import { MessengerFriend } from './MessengerFriend';

/**
 * Filter a friend list to a single category. categoryId 0 means
 * "All" (no filtering) and returns the list unchanged.
 */
export const filterFriendsByCategory = (friends: MessengerFriend[], categoryId: number): MessengerFriend[] =>
{
    if(!friends) return [];

    if(!categoryId) return friends;

    return friends.filter(friend => (friend.categoryId === categoryId));
};

/**
 * Count how many friends belong to each category id. Used to render
 * member counts on the group chips.
 */
export const countFriendsByCategory = (friends: MessengerFriend[]): Map<number, number> =>
{
    const counts = new Map<number, number>();

    if(!friends) return counts;

    for(const friend of friends)
    {
        counts.set(friend.categoryId, (counts.get(friend.categoryId) ?? 0) + 1);
    }

    return counts;
};