/**

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 *

 * @flow

 */

import type {Lane, Lanes} from './ReactFiberLane';

import {

  NoLane,

  SyncLane,

  InputContinuousLane,

  DefaultLane,

  IdleLane,

  getHighestPriorityLane,

  includesNonIdleWork,

} from './ReactFiberLane';

export opaque type EventPriority = Lane;

export const DiscreteEventPriority: EventPriority = SyncLane;

export const ContinuousEventPriority: EventPriority = InputContinuousLane;

export const DefaultEventPriority: EventPriority = DefaultLane;

export const IdleEventPriority: EventPriority = IdleLane;

let currentUpdatePriority: EventPriority = NoLane;

export function getCurrentUpdatePriority(): EventPriority {

  return currentUpdatePriority;

}

export function setCurrentUpdatePriority(newPriority: EventPriority) {

  currentUpdatePriority = newPriority;

}

export function runWithPriority<T>(priority: EventPriority, fn: () => T): T {

  const previousPriority = currentUpdatePriority;

  try {

    currentUpdatePriority = priority;

    return fn();

  } finally {

    currentUpdatePriority = previousPriority;

  }

}

export function higherEventPriority(

  a: EventPriority,

  b: EventPriority,

): EventPriority {

  return a !== 0 && a < b ? a : b;

}

export function lowerEventPriority(

  a: EventPriority,

  b: EventPriority,

): EventPriority {

  return a === 0 || a > b ? a : b;

}

export function isHigherEventPriority(

  a: EventPriority,

  b: EventPriority,

): boolean {

  return a !== 0 && a < b;

}

export function lanesToEventPriority(lanes: Lanes): EventPriority {

  const lane = getHighestPriorityLane(lanes);

  if (!isHigherEventPriority(DiscreteEventPriority, lane)) {

    return DiscreteEventPriority;

  }

  if (!isHigherEventPriority(ContinuousEventPriority, lane)) {

    return ContinuousEventPriority;

  }

  if (includesNonIdleWork(lane)) {

    return DefaultEventPriority;

  }

  return IdleEventPriority;

}