package controllers

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

	"doormile/constants"
	"doormile/db"
	"doormile/internal/notify"
	"doormile/models"
	"doormile/utils"

	"gorm.io/gorm"
)

// milerStopSequence carries the road-optimized ordering the Route Optimization
// API produced for one stop. Passed to assignMilerTx when the caller already
// knows the sequence (the express-batch path), nil when it does not (a plain
// manual assignment, which leaves the stop unsequenced at step 0).
type milerStopSequence struct {
	Step          int
	Previouskms   float64
	Cumulativekms float64
	Etaminutes    int
	Cumulativeeta int
}

// assignMilerTx performs the DB half of a miler assignment inside the given
// transaction: flip the booking to Miler_Assigned, create the BookingAssignment
// (optionally already sequenced), and mark the miler Assigned. It does not
// commit, publish, or notify — those are the caller's job, so the same writes
// can be reused by the single-booking path (AssignMilerToBooking) and the
// batch express path (assignExpressStops) without duplicating the SQL or firing
// one notification per stop.
func assignMilerTx(tx *gorm.DB, bookingID, milerUserID int, assignedByUserID *int, seq *milerStopSequence) (*models.PickupBooking, error) {
	var booking models.PickupBooking
	if err := tx.First(&booking, bookingID).Error; err != nil {
		return nil, fmt.Errorf("booking not found")
	}

	booking.Status = constants.BookingMilerAssigned
	booking.Assignedmileruserid = &milerUserID
	booking.Updatedat = time.Now()
	if err := tx.Save(&booking).Error; err != nil {
		return nil, fmt.Errorf("failed to update booking: %w", err)
	}

	assignment := models.BookingAssignment{
		Bookingid:        booking.Bookingid,
		Mileruserid:      milerUserID,
		Assignedbyuserid: assignedByUserID,
		Assignmentstatus: constants.AssignmentAssigned,
	}
	if seq != nil {
		now := time.Now()
		assignment.Step = seq.Step
		assignment.Previouskms = seq.Previouskms
		assignment.Cumulativekms = seq.Cumulativekms
		assignment.Etaminutes = seq.Etaminutes
		assignment.Cumulativeeta = seq.Cumulativeeta
		assignment.Sequencedat = &now
	}
	if err := tx.Create(&assignment).Error; err != nil {
		return nil, fmt.Errorf("failed to create assignment: %w", err)
	}

	if err := tx.Model(&models.MilerProfile{}).Where("userid = ?", milerUserID).
		Update("availabilitystatus", constants.MilerAssigned).Error; err != nil {
		return nil, fmt.Errorf("failed to update miler availability: %w", err)
	}

	return &booking, nil
}

// publishAssignmentUpdate emits the best-effort booking.update NATS event and
// pushes the FCM notification for one assignment. Shared by both assignment
// paths so the outward side effects stay identical.
func publishAssignmentUpdate(booking *models.PickupBooking, milerUserID int) {
	if db.Js != nil {
		payload := map[string]interface{}{
			"booking_id": booking.Bookingid,
			"booking_no": booking.Bookingno,
			"status":     booking.Status,
			"miler_id":   milerUserID,
			"updated_at": time.Now().UnixMilli(),
		}
		if data, err := json.Marshal(payload); err == nil {
			if _, err := db.Js.Publish("api.v1.bookings.update", data); err != nil {
				utils.Warn("Failed to publish booking.update to NATS", "booking_id", booking.Bookingid, "error", err)
			}
		}
	}

	var miler models.MilerProfile
	if db.DB.Where("userid = ?", milerUserID).First(&miler).Error == nil && miler.Devicetoken != "" {
		if err := notify.SendToDevice(
			miler.Devicetoken,
			"New Pickup Assigned",
			"New booking assigned — tap to view details",
			map[string]string{"booking_id": fmt.Sprintf("%d", booking.Bookingid)},
		); err != nil {
			utils.Warn("FCM: failed to notify miler on assignment",
				"miler_id", milerUserID, "booking_id", booking.Bookingid, "error", err)
		}
	}
}

// AssignMilerToBooking is the single source of truth for manually assigning a
// miler to a pickup booking — shared by the admin console (AdminAssignMiler)
// and the hub console (HubAssignMiler) so both go through identical DB
// updates, NATS publish, and FCM notify instead of duplicating the logic.
func AssignMilerToBooking(bookingID, milerUserID int, assignedByUserID *int) (*models.PickupBooking, error) {
	tx := db.DB.Begin()

	booking, err := assignMilerTx(tx, bookingID, milerUserID, assignedByUserID, nil)
	if err != nil {
		tx.Rollback()
		return nil, err
	}

	if err := tx.Commit().Error; err != nil {
		return nil, fmt.Errorf("failed to commit miler assignment: %w", err)
	}

	publishAssignmentUpdate(booking, milerUserID)
	return booking, nil
}

// ExpressStop is one already-decided assignment from the ExpressDispatchAgent:
// which miler carries which booking, in what road-optimized order. The agent
// chose the miler and called the Route Optimization API for the sequence; this
// struct is the writeback contract.
type ExpressStop struct {
	BookingID     int     `json:"booking_id"`
	MilerUserID   int     `json:"miler_user_id"`
	Step          int     `json:"step"`
	Previouskms   float64 `json:"previouskms"`
	Cumulativekms float64 `json:"cumulativekms"`
	Etaminutes    int     `json:"etaminutes"`
	Cumulativeeta int     `json:"cumulativeeta"`
}

// ExpressAssignResult is the per-booking outcome of a batch writeback.
type ExpressAssignResult struct {
	BookingID   int    `json:"booking_id"`
	MilerUserID int    `json:"miler_user_id"`
	Success     bool   `json:"success"`
	Error       string `json:"error,omitempty"`
}

// assignExpressStops writes a batch of agent-decided assignments. Each stop is
// its own transaction so one bad booking id cannot roll back the whole batch —
// the same per-row-independence the bulk-create endpoint gives. Each carries its
// sequence, so the assignment lands already ordered rather than needing a second
// sequencing pass. A miler is notified once for the whole batch, not once per
// stop, so a rider handed five stops gets one push, not five.
func assignExpressStops(stops []ExpressStop) []ExpressAssignResult {
	results := make([]ExpressAssignResult, 0, len(stops))
	// Preserve first-seen miler order so the summary notification is deterministic.
	notifyBooking := map[int]*models.PickupBooking{}
	notifyOrder := []int{}

	for _, s := range stops {
		tx := db.DB.Begin()
		booking, err := assignMilerTx(tx, s.BookingID, s.MilerUserID, nil, &milerStopSequence{
			Step:          s.Step,
			Previouskms:   s.Previouskms,
			Cumulativekms: s.Cumulativekms,
			Etaminutes:    s.Etaminutes,
			Cumulativeeta: s.Cumulativeeta,
		})
		if err != nil {
			tx.Rollback()
			results = append(results, ExpressAssignResult{
				BookingID: s.BookingID, MilerUserID: s.MilerUserID, Success: false, Error: err.Error()})
			continue
		}
		if err := tx.Commit().Error; err != nil {
			results = append(results, ExpressAssignResult{
				BookingID: s.BookingID, MilerUserID: s.MilerUserID, Success: false, Error: "commit failed"})
			continue
		}

		// booking.update per stop keeps live trackers accurate; the FCM push is
		// deferred and coalesced per miler below.
		if db.Js != nil {
			payload := map[string]interface{}{
				"booking_id": booking.Bookingid,
				"booking_no": booking.Bookingno,
				"status":     booking.Status,
				"miler_id":   s.MilerUserID,
				"updated_at": time.Now().UnixMilli(),
			}
			if data, err := json.Marshal(payload); err == nil {
				if _, err := db.Js.Publish("api.v1.bookings.update", data); err != nil {
					utils.Warn("Failed to publish booking.update to NATS", "booking_id", booking.Bookingid, "error", err)
				}
			}
		}

		if _, seen := notifyBooking[s.MilerUserID]; !seen {
			notifyOrder = append(notifyOrder, s.MilerUserID)
		}
		notifyBooking[s.MilerUserID] = booking
		results = append(results, ExpressAssignResult{
			BookingID: s.BookingID, MilerUserID: s.MilerUserID, Success: true})
	}

	for _, milerUserID := range notifyOrder {
		count := 0
		for _, r := range results {
			if r.MilerUserID == milerUserID && r.Success {
				count++
			}
		}
		var miler models.MilerProfile
		if db.DB.Where("userid = ?", milerUserID).First(&miler).Error == nil && miler.Devicetoken != "" {
			msg := "New pickups assigned — tap to view your route"
			if count == 1 {
				msg = "New booking assigned — tap to view details"
			}
			if err := notify.SendToDevice(
				miler.Devicetoken,
				"New Pickups Assigned",
				msg,
				map[string]string{"count": fmt.Sprintf("%d", count)},
			); err != nil {
				utils.Warn("FCM: failed to notify miler on express batch assignment",
					"miler_id", milerUserID, "error", err)
			}
		}
	}

	return results
}