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

    def test_div_binds_tighter_than_sub(self):
        # 6-4/2 => BinOp(-, Num(6), BinOp(/, Num(4), Num(2)))
        tree = p('6-4/2')
        self.assertEqual(tree, BinOp('-', Num(6), BinOp('/', Num(4), Num(2))))

    def test_mul_binds_tighter_than_sub(self):
        tree = p('5-2*3')
        self.assertEqual(tree, BinOp('-', Num(5), BinOp('*', Num(2), Num(3))))


class TestLeftAssociativity(unittest.TestCase):
    def test_sub_left_assoc(self):
        # 8-3-2 => BinOp(-, BinOp(-, Num(8), Num(3)), Num(2))
        tree = p('8-3-2')
        self.assertEqual(tree, 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))
        tree = p('8/4/2')
        self.assertEqual(tree, BinOp('/', BinOp('/', Num(8), Num(4)), Num(2)))

    def test_add_left_assoc(self):
        tree = p('1+2+3')
        self.assertEqual(tree, BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))

    def test_mul_left_assoc(self):
        tree = p('2*3*4')
        self.assertEqual(tree, BinOp('*', BinOp('*', Num(2), Num(3)), Num(4)))


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

    def test_nested_parens(self):
        tree = p('((2+3))')
        self.assertEqual(tree, BinOp('+', Num(2), Num(3)))

    def test_parens_right_side(self):
        tree = p('3*(1+2)')
        self.assertEqual(tree, BinOp('*', Num(3), BinOp('+', Num(1), Num(2))))


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

    def test_unary_paren(self):
        tree = p('-(1+2)')
        self.assertEqual(tree, Unary('-', BinOp('+', Num(1), Num(2))))

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

    def test_double_unary(self):
        tree = p('--5')
        self.assertEqual(tree, 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_two_numbers(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()