using Marathon.Application.UseCases;
using Marathon.Domain.ValueObjects;
using Marathon.Infrastructure.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Marathon.Infrastructure.Workers;

/// <summary>
/// Forward-test engine: each cycle opens flat-stake paper bets for newly detected
/// directional anomalies, then settles any open bets whose events have been graded.
/// Idle (cheap re-check) while <see cref="PaperTradingOptions.Enabled"/> is false.
/// </summary>
/// <remarks>
/// The "since" marker is baselined to startup so pre-existing anomalies are not
/// retro-traded, and advances to each cycle's upper bound only after the open pass
/// succeeds. A unique index on <c>PaperBets.AnomalyId</c> backstops any double-open.
/// Scoped use cases are resolved per cycle (EF Core DbContext lifetime).
/// </remarks>
internal sealed class PaperTradingWorker : BackgroundService
{
    private readonly IServiceProvider _services;
    private readonly IOptionsMonitor<PaperTradingOptions> _opts;
    private readonly ILogger<PaperTradingWorker> _logger;

    private DateTimeOffset _since;

    public PaperTradingWorker(
        IServiceProvider services,
        IOptionsMonitor<PaperTradingOptions> opts,
        ILogger<PaperTradingWorker> logger)
    {
        _services = services ?? throw new ArgumentNullException(nameof(services));
        _opts = opts ?? throw new ArgumentNullException(nameof(opts));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        // Baseline: only forward-test anomalies detected after this worker started.
        _since = MoscowTime.Now;
        _logger.LogInformation("PaperTradingWorker: started");

        while (!stoppingToken.IsCancellationRequested)
        {
            var opts = _opts.CurrentValue;
            if (!opts.Enabled)
            {
                await DelayQuietly(TimeSpan.FromSeconds(10), stoppingToken);
                continue;
            }

            try
            {
                var until = MoscowTime.Now;
                await using var scope = _services.CreateAsyncScope();

                var open = scope.ServiceProvider.GetRequiredService<OpenPaperBetsUseCase>();
                await open.ExecuteAsync(_since, until, opts.MinScore, opts.FlatStake, stoppingToken);
                // Advance only after a successful open pass, so a failure replays the window.
                _since = until;

                var settle = scope.ServiceProvider.GetRequiredService<SettlePaperBetsUseCase>();
                await settle.ExecuteAsync(stoppingToken);
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
            {
                break;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "PaperTradingWorker: cycle failed — will retry after interval");
            }

            await DelayQuietly(TimeSpan.FromSeconds(Math.Max(5, opts.PollIntervalSeconds)), stoppingToken);
        }

        _logger.LogInformation("PaperTradingWorker: stopping");
    }

    private static async Task DelayQuietly(TimeSpan delay, CancellationToken ct)
    {
        try
        {
            await Task.Delay(delay, ct);
        }
        catch (OperationCanceledException)
        {
            // Shutting down — swallow so ExecuteAsync's loop check exits cleanly.
        }
    }
}