using MiaoJiZhang.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

namespace MiaoJiZhang.Api.Services;

public class RecycleBinCleanupService(
    IServiceScopeFactory scopeFactory,
    ILogger<RecycleBinCleanupService> logger) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await Cleanup(stoppingToken);
        using var timer = new PeriodicTimer(TimeSpan.FromHours(24));
        while (await timer.WaitForNextTickAsync(stoppingToken))
            await Cleanup(stoppingToken);
    }

    private async Task Cleanup(CancellationToken ct)
    {
        try
        {
            using var scope = scopeFactory.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
            var cutoff = DateTime.UtcNow.AddDays(-30);
            var ids = await db.Transactions.IgnoreQueryFilters()
                .Where(t => t.IsDeleted && t.DeletedAt < cutoff)
                .Select(t => t.Id)
                .ToListAsync(ct);
            if (ids.Count == 0) return;

            await db.ChatMessages
                .Where(message =>
                    message.TransactionId.HasValue &&
                    ids.Contains(message.TransactionId.Value))
                .ExecuteUpdateAsync(setters => setters
                    .SetProperty(message => message.TransactionId, (long?)null)
                    .SetProperty(message => message.Content, """{"deleted":true}"""), ct);
            await db.Transactions.IgnoreQueryFilters()
                .Where(t => ids.Contains(t.Id))
                .ExecuteDeleteAsync(ct);
            logger.LogInformation(
                "Permanently removed {Count} transactions after recycle-bin retention",
                ids.Count);
        }
        catch (OperationCanceledException) when (ct.IsCancellationRequested)
        {
        }
        catch (Exception exception)
        {
            logger.LogError(exception, "Recycle-bin cleanup failed");
        }
    }
}