import 'package:flutter_test/flutter_test.dart';
import 'package:fuel_tax_tracker/services/receipt_parser.dart';

void main() {
  group('ReceiptParser', () {
    test('parses a typical gas station receipt', () {
      const receipt = '''
        SHELL OIL 12345
        123 MAIN ST
        PUMP 04
        GALLONS       12.345
        PRICE/GAL     \$3.599
        FUEL TOTAL    \$44.44
        THANK YOU
      ''';

      final result = ReceiptParser.parse(receipt);

      expect(result.gallons, 12.345);
      expect(result.pricePerGallon, 3.599);
      expect(result.totalCost, 44.44);
    });

    test('does not confuse SUBTOTAL with TOTAL', () {
      const receipt = '''
        SUBTOTAL 10.00
        TAX 0.50
        TOTAL 10.50
      ''';

      final result = ReceiptParser.parse(receipt);

      expect(result.totalCost, 10.50);
    });

    test('derives total when gallons and price per gallon are known', () {
      const receipt = '''
        GALLONS 10.000
        PPG 3.500
      ''';

      final result = ReceiptParser.parse(receipt);

      expect(result.gallons, 10.0);
      expect(result.pricePerGallon, 3.5);
      expect(result.totalCost, 35.0);
    });

    test('derives gallons when total and price per gallon are known', () {
      const receipt = '''
        PRICE PER GALLON \$4.000
        TOTAL \$20.00
      ''';

      final result = ReceiptParser.parse(receipt);

      expect(result.pricePerGallon, 4.0);
      expect(result.totalCost, 20.0);
      expect(result.gallons, 5.0);
    });

    test('returns nulls when nothing recognizable is present', () {
      const receipt = 'THANK YOU FOR YOUR PURCHASE';

      final result = ReceiptParser.parse(receipt);

      expect(result.gallons, isNull);
      expect(result.pricePerGallon, isNull);
      expect(result.totalCost, isNull);
    });
  });
}