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_add_then_mul(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_mul_then_add(self):
        # 2*3+1 => BinOp('+', BinOp('*', Num(2), Num(3)), Num(1))
        result = p("2*3+1")
        self.assertEqual(result, BinOp('+', BinOp('*', Num(2), Num(3)), Num(1)))

    def test_sub_then_div(self):
        # 10-4/2 => BinOp('-', Num(10), BinOp('/', Num(4), Num(2)))
        result = p("10-4/2")
        self.assertEqual(result, BinOp('-', Num(10), BinOp('/', Num(4), Num(2))))

    def test_single_number(self):
        self.assertEqual(p("42"), Num(42))

    def test_single_add(self):
        self.assertEqual(p("1+2"), BinOp('+', Num(1), Num(2)))


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

    def test_subtraction_left(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_division_left(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_addition_left(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_multiplication_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)))


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

    def test_parens_override_mul(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_parens_inside(self):
        # 3*(1+2) => BinOp('*', Num(3), BinOp('+', Num(1), Num(2)))
        result = p("3*(1+2)")
        self.assertEqual(result, BinOp('*', Num(3), BinOp('+', Num(1), Num(2))))

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

    def test_parens_in_add_chain(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))))


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

    def test_simple_unary(self):
        # -5 => Unary('-', Num(5))
        result = p("-5")
        self.assertEqual(result, Unary('-', Num(5)))

    def test_unary_paren(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_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_unary(self):
        # --5 => Unary('-', Unary('-', Num(5)))
        result = p("--5")
        self.assertEqual(result, Unary('-', Unary('-', Num(5))))

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


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

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

    def test_mismatched_parens(self):
        with self.assertRaises(ParseError):
            p(")(")

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

    def test_just_operator(self):
        with self.assertRaises(ParseError):
            p("*")

    def test_error_is_parse_error_not_other(self):
        for bad in ("1 +", "(1", "1 2", ")(", ""):
            with self.subTest(src=bad):
                with self.assertRaises(ParseError):
                    p(bad)


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