using Microsoft.EntityFrameworkCore;
using MilliSim.Common.Models;
using MilliSim.Data;

namespace MilliSim.Services;

/// <summary>
/// 后台定时任务：每天检查即将到期（7 天内）的授权，给被授权用户发送提醒通知。
/// 使用 EventId = "auth-expiring-{authId}-{expiryDate}" 进行幂等，避免重复发送。
/// </summary>
public class AuthorizationNotificationJob : IHostedService, IDisposable
{
    private readonly IServiceProvider _serviceProvider;
    private Timer? _timer;

    // 检查间隔：6 小时（既能在到期日及时触发，又避免频繁扫描）
    private static readonly TimeSpan CheckInterval = TimeSpan.FromHours(6);
    // 提前提醒天数
    private const int ExpiringSoonDays = 7;

    public AuthorizationNotificationJob(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        // 启动后 30 秒执行第一次，之后每 6 小时一次
        _timer = new Timer(DoWork, null, TimeSpan.FromSeconds(30), CheckInterval);
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _timer?.Change(Timeout.Infinite, 0);
        return Task.CompletedTask;
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }

    private async void DoWork(object? state)
    {
        try
        {
            using var scope = _serviceProvider.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<MilliSimDbContext>();
            var notification = scope.ServiceProvider.GetRequiredService<INotificationService>();

            var now = DateTime.Now;
            var deadline = now.AddDays(ExpiringSoonDays);

            // 查询 7 天内即将到期、且尚未过期的有效授权
            var expiringSoon = await db.Authorizations
                .Where(a => a.Status == AuthorizationStatus.Active
                    && a.EndTime > now
                    && a.EndTime <= deadline)
                .ToListAsync();

            foreach (var auth in expiringSoon)
            {
                var daysRemaining = Math.Max(1, (int)Math.Ceiling((auth.EndTime - now).TotalDays));
                // 按到期日期去重：同一天内只发一次
                var eventId = $"auth-expiring-{auth.Id}-{auth.EndTime:yyyyMMdd}";
                try
                {
                    await notification.CreateNotificationAsync(
                        NotificationType.Authorization,
                        "授权即将到期",
                        $"您的客户级授权将在 {daysRemaining} 天后到期（{auth.EndTime:yyyy-MM-dd}），请及时联系销售续期。",
                        userId: auth.UserId,
                        eventId: eventId);
                }
                catch
                {
                    // 单条失败不影响其他通知
                }
            }
        }
        catch
        {
            // 后台任务异常不应影响应用运行
        }
    }
}