import 'package:equatable/equatable.dart';

import '../../core/utils/extensions.dart';
import 'cart.dart';
import 'customer.dart';

enum PaymentMethod {
  cash('Cash', '💵', true),
  card('Card', '💳', false),
  upi('UPI', '📱', false),
  wallet('Wallet', '👛', false),
  giftCard('Gift Card', '🎁', false),
  loyalty('Loyalty Points', '⭐', false);

  const PaymentMethod(this.label, this.emoji, this.needsChange);

  final String label;
  final String emoji;

  /// Only cash tenders can be over-paid and produce change.
  final bool needsChange;

  /// Non-cash tenders normally capture a reference number.
  bool get needsReference =>
      this == PaymentMethod.card ||
      this == PaymentMethod.upi ||
      this == PaymentMethod.giftCard;
}

/// A single tender against a bill. A split payment holds several of these.
class PaymentSplit extends Equatable {
  const PaymentSplit({
    required this.method,
    required this.amount,
    this.tendered,
    this.reference,
  });

  final PaymentMethod method;

  /// Amount settled by this tender.
  final double amount;

  /// Cash handed over — may exceed [amount].
  final double? tendered;

  /// Card approval code, UPI txn id, gift card number.
  final String? reference;

  double get change {
    if (!method.needsChange || tendered == null) return 0;
    final diff = tendered! - amount;
    return diff > 0 ? diff.asMoney : 0;
  }

  @override
  List<Object?> get props => [method, amount, tendered, reference];
}

enum TransactionStatus { completed, parked, voided, refunded }

/// An immutable record of a finished sale.
class SaleTransaction extends Equatable {
  const SaleTransaction({
    required this.id,
    required this.invoiceNumber,
    required this.cart,
    required this.payments,
    required this.createdAt,
    required this.cashierName,
    this.status = TransactionStatus.completed,
    this.terminalId = 'TERM-01',
    this.storedTotal,
    this.storedPointsEarned,
  });

  final String id;
  final String invoiceNumber;
  final Cart cart;
  final List<PaymentSplit> payments;
  final DateTime createdAt;
  final String cashierName;
  final TransactionStatus status;
  final String terminalId;

  /// The figure actually charged, as recorded at sale time.
  ///
  /// Set only when a bill is read back from storage. Deriving the total from
  /// [cart] is correct for a live sale, but a rehydrated cart is a
  /// reconstruction — if it ever loses a component the money must not move with
  /// it. The recorded value wins whenever there is one.
  final double? storedTotal;

  /// Points issued by this sale, as recorded at sale time. See [storedTotal].
  final int? storedPointsEarned;

  Customer? get customer => cart.customer;

  double get total => storedTotal ?? cart.grandTotal;

  double get amountPaid =>
      payments.fold(0.0, (sum, p) => sum + p.amount).asMoney;

  double get amountTendered => payments
      .fold(0.0, (sum, p) => sum + (p.tendered ?? p.amount))
      .asMoney;

  double get changeDue =>
      payments.fold(0.0, (sum, p) => sum + p.change).asMoney;

  double get balanceDue => (total - amountPaid).clamp(0, double.infinity);

  bool get isFullySettled => balanceDue <= 0.001;

  bool get isSplit => payments.length > 1;

  int get pointsEarned => storedPointsEarned ?? cart.pointsEarned;
  int get pointsRedeemed => cart.pointsRedeemed;

  String get paymentSummary =>
      payments.map((p) => p.method.label).toSet().join(' + ');

  @override
  List<Object?> get props => [id, invoiceNumber, createdAt, status];
}

/// A bill set aside so the cashier can serve the next shopper.
class ParkedBill extends Equatable {
  const ParkedBill({
    required this.id,
    required this.cart,
    required this.parkedAt,
    this.label,
  });

  final String id;
  final Cart cart;
  final DateTime parkedAt;
  final String? label;

  String get displayLabel =>
      label ?? cart.customer?.name ?? 'Walk-in #${id.substring(0, 4)}';

  @override
  List<Object?> get props => [id, parkedAt];
}