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(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(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(self):
        # 10-6/2 -> BinOp('-', Num(10), BinOp('/', Num(6), Num(2)))
        tree = p("10-6/2")
        self.assertEqual(tree, BinOp('-', Num(10), BinOp('/', Num(6), Num(2))))


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))
        tree = p("8-3-2")
        self.assertEqual(tree, BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

    def test_div_div(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_add(self):
        tree = p("1+2+3")
        self.assertEqual(tree, BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))

    def test_mul_mul(self):
        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_overrides(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("((2+3))")
        self.assertEqual(tree, BinOp('+', Num(2), Num(3)))

    def test_paren_in_sum(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))))


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

    def test_simple_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))))

    def test_unary_in_expr(self):
        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_two_numbers(self):
        with self.assertRaises(ParseError):
            p("1 2")

    def test_close_open_paren(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_unclosed_paren_complex(self):
        with self.assertRaises(ParseError):
            p("(1+2")


class TestSimpleCases(unittest.TestCase):
    """Basic sanity checks."""

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

    def test_float(self):
        self.assertEqual(p("3.14"), Num(3.14))

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

    def test_simple_sub(self):
        self.assertEqual(p("5-3"), BinOp('-', Num(5), Num(3)))

    def test_simple_mul(self):
        self.assertEqual(p("4*2"), BinOp('*', Num(4), Num(2)))

    def test_simple_div(self):
        self.assertEqual(p("8/2"), BinOp('/', Num(8), Num(2)))


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