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

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


class TestLeftAssociativity(unittest.TestCase):
    # D2: same-precedence operators associate left
    def test_subtraction_left_assoc(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_division_left_assoc(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_addition_left_assoc(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_mul_left_assoc(self):
        # 2*3*4 => BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))
        tree = p("2*3*4")
        self.assertEqual(tree, BinOp('*', BinOp('*', Num(2), Num(3)), Num(4)))


class TestParentheses(unittest.TestCase):
    # D3: parens override precedence
    def test_paren_plus_under_mul(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):
        tree = p("((4))")
        self.assertEqual(tree, Num(4))

    def test_paren_changes_assoc(self):
        # 8-(3-2) => BinOp('-', Num(8), BinOp('-', Num(3), Num(2)))
        tree = p("8-(3-2)")
        self.assertEqual(tree, BinOp('-', Num(8), BinOp('-', Num(3), Num(2))))


class TestUnaryMinus(unittest.TestCase):
    # D4: unary minus
    def test_simple_unary(self):
        tree = p("-5")
        self.assertEqual(tree, Unary('-', Num(5)))

    def test_unary_in_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_unary_in_mul(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))))

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


class TestErrors(unittest.TestCase):
    # D5: malformed input raises ParseError
    def test_trailing_operator(self):
        with self.assertRaises(ParseError):
            p("1 +")

    def test_unclosed_paren(self):
        with self.assertRaises(ParseError):
            p("(1")

    def test_extra_number(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_mismatched_paren(self):
        with self.assertRaises(ParseError):
            p("(1+2")


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