetCollection<ClosedTrade>("closed_trades");
            col.EnsureIndex(x => x.TradeId);
            col.EnsureIndex(x => x.AccountId);
            col.EnsureIndex(x => x.TokenId);

            // We do a loop waiting for items in the channel
            await foreach(var trade in _tradeReader.ReadAllAsync(stoppingToken))
            {
                if (!_jobStatus.IsEnabled)
                {
                    // If paused, we just drop the trade for now or log a warning
                    _logger.Warning("PersistenceService is paused, ignoring trade log.");
                    continue;
                }

                try
                {
                    _jobStatus.StatusText = "Writing to DB...";
                    
                    // ===== DEDUPLIZIERUNG: Verhindert das Mehrfach-Einfügen desselben Trades =====
                    // Prüft ob für diesen Account + TokenId bereits ein ClosedTrade existiert.
                    // Dies verhindert den "Background Sync Duplicate Bug", bei dem geschlossene
                    // Trades bei jedem Sync-Zyklus oder nach einem Neustart erneut eingefügt werden.
                    if (!string.IsNullOrEmpty(trade.TokenId))
                    {
                        var existing = col.LiteFindOne(x => x.AccountId == trade.AccountId && x.TokenId == trade.TokenId);
                        if (existing != null)
                        {
                            _logger.Debug($"Duplikat ignoriert: ClosedTrade für Account {trade.AccountId} + Token {trade.TokenId.Substring(0, Math.Min(10, trade.TokenId.Length))}... existiert bereits (DB-ID: {existing.TradeId}).");
                            continue;
                        }
                    }
                    
                    col.Insert(trade);
                    
                    _logger.Debug($"Saved ClosedTrade {trade.TradeId} to MongoDB");
                    _jobStatus.LastRun = DateTime.Now;
                }
                catch (Exception ex)
                {
                    _logger.Error($"Failed to persist ClosedTrade (ID: {trade.TradeId}): {ex.Message}");
                    _jobStatus.StatusText = "Error!";
                }
                finally
                {
                    if (_jobStatus.StatusText != "Error!")
                        _jobStatus.StatusText = "Listening (Channel)...";
                }
            }
        }
    }
}