using System.Globalization;
using System.Text;
using System.Text.Json;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using SPMS.Application.DTOs.Push;
using SPMS.Application.Interfaces;
using SPMS.Application.Settings;
using SPMS.Infrastructure.Messaging;

namespace SPMS.Infrastructure.Workers;

public class ScheduleWorker : BackgroundService
{
    private const int PollingIntervalSeconds = 30;

    private readonly RabbitMQConnection _rabbitConnection;
    private readonly RabbitMQSettings _rabbitSettings;
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<ScheduleWorker> _logger;

    public ScheduleWorker(
        RabbitMQConnection rabbitConnection,
        IOptions<RabbitMQSettings> rabbitSettings,
        IServiceScopeFactory scopeFactory,
        ILogger<ScheduleWorker> logger)
    {
        _rabbitConnection = rabbitConnection;
        _rabbitSettings = rabbitSettings.Value;
        _scopeFactory = scopeFactory;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("ScheduleWorker 시작 (폴링 간격: {Interval}초)", PollingIntervalSeconds);

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await PollScheduleQueueAsync(stoppingToken);
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
            {
                break;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "ScheduleWorker 오류 — 5초 후 재시도");
            }

            await Task.Delay(TimeSpan.FromSeconds(PollingIntervalSeconds), stoppingToken);
        }

        _logger.LogInformation("ScheduleWorker 종료");
    }

    private async Task PollScheduleQueueAsync(CancellationToken ct)
    {
        await using var channel = await _rabbitConnection.CreateChannelAsync(ct);
        await channel.BasicQosAsync(0, 100, false, ct);

        int processedCount = 0;
        int requeuedCount = 0;

        while (!ct.IsCancellationRequested)
        {
            var result = await channel.BasicGetAsync(_rabbitSettings.ScheduleQueue, false, ct);
            if (result == null)
                break;

            try
            {
                var body = Encoding.UTF8.GetString(result.Body.ToArray());
                var scheduleMessage = JsonSerializer.Deserialize<ScheduleMessageDto>(body);

                if (scheduleMessage == null)
                {
                    _logger.LogWarning("Schedule 메시지 역직렬화 실패 — ACK 후 스킵");
                    await channel.BasicAckAsync(result.DeliveryTag, false, ct);
                    continue;
                }

                var scheduledAt = ParseScheduledAt(scheduleMessage.ScheduledAt);
                if (scheduledAt == null)
                {
                    _logger.LogWarning("scheduled_at 파싱 실패: {Value} — ACK 후 스킵", scheduleMessage.ScheduledAt);
                    await channel.BasicAckAsync(result.DeliveryTag, false, ct);
                    continue;
                }

                // 아직 예약 시간이 도래하지 않음 → NACK + requeue
                if (scheduledAt.Value > DateTime.UtcNow)
                {
                    await channel.BasicNackAsync(result.DeliveryTag, false, true, ct);
                    requeuedCount++;
                    continue;
                }

                // 예약 시간 도래 → push queue로 전달
                using var scope = _scopeFactory.CreateScope();
                var pushQueueService = scope.ServiceProvider.GetRequiredService<IPushQueueService>();
                await pushQueueService.PublishPushMessageAsync(scheduleMessage.PushMessage, ct);

                await channel.BasicAckAsync(result.DeliveryTag, false, ct);
                processedCount++;

                _logger.LogInformation(
                    "예약 메시지 발송 전달: scheduleId={ScheduleId}, messageId={MessageId}",
                    scheduleMessage.ScheduleId, scheduleMessage.MessageId);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Schedule 메시지 처리 중 오류");
                await channel.BasicNackAsync(result.DeliveryTag, false, true, ct);
            }
        }

        if (processedCount > 0 || requeuedCount > 0)
        {
            _logger.LogInformation(
                "ScheduleWorker 폴링 완료: 처리={Processed}, 대기={Requeued}",
                processedCount, requeuedCount);
        }
    }

    private static DateTime? ParseScheduledAt(string value)
    {
        if (DateTime.TryParse(value, CultureInfo.InvariantCulture, DateTimeStyles.AdjustToUniversal, out var dt))
            return dt;

        if (DateTimeOffset.TryParse(value, CultureInfo.InvariantCulture, DateTimeStyles.None, out var dto))
            return dto.UtcDateTime;

        return null;
    }
}