using WenChuanyi.Api.Models;

namespace WenChuanyi.Api.Services;

/// <summary>过期文件定时清理：每 N 分钟扫描 IsPermanent=false 且已过期的记录，先删记录再删 OSS 对象</summary>
public class ExpiredFileCleanerService : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<ExpiredFileCleanerService> _logger;
    private readonly TimeSpan _interval;

    public ExpiredFileCleanerService(
        IServiceScopeFactory scopeFactory,
        IConfiguration cfg,
        ILogger<ExpiredFileCleanerService> logger)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
        var minutes = cfg.GetValue<int>("Cleaner:IntervalMinutes", 30);
        _interval = TimeSpan.FromMinutes(Math.Max(1, minutes));
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("过期文件清理任务启动，间隔 {Minutes} 分钟", _interval.TotalMinutes);
        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await CleanExpiredAsync(stoppingToken);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "过期文件清理任务异常");
            }
            await Task.Delay(_interval, stoppingToken);
        }
    }

    private async Task CleanExpiredAsync(CancellationToken ct)
    {
        await using var scope = _scopeFactory.CreateAsyncScope();
        var fsql = scope.ServiceProvider.GetRequiredService<IFreeSql>();
        var oss = scope.ServiceProvider.GetRequiredService<OssStorageService>();

        var expired = await fsql.Select<FileItem>()
            .Where(f => !f.IsPermanent && f.ExpiresAt != null && f.ExpiresAt < DateTime.Now)
            .ToListAsync(ct);

        if (expired.Count == 0)
        {
            return;
        }

        _logger.LogInformation("发现 {Count} 个过期文件，开始清理", expired.Count);
        foreach (var item in expired)
        {
            // 先删数据库记录
            var deleted = await fsql.Delete<FileItem>().Where(f => f.Id == item.Id).ExecuteAffrowsAsync(ct) > 0;
            // 再删 OSS 对象（失败仅记日志，不阻塞任务）
            if (deleted)
            {
                oss.TryDeleteObject(item.ObjectKey);
            }
        }
    }
}