import unittest
from calc.lexer import tokenize
from calc.parser import parse, ParseError, Num, BinOp, Unary


def p(src):
    return parse(tokenize(src))


class TestPrecedence(unittest.TestCase):
    def test_add_mul(self):
        # 1+2*3 must parse as 1+(2*3), not (1+2)*3
        self.assertEqual(p('1+2*3'), BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_div_add(self):
        # 6/2+1 must parse as (6/2)+1
        self.assertEqual(p('6/2+1'), BinOp('+', BinOp('/', Num(6), Num(2)), Num(1)))

    def test_mul_sub(self):
        # 4-2*3 => 4-(2*3)
        self.assertEqual(p('4-2*3'), BinOp('-', Num(4), BinOp('*', Num(2), Num(3))))


class TestLeftAssoc(unittest.TestCase):
    def test_subtraction(self):
        # 8-3-2 => (8-3)-2
        self.assertEqual(p('8-3-2'), BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

    def test_division(self):
        # 8/4/2 => (8/4)/2
        self.assertEqual(p('8/4/2'), BinOp('/', BinOp('/', Num(8), Num(4)), Num(2)))

    def test_addition(self):
        # 1+2+3 => (1+2)+3
        self.assertEqual(p('1+2+3'), BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))


class TestParentheses(unittest.TestCase):
    def test_parens_override_precedence(self):
        # (1+2)*3 => BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
        self.assertEqual(
            p('(1+2)*3'),
            BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
        )

    def test_nested_parens(self):
        self.assertEqual(p('((5))'), Num(5))

    def test_parens_in_add(self):
        # 2*(3+4) => BinOp('*', Num(2), BinOp('+', Num(3), Num(4)))
        self.assertEqual(
            p('2*(3+4)'),
            BinOp('*', Num(2), BinOp('+', Num(3), Num(4)))
        )


class TestUnaryMinus(unittest.TestCase):
    def test_simple(self):
        self.assertEqual(p('-5'), Unary('-', Num(5)))

    def test_paren(self):
        # -(1+2) => Unary('-', BinOp('+', Num(1), Num(2)))
        self.assertEqual(p('-(1+2)'), Unary('-', BinOp('+', Num(1), Num(2))))

    def test_after_mul(self):
        # 3 * -2 => BinOp('*', Num(3), Unary('-', Num(2)))
        self.assertEqual(p('3 * -2'), BinOp('*', Num(3), Unary('-', Num(2))))

    def test_double_unary(self):
        # --5 => Unary('-', Unary('-', Num(5)))
        self.assertEqual(p('--5'), Unary('-', Unary('-', Num(5))))


class TestErrors(unittest.TestCase):
    def test_trailing_op(self):
        with self.assertRaises(ParseError):
            p('1 +')

    def test_unclosed_paren(self):
        with self.assertRaises(ParseError):
            p('(1')

    def test_extra_number(self):
        with self.assertRaises(ParseError):
            p('1 2')

    def test_close_before_open(self):
        with self.assertRaises(ParseError):
            p(')(')

    def test_empty_string(self):
        with self.assertRaises(ParseError):
            p('')


if __name__ == '__main__':
    unittest.main()