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


def tree(src):
    return repr(parse(tokenize(src)))


class TestPrecedence(unittest.TestCase):
    """D1 — * and / bind tighter than + and -."""

    def test_add_then_mul(self):
        # 1+2*3 -> BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
        self.assertEqual(
            tree('1+2*3'),
            "BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))",
        )

    def test_mul_then_add(self):
        # 2*3+1 -> BinOp('+', BinOp('*', Num(2), Num(3)), Num(1))
        self.assertEqual(
            tree('2*3+1'),
            "BinOp('+', BinOp('*', Num(2), Num(3)), Num(1))",
        )

    def test_sub_then_div(self):
        # 10-6/2 -> BinOp('-', Num(10), BinOp('/', Num(6), Num(2)))
        self.assertEqual(
            tree('10-6/2'),
            "BinOp('-', Num(10), BinOp('/', Num(6), Num(2)))",
        )

    def test_div_then_sub(self):
        # 6/2-1 -> BinOp('-', BinOp('/', Num(6), Num(2)), Num(1))
        self.assertEqual(
            tree('6/2-1'),
            "BinOp('-', BinOp('/', Num(6), Num(2)), Num(1))",
        )


class TestLeftAssociativity(unittest.TestCase):
    """D2 — same-precedence operators associate left."""

    def test_sub_left_assoc(self):
        # 8-3-2 -> BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
        self.assertEqual(
            tree('8-3-2'),
            "BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))",
        )

    def test_div_left_assoc(self):
        # 8/4/2 -> BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
        self.assertEqual(
            tree('8/4/2'),
            "BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))",
        )

    def test_add_left_assoc(self):
        # 1+2+3 -> BinOp('+', BinOp('+', Num(1), Num(2)), Num(3))
        self.assertEqual(
            tree('1+2+3'),
            "BinOp('+', BinOp('+', Num(1), Num(2)), Num(3))",
        )

    def test_mul_left_assoc(self):
        # 2*3*4 -> BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))
        self.assertEqual(
            tree('2*3*4'),
            "BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))",
        )


class TestParentheses(unittest.TestCase):
    """D3 — parens override precedence."""

    def test_paren_overrides_mul(self):
        # (1+2)*3 -> BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
        self.assertEqual(
            tree('(1+2)*3'),
            "BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))",
        )

    def test_paren_overrides_div(self):
        # 8/(2+2) -> BinOp('/', Num(8), BinOp('+', Num(2), Num(2)))
        self.assertEqual(
            tree('8/(2+2)'),
            "BinOp('/', Num(8), BinOp('+', Num(2), Num(2)))",
        )

    def test_nested_parens(self):
        # ((3)) -> Num(3)
        self.assertEqual(tree('((3))'), 'Num(3)')

    def test_paren_in_sub(self):
        # 10-(3+2) -> BinOp('-', Num(10), BinOp('+', Num(3), Num(2)))
        self.assertEqual(
            tree('10-(3+2)'),
            "BinOp('-', Num(10), BinOp('+', Num(3), Num(2)))",
        )


class TestUnaryMinus(unittest.TestCase):
    """D4 — unary minus."""

    def test_unary_simple(self):
        self.assertEqual(tree('-5'), "Unary('-', Num(5))")

    def test_unary_grouped(self):
        self.assertEqual(
            tree('-(1+2)'),
            "Unary('-', BinOp('+', Num(1), Num(2)))",
        )

    def test_unary_in_mul(self):
        # 3 * -2 -> BinOp('*', Num(3), Unary('-', Num(2)))
        self.assertEqual(
            tree('3 * -2'),
            "BinOp('*', Num(3), Unary('-', Num(2)))",
        )

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

    def test_unary_in_add(self):
        # 1 + -2 -> BinOp('+', Num(1), Unary('-', Num(2)))
        self.assertEqual(
            tree('1 + -2'),
            "BinOp('+', Num(1), Unary('-', Num(2)))",
        )


class TestErrors(unittest.TestCase):
    """D5 — malformed input raises ParseError."""

    def _raises(self, src):
        with self.assertRaises(ParseError):
            parse(tokenize(src))

    def test_trailing_operator(self):
        self._raises('1 +')

    def test_unclosed_paren(self):
        self._raises('(1')

    def test_two_numbers(self):
        self._raises('1 2')

    def test_close_open_paren(self):
        self._raises(')(')

    def test_empty_string(self):
        self._raises('')

    def test_just_operator(self):
        self._raises('+')

    def test_mismatched_paren(self):
        self._raises('(1+2')

    def test_extra_close_paren(self):
        self._raises('1+2)')


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