"""Tests for calc/parser.py covering DoD gates D1–D5."""
import unittest

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


def p(src: str):
    """Shorthand: tokenize then parse."""
    return parse(tokenize(src))


class TestD1Precedence(unittest.TestCase):
    def test_mul_binds_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_div_binds_tighter_than_sub(self):
        # 9-6/2  =>  BinOp('-', Num(9), BinOp('/', Num(6), Num(2)))
        tree = p("9-6/2")
        self.assertEqual(tree, BinOp("-", Num(9), BinOp("/", Num(6), Num(2))))

    def test_add_before_mul_different_shape(self):
        # 1+2*3 must NOT parse as (1+2)*3
        tree = p("1+2*3")
        self.assertNotEqual(tree, BinOp("*", BinOp("+", Num(1), Num(2)), Num(3)))


class TestD2LeftAssociativity(unittest.TestCase):
    def test_sub_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_div_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_add_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 TestD3Parentheses(unittest.TestCase):
    def test_parens_override_precedence(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))  (extra parens transparent)
        tree = p("((2+3))")
        self.assertEqual(tree, BinOp("+", Num(2), Num(3)))

    def test_parens_and_precedence_mixed(self):
        # 2*(3+4*5)  =>  BinOp('*', Num(2), BinOp('+', Num(3), BinOp('*', Num(4), Num(5))))
        tree = p("2*(3+4*5)")
        self.assertEqual(
            tree,
            BinOp("*", Num(2), BinOp("+", Num(3), BinOp("*", Num(4), Num(5)))),
        )


class TestD4UnaryMinus(unittest.TestCase):
    def test_leading_unary(self):
        # -5  =>  Unary('-', Num(5))
        tree = p("-5")
        self.assertEqual(tree, Unary("-", Num(5)))

    def test_unary_in_parens(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_after_binop(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 TestD5Errors(unittest.TestCase):
    def _raises(self, src: str):
        with self.assertRaises(ParseError, msg=f"expected ParseError for {src!r}"):
            p(src)

    def test_trailing_operator(self):
        self._raises("1 +")

    def test_unclosed_paren(self):
        self._raises("(1")

    def test_two_numbers_no_op(self):
        self._raises("1 2")

    def test_close_before_open(self):
        self._raises(")(")

    def test_empty_string(self):
        self._raises("")

    def test_open_close_no_expr(self):
        # "()" should fail — no expression inside
        self._raises("()")


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