manageUsers.js

const users = [];

//this method will return two values {error || user}
const addUser = ({ id, name, room }) => {
  name = name.trim().toLowerCase();
  room = room.trim().toLowerCase();

  /*
      find method retrun 1-  undefiend if element not exist.
                         2- true if element is exist.
    */
  const found = users.find((user) => user.name === name && user.room === room);
  if (found) return { error: "this user in the db" };

  let user = { id, name, room };
  users.push(user);
  
  return { user };
};

//this methd will return two values{error || removedUser}
const removeUser = (id) => {
  /*
    findIndex method return 1-  -1 if element not exist.
                            2- the index of the element if it's exist.
  */
  let index = users.findIndex((user) => user.id === id);

  if (index !== -1) {
    // return the removed user if it's exist.
    let removedUser = users.splice(index, 1)[0];
    return removedUser;
  } else {
    return { err: `this user of id: ${id} not exist.` };
  }
};

const getUser = (id) => users.find((user) => user.id === id);

const getUsersInRoom = (room) => users.filter((user) => user.room === room);

module.exports = { addUser, removeUser, getUser, getUsersInRoom };