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

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

    def test_add_then_div(self):
        # 1+6/2  →  BinOp('+', Num(1), BinOp('/', Num(6), Num(2)))
        self.assertEqual(p('1+6/2'), BinOp('+', Num(1), BinOp('/', Num(6), Num(2))))

    def test_sub_then_mul(self):
        # 10-2*3  →  BinOp('-', Num(10), BinOp('*', Num(2), Num(3)))
        self.assertEqual(p('10-2*3'), BinOp('-', Num(10), BinOp('*', Num(2), Num(3))))


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

    def test_sub_sub(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_div(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_add(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_mul_mul(self):
        # 2*3*4  →  BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))
        self.assertEqual(p('2*3*4'), BinOp('*', BinOp('*', Num(2), Num(3)), Num(4)))


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

    def test_parens_override_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_nested_parens(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_parens_on_right(self):
        # 3*(1+2)  →  BinOp('*', Num(3), BinOp('+', Num(1), Num(2)))
        self.assertEqual(p('3*(1+2)'), BinOp('*', Num(3), BinOp('+', Num(1), Num(2))))

    def test_double_parens(self):
        # ((7))  →  Num(7)
        self.assertEqual(p('((7))'), Num(7))


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

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

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

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

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

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


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

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


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