package controllers

import (
	"math"
	"time"

	"doormile/constants"
	"doormile/db"
	"doormile/models"
	"doormile/utils"

	"gorm.io/gorm"
)

// Pickup fan-out: one visit becomes N orders.
//
// This is the change §1 of the customer contract turns on. A pickup booking
// used to convert into exactly one consignment, because a booking carried
// exactly one delivery address in its own columns. A customer-app booking
// carries 1..N destinations, and each of those has to become its own
// consignment with its own tracking number and its own journey — three parcels
// collected in one visit for Chennai, Kochi and Bengaluru travel three separate
// routes the moment they leave the door.
//
// A booking with no destination rows — every console-created express booking,
// and every row written before this table existed — produces exactly one leg
// built from the flat delivery columns, which is byte-for-byte the behaviour
// that was there before. Single-destination is not a special case in either
// direction: it is one leg, through the same code.

// cxPickupLeg is one journey to create at pickup completion.
type cxPickupLeg struct {
	// Destination is nil for a booking that has no destination rows.
	Destination *models.BookingDestination

	DeliveryLatitude  float64
	DeliveryLongitude float64
	DeliveryPincode   string
	CodAmount         float64

	// Parcels are the packages going to this destination, already weighed by
	// the miler.
	Parcels []models.BookingParcel
}

// cxPickupLegs splits a booking into the journeys its parcels are about to
// take.
func cxPickupLegs(tx *gorm.DB, booking *models.PickupBooking) ([]cxPickupLeg, error) {
	var destinations []models.BookingDestination
	if err := tx.Where("bookingid = ?", booking.Bookingid).
		Order("seq ASC").Find(&destinations).Error; err != nil {
		return nil, err
	}

	var parcels []models.BookingParcel
	if err := tx.Where("bookingid = ?", booking.Bookingid).Find(&parcels).Error; err != nil {
		return nil, err
	}

	if len(destinations) == 0 {
		// The pre-existing shape: one consignment from the booking's own
		// delivery columns, carrying every parcel on the booking.
		return []cxPickupLeg{{
			DeliveryLatitude:  booking.Deliverylatitude,
			DeliveryLongitude: booking.Deliverylongitude,
			DeliveryPincode:   booking.Deliverypincode,
			Parcels:           parcels,
		}}, nil
	}

	byDestination := map[int][]models.BookingParcel{}
	unassigned := []models.BookingParcel{}
	for _, p := range parcels {
		if p.Bookingdestinationid == nil {
			unassigned = append(unassigned, p)
			continue
		}
		byDestination[*p.Bookingdestinationid] = append(byDestination[*p.Bookingdestinationid], p)
	}

	legs := make([]cxPickupLeg, 0, len(destinations))
	for i := range destinations {
		d := destinations[i]

		lat, lng := cxDestinationPoint(&d)
		leg := cxPickupLeg{
			Destination:       &destinations[i],
			DeliveryLatitude:  lat,
			DeliveryLongitude: lng,
			DeliveryPincode:   d.Pincode,
			CodAmount:         d.Codamount,
			Parcels:           byDestination[d.Bookingdestinationid],
		}
		// Parcels the miler added at the door without naming a destination go
		// with the first one. Attributing them to nothing would drop them out
		// of every weight total, and the first destination is the one the rider
		// was shown.
		if i == 0 {
			leg.Parcels = append(leg.Parcels, unassigned...)
		}
		legs = append(legs, leg)
	}
	return legs, nil
}

// cxDestinationPoint gives a destination the best coordinates it has: the
// customer's own map pin if they dropped one, otherwise the district centre.
// Only state and district are required at booking time, so the centre is
// frequently all there is — and routing skips stops sitting at 0,0.
func cxDestinationPoint(d *models.BookingDestination) (lat, lng float64) {
	if d.Pinlatitude != nil && d.Pinlongitude != nil &&
		(*d.Pinlatitude != 0 || *d.Pinlongitude != 0) {
		return *d.Pinlatitude, *d.Pinlongitude
	}
	var district models.ServiceableDistrict
	if err := db.DB.Select("centrelatitude, centrelongitude").
		Where("districtcode = ?", d.Districtcode).First(&district).Error; err == nil {
		return district.Centrelatitude, district.Centrelongitude
	}
	return 0, 0
}

// cxLegWeights totals a leg's packages the way the consignment records them.
// A leg whose packages were never weighed falls back to the same 0.5 kg
// placeholder the single-consignment path already used, so an unweighed pickup
// still produces a chargeable consignment rather than a zero-weight one.
func cxLegWeights(leg cxPickupLeg) (deadWeight, chargeable, maxL, maxW, maxH float64) {
	for _, p := range leg.Parcels {
		vol := calculateVolumetricWeight(p.Length, p.Width, p.Height)
		deadWeight += p.Weight
		chargeable += math.Max(p.Weight, vol)
		if p.Length > maxL {
			maxL = p.Length
		}
		if p.Width > maxW {
			maxW = p.Width
		}
		if p.Height > maxH {
			maxH = p.Height
		}
	}
	if len(leg.Parcels) == 0 || chargeable == 0 {
		deadWeight, chargeable = 0.5, 0.5
	}
	return
}

// cxLinkLegToOrder records that a destination has become an order: its tracking
// number, its consignment, and the delivery date the customer is promised.
func cxLinkLegToOrder(tx *gorm.DB, leg cxPickupLeg, consignmentID int, trackingNo string, expected *time.Time, at time.Time) error {
	if leg.Destination == nil {
		return nil
	}
	updates := map[string]interface{}{
		"consignmentid": consignmentID,
		"trackingno":    trackingNo,
		"stage":         constants.CxStageOrderCreated,
		"updatedat":     at,
	}
	if expected != nil {
		updates["expecteddeliveryat"] = *expected
	}
	return tx.Model(&models.BookingDestination{}).
		Where("bookingdestinationid = ?", leg.Destination.Bookingdestinationid).
		Updates(updates).Error
}

// cxRecordVerification stores what the miler measured at the door: the weight
// the price settles on, when, and who took the reading. It is the evidence half
// of the receipt, and it is per destination because each order is weighed
// separately.
func cxRecordVerification(tx *gorm.DB, destinationID int, weightKg float64, byUserID int, at time.Time) error {
	return tx.Model(&models.BookingDestination{}).
		Where("bookingdestinationid = ?", destinationID).
		Updates(map[string]interface{}{
			"verifiedweightkg": weightKg,
			"verifiedat":       at,
			"verifiedbyuserid": byUserID,
			"updatedat":        at,
		}).Error
}

// cxDestinationForConsignment finds which order a consignment belongs to.
//
// The delivery handlers used to reach the booking with
// `WHERE consignmentid = ?` on pickupbookings, which held exactly one
// consignment id. With a fan-out that column only names the FIRST order, so
// that lookup silently found nothing for destinations 2..N — no customer
// notification, no stage advance, on every multi-destination booking. The join
// goes through bookingdestinations now, which is the table that actually knows.
func cxDestinationForConsignment(consignmentID int) (*models.BookingDestination, *models.PickupBooking, bool) {
	var dest models.BookingDestination
	if err := db.DB.Where("consignmentid = ?", consignmentID).First(&dest).Error; err == nil {
		var booking models.PickupBooking
		if err := db.DB.First(&booking, dest.Bookingid).Error; err == nil {
			return &dest, &booking, true
		}
		return &dest, nil, false
	}

	// No destination row: a console-created booking, or one written before the
	// fan-out existed. The legacy link still answers for those.
	var booking models.PickupBooking
	if err := db.DB.Where("consignmentid = ?", consignmentID).First(&booking).Error; err != nil {
		return nil, nil, false
	}
	return nil, &booking, true
}

// cxDestinationIDFor returns the destination id to attribute a per-order stage
// to, or nil when the booking has no destination rows.
func cxDestinationIDFor(dest *models.BookingDestination) *int {
	if dest == nil {
		return nil
	}
	id := dest.Bookingdestinationid
	return &id
}

// cxEstimatedDelivery is the promise shown to the customer, derived from the
// serving district's own promise text rather than a single platform-wide SLA —
// "Next-day delivery" into Chennai and "2-day delivery" into a district two
// states away are different promises and must not resolve to the same date.
func cxEstimatedDelivery(leg cxPickupLeg, from time.Time) *time.Time {
	days := 2
	if leg.Destination != nil {
		var district models.ServiceableDistrict
		if err := db.DB.Select("promise").
			Where("districtcode = ?", leg.Destination.Districtcode).
			First(&district).Error; err == nil {
			switch district.Promise {
			case "Same-day delivery":
				days = 0
			case "Next-day delivery":
				days = 1
			case "2-day delivery":
				days = 2
			case "3-day delivery":
				days = 3
			}
		}
	}
	// Delivered by end of the promised day, expressed in the wall clock this
	// database stores.
	target := from.AddDate(0, 0, days)
	expected := time.Date(target.Year(), target.Month(), target.Day(), 20, 0, 0, 0, time.UTC)
	if utils.EpochMillis(expected) < utils.EpochMillis(from) {
		expected = from
	}
	return &expected
}