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):
    """D1 — * and / bind tighter than + and -"""

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

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

    def test_sub_div(self):
        # 10-4/2 → 10-(4/2)
        tree = p("10-4/2")
        self.assertEqual(
            tree,
            BinOp("-", Num(10), BinOp("/", Num(4), Num(2))),
        )


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

    def test_sub_left(self):
        # 8-3-2 → (8-3)-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 → (8/4)/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 → (1+2)+3
        tree = p("1+2+3")
        self.assertEqual(
            tree,
            BinOp("+", BinOp("+", Num(1), Num(2)), Num(3)),
        )

    def test_mul_left(self):
        # 2*3*4 → (2*3)*4
        tree = p("2*3*4")
        self.assertEqual(
            tree,
            BinOp("*", BinOp("*", Num(2), Num(3)), Num(4)),
        )


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

    def test_parens_force_add_first(self):
        # (1+2)*3 → mul at root, add under left
        tree = p("(1+2)*3")
        self.assertEqual(
            tree,
            BinOp("*", BinOp("+", Num(1), Num(2)), Num(3)),
        )

    def test_nested_parens(self):
        # ((4)) → Num(4)
        tree = p("((4))")
        self.assertEqual(tree, Num(4))

    def test_parens_right(self):
        # 2*(3+4) → mul at root, add under right
        tree = p("2*(3+4)")
        self.assertEqual(
            tree,
            BinOp("*", Num(2), BinOp("+", Num(3), Num(4))),
        )


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

    def test_simple(self):
        tree = p("-5")
        self.assertEqual(tree, Unary("-", Num(5)))

    def test_unary_paren(self):
        # -(1+2) → Unary at root
        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):
    """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_open(self):
        with self.assertRaises(ParseError):
            p(")(")

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

    def test_just_op(self):
        with self.assertRaises(ParseError):
            p("+")

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


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