import 'package:equatable/equatable.dart';

import '../../core/utils/extensions.dart';
import 'transaction.dart';

/// Everything the back office needs from a day at this terminal.
///
/// Computed from the locally stored transactions, so it can be produced with
/// no connection and pushed whenever one is available.
class ShiftReport extends Equatable {
  const ShiftReport({
    required this.businessDate,
    required this.terminalId,
    required this.cashierName,
    required this.billCount,
    required this.itemCount,
    required this.grossSales,
    required this.taxCollected,
    required this.discountGiven,
    required this.roundOff,
    required this.paymentBreakdown,
    required this.loyaltyPointsIssued,
    required this.loyaltyPointsRedeemed,
    this.firstBillAt,
    this.lastBillAt,
  });

  final DateTime businessDate;
  final String terminalId;
  final String cashierName;

  final int billCount;

  /// Total units sold across every bill.
  final double itemCount;

  final double grossSales;
  final double taxCollected;
  final double discountGiven;
  final double roundOff;

  final Map<PaymentMethod, double> paymentBreakdown;

  final int loyaltyPointsIssued;
  final int loyaltyPointsRedeemed;

  final DateTime? firstBillAt;
  final DateTime? lastBillAt;

  /// A zeroed report for a day with no trading. Not a const — [DateTime]
  /// cannot appear in a constant expression.
  factory ShiftReport.blank({
    required DateTime businessDate,
    required String terminalId,
    required String cashierName,
  }) =>
      ShiftReport(
        businessDate: businessDate,
        terminalId: terminalId,
        cashierName: cashierName,
        billCount: 0,
        itemCount: 0,
        grossSales: 0,
        taxCollected: 0,
        discountGiven: 0,
        roundOff: 0,
        paymentBreakdown: const {},
        loyaltyPointsIssued: 0,
        loyaltyPointsRedeemed: 0,
      );

  bool get isEmpty => billCount == 0;

  double get averageBasket =>
      billCount == 0 ? 0 : (grossSales / billCount).asMoney;

  double get netOfTax => (grossSales - taxCollected).asMoney;

  /// Builds the report from the day's transactions.
  factory ShiftReport.fromTransactions({
    required List<SaleTransaction> transactions,
    required DateTime businessDate,
    required String terminalId,
    required String cashierName,
  }) {
    final completed = transactions
        .where((t) =>
            t.status == TransactionStatus.completed &&
            t.createdAt.year == businessDate.year &&
            t.createdAt.month == businessDate.month &&
            t.createdAt.day == businessDate.day)
        .toList()
      ..sort((a, b) => a.createdAt.compareTo(b.createdAt));

    final byMethod = <PaymentMethod, double>{};
    for (final t in completed) {
      for (final p in t.payments) {
        byMethod[p.method] = ((byMethod[p.method] ?? 0) + p.amount).asMoney;
      }
    }

    return ShiftReport(
      businessDate: businessDate,
      terminalId: terminalId,
      cashierName: cashierName,
      billCount: completed.length,
      itemCount:
          completed.fold(0.0, (s, t) => s + t.cart.totalQuantity),
      grossSales: completed.fold(0.0, (s, t) => s + t.total).asMoney,
      taxCollected:
          completed.fold(0.0, (s, t) => s + t.cart.taxAmount).asMoney,
      discountGiven: completed
          .fold(0.0,
              (s, t) => s + t.cart.billDiscountTotal + t.cart.lineDiscountTotal)
          .asMoney,
      roundOff: completed.fold(0.0, (s, t) => s + t.cart.roundOff).asMoney,
      paymentBreakdown: byMethod,
      loyaltyPointsIssued:
          completed.fold(0, (s, t) => s + t.pointsEarned),
      loyaltyPointsRedeemed:
          completed.fold(0, (s, t) => s + t.pointsRedeemed),
      firstBillAt: completed.isEmpty ? null : completed.first.createdAt,
      lastBillAt: completed.isEmpty ? null : completed.last.createdAt,
    );
  }

  /// The JSON body that would be sent to the back office.
  Map<String, Object?> toPayload() => {
        'business_date': businessDate.toIso8601String().substring(0, 10),
        'terminal_id': terminalId,
        'cashier': cashierName,
        'bill_count': billCount,
        'item_count': itemCount,
        'gross_sales': grossSales,
        'net_of_tax': netOfTax,
        'tax_collected': taxCollected,
        'discount_given': discountGiven,
        'round_off': roundOff,
        'average_basket': averageBasket,
        'loyalty_points_issued': loyaltyPointsIssued,
        'loyalty_points_redeemed': loyaltyPointsRedeemed,
        'first_bill_at': firstBillAt?.toIso8601String(),
        'last_bill_at': lastBillAt?.toIso8601String(),
        'payments': {
          for (final e in paymentBreakdown.entries) e.key.name: e.value,
        },
      };

  @override
  List<Object?> get props =>
      [businessDate, terminalId, billCount, grossSales];
}