package realtime

import (
	"context"
	"encoding/json"
	"errors"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/redis/go-redis/v9"

	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
)

type Repository struct {
	client *redis.Client
	cfg    Config
}

func NewRepository(client *redis.Client, cfg Config) *Repository {
	if client == nil {
		panic("redis client must not be nil")
	}
	return &Repository{client: client, cfg: cfg}
}

func (r *Repository) Update(ctx context.Context, env envelope.FrameEnvelope) error {
	vin := strings.TrimSpace(env.VIN)
	vehicleKey := strings.TrimSpace(env.VehicleKey())
	if vehicleKey == "" || strings.HasSuffix(vehicleKey, ":unknown") {
		return nil
	}
	nowMS := time.Now().UnixMilli()
	eventMS := env.EventTimeMS
	if eventMS <= 0 {
		eventMS = env.ReceivedAtMS
	}
	protocolSnapshot := Snapshot{
		VehicleKey:     vehicleKey,
		VIN:            vin,
		Protocol:       env.Protocol,
		EventID:        env.StableEventID(),
		EventTimeMS:    eventMS,
		ReceivedAtMS:   env.ReceivedAtMS,
		SourceEndpoint: env.SourceEndpoint,
		Fields:         cloneFields(env.Fields),
		FieldTimesMS:   fieldTimes(env.Fields, eventMS),
		UpdatedAtMS:    nowMS,
	}
	if err := r.setJSON(ctx, protocolKey(vehicleKey, env.Protocol), protocolSnapshot, r.cfg.ttl()); err != nil {
		return err
	}

	merged, err := r.GetMerged(ctx, vehicleKey)
	if err != nil && !errors.Is(err, redis.Nil) {
		return err
	}
	if merged.VehicleKey == "" {
		merged = Snapshot{VehicleKey: vehicleKey, VIN: vin, Fields: map[string]any{}, FieldTimesMS: map[string]int64{}}
	} else if merged.VIN == "" && vin != "" {
		merged.VIN = vin
	}
	mergeFields(&merged, env.Fields, eventMS)
	if eventMS >= merged.EventTimeMS {
		merged.EventTimeMS = eventMS
		merged.EventID = env.StableEventID()
		merged.ReceivedAtMS = env.ReceivedAtMS
		merged.SourceEndpoint = env.SourceEndpoint
	}
	merged.UpdatedAtMS = nowMS
	if err := r.setJSON(ctx, mergedKey(vehicleKey), merged, r.cfg.ttl()); err != nil {
		return err
	}

	protocols, err := r.addProtocol(ctx, vehicleKey, env.Protocol)
	if err != nil {
		return err
	}
	online := OnlineStatus{
		VehicleKey: vehicleKey,
		VIN:        vin,
		Online:     true,
		LastSeenMS: env.ReceivedAtMS,
		Protocols:  protocols,
		TTLSeconds: int64(r.cfg.ttl().Seconds()),
	}
	if err := r.setJSON(ctx, onlineKey(vehicleKey), online, r.cfg.ttl()); err != nil {
		return err
	}
	return r.client.ZAdd(ctx, "vehicle:last_seen", redis.Z{Score: float64(env.ReceivedAtMS), Member: vehicleKey}).Err()
}

func (r *Repository) GetMerged(ctx context.Context, vehicleKey string) (Snapshot, error) {
	return r.getSnapshot(ctx, mergedKey(vehicleKey))
}

func (r *Repository) GetProtocol(ctx context.Context, vehicleKey string, protocol envelope.Protocol) (Snapshot, error) {
	return r.getSnapshot(ctx, protocolKey(vehicleKey, protocol))
}

func (r *Repository) IsOnline(ctx context.Context, vehicleKey string) (OnlineStatus, error) {
	vehicleKey = strings.TrimSpace(vehicleKey)
	var status OnlineStatus
	payload, err := r.client.Get(ctx, onlineKey(vehicleKey)).Bytes()
	if err != nil {
		if errors.Is(err, redis.Nil) {
			return OnlineStatus{VehicleKey: vehicleKey, VIN: vehicleKey, Online: false}, nil
		}
		return status, err
	}
	if err := json.Unmarshal(payload, &status); err != nil {
		return status, err
	}
	ttl := r.client.TTL(ctx, onlineKey(vehicleKey)).Val()
	status.Online = ttl > 0
	status.TTLSeconds = int64(ttl.Seconds())
	return status, nil
}

func (r *Repository) getSnapshot(ctx context.Context, key string) (Snapshot, error) {
	var snapshot Snapshot
	payload, err := r.client.Get(ctx, key).Bytes()
	if err != nil {
		return snapshot, err
	}
	return snapshot, json.Unmarshal(payload, &snapshot)
}

func (r *Repository) setJSON(ctx context.Context, key string, value any, ttl time.Duration) error {
	payload, err := json.Marshal(value)
	if err != nil {
		return err
	}
	return r.client.Set(ctx, key, payload, ttl).Err()
}

func (r *Repository) addProtocol(ctx context.Context, vehicleKey string, protocol envelope.Protocol) ([]envelope.Protocol, error) {
	key := protocolsKey(vehicleKey)
	if err := r.client.SAdd(ctx, key, string(protocol)).Err(); err != nil {
		return nil, err
	}
	_ = r.client.Expire(ctx, key, r.cfg.ttl()).Err()
	values, err := r.client.SMembers(ctx, key).Result()
	if err != nil {
		return nil, err
	}
	sort.Strings(values)
	out := make([]envelope.Protocol, 0, len(values))
	for _, value := range values {
		out = append(out, envelope.Protocol(value))
	}
	return out, nil
}

func mergeFields(snapshot *Snapshot, fields map[string]any, eventMS int64) {
	if snapshot.Fields == nil {
		snapshot.Fields = map[string]any{}
	}
	if snapshot.FieldTimesMS == nil {
		snapshot.FieldTimesMS = map[string]int64{}
	}
	for key, value := range fields {
		if key == envelope.FieldTotalMileageKM && !positiveNumber(value) {
			continue
		}
		if eventMS >= snapshot.FieldTimesMS[key] {
			snapshot.Fields[key] = value
			snapshot.FieldTimesMS[key] = eventMS
		}
	}
}

func positiveNumber(value any) bool {
	switch typed := value.(type) {
	case float64:
		return typed > 0
	case float32:
		return typed > 0
	case int:
		return typed > 0
	case int64:
		return typed > 0
	case uint16:
		return typed > 0
	case uint32:
		return typed > 0
	case string:
		parsed, err := strconv.ParseFloat(strings.TrimSpace(typed), 64)
		return err == nil && parsed > 0
	default:
		return false
	}
}

func cloneFields(fields map[string]any) map[string]any {
	if len(fields) == 0 {
		return map[string]any{}
	}
	out := make(map[string]any, len(fields))
	for key, value := range fields {
		out[key] = value
	}
	return out
}

func fieldTimes(fields map[string]any, eventMS int64) map[string]int64 {
	out := make(map[string]int64, len(fields))
	for key := range fields {
		out[key] = eventMS
	}
	return out
}

func mergedKey(vehicleKey string) string {
	return "vehicle:latest:" + strings.TrimSpace(vehicleKey)
}

func protocolKey(vehicleKey string, protocol envelope.Protocol) string {
	return "vehicle:latest:" + strings.TrimSpace(vehicleKey) + ":" + string(protocol)
}

func onlineKey(vehicleKey string) string {
	return "vehicle:online:" + strings.TrimSpace(vehicleKey)
}

func protocolsKey(vehicleKey string) string {
	return "vehicle:protocols:" + strings.TrimSpace(vehicleKey)
}