package mqtt

import (
	"context"
	"crypto/sha1"
	"crypto/tls"
	"encoding/hex"
	"fmt"
	"hr_receiver/config"
	"hr_receiver/models"
	whgw_hrpb "hr_receiver/proto"
	"log"
	"strings"
	"sync"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
	"google.golang.org/protobuf/proto"
	"gorm.io/gorm"
)

const (
	maxReplayRecordCount  = 20000
	maxReplaySleepGap     = 24 * time.Hour
	replayMarkerRetention = 10 * time.Minute
)

type ReplayStartRequest struct {
	Addr      string `json:"addr"`
	EndTime   int64  `json:"endTime"`
	RegionID  uint32 `json:"regionId"`
	StartTime int64  `json:"startTime"`
}

type ReplayStatus struct {
	Addr             string `json:"addr"`
	CompletedAt      int64  `json:"completedAt"`
	CurrentAddr      string `json:"currentAddr"`
	CurrentHeartRate int    `json:"currentHeartRate"`
	EndTime          int64  `json:"endTime"`
	ErrorMessage     string `json:"errorMessage"`
	LastPublishedAt  int64  `json:"lastPublishedAt"`
	LastTopic        string `json:"lastTopic"`
	ProcessedCount   int    `json:"processedCount"`
	RegionID         uint32 `json:"regionId"`
	Running          bool   `json:"running"`
	StartedAt        int64  `json:"startedAt"`
	StartTime        int64  `json:"startTime"`
	StoppedAt        int64  `json:"stoppedAt"`
	TotalCount       int    `json:"totalCount"`
}

type ReplayService struct {
	cfg    config.MQTTConfig
	db     *gorm.DB
	cancel context.CancelFunc
	mu     sync.RWMutex
	status ReplayStatus
}

type replayFingerprintStore struct {
	items map[string]time.Time
	mu    sync.Mutex
}

var (
	globalReplayService = &ReplayService{}
	replayFingerprints  = &replayFingerprintStore{items: map[string]time.Time{}}
)

func InitReplayService(db *gorm.DB, cfg config.MQTTConfig) {
	globalReplayService = &ReplayService{
		cfg: cfg,
		db:  db,
	}
}

func GetReplayService() *ReplayService {
	return globalReplayService
}

func (s *ReplayService) Status() ReplayStatus {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.status
}

func (s *ReplayService) Start(req ReplayStartRequest) (ReplayStatus, error) {
	req.Addr = strings.TrimSpace(req.Addr)
	if req.StartTime <= 0 || req.EndTime <= 0 {
		return ReplayStatus{}, fmt.Errorf("startTime and endTime are required")
	}
	req.EndTime = normalizeReplayEndTime(req.EndTime)
	if req.EndTime < req.StartTime {
		return ReplayStatus{}, fmt.Errorf("endTime must be greater than or equal to startTime")
	}
	if err := validateConfig(s.cfg); err != nil {
		return ReplayStatus{}, err
	}

	s.mu.Lock()
	if s.status.Running {
		current := s.status
		s.mu.Unlock()
		return current, fmt.Errorf("mqtt replay is already running")
	}
	s.mu.Unlock()

	query := s.db.Model(&models.MqttHeartRateRecord{}).
		Where("received_at >= ? AND received_at <= ?", req.StartTime, req.EndTime)
	if req.RegionID > 0 {
		query = query.Where("region_id = ?", req.RegionID)
	}
	if req.Addr != "" {
		query = query.Where("belt_addr LIKE ?", "%"+req.Addr+"%")
	}

	var total int64
	if err := query.Count(&total).Error; err != nil {
		return ReplayStatus{}, err
	}
	if total == 0 {
		log.Printf("mqtt replay found no records start=%d end=%d region=%d addr=%q", req.StartTime, req.EndTime, req.RegionID, req.Addr)
		return ReplayStatus{}, fmt.Errorf("no heart rate records found in the selected range")
	}
	if total > maxReplayRecordCount {
		return ReplayStatus{}, fmt.Errorf("replay record count exceeds limit: %d > %d", total, maxReplayRecordCount)
	}

	var records []models.MqttHeartRateRecord
	if err := query.Order("received_at ASC, id ASC").Find(&records).Error; err != nil {
		return ReplayStatus{}, err
	}

	status := ReplayStatus{
		Addr:       req.Addr,
		EndTime:    req.EndTime,
		RegionID:   req.RegionID,
		Running:    true,
		StartedAt:  time.Now().UnixMilli(),
		StartTime:  req.StartTime,
		TotalCount: len(records),
	}

	ctx, cancel := context.WithCancel(context.Background())

	s.mu.Lock()
	s.cancel = cancel
	s.status = status
	s.mu.Unlock()

	go s.run(ctx, records)
	return status, nil
}

func (s *ReplayService) Stop() ReplayStatus {
	s.mu.Lock()
	cancel := s.cancel
	if cancel != nil {
		cancel()
		s.cancel = nil
	}
	if s.status.Running {
		s.status.Running = false
		s.status.StoppedAt = time.Now().UnixMilli()
	}
	status := s.status
	s.mu.Unlock()
	return status
}

func (s *ReplayService) run(ctx context.Context, records []models.MqttHeartRateRecord) {
	client, err := s.connectReplayClient()
	if err != nil {
		s.fail(err)
		return
	}
	defer func() {
		if client.IsConnected() {
			client.Disconnect(250)
		}
	}()

	for idx, record := range records {
		if idx > 0 {
			wait := time.Duration(record.ReceivedAt-records[idx-1].ReceivedAt) * time.Millisecond
			if wait < 0 {
				wait = 0
			}
			if wait > maxReplaySleepGap {
				wait = maxReplaySleepGap
			}
			timer := time.NewTimer(wait)
			select {
			case <-ctx.Done():
				timer.Stop()
				s.stopWithContext()
				return
			case <-timer.C:
			}
		}

		if err := s.publishRecord(client, record); err != nil {
			s.fail(err)
			return
		}
		s.updateProgress(record, idx+1)
	}

	s.complete()
}

func (s *ReplayService) connectReplayClient() (mqtt.Client, error) {
	opts := mqtt.NewClientOptions()
	scheme := "tcp"
	if s.cfg.UseTLS {
		scheme = "ssl"
		opts.SetTLSConfig(&tls.Config{MinVersion: tls.VersionTLS12})
	}
	broker := fmt.Sprintf("%s://%s:%d", scheme, s.cfg.Host, s.cfg.Port)
	username := strings.TrimSpace(s.cfg.GWUsername)
	password := s.cfg.GWPassword
	if username == "" {
		username = s.cfg.Username
		password = s.cfg.Password
	}
	opts.AddBroker(broker)
	opts.SetClientID(fmt.Sprintf("%s-replay-%d", s.cfg.ClientIDPrefix, time.Now().UnixNano()))
	opts.SetUsername(username)
	opts.SetPassword(password)
	opts.SetKeepAlive(60 * time.Second)
	opts.SetAutoReconnect(false)
	opts.SetConnectRetry(false)

	client := mqtt.NewClient(opts)
	token := client.Connect()
	if !token.WaitTimeout(15 * time.Second) {
		return nil, fmt.Errorf("mqtt replay connect timeout")
	}
	if err := token.Error(); err != nil {
		return nil, err
	}
	log.Printf("mqtt replay connected broker=%s username=%s", broker, username)
	return client, nil
}

func (s *ReplayService) publishRecord(client mqtt.Client, record models.MqttHeartRateRecord) error {
	payloadMessage := buildReplayHeartRateMessage(record)
	payload, err := proto.Marshal(payloadMessage)
	if err != nil {
		return fmt.Errorf("marshal replay heart rate payload: %w", err)
	}
	topic := strings.TrimSpace(record.Topic)
	if topic == "" {
		topic = fmt.Sprintf("/whgw/v2/region/%d/measurement/band/%d/hr", record.RegionID, record.BandID)
	}
	markReplayPayload(topic, payload)
	token := client.Publish(topic, byte(s.cfg.QoS), false, payload)
	if !token.WaitTimeout(10 * time.Second) {
		return fmt.Errorf("mqtt replay publish timeout")
	}
	if err := token.Error(); err != nil {
		return err
	}
	log.Printf("mqtt replay published region=%d addr=%s hr=%d packet=%d topic=%s", record.RegionID, record.BeltAddr, record.HeartRate, record.PacketNum, topic)
	return nil
}

func buildReplayHeartRateMessage(record models.MqttHeartRateRecord) *whgw_hrpb.GatewaySlaveOutCloudMasterInMsg {
	return &whgw_hrpb.GatewaySlaveOutCloudMasterInMsg{
		Choice: &whgw_hrpb.GatewaySlaveOutCloudMasterInMsg_NtfHrMeasurement{
			NtfHrMeasurement: &whgw_hrpb.HrMeasurement{
				HrPacket: &whgw_hrpb.HrPacket{
					Hr:        uint32(record.HeartRate),
					Id:        record.BandID,
					PacketNum: record.PacketNum,
					Status: &whgw_hrpb.StatusFlag{
						Battery:      record.Battery,
						HrConfidence: whgw_hrpb.HrConfidence(record.HrConfidence),
						IsActive:     record.IsActive,
						IsOnSkin:     record.IsOnSkin,
					},
				},
				PacketStatus: buildReplayPacketStatus(record),
				GatewayInfo: &whgw_hrpb.GatewayInfo{
					Extra: &whgw_hrpb.GatewayInfoExtra{
						ActiveUplink: whgw_hrpb.NetworkUplinkKind(record.GatewayActiveUplink),
						CellularModem: &whgw_hrpb.CellularModemInfo{
							Ber:  record.GatewayCellularBER,
							Imei: record.GatewayCellularIMEI,
							Rssi: record.GatewayCellularRSSI,
						},
						SchemaVersion: record.GatewaySchemaVersion,
					},
					GatewayMac: parseMAC(record.GatewayMAC),
					RegionId:   record.RegionID,
				},
				HubInfo: &whgw_hrpb.HubInfo{
					BusId:    record.HubBusID,
					SubDevId: record.HubSubDevID,
					RadioParameters: &whgw_hrpb.LoRaParameters{
						Bw:           whgw_hrpb.LoRaBW(record.HubRadioBW),
						FrequencyMhz: float32(record.HubRadioFrequencyMHz),
						Sf:           record.HubRadioSF,
					},
				},
			},
		},
	}
}

func buildReplayPacketStatus(record models.MqttHeartRateRecord) *whgw_hrpb.IPacketStatus {
	switch strings.TrimSpace(record.PacketStatusSource) {
	case "raw":
		return &whgw_hrpb.IPacketStatus{
			Choice: &whgw_hrpb.IPacketStatus_Raw{
				Raw: &whgw_hrpb.RawPacketStatus{
					SignalRssiX2Neg: record.RawSignalRSSIX2Neg,
					SnrPktX4:        record.RawSnrPktX4,
				},
			},
		}
	case "parsed":
		return &whgw_hrpb.IPacketStatus{
			Choice: &whgw_hrpb.IPacketStatus_Parsed{
				Parsed: &whgw_hrpb.PacketStatus{
					SignalRssiNeg: float32(record.SignalRSSINeg),
					SnrPkt:        float32(record.SNR),
				},
			},
		}
	default:
		if record.RawSignalRSSIX2Neg > 0 || record.RawSnrPktX4 != 0 {
			return &whgw_hrpb.IPacketStatus{
				Choice: &whgw_hrpb.IPacketStatus_Raw{
					Raw: &whgw_hrpb.RawPacketStatus{
						SignalRssiX2Neg: record.RawSignalRSSIX2Neg,
						SnrPktX4:        record.RawSnrPktX4,
					},
				},
			}
		}
		return &whgw_hrpb.IPacketStatus{
			Choice: &whgw_hrpb.IPacketStatus_Parsed{
				Parsed: &whgw_hrpb.PacketStatus{
					SignalRssiNeg: float32(record.SignalRSSINeg),
					SnrPkt:        float32(record.SNR),
				},
			},
		}
	}
}

func parseMAC(value string) []byte {
	value = strings.TrimSpace(value)
	if value == "" {
		return nil
	}
	parts := strings.Split(value, ":")
	result := make([]byte, 0, len(parts))
	for _, part := range parts {
		if len(part) == 1 {
			part = "0" + part
		}
		decoded, err := hex.DecodeString(part)
		if err != nil || len(decoded) != 1 {
			return nil
		}
		result = append(result, decoded[0])
	}
	return result
}

func (s *ReplayService) updateProgress(record models.MqttHeartRateRecord, processed int) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.status.CurrentAddr = record.BeltAddr
	s.status.CurrentHeartRate = record.HeartRate
	s.status.LastPublishedAt = time.Now().UnixMilli()
	s.status.LastTopic = record.Topic
	s.status.ProcessedCount = processed
}

func (s *ReplayService) complete() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.cancel = nil
	s.status.CompletedAt = time.Now().UnixMilli()
	s.status.Running = false
}

func (s *ReplayService) fail(err error) {
	log.Printf("mqtt replay failed: %v", err)
	s.mu.Lock()
	defer s.mu.Unlock()
	s.cancel = nil
	s.status.CompletedAt = time.Now().UnixMilli()
	s.status.ErrorMessage = err.Error()
	s.status.Running = false
}

func (s *ReplayService) stopWithContext() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.cancel = nil
	if s.status.Running {
		s.status.Running = false
		s.status.StoppedAt = time.Now().UnixMilli()
	}
}

func markReplayPayload(topic string, payload []byte) {
	replayFingerprints.mu.Lock()
	defer replayFingerprints.mu.Unlock()

	now := time.Now()
	for key, expiresAt := range replayFingerprints.items {
		if now.After(expiresAt) {
			delete(replayFingerprints.items, key)
		}
	}
	replayFingerprints.items[buildReplayFingerprint(topic, payload)] = now.Add(replayMarkerRetention)
}

func consumeReplayPayload(topic string, payload []byte) bool {
	replayFingerprints.mu.Lock()
	defer replayFingerprints.mu.Unlock()

	now := time.Now()
	key := buildReplayFingerprint(topic, payload)
	expiresAt, ok := replayFingerprints.items[key]
	if !ok {
		return false
	}
	delete(replayFingerprints.items, key)
	if now.After(expiresAt) {
		return false
	}
	return true
}

func buildReplayFingerprint(topic string, payload []byte) string {
	sum := sha1.Sum(append([]byte(topic+"|"), payload...))
	return hex.EncodeToString(sum[:])
}

func normalizeReplayEndTime(endTime int64) int64 {
	if endTime <= 0 {
		return endTime
	}
	if endTime%1000 == 0 {
		return endTime + 999
	}
	return endTime
}