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_tighter_than_add(self):
        # 1+2*3 → PLUS(1, STAR(2, 3))  NOT STAR(PLUS(1,2), 3)
        self.assertEqual(p('1+2*3'), BinOp('PLUS', Num(1), BinOp('STAR', Num(2), Num(3))))

    def test_mul_tighter_than_sub(self):
        # 2*3-1 → MINUS(STAR(2,3), 1)
        self.assertEqual(p('2*3-1'), BinOp('MINUS', BinOp('STAR', Num(2), Num(3)), Num(1)))

    def test_div_tighter_than_add(self):
        # 4/2+1 → PLUS(SLASH(4,2), 1)
        self.assertEqual(p('4/2+1'), BinOp('PLUS', BinOp('SLASH', Num(4), Num(2)), Num(1)))

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


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

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

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

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


class TestParentheses(unittest.TestCase):
    def test_paren_overrides_precedence(self):
        # (1+2)*3 → STAR(PLUS(1,2), 3)  — plus is UNDER star
        self.assertEqual(p('(1+2)*3'), BinOp('STAR', BinOp('PLUS', Num(1), Num(2)), Num(3)))

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

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

    def test_single_number_in_parens(self):
        self.assertEqual(p('(42)'), Num(42))


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

    def test_unary_on_paren(self):
        # -(1+2) → UNARY(-, PLUS(1,2))
        self.assertEqual(p('-(1+2)'), Unary('MINUS', BinOp('PLUS', Num(1), Num(2))))

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

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

    def test_unary_in_add(self):
        # 1 + -2 → PLUS(1, UNARY(-,2))
        self.assertEqual(p('1 + -2'), BinOp('PLUS', Num(1), Unary('MINUS', Num(2))))


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

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

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


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