app/api/CircleAPI.jsx

/**
 * Get the circles which the specify users is in that circle 
 * @param {object} circles 
 * @param {string} followingId 
 */
export const getUserBelongCircles = (circles, followingId) => {
    let userBelongCircles = [];
    Object.keys(circles).forEach((cid) => {
        if (cid.trim() !== '-Followers' && circles[cid].users) {
            let isExist = Object.keys(circles[cid].users).indexOf(followingId) > -1;
            if (isExist) {
                userBelongCircles.push(cid);
            }
        }
    });

    return userBelongCircles;
}

/**
 * Get the following users
 * @param {object} circles 
 */
export const getFollowingUsers = (circles) => {
    let followingUsers = {};
    Object.keys(circles).forEach((cid) => {
        if (cid.trim() !== '-Followers' && circles[cid].users) {
            Object.keys(circles[cid].users).forEach((userId) => {
                let isExist = Object.keys(followingUsers).indexOf(userId) > -1;
                if (!isExist) {
                    followingUsers[userId] = {
                        ...circles[cid].users[userId]
                    };
                }
            });
        }
    });

    return followingUsers;
}

export default {
    getUserBelongCircles,
    getFollowingUsers
};