import hashlib
import mimetypes

MEDIA_EXTS_CACHE = []


def media_exts():
    """ List of media file extensions from local system mimetypes """
    if not MEDIA_EXTS_CACHE:
        mimetypes.init()
        for ext in mimetypes.types_map:
            if mimetypes.types_map[ext].split('/')[0] in ('audio', 'video'):
                MEDIA_EXTS_CACHE.append(ext)
    return MEDIA_EXTS_CACHE


def is_media_file_ext(ext):
    """ Is the given extension a media file extension according to the local system mimetypes """
    return ext.lower().lstrip('.') in [e.lower().lstrip('.') for e in media_exts()]


HASHER = hashlib.md5()


def hash_file(filename):
    """ return a hash for the given file """
    with open(filename, 'rb') as f:
        buf = f.read()
        HASHER.update(buf)
    return HASHER.hexdigest()