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

    def test_mul_over_sub(self):
        self.assertEqual(p('1-2*3'), BinOp('-', Num(1), BinOp('*', Num(2), Num(3))))

    def test_div_over_add(self):
        self.assertEqual(p('4+6/2'), BinOp('+', Num(4), BinOp('/', Num(6), Num(2))))


class TestLeftAssociativity(unittest.TestCase):
    """D2 — same-precedence operators associate left."""

    def test_sub_left(self):
        self.assertEqual(p('8-3-2'), BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

    def test_div_left(self):
        self.assertEqual(p('8/4/2'), BinOp('/', BinOp('/', Num(8), Num(4)), Num(2)))

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

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


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

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

    def test_nested_parens(self):
        self.assertEqual(p('((2+3))*4'), BinOp('*', BinOp('+', Num(2), Num(3)), Num(4)))

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


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

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

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

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

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


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

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

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

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

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

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


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