A minimal backend user service

user.service.ts

export class UserService {
    private _change = new Subject<UserChange>();
    private _users = new Map<string, User>();

    public readonly change = this._change.asObservable();
    
    public get users(): User[] {
        return Array.from(this._users.values());
    }


    public join(user: User): User {
        if (this._users.get(user.email)) throw Error("User already exists");
        this._users.set(user.email, user);
        this._change.next({ action: UserAction.join, user });
        return user;
    }

    public leave(user: User): void {
        if (!this._users.get(user.email)) throw Error("User not found");
        this._users.delete(user.email);
        this._change.next({ action: UserAction.leave, user });
    }

    public position(updated: User): void {
        const user = this._users.get(updated.email);
        if (!user) throw Error("User not found. Can't update position");
        user.position = updated.position;
        this._change.next({ action: UserAction.position, user });
    }
}