Dart 2 Decimal Money

Money.dart

#import('unittest/unittest.dart');

class Money {
  bool _isNegative = false;
  int _dollars = 0;
  int _cents = 0;
  
  Money(String money) {
    if (money.contains("-")) {
      _isNegative = true;
      money = money.replaceFirst("-", "");
    }
      
    if (!money.contains(".")) {
      _setDollars(money);
      _cents = 0;
      
    } else {
      List<String> split = money.split(".");
      _setDollars(split[0]);
      _setCents(split[1]);
    }
  }
  
  Money.create(bool isNegative, int dollars, int cents) : 
    _isNegative = isNegative, _dollars = dollars, _cents = cents;
  
  _setDollars(String dollars) {
    _dollars = Math.parseInt(dollars);
  }
  
  _setCents(String cents) {
    _cents = Math.parseInt(cents);
  }
  
  bool get isNegative() => _isNegative;
  
  int get dollars() {
    int dollars = _dollars;
    if (_isNegative == true && _dollars != 0) {
      dollars = -_dollars; 
    }
    return dollars;
  }
  
  int get cents() {
    int cents = _cents;
    if (_isNegative == true && _cents != 0) {
      cents = -_cents; 
    }
    return cents;
  }

  Money operator +(Money money) {
    int dollarsTotal = this.dollars + money.dollars;
    
    int centsTotal = this.cents + money.cents;
    if (centsTotal <= -100) {
      dollarsTotal--;
      centsTotal += 100;
      centsTotal *= -1;
    } else if (centsTotal >= 100) {
      dollarsTotal++;
      centsTotal -= 100; 
    }
    
    bool isNegative = false;
    if (dollarsTotal < 0) {
      isNegative = true;
      dollarsTotal *= -1;
      if (centsTotal < 0) {
        centsTotal *= -1;
      }
    }
    
    return new Money.create(isNegative, dollarsTotal, centsTotal);
  }
  
  bool operator ==(Money money) {
    if (this !== null && money !== null && 
        this.dollars == money.dollars && 
        this.cents == money.cents) {
      return true;
    } else {
      return false;
    }
  }
  
  String toString() {
    String sign = "";
    if (_isNegative) {
      sign = "-";
    }
    String s = "\$$sign$_dollars.$_cents";
    return s;
  }
}

main() {
  
  test('get dollars -', () {
    var money = new Money("-1.99");
    expect(-1, money.dollars, "dollars compare"); 
  });
  
  test('get cents -', () {
    var money = new Money("-1.99");
    expect(-99, money.cents, "cents compare"); 
  });
  
  test('get dollars +', () {
    var money = new Money("1.99");
    expect(1, money.dollars, "dollars compare"); 
  });
  
  test('get cents +', () {
    var money = new Money("1.99");
    expect(99, money.cents, "cents compare"); 
  });
  
  test('adding negatives', () {
    var left = new Money("-1.99");
    var right = new Money("-1.99");
    var total = left + right;
    print("$left + $right = $total");
    var expected = new Money("-3.98");
    expect(expected, total); 
  });
  
  test('adding positives', () {
    var left = new Money("1.99");
    var right = new Money("1.99");
    var total = left + right;
    print("$left + $right = $total");
    var expected = new Money("3.98");
    expect(expected, total); 
  });
  
  test('adding positives', () {
    var left = new Money("1.99");
    var right = new Money("-1.99");
    var total = left + right;
    print("$left + $right = $total");
    var expected = new Money("0.0");
    expect(expected, total); 
  });
   
}