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.Domain.Entities;
using SPMS.Domain.Enums;
using SPMS.Domain.Interfaces;
using SPMS.Infrastructure.Messaging;

namespace SPMS.Infrastructure.Workers;

public class PushWorker : BackgroundService
{
    private const int MaxRetryCount = 3;

    private readonly RabbitMQConnection _rabbitConnection;
    private readonly RabbitMQSettings _rabbitSettings;
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly IDuplicateChecker _duplicateChecker;
    private readonly IBulkJobStore _bulkJobStore;
    private readonly ITokenCacheService _tokenCache;
    private readonly IFcmSender _fcmSender;
    private readonly IApnsSender _apnsSender;
    private readonly ILogger<PushWorker> _logger;

    public PushWorker(
        RabbitMQConnection rabbitConnection,
        IOptions<RabbitMQSettings> rabbitSettings,
        IServiceScopeFactory scopeFactory,
        IDuplicateChecker duplicateChecker,
        IBulkJobStore bulkJobStore,
        ITokenCacheService tokenCache,
        IFcmSender fcmSender,
        IApnsSender apnsSender,
        ILogger<PushWorker> logger)
    {
        _rabbitConnection = rabbitConnection;
        _rabbitSettings = rabbitSettings.Value;
        _scopeFactory = scopeFactory;
        _duplicateChecker = duplicateChecker;
        _bulkJobStore = bulkJobStore;
        _tokenCache = tokenCache;
        _fcmSender = fcmSender;
        _apnsSender = apnsSender;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("PushWorker 시작");

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await ConsumeAsync(stoppingToken);
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
            {
                break;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "PushWorker 오류 — 5초 후 재시도");
                await Task.Delay(TimeSpan.FromSeconds(5), stoppingToken);
            }
        }

        _logger.LogInformation("PushWorker 종료");
    }

    private async Task ConsumeAsync(CancellationToken stoppingToken)
    {
        await using var channel = await _rabbitConnection.CreateChannelAsync(stoppingToken);
        await channel.BasicQosAsync(0, _rabbitSettings.PrefetchCount, false, stoppingToken);

        var tcs = new TaskCompletionSource();
        stoppingToken.Register(() => tcs.TrySetResult());

        var consumer = new AsyncEventingBasicConsumer(channel);
        consumer.ReceivedAsync += async (_, ea) =>
        {
            try
            {
                await ProcessMessageAsync(channel, ea, stoppingToken);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "메시지 처리 중 예외 발생");
                await HandleRetryAsync(channel, ea, stoppingToken);
            }
        };

        await channel.BasicConsumeAsync(
            queue: _rabbitSettings.PushQueue,
            autoAck: false,
            consumer: consumer,
            cancellationToken: stoppingToken);

        _logger.LogInformation("PushWorker Consumer 등록 완료: queue={Queue}", _rabbitSettings.PushQueue);

        await tcs.Task;
    }

    private async Task ProcessMessageAsync(IChannel channel, BasicDeliverEventArgs ea, CancellationToken ct)
    {
        var body = Encoding.UTF8.GetString(ea.Body.ToArray());
        var pushMessage = JsonSerializer.Deserialize<PushMessageDto>(body);

        if (pushMessage == null)
        {
            _logger.LogWarning("메시지 역직렬화 실패 — ACK 후 스킵");
            await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
            return;
        }

        // [0] Bulk job 취소 체크
        if (!string.IsNullOrEmpty(pushMessage.JobId) &&
            await _bulkJobStore.IsCancelledAsync(pushMessage.JobId, ct))
        {
            _logger.LogInformation("Bulk job 취소됨 — 스킵: jobId={JobId}, requestId={RequestId}",
                pushMessage.JobId, pushMessage.RequestId);
            await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
            return;
        }

        // [1] Redis 중복 체크
        if (await _duplicateChecker.IsDuplicateAsync(pushMessage.RequestId, ct))
        {
            _logger.LogInformation("중복 메시지 스킵: requestId={RequestId}", pushMessage.RequestId);
            await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
            return;
        }

        // [1.5] Bulk job processing 상태 전환
        if (!string.IsNullOrEmpty(pushMessage.JobId))
            await _bulkJobStore.SetProcessingAsync(pushMessage.JobId, ct);

        using var scope = _scopeFactory.CreateScope();
        var serviceRepo = scope.ServiceProvider.GetRequiredService<IServiceRepository>();
        var deviceRepo = scope.ServiceProvider.GetRequiredService<IDeviceRepository>();
        var unitOfWork = scope.ServiceProvider.GetRequiredService<IUnitOfWork>();

        // 서비스 조회
        var service = await serviceRepo.GetByIdAsync(pushMessage.ServiceId);
        if (service == null)
        {
            _logger.LogWarning("서비스 없음: serviceId={ServiceId}", pushMessage.ServiceId);
            await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
            return;
        }

        // [2] send_type별 대상 Device 조회
        var devices = await ResolveDevicesAsync(deviceRepo, pushMessage, ct);
        if (devices.Count == 0)
        {
            _logger.LogInformation("발송 대상 없음: requestId={RequestId}", pushMessage.RequestId);
            await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
            return;
        }

        // [3] 플랫폼별 분류
        var iosDevices = devices.Where(d => d.Platform == Platform.iOS).ToList();
        var androidDevices = devices.Where(d => d.Platform == Platform.Android).ToList();

        var customData = pushMessage.CustomData?
            .ToDictionary(kv => kv.Key, kv => kv.Value.ToString() ?? string.Empty);

        if (!string.IsNullOrEmpty(pushMessage.LinkUrl))
            (customData ??= new Dictionary<string, string>())["link_url"] = pushMessage.LinkUrl;

        // [4] 배치 발송
        var allResults = new List<(Device Device, PushResultDto Result)>();

        if (androidDevices.Count > 0 && !string.IsNullOrEmpty(service.FcmCredentials))
        {
            var fcmResults = await SendFcmBatchAsync(
                service.FcmCredentials, androidDevices, pushMessage, customData, ct);
            allResults.AddRange(fcmResults);
        }

        if (iosDevices.Count > 0 &&
            !string.IsNullOrEmpty(service.ApnsPrivateKey) &&
            !string.IsNullOrEmpty(service.ApnsKeyId) &&
            !string.IsNullOrEmpty(service.ApnsTeamId) &&
            !string.IsNullOrEmpty(service.ApnsBundleId))
        {
            var apnsResults = await SendApnsBatchAsync(
                service, iosDevices, pushMessage, customData, ct);
            allResults.AddRange(apnsResults);
        }

        // [5] 결과 처리: PushSendLog INSERT + Device 상태 변경
        var pushSendLogRepo = scope.ServiceProvider.GetRequiredService<IRepository<PushSendLog>>();
        var dailyStatRepo = scope.ServiceProvider.GetRequiredService<IRepository<DailyStat>>();

        int successCount = 0, failCount = 0;

        foreach (var (device, result) in allResults)
        {
            var log = new PushSendLog
            {
                ServiceId = pushMessage.ServiceId,
                MessageId = long.TryParse(pushMessage.MessageId, out var mid) ? mid : 0,
                DeviceId = device.Id,
                Status = result.IsSuccess ? PushResult.Success : PushResult.Failed,
                FailReason = result.ErrorMessage,
                SentAt = DateTime.UtcNow
            };
            await pushSendLogRepo.AddAsync(log);

            if (result.IsSuccess)
                successCount++;
            else
                failCount++;

            // 영구 오류: 디바이스 비활성화
            if (result.ShouldRemoveDevice)
            {
                device.IsActive = false;
                device.UpdatedAt = DateTime.UtcNow;
                deviceRepo.Update(device);
            }
        }

        // [6] DailyStat 증분 업데이트
        var today = DateOnly.FromDateTime(DateTime.UtcNow);
        var stats = await dailyStatRepo.FindAsync(
            s => s.ServiceId == pushMessage.ServiceId && s.StatDate == today);
        var stat = stats.FirstOrDefault();

        if (stat != null)
        {
            stat.SentCnt += allResults.Count;
            stat.SuccessCnt += successCount;
            stat.FailCnt += failCount;
            dailyStatRepo.Update(stat);
        }
        else
        {
            await dailyStatRepo.AddAsync(new DailyStat
            {
                ServiceId = pushMessage.ServiceId,
                StatDate = today,
                SentCnt = allResults.Count,
                SuccessCnt = successCount,
                FailCnt = failCount,
                CreatedAt = DateTime.UtcNow
            });
        }

        await unitOfWork.SaveChangesAsync(ct);

        _logger.LogInformation(
            "푸시 발송 완료: requestId={RequestId}, 성공={Success}, 실패={Fail}, 총={Total}",
            pushMessage.RequestId, successCount, failCount, allResults.Count);

        // [7] Bulk job 진행률 업데이트
        if (!string.IsNullOrEmpty(pushMessage.JobId))
        {
            if (successCount > 0)
                await _bulkJobStore.IncrementSentAsync(pushMessage.JobId, ct);
            else
                await _bulkJobStore.IncrementFailedAsync(pushMessage.JobId, ct);

            await _bulkJobStore.TryCompleteAsync(pushMessage.JobId, ct);
        }

        // [8] ACK
        await channel.BasicAckAsync(ea.DeliveryTag, false, ct);
    }

    private async Task<List<Device>> ResolveDevicesAsync(
        IDeviceRepository deviceRepo, PushMessageDto message, CancellationToken ct)
    {
        var sendType = message.SendType.ToLowerInvariant();

        switch (sendType)
        {
            case "single":
            {
                var deviceIds = ParseDeviceIds(message.Target);
                if (deviceIds.Count == 0) return [];

                var devices = new List<Device>();
                foreach (var id in deviceIds)
                {
                    // Redis 캐시 우선 조회
                    var cached = await _tokenCache.GetDeviceInfoAsync(message.ServiceId, id);
                    if (cached != null)
                    {
                        if (cached.IsActive && cached.PushAgreed)
                        {
                            devices.Add(new Device
                            {
                                Id = id,
                                ServiceId = message.ServiceId,
                                DeviceToken = cached.Token,
                                Platform = (Platform)cached.Platform,
                                IsActive = true,
                                PushAgreed = true
                            });
                        }
                        continue;
                    }

                    // 캐시 미스 → DB 조회 후 캐시 저장
                    var device = await deviceRepo.GetByIdAndServiceAsync(id, message.ServiceId);
                    if (device != null)
                    {
                        await _tokenCache.SetDeviceInfoAsync(message.ServiceId, id,
                            new CachedDeviceInfo(device.DeviceToken, (int)device.Platform,
                                device.IsActive, device.PushAgreed));

                        if (device is { IsActive: true, PushAgreed: true })
                            devices.Add(device);
                    }
                }
                return devices;
            }

            case "group":
            {
                var tags = ParseTags(message.Target);
                if (tags.Count == 0) return [];

                var allDevices = await deviceRepo.FindAsync(
                    d => d.ServiceId == message.ServiceId && d.IsActive && d.PushAgreed);

                return allDevices
                    .Where(d => !string.IsNullOrEmpty(d.Tags) &&
                                tags.Any(tag => d.Tags.Contains(tag)))
                    .ToList();
            }

            case "broadcast":
            {
                var allDevices = await deviceRepo.FindAsync(
                    d => d.ServiceId == message.ServiceId && d.IsActive && d.PushAgreed);
                return allDevices.ToList();
            }

            default:
                _logger.LogWarning("지원하지 않는 send_type: {SendType}", sendType);
                return [];
        }
    }

    private static List<long> ParseDeviceIds(PushTargetDto target)
    {
        if (target.Value == null) return [];

        try
        {
            if (target.Value.Value.ValueKind == JsonValueKind.Array)
            {
                return target.Value.Value.EnumerateArray()
                    .Where(e => e.ValueKind == JsonValueKind.Number)
                    .Select(e => e.GetInt64())
                    .ToList();
            }
        }
        catch { }

        return [];
    }

    private static List<string> ParseTags(PushTargetDto target)
    {
        if (target.Value == null) return [];

        try
        {
            if (target.Value.Value.ValueKind == JsonValueKind.Array)
            {
                return target.Value.Value.EnumerateArray()
                    .Where(e => e.ValueKind == JsonValueKind.String)
                    .Select(e => e.GetString()!)
                    .ToList();
            }
        }
        catch { }

        return [];
    }

    private async Task<List<(Device Device, PushResultDto Result)>> SendFcmBatchAsync(
        string fcmCredentials, List<Device> devices, PushMessageDto message,
        Dictionary<string, string>? customData, CancellationToken ct)
    {
        var results = new List<(Device, PushResultDto)>();
        var tokens = devices.Select(d => d.DeviceToken).ToList();

        var batchResults = await _fcmSender.SendBatchAsync(
            fcmCredentials, tokens, message.Title, message.Body,
            message.ImageUrl, customData, ct);

        for (int i = 0; i < batchResults.Count && i < devices.Count; i++)
            results.Add((devices[i], batchResults[i]));

        return results;
    }

    private async Task<List<(Device Device, PushResultDto Result)>> SendApnsBatchAsync(
        Service service, List<Device> devices, PushMessageDto message,
        Dictionary<string, string>? customData, CancellationToken ct)
    {
        var results = new List<(Device, PushResultDto)>();
        var tokens = devices.Select(d => d.DeviceToken).ToList();

        var batchResults = await _apnsSender.SendBatchAsync(
            service.ApnsPrivateKey!, service.ApnsKeyId!, service.ApnsTeamId!, service.ApnsBundleId!,
            tokens, message.Title, message.Body,
            message.ImageUrl, customData, ct);

        for (int i = 0; i < batchResults.Count && i < devices.Count; i++)
            results.Add((devices[i], batchResults[i]));

        return results;
    }

    private async Task HandleRetryAsync(IChannel channel, BasicDeliverEventArgs ea, CancellationToken ct)
    {
        var retryCount = 0;
        if (ea.BasicProperties.Headers?.TryGetValue("x-retry-count", out var retryObj) == true)
        {
            retryCount = retryObj is int r ? r : 0;
        }

        if (retryCount < MaxRetryCount)
        {
            _logger.LogWarning("메시지 재시도 ({RetryCount}/{MaxRetry})", retryCount + 1, MaxRetryCount);
            await channel.BasicNackAsync(ea.DeliveryTag, false, true, ct);
        }
        else
        {
            _logger.LogError("메시지 최대 재시도 초과 — 폐기: deliveryTag={Tag}", ea.DeliveryTag);
            await channel.BasicNackAsync(ea.DeliveryTag, false, false, ct);
        }
    }
}