import { concreteTPriorityQueue } from "@effect/core/stm/TPriorityQueue/operations/_internal/InternalTPriorityQueue"

/**
 * Takes a value from the queue, returning `None` if there is not a value in
 * the queue.
 *
 * @tsplus getter effect/core/stm/TPriorityQueue takeMaybe
 */
export function takeMaybe<A>(self: TPriorityQueue<A>): USTM<Maybe<A>> {
  return STM.Effect((journal) => {
    concreteTPriorityQueue(self)
    const map = self.map.unsafeGet(journal)

    return map.headMaybe.flatMap((tuple) => {
      const a = tuple[1].tail.flatMap((c) => Maybe.fromPredicate(c, (_) => _.isNonEmpty))
      const k = tuple[0]

      self.map.unsafeSet(a._tag === "None" ? map.remove(k) : map.set(k, a.value), journal)

      return tuple[1].head
    })
  })
}