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  → BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
        self.assertEqual(p('1+2*3'), BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_div_over_sub(self):
        # 10-6/2  → BinOp('-', Num(10), BinOp('/', Num(6), Num(2)))
        self.assertEqual(p('10-6/2'), BinOp('-', Num(10), BinOp('/', Num(6), Num(2))))

    def test_add_left_of_mul(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)))


class TestLeftAssociativity(unittest.TestCase):
    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)))


class TestParentheses(unittest.TestCase):
    def test_paren_overrides_mul(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_paren_overrides_div(self):
        # 8/(2+2)  → BinOp('/', Num(8), BinOp('+', Num(2), Num(2)))
        self.assertEqual(p('8/(2+2)'), BinOp('/', Num(8), BinOp('+', Num(2), Num(2))))

    def test_nested_parens(self):
        # ((5))  → Num(5)
        self.assertEqual(p('((5))'), Num(5))


class TestUnaryMinus(unittest.TestCase):
    def test_simple_neg(self):
        # -5  → Unary('-', Num(5))
        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):
    def test_trailing_plus(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_then_open(self):
        with self.assertRaises(ParseError):
            p(')(')

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

    def test_only_operator(self):
        with self.assertRaises(ParseError):
            p('*')

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


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