"""Count number of 1 bits in a number."""

from dataclasses import dataclass
from random import Random
from typing import Optional

from ..factory import ProceduralDataset, register_dataset

QUESTION_TEMPLATE = """How many 1 bits are there in the binary representation of the number {number}?"""


@dataclass
class CountBitsConfig:
    """Configuration for Count Bits dataset generation"""

    max_n: int = 2**31 - 1  # Maximum number to consider

    size: int = 500  # Virtual dataset size
    seed: Optional[int] = None

    def validate(self):
        """Validate configuration parameters"""
        assert 1 <= self.max_n, "max_n must be at least 1"


class CountBitsDataset(ProceduralDataset):
    """Generates Count Bits exercises with configurable difficulty"""

    def __init__(self, config: CountBitsConfig):
        super().__init__(config=config, seed=config.seed, size=config.size)

    def __getitem__(self, idx: int) -> dict:
        """Generate a single Count Bits question"""
        rng = Random(self.seed + idx)

        number = rng.randint(1, self.config.max_n)
        binary = bin(number)[2:]
        answer = binary.count("1")

        return {
            "question": QUESTION_TEMPLATE.format(number=number),
            "answer": str(answer),
            "metadata": {"number": number, "solution": answer, "binary": binary},
        }


register_dataset("count_bits", CountBitsDataset, CountBitsConfig)