import unittest

from calc.lexer import tokenize
from calc.parser import BinOp, Num, ParseError, Unary, parse


def p(src):
    return parse(tokenize(src))


class TestPrecedence(unittest.TestCase):
    def test_mul_tighter_than_add(self):
        # 1+2*3 => BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
        tree = p("1+2*3")
        self.assertEqual(tree, BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_mul_tighter_than_sub(self):
        # 5-2*3 => BinOp('-', Num(5), BinOp('*', Num(2), Num(3)))
        tree = p("5-2*3")
        self.assertEqual(tree, BinOp('-', Num(5), BinOp('*', Num(2), Num(3))))

    def test_div_tighter_than_add(self):
        # 4+6/2 => BinOp('+', Num(4), BinOp('/', Num(6), Num(2)))
        tree = p("4+6/2")
        self.assertEqual(tree, BinOp('+', Num(4), BinOp('/', Num(6), Num(2))))


class TestLeftAssociativity(unittest.TestCase):
    def test_sub_left(self):
        # 8-3-2 => BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
        tree = p("8-3-2")
        self.assertEqual(tree, BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

    def test_div_left(self):
        # 8/4/2 => BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
        tree = p("8/4/2")
        self.assertEqual(tree, BinOp('/', BinOp('/', Num(8), Num(4)), Num(2)))

    def test_add_left(self):
        # 1+2+3 => BinOp('+', BinOp('+', Num(1), Num(2)), Num(3))
        tree = p("1+2+3")
        self.assertEqual(tree, BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))


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

    def test_nested_parens(self):
        # ((2+3)) => BinOp('+', Num(2), Num(3))  — parens unwrap
        tree = p("((2+3))")
        self.assertEqual(tree, BinOp('+', Num(2), Num(3)))

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


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

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

    def test_mul_unary(self):
        # 3 * -2 => BinOp('*', Num(3), Unary('-', Num(2)))
        tree = p("3 * -2")
        self.assertEqual(tree, BinOp('*', Num(3), Unary('-', Num(2))))

    def test_double_unary(self):
        # --5 => Unary('-', Unary('-', Num(5)))
        tree = p("--5")
        self.assertEqual(tree, 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_adjacent_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("")


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