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)))
        result = p("1+2*3")
        self.assertEqual(result, BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_add_over_mul_left(self):
        # 2*3+4 → BinOp('+', BinOp('*', Num(2), Num(3)), Num(4))
        result = p("2*3+4")
        self.assertEqual(result, BinOp('+', BinOp('*', Num(2), Num(3)), Num(4)))

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


class TestLeftAssociativity(unittest.TestCase):
    def test_sub_left_assoc(self):
        # 8-3-2 → BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
        result = p("8-3-2")
        self.assertEqual(result, 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))
        result = p("8/4/2")
        self.assertEqual(result, 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))
        result = p("1+2+3")
        self.assertEqual(result, BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))


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

    def test_nested_parens(self):
        # ((4)) → Num(4)
        result = p("((4))")
        self.assertEqual(result, Num(4))

    def test_parens_in_sum(self):
        # 2*(3+4) → BinOp('*', Num(2), BinOp('+', Num(3), Num(4)))
        result = p("2*(3+4)")
        self.assertEqual(result, BinOp('*', Num(2), BinOp('+', Num(3), Num(4))))


class TestUnaryMinus(unittest.TestCase):
    def test_simple_negation(self):
        # -5 → Unary('-', Num(5))
        result = p("-5")
        self.assertEqual(result, Unary('-', Num(5)))

    def test_negation_of_group(self):
        # -(1+2) → Unary('-', BinOp('+', Num(1), Num(2)))
        result = p("-(1+2)")
        self.assertEqual(result, Unary('-', BinOp('+', Num(1), Num(2))))

    def test_mul_with_unary(self):
        # 3 * -2 → BinOp('*', Num(3), Unary('-', Num(2)))
        result = p("3 * -2")
        self.assertEqual(result, BinOp('*', Num(3), Unary('-', Num(2))))

    def test_double_negation(self):
        # --5 → Unary('-', Unary('-', Num(5)))
        result = p("--5")
        self.assertEqual(result, 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(self):
        with self.assertRaises(ParseError):
            p("")


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