from re import search
from typing import Optional
from .crc32 import CRC32

CKTYPES = [
    (CRC32)
]

def resolve(fname: str, esum: Optional[str] = None, cstype: Optional[str] = None):
    """
      Checks fname input for checksum pattern and returns first match.
      Can be overridden with cstype.
      If neither is applicable the first possible checksum type will be returned.
    """
    if esum is None and (match := CKTYPES[0].REGEX.search(fname)):
        esum = match.group(0)

    return CKTYPES[0](), esum