getState = (store, client) => {
  const structs = store.clients.get(client);

  if (structs === undefined) {
    return 0;
  }

  const lastStruct = structs[structs.length - 1];
  return lastStruct.id.clock + lastStruct.length;
}
@param {StructStore} store
@param {number} client
@return {number}

@public
@function