/**
 * Copyright (c) Facebook, Inc. and its 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 {ReactNodeList, Wakeable} from 'shared/ReactTypes';
import type {Fiber} from './ReactInternalTypes';
import type {SuspenseInstance} from './ReactFiberHostConfig';
import type {Lane} from './ReactFiberLane';
import {SuspenseComponent, SuspenseListComponent} from './ReactWorkTags';
import {NoFlags, DidCapture} from './ReactFiberFlags';
import {
  isSuspenseInstancePending,
  isSuspenseInstanceFallback,
} from './ReactFiberHostConfig';

export type SuspenseProps = {|
  children?: ReactNodeList,
  fallback?: ReactNodeList,

  // TODO: Add "unstable_" prefix?
  suspenseCallback?: (Set<Wakeable> | null) => mixed,

  unstable_expectedLoadTime?: number,
|};

// A null SuspenseState represents an unsuspended normal Suspense boundary.
// A non-null SuspenseState means that it is blocked for one reason or another.
// - A non-null dehydrated field means it's blocked pending hydration.
//   - A non-null dehydrated field can use isSuspenseInstancePending or
//     isSuspenseInstanceFallback to query the reason for being dehydrated.
// - A null dehydrated field means it's blocked by something suspending and
//   we're currently showing a fallback instead.
export type SuspenseState = {|
  // If this boundary is still dehydrated, we store the SuspenseInstance
  // here to indicate that it is dehydrated (flag) and for quick access
  // to check things like isSuspenseInstancePending.
  dehydrated: null | SuspenseInstance,
  // Represents the lane we should attempt to hydrate a dehydrated boundary at.
  // OffscreenLane is the default for dehydrated boundaries.
  // NoLane is the default for normal boundaries, which turns into "normal" pri.
  retryLane: Lane,
|};

export type SuspenseListTailMode = 'collapsed' | 'hidden' | void;

export type SuspenseListRenderState = {|
  isBackwards: boolean,
  // The currently rendering tail row.
  rendering: null | Fiber,
  // The absolute time when we started rendering the most recent tail row.
  renderingStartTime: number,
  // The last of the already rendered children.
  last: null | Fiber,
  // Remaining rows on the tail of the list.
  tail: null | Fiber,
  // Tail insertions setting.
  tailMode: SuspenseListTailMode,
  // Last Effect before we rendered the "rendering" item.
  // Used to remove new effects added by the rendered item.
  lastEffect: null | Fiber,
|};

export function shouldCaptureSuspense(
  workInProgress: Fiber,
  hasInvisibleParent: boolean,
): boolean {
  // If it was the primary children that just suspended, capture and render the
  // fallback. Otherwise, don't capture and bubble to the next boundary.
  const nextState: SuspenseState | null = workInProgress.memoizedState;
  if (nextState !== null) {
    if (nextState.dehydrated !== null) {
      // A dehydrated boundary always captures.
      return true;
    }
    return false;
  }
  const props = workInProgress.memoizedProps;
  // In order to capture, the Suspense component must have a fallback prop.
  if (props.fallback === undefined) {
    return false;
  }
  // Regular boundaries always capture.
  if (props.unstable_avoidThisFallback !== true) {
    return true;
  }
  // If it's a boundary we should avoid, then we prefer to bubble up to the
  // parent boundary if it is currently invisible.
  if (hasInvisibleParent) {
    return false;
  }
  // If the parent is not able to handle it, we must handle it.
  return true;
}

export function findFirstSuspended(row: Fiber): null | Fiber {
  let node = row;
  while (node !== null) {
    if (node.tag === SuspenseComponent) {
      const state: SuspenseState | null = node.memoizedState;
      if (state !== null) {
        const dehydrated: null | SuspenseInstance = state.dehydrated;
        if (
          dehydrated === null ||
          isSuspenseInstancePending(dehydrated) ||
          isSuspenseInstanceFallback(dehydrated)
        ) {
          return node;
        }
      }
    } else if (
      node.tag === SuspenseListComponent &&
      // revealOrder undefined can't be trusted because it don't
      // keep track of whether it suspended or not.
      node.memoizedProps.revealOrder !== undefined
    ) {
      const didSuspend = (node.flags & DidCapture) !== NoFlags;
      if (didSuspend) {
        return node;
      }
    } else if (node.child !== null) {
      node.child.return = node;
      node = node.child;
      continue;
    }
    if (node === row) {
      return null;
    }
    while (node.sibling === null) {
      if (node.return === null || node.return === row) {
        return null;
      }
      node = node.return;
    }
    node.sibling.return = node.return;
    node = node.sibling;
  }
  return null;
}
