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_mul_over_add(self):
        # 1+2*3 → 1+(2*3)
        self.assertEqual(repr(p('1+2*3')),
                         'BinOp(PLUS, Num(1), BinOp(STAR, Num(2), Num(3)))')

    def test_div_over_sub(self):
        # 6-4/2 → 6-(4/2)
        self.assertEqual(repr(p('6-4/2')),
                         'BinOp(MINUS, Num(6), BinOp(SLASH, Num(4), Num(2)))')

    def test_mul_over_add_reversed(self):
        # 2*3+1 → (2*3)+1
        self.assertEqual(repr(p('2*3+1')),
                         'BinOp(PLUS, BinOp(STAR, Num(2), Num(3)), Num(1))')


class TestLeftAssociativity(unittest.TestCase):
    def test_subtraction_left(self):
        # 8-3-2 → (8-3)-2
        self.assertEqual(repr(p('8-3-2')),
                         'BinOp(MINUS, BinOp(MINUS, Num(8), Num(3)), Num(2))')

    def test_division_left(self):
        # 8/4/2 → (8/4)/2
        self.assertEqual(repr(p('8/4/2')),
                         'BinOp(SLASH, BinOp(SLASH, Num(8), Num(4)), Num(2))')

    def test_addition_left(self):
        # 1+2+3 → (1+2)+3
        self.assertEqual(repr(p('1+2+3')),
                         'BinOp(PLUS, BinOp(PLUS, Num(1), Num(2)), Num(3))')

    def test_mul_left(self):
        # 2*3*4 → (2*3)*4
        self.assertEqual(repr(p('2*3*4')),
                         'BinOp(STAR, BinOp(STAR, Num(2), Num(3)), Num(4))')


class TestParentheses(unittest.TestCase):
    def test_parens_override_precedence(self):
        # (1+2)*3 → STAR at top, PLUS inside
        self.assertEqual(repr(p('(1+2)*3')),
                         'BinOp(STAR, BinOp(PLUS, Num(1), Num(2)), Num(3))')

    def test_parens_on_right(self):
        # 3*(1+2)
        self.assertEqual(repr(p('3*(1+2)')),
                         'BinOp(STAR, Num(3), BinOp(PLUS, Num(1), Num(2)))')

    def test_nested_parens(self):
        self.assertEqual(repr(p('((2))')), 'Num(2)')


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

    def test_unary_paren(self):
        self.assertEqual(repr(p('-(1+2)')),
                         'Unary(MINUS, BinOp(PLUS, Num(1), Num(2)))')

    def test_unary_in_mul(self):
        self.assertEqual(repr(p('3 * -2')),
                         'BinOp(STAR, Num(3), Unary(MINUS, Num(2)))')

    def test_double_unary(self):
        self.assertEqual(repr(p('--5')),
                         'Unary(MINUS, Unary(MINUS, Num(5)))')


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

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

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

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

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


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