Function appendCappedMessage

src/tasks/InProcessTeammateTask/types.ts:108–121

(
  prev: readonly T[] | undefined,
  item: T,
)

 * a new array (AppState immutability).
 */
export function appendCappedMessage<T>(
  prev: readonly T[] | undefined,
  item: T,
): T[] {
  if (prev === undefined || prev.length === 0) {
    return [item]
  }
  if (prev.length >= TEAMMATE_MESSAGES_UI_CAP) {
    const next = prev.slice(-(TEAMMATE_MESSAGES_UI_CAP - 1))
    next.push(item)
    return next
  }
  return [...prev, item]
}