using WebDrop.Core;

namespace WebDrop.Api;

/// <summary>定期清理过期条目、下载达上限的条目、过期频道,并低频清理孤立 blob。</summary>
public sealed class SweepWorker(ChannelService service, ShareService shares, WebDropOptions options, ILogger<SweepWorker> logger) : BackgroundService
{
    private const int OrphanSweepEvery = 20;

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var interval = TimeSpan.FromSeconds(Math.Max(1, options.SweepIntervalSeconds));
        using var timer = new PeriodicTimer(interval);
        int round = 0;

        do
        {
            try
            {
                bool orphans = round++ % OrphanSweepEvery == 0;
                int removed = await Task.Run(() => service.Sweep(orphans) + shares.Sweep(), stoppingToken).ConfigureAwait(false);
                if (removed > 0) logger.LogInformation("清理了 {Count} 个过期条目或频道", removed);
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
            {
                break;
            }
            catch (Exception e)
            {
                // 只记录异常类型,不记录可能含频道 id 的细节
                logger.LogError("清理任务失败:{Type}", e.GetType().Name);
            }
        }
        while (await WaitAsync(timer, stoppingToken).ConfigureAwait(false));
    }

    private static async Task<bool> WaitAsync(PeriodicTimer timer, CancellationToken ct)
    {
        try { return await timer.WaitForNextTickAsync(ct).ConfigureAwait(false); }
        catch (OperationCanceledException) { return false; }
    }
}