using Domain.Entities.Common.ValueObject;
using Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace MailWorker;

/// <summary>
/// EmailLog 정리 BackgroundService.
/// - Sent 7일 후 삭제
/// - Failed 30일 후 삭제
/// - Pending 24시간 이상 쌓인 stale 항목은 Failed 로 전환 (Worker 다운/SMTP 장기 장애 회수)
///
/// 매 24시간마다 실행 (시작 직후 30초 후 첫 실행).
/// </summary>
public sealed class EmailLogJanitor : BackgroundService
{
    private static readonly TimeSpan FirstRunDelay = TimeSpan.FromSeconds(30);
    private static readonly TimeSpan RunInterval = TimeSpan.FromHours(24);
    private const int SentRetentionDays = 7;
    private const int FailedRetentionDays = 30;
    private const int StalePendingHours = 24;

    private readonly ILogger<EmailLogJanitor> _logger;
    private readonly IServiceScopeFactory _scopeFactory;

    public EmailLogJanitor(ILogger<EmailLogJanitor> logger, IServiceScopeFactory scopeFactory)
    {
        _logger = logger;
        _scopeFactory = scopeFactory;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("EmailLogJanitor started (firstRun in {Delay}, then every {Interval})", FirstRunDelay, RunInterval);

        try
        {
            await Task.Delay(FirstRunDelay, stoppingToken);
        }
        catch (OperationCanceledException)
        {
            return;
        }

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await RunOnceAsync(stoppingToken);
            }
            catch (OperationCanceledException)
            {
                break;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "EmailLogJanitor cycle failed");
            }

            try
            {
                await Task.Delay(RunInterval, stoppingToken);
            }
            catch (OperationCanceledException)
            {
                break;
            }
        }
    }

    private async Task RunOnceAsync(CancellationToken ct)
    {
        using var scope = _scopeFactory.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var now = DateTime.UtcNow;
        var sentCutoff = now.AddDays(-SentRetentionDays);
        var failedCutoff = now.AddDays(-FailedRetentionDays);
        var staleCutoff = now.AddHours(-StalePendingHours);

        var sentDeleted = await db.EmailLog
            .Where(x => x.Status == MailStatus.Sent && x.ProcessedAt != null && x.ProcessedAt < sentCutoff)
            .ExecuteDeleteAsync(ct);

        var failedDeleted = await db.EmailLog
            .Where(x => x.Status == MailStatus.Failed && x.FailedAt != null && x.FailedAt < failedCutoff)
            .ExecuteDeleteAsync(ct);

        var staleMarked = await db.EmailLog
            .Where(x => x.Status == MailStatus.Pending && x.CreatedAt < staleCutoff)
            .ExecuteUpdateAsync(s => s
                .SetProperty(x => x.Status, MailStatus.Failed)
                .SetProperty(x => x.FailedAt, now)
                .SetProperty(x => x.LastError, "stale_in_queue"), ct);

        _logger.LogInformation("Janitor cycle: sentDeleted={SentDeleted}, failedDeleted={FailedDeleted}, staleMarked={StaleMarked}",
            sentDeleted, failedDeleted, staleMarked);
    }
}