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):
    """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(p('1+2*3'), BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

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

    def test_sub_mul(self):
        # 6-2*3 => BinOp('-', Num(6), BinOp('*', Num(2), Num(3)))
        self.assertEqual(p('6-2*3'), BinOp('-', Num(6), BinOp('*', Num(2), Num(3))))

    def test_div_before_add(self):
        # 1+6/2 => BinOp('+', Num(1), BinOp('/', Num(6), Num(2)))
        self.assertEqual(p('1+6/2'), BinOp('+', Num(1), BinOp('/', Num(6), Num(2))))


class TestAssociativity(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(p('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(p('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(p('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(p('2*3*4'), BinOp('*', BinOp('*', Num(2), Num(3)), Num(4)))


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

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

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


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

    def test_simple_neg(self):
        self.assertEqual(p('-5'), Unary('-', Num(5)))

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

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

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


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

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

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

    def test_two_nums(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()