import hashlib
import re
import secrets
from typing import TYPE_CHECKING, Callable, List, Optional, TypeVar

if TYPE_CHECKING:
    from hashlib import _Hash

T = TypeVar("T")


def make_safe_digest(string: str, hash_func: "Callable[[bytes], _Hash]" = hashlib.sha1) -> str:
    """
    return a hex digest of `string`.
    """
    # hashlib.sha1, md5, etc. expect bytes, so non-ASCII strings must
    # be encoded.
    return hash_func(string.encode()).hexdigest()


def generate_api_key() -> str:
    api_key = ""
    while len(api_key) < 32:
        # One iteration suffices 99.4992% of the time.
        api_key += secrets.token_urlsafe(3 * 9).replace("_", "").replace("-", "")
    return api_key[:32]


def has_api_key_format(key: str) -> bool:
    return bool(re.fullmatch(r"([A-Za-z0-9]){32}", key))


def assert_is_not_none(value: Optional[T]) -> T:
    assert value is not None
    return value


def process_list_in_batches(
    lst: List[T], chunk_size: int, process_batch: Callable[[List[T]], None]
) -> None:
    offset = 0

    while True:
        items = lst[offset : offset + chunk_size]
        if not items:
            break
        process_batch(items)
        offset += chunk_size