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


def p(src: str):
    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):
        # 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(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(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(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_multiplication(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_add_then_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):
        # ((4)) → Num(4)
        tree = p("((4))")
        self.assertEqual(tree, Num(4))

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


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

    def test_simple_unary(self):
        # -5 → Unary('-', Num(5))
        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_unary_in_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 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_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_parens(self):
        with self.assertRaises(ParseError):
            p("(1+2")


class TestAtoms(unittest.TestCase):
    """Basic atoms parse cleanly"""

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

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

    def test_single_in_parens(self):
        self.assertEqual(p("(7)"), Num(7))


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