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


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


class TestD1Precedence(unittest.TestCase):
    def test_add_then_mul(self):
        # 1+2*3 must be 1+(2*3), not (1+2)*3
        self.assertEqual(p('1+2*3'), BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_mul_then_add(self):
        # 2*3+1 must be (2*3)+1
        self.assertEqual(p('2*3+1'), BinOp('+', BinOp('*', Num(2), Num(3)), Num(1)))

    def test_sub_then_div(self):
        # 9-4/2 must be 9-(4/2)
        self.assertEqual(p('9-4/2'), BinOp('-', Num(9), BinOp('/', Num(4), Num(2))))


class TestD2LeftAssociativity(unittest.TestCase):
    def test_subtraction(self):
        # 8-3-2 must be (8-3)-2
        self.assertEqual(p('8-3-2'), BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

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

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


class TestD3Parentheses(unittest.TestCase):
    def test_override_precedence(self):
        # (1+2)*3: + is under *
        self.assertEqual(p('(1+2)*3'), BinOp('*', BinOp('+', Num(1), Num(2)), Num(3)))

    def test_nested_parens(self):
        # ((2+3)) same as 2+3
        self.assertEqual(p('((2+3))'), BinOp('+', Num(2), Num(3)))

    def test_parens_right(self):
        # 3*(1+2): + is under *, on the right
        self.assertEqual(p('3*(1+2)'), BinOp('*', Num(3), BinOp('+', Num(1), Num(2))))


class TestD4UnaryMinus(unittest.TestCase):
    def test_simple(self):
        self.assertEqual(p('-5'), Unary('-', Num(5)))

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

    def test_after_mul(self):
        # 3 * -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 TestD5Errors(unittest.TestCase):
    def _raises(self, src):
        with self.assertRaises(ParseError, msg=f"expected ParseError for {src!r}"):
            p(src)

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


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