from collections import AsyncIterable
from typing import Callable, AsyncGenerator, Optional
import discord


async def async_filter(fun: Callable, iterable: AsyncIterable) -> AsyncGenerator:
    async for val in iterable:
        if fun(val):
            yield val


def find_category(guild: discord.Guild, group: str) -> Optional[discord.CategoryChannel]:
    group = group.lower()
    for cat in guild.categories:
        if cat.name.lower() == group:
            return cat
    return None


async def find_role_case_insensitive(guild: discord.Guild, name: str, prefix: str = '') -> Optional[discord.Role]:
    for role in await guild.fetch_roles():
        if name.strip().lower() == role.name[len(prefix):].lower():
            return role
    return None