package payments

import (
	"context"
	"log"
	"math"
	"time"

	"crussell/db"
	"crussell/internal/square"
)

type RefundCalculationResult struct {
	TotalPrePaid          float64 `json:"total_pre_paid"`
	ProtectedDeposit      float64 `json:"protected_deposit"`
	RefundableAmount      float64 `json:"refundable_amount"`
	KeptAmount            float64 `json:"kept_amount"`
	HoursUntilAppointment float64 `json:"hours_until_appointment"`
	Tier                  string  `json:"tier"`
}

// CalculateRefundForCancellation computes the refund amounts for a cancelled booking.
//
// Track A (universal — same rules for all bookings):
//   - >72 hours notice:        Full refund of all pre-payments
//   - 24-72 hours notice:      Keep protected deposit (up to 50%), refund the rest
//   - <24 hours or no-show:    Keep all pre-payments
//
// The "protected deposit" is defined as min(totalPrePaid, subtotal * 0.50).
// This means up to 50% of the subtotal is always treated as a deposit for
// refund purposes, regardless of whether deposit_required was set on the booking.
func CalculateRefundForCancellation(
	subtotal float64,
	totalPrePaid float64,
	cancellationTime time.Time,
	startTime time.Time,
) RefundCalculationResult {
	hoursUntilAppointment := startTime.Sub(cancellationTime).Hours()

	protectedDeposit := math.Min(totalPrePaid, subtotal*ProtectedDepositMaxPct)

	// Round to 2 decimal places
	protectedDeposit = math.Round(protectedDeposit*100) / 100
	totalPrePaidRounded := math.Round(totalPrePaid*100) / 100

	var refundableAmount, keptAmount float64
	var tier string

	fullHrs := FullRefundThreshold.Hours()
	partHrs := PartialRefundThreshold.Hours()

	switch {
	case hoursUntilAppointment > fullHrs:
		refundableAmount = totalPrePaidRounded
		keptAmount = 0
		tier = FullRefundTier

	case hoursUntilAppointment >= partHrs:
		keptAmount = protectedDeposit
		refundableAmount = totalPrePaidRounded - keptAmount
		if refundableAmount < 0 {
			refundableAmount = 0
		}
		tier = PartialRefundTier

	default:
		keptAmount = totalPrePaidRounded
		refundableAmount = 0
		tier = NoRefundTier
	}

	return RefundCalculationResult{
		TotalPrePaid:          totalPrePaidRounded,
		ProtectedDeposit:      protectedDeposit,
		RefundableAmount:      refundableAmount,
		KeptAmount:            keptAmount,
		HoursUntilAppointment: hoursUntilAppointment,
		Tier:                  tier,
	}
}

// ProcessCancellationRefund calculates and records refunds for a cancelled booking.
// It processes refunds against completed payments on the booking up to the
// calculated refundable amount, creating refund records in the database.
// Returns the refund calculation and whether any refunds were processed.
func ProcessCancellationRefund(
	ctx context.Context,
	bookingID string,
	subtotal float64,
	totalPrePaid float64,
	startTime time.Time,
	cancellationTime time.Time,
	reason string,
	actorID *string,
) (*RefundCalculationResult, error) {
	calc := CalculateRefundForCancellation(subtotal, totalPrePaid, cancellationTime, startTime)

	if calc.RefundableAmount <= 0 {
		return &calc, nil
	}

	// Get the booking's user info for refund routing.
	var bookingUserID string
	var isGuest bool
	if err := db.DB.QueryRow(ctx, `
		SELECT b.user_id, COALESCE(u.account_role = 'guest', false)
		FROM bookings b
		LEFT JOIN users u ON b.user_id = u.id
		WHERE b.id = $1
	`, bookingID).Scan(&bookingUserID, &isGuest); err != nil {
		log.Printf("Failed to get booking user info for refund: %v", err)
		// Non-fatal — we'll still process Square refunds but skip balance credits.
	}

	rows, err := db.DB.Query(ctx, `
		SELECT id, amount, payment_method, square_payment_id, gift_card_id
		FROM payments
		WHERE booking_id = $1 AND status = 'completed' AND payment_method NOT IN ('discount', 'on_the_house')
		ORDER BY created_at ASC
	`, bookingID)
	if err != nil {
		log.Printf("Failed to fetch payments for refund: %v", err)
		return &calc, nil
	}
	defer rows.Close()

	refundRemaining := calc.RefundableAmount
	// Track which Square payment IDs have already been refunded through Square.
	// Multiple split payment records (deposit + balance) can share the same
	// square_payment_id — we must only refund each Square payment once.
	refundedSquareIDs := make(map[string]bool)

	for rows.Next() {
		if refundRemaining <= 0 {
			break
		}

		var paymentID, paymentMethod string
		var amount float64
		var squarePaymentID *string
		var giftCardID *string
		if err := rows.Scan(&paymentID, &amount, &paymentMethod, &squarePaymentID, &giftCardID); err != nil {
			log.Printf("Failed to scan payment row: %v", err)
			continue
		}

		refundThisPayment := math.Min(amount, refundRemaining)
		refundCents := int64(math.Round(refundThisPayment * 100))
		var squareRefundID *string

		switch paymentMethod {
		case "online_square", "in_person_card":
			// Card payments can be refunded through Square if we have a payment reference.
			// Skip the Square API call if this square_payment_id was already processed
			// (possible when split payment records share the same charge).
			if squarePaymentID != nil && *squarePaymentID != "" && !refundedSquareIDs[*squarePaymentID] {
				refundReq := square.RefundPaymentReq{
					PaymentID:      *squarePaymentID,
					Amount:         refundCents,
					IdempotencyKey: paymentID + "-cancel-" + time.Now().Format("20060102150405"),
					Reason:         reason,
				}
				result, sqErr := SquareClient.RefundPayment(ctx, refundReq)
				if sqErr != nil {
					log.Printf("Square refund failed for payment %s (will record refund locally): %v", paymentID, sqErr)
				} else {
					squareRefundID = &result.ID
					refundedSquareIDs[*squarePaymentID] = true
				}
			} else if squarePaymentID != nil && refundedSquareIDs[*squarePaymentID] {
				log.Printf("Square payment %s already refunded through split record %s — crediting balance for £%.2f", *squarePaymentID, paymentID, refundThisPayment)
			}

			// If Square refund failed or wasn't available, credit the user's balance.
			// Guests don't get balance credits — admin handles those manually.
			if squareRefundID == nil && bookingUserID != "" {
				if isGuest {
					log.Printf("Guest card refund (Square unavailable): booking %s, payment %s, amount £%.2f — admin must process at till", bookingID, paymentID, refundThisPayment)
				} else {
					log.Printf("Crediting £%.2f to user %s balance for card payment %s (Square refund unavailable)", refundThisPayment, bookingUserID, paymentID)
					creditUserBalance(ctx, bookingUserID, bookingID, paymentID, refundThisPayment, reason)
				}
			}

		case "giftcard":
			if giftCardID == nil || *giftCardID == "" {
				log.Printf("Giftcard payment %s has no gift_card_id — cannot refund to card. Skipping.", paymentID)
				break
			}
			var expired bool
			if err := db.DB.QueryRow(ctx, `
				SELECT expiry_date IS NOT NULL AND expiry_date < NOW()
				FROM gift_cards WHERE id = $1
			`, *giftCardID).Scan(&expired); err != nil {
				log.Printf("Failed to check gift card %s expiry: %v — proceeding with refund", *giftCardID, err)
			} else if expired {
				log.Printf("Gift card %s has expired — money retained by salon, no refund due for booking %s", *giftCardID, bookingID)
				break
			}
			if _, err := db.DB.Exec(ctx, `
				UPDATE gift_cards SET amount_remaining = amount_remaining + $1, last_used_at = NOW()
				WHERE id = $2
			`, refundThisPayment, *giftCardID); err != nil {
				log.Printf("Failed to refund £%.2f to gift card %s: %v", refundThisPayment, *giftCardID, err)
				break
			}
			if _, err := db.DB.Exec(ctx, `
				INSERT INTO gift_card_transactions (gift_card_id, transaction_type, amount, reference_type, reference_id, user_id, notes)
				VALUES ($1, 'refund', $2, 'booking', $3, $4, $5)
			`, *giftCardID, refundThisPayment, bookingID, bookingUserID, "Refund from cancelled booking"); err != nil {
				log.Printf("Failed to create gift card transaction for refund: %v", err)
			}

		case "cash":
			if isGuest || bookingUserID == "" {
				log.Printf("Guest cash refund: booking %s, payment %s, amount £%.2f — admin must process cash refund at till", bookingID, paymentID, refundThisPayment)
			} else {
				log.Printf("Crediting £%.2f to user %s balance for cash payment %s", refundThisPayment, bookingUserID, paymentID)
				creditUserBalance(ctx, bookingUserID, bookingID, paymentID, refundThisPayment, reason)
			}

		default:
			// discount, on_the_house — no real money to refund.
			log.Printf("Skipping refund for payment %s with method %q (no money exchanged)", paymentID, paymentMethod)
		}

		record := RefundRecord{
			PaymentID:      paymentID,
			BookingID:      bookingID,
			Amount:         refundThisPayment,
			SquareRefundID: squareRefundID,
			Status:         "completed",
			Reason:         reason,
			CreatedBy:      actorID,
			CreatedAt:      time.Now(),
		}

		_, dbErr := db.DB.Exec(ctx, `
			INSERT INTO refunds (payment_id, booking_id, amount, square_refund_id, status, reason, created_by, created_at)
			VALUES ($1, $2, $3, $4, 'completed', $5, $6, $7)
		`, record.PaymentID, record.BookingID, record.Amount, record.SquareRefundID, record.Reason, record.CreatedBy, record.CreatedAt)
		if dbErr != nil {
			log.Printf("Failed to create refund record for payment %s: %v", paymentID, dbErr)
			continue
		}

		refundRemaining -= refundThisPayment
	}

	if bookingUserID != "" {
		var loyaltyUsed bool
		db.DB.QueryRow(ctx, "SELECT EXISTS(SELECT 1 FROM booking_discounts WHERE booking_id = $1 AND discount_source = 'loyalty')", bookingID).Scan(&loyaltyUsed)
		if loyaltyUsed {
			_, err := db.DB.Exec(ctx, "UPDATE users SET loyalty_stamps = loyalty_stamps + $1 WHERE id = $2", LoyaltyStampCost, bookingUserID)
			if err != nil {
				log.Printf("Failed to refund loyalty stamps for booking %s: %v", bookingID, err)
			} else {
				log.Printf("Refunded 10 loyalty stamps to user %s after cancellation of booking %s", bookingUserID, bookingID)
			}
		}
	}

	return &calc, nil
}

// creditUserBalance credits a refund amount to the user's gift card balance.
// The refunds table (payment_id, booking_id, amount, reason, created_by, created_at)
// provides the primary audit trail for FreeAgent reconciliation.
func creditUserBalance(ctx context.Context, userID, bookingID, paymentID string, amount float64, reason string) {
	_, err := db.DB.Exec(ctx, `
		INSERT INTO user_giftcard_balances (user_id, balance, updated_at)
		VALUES ($1, $2, NOW())
		ON CONFLICT (user_id) DO UPDATE SET
			balance = user_giftcard_balances.balance + EXCLUDED.balance,
			updated_at = NOW()
	`, userID, amount)
	if err != nil {
		log.Printf("Failed to credit user %s balance for refund of booking %s: %v", userID, bookingID, err)
	}
}