package worker

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"doormile/db"
	"doormile/utils"

	nats "github.com/nats-io/nats.go"
)

func StartBookingWorker() {
	defer func() {
		if r := recover(); r != nil {
			utils.Error("BookingWorker: panic recovered, restarting", "error", r)
			time.Sleep(5 * time.Second)
			go StartBookingWorker()
		}
	}()

	if db.Js == nil {
		utils.Warn("BookingWorker: NATS JetStream not available, worker not started")
		return
	}

	type consumerDef struct {
		subject  string
		consumer string
	}

	consumers := []consumerDef{
		{"api.v1.bookings.create", "bookings_create"},
		{"api.v1.bookings.update", "bookings_update"},
		{"api.v1.bookings.cancel", "bookings_cancel"},
	}

	type subscription struct {
		subject string
		sub     *nats.Subscription
	}

	var subs []subscription
	for _, c := range consumers {
		sub, err := db.Js.PullSubscribe(c.subject, c.consumer, nats.BindStream("BOOKINGS"))
		if err != nil {
			utils.Error("BookingWorker: subscribe failed", "subject", c.subject, "consumer", c.consumer, "error", err)
			continue
		}
		subs = append(subs, subscription{c.subject, sub})
		utils.Info("BookingWorker: subscribed", "subject", c.subject, "consumer", c.consumer)
	}

	if len(subs) == 0 {
		utils.Error("BookingWorker: no subscriptions established, worker exiting")
		return
	}

	utils.Info("BookingWorker: running, waiting for messages...")

	for {
		for _, s := range subs {
			msgs, err := s.sub.Fetch(10, nats.MaxWait(1*time.Second))
			if err != nil {
				if err == nats.ErrTimeout {
					continue
				}
				utils.Warn("BookingWorker: fetch error", "subject", s.subject, "error", err)
				time.Sleep(1 * time.Second)
				continue
			}
			for _, msg := range msgs {
				processMessage(msg)
			}
		}
	}
}

func processMessage(msg *nats.Msg) {
	defer func() {
		if r := recover(); r != nil {
			utils.Error("BookingWorker: panic in message handler", "error", r)
			msg.Nak()
		}
	}()

	var payload map[string]interface{}
	if err := json.Unmarshal(msg.Data, &payload); err != nil {
		utils.Error("BookingWorker: invalid JSON", "subject", msg.Subject, "error", err)
		msg.Term()
		return
	}

	utils.Info("BookingWorker: processing message", "subject", msg.Subject, "booking_id", payload["booking_id"])

	var ok bool
	switch msg.Subject {
	case "api.v1.bookings.create":
		ok = handleCreate(payload)
	case "api.v1.bookings.update":
		ok = handleUpdate(payload)
	case "api.v1.bookings.cancel":
		ok = handleCancel(payload)
	default:
		utils.Warn("BookingWorker: no handler for subject", "subject", msg.Subject)
		msg.Ack()
		return
	}

	if ok {
		msg.Ack()
	} else {
		msg.Nak()
	}
}

func handleCreate(payload map[string]interface{}) bool {
	bid, ok := extractBookingID(payload)
	if !ok {
		utils.Error("BookingWorker: missing booking_id in create payload")
		return false
	}

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	mapping := pickFields(payload, "booking_id", "booking_no", "customer_id",
		"pickup_address", "pickup_pincode", "delivery_address", "delivery_pincode",
		"status", "created_at")

	if err := db.Rdb.HSet(ctx, fmt.Sprintf("bookings:%s", bid), mapping).Err(); err != nil {
		utils.Error("BookingWorker: HSET failed on create", "booking_id", bid, "error", err)
		return false
	}

	ctx2, cancel2 := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel2()
	db.Rdb.SAdd(ctx2, "bookings:all", bid)

	if cid := strOf(payload["customer_id"]); cid != "" {
		ctx3, cancel3 := context.WithTimeout(context.Background(), 3*time.Second)
		defer cancel3()
		db.Rdb.SAdd(ctx3, fmt.Sprintf("bookings:customer:%s", cid), bid)
	}

	utils.Info("BookingWorker: created booking in Redis", "booking_id", bid)
	return true
}

func handleUpdate(payload map[string]interface{}) bool {
	bid, ok := extractBookingID(payload)
	if !ok {
		return false
	}

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	exists, err := db.Rdb.Exists(ctx, fmt.Sprintf("bookings:%s", bid)).Result()
	if err != nil || exists == 0 {
		utils.Warn("BookingWorker: booking not in cache for update", "booking_id", bid)
		return false
	}

	ctx2, cancel2 := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel2()

	mapping := pickFields(payload, "status", "miler_id", "updated_at")
	if err := db.Rdb.HSet(ctx2, fmt.Sprintf("bookings:%s", bid), mapping).Err(); err != nil {
		utils.Error("BookingWorker: HSET failed on update", "booking_id", bid, "error", err)
		return false
	}

	utils.Info("BookingWorker: updated booking in Redis", "booking_id", bid)
	return true
}

func handleCancel(payload map[string]interface{}) bool {
	bid, ok := extractBookingID(payload)
	if !ok {
		return false
	}

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	mapping := pickFields(payload, "cancelled_at")
	mapping["status"] = "Cancelled"

	if err := db.Rdb.HSet(ctx, fmt.Sprintf("bookings:%s", bid), mapping).Err(); err != nil {
		utils.Error("BookingWorker: HSET failed on cancel", "booking_id", bid, "error", err)
		return false
	}

	utils.Info("BookingWorker: cancelled booking in Redis", "booking_id", bid)
	return true
}

func extractBookingID(payload map[string]interface{}) (string, bool) {
	v, exists := payload["booking_id"]
	if !exists || v == nil {
		return "", false
	}
	s := strOf(v)
	return s, s != ""
}

func strOf(v interface{}) string {
	if v == nil {
		return ""
	}
	return fmt.Sprintf("%v", v)
}

func pickFields(payload map[string]interface{}, keys ...string) map[string]interface{} {
	m := make(map[string]interface{}, len(keys))
	for _, k := range keys {
		if v, ok := payload[k]; ok && v != nil {
			m[k] = strOf(v)
		}
	}
	return m
}