import type { FlightRouterState } from '../../../shared/lib/app-router-types';
import type { RouteCacheKey } from './cache-key';
import { type PrefetchTaskFetchStrategy, PrefetchPriority } from './types';
import type { SegmentRequestKey } from '../../../shared/lib/segment-cache/segment-value-encoding';
export type PrefetchTask = {
    key: RouteCacheKey;
    /**
     * The FlightRouterState at the time the task was initiated. This is needed
     * when falling back to the non-PPR behavior, which only prefetches up to
     * the first loading boundary.
     */
    treeAtTimeOfPrefetch: FlightRouterState;
    /**
     * The cache version at the time the task was initiated. This is used to
     * determine if the cache was invalidated since the task was initiated.
     */
    cacheVersion: number;
    /**
     * Whether to prefetch dynamic data, in addition to static data. This is
     * used by `<Link prefetch={true}>`.
     *
     * Note that a task with `FetchStrategy.PPR` might need to use
     * `FetchStrategy.LoadingBoundary` instead if we find out that a route
     * does not support PPR after doing the initial route prefetch.
     */
    fetchStrategy: PrefetchTaskFetchStrategy;
    /**
     * sortId is an incrementing counter
     *
     * Newer prefetches are prioritized over older ones, so that as new links
     * enter the viewport, they are not starved by older links that are no
     * longer relevant. In the future, we can add additional prioritization
     * heuristics, like removing prefetches once a link leaves the viewport.
     *
     * The sortId is assigned when the prefetch is initiated, and reassigned if
     * the same task is prefetched again (effectively bumping it to the top of
     * the queue).
     *
     * TODO: We can add additional fields here to indicate what kind of prefetch
     * it is. For example, was it initiated by a link? Or was it an imperative
     * call? If it was initiated by a link, we can remove it from the queue when
     * the link leaves the viewport, but if it was an imperative call, then we
     * should keep it in the queue until it's fulfilled.
     *
     * We can also add priority levels. For example, hovering over a link could
     * increase the priority of its prefetch.
     */
    sortId: number;
    /**
     * The priority of the task. Like sortId, this affects the task's position in
     * the queue, so it must never be updated without resifting the heap.
     */
    priority: PrefetchPriority;
    /**
     * The phase of the task. Tasks are split into multiple phases so that their
     * priority can be adjusted based on what kind of work they're doing.
     * Concretely, prefetching the route tree is higher priority than prefetching
     * segment data.
     */
    phase: PrefetchPhase;
    /**
     * These fields are temporary state for tracking the currently running task.
     * They are reset after each iteration of the task queue.
     */
    hasBackgroundWork: boolean;
    spawnedRuntimePrefetches: Set<SegmentRequestKey> | null;
    /**
     * True if the prefetch was cancelled.
     */
    isCanceled: boolean;
    /**
     * The callback passed to `router.prefetch`, if given.
     */
    onInvalidate: null | (() => void);
    /**
     * The index of the task in the heap's backing array. Used to efficiently
     * change the priority of a task by re-sifting it, which requires knowing
     * where it is in the array. This is only used internally by the heap
     * algorithm. The naive alternative is indexOf every time a task is queued,
     * which has O(n) complexity.
     *
     * We also use this field to check whether a task is currently in the queue.
     */
    _heapIndex: number;
};
/**
 * Prefetch tasks are processed in two phases: first the route tree is fetched,
 * then the segments. We use this to priortize tasks that have not yet fetched
 * the route tree.
 */
declare const enum PrefetchPhase {
    RouteTree = 1,
    Segments = 0
}
export type PrefetchSubtaskResult<T> = {
    /**
     * A promise that resolves when the network connection is closed.
     */
    closed: Promise<void>;
    value: T;
};
/**
 * Called by the cache when revalidation occurs. Starts a cooldown period
 * during which prefetch requests are blocked to allow CDN cache propagation.
 */
export declare function startRevalidationCooldown(): void;
export type IncludeDynamicData = null | 'full' | 'dynamic';
/**
 * Initiates a prefetch task for the given URL. If a prefetch for the same URL
 * is already in progress, this will bump it to the top of the queue.
 *
 * This is not a user-facing function. By the time this is called, the href is
 * expected to be validated and normalized.
 *
 * @param key The RouteCacheKey to prefetch.
 * @param treeAtTimeOfPrefetch The app's current FlightRouterState
 * @param fetchStrategy Whether to prefetch dynamic data, in addition to
 * static data. This is used by `<Link prefetch={true}>`.
 */
export declare function schedulePrefetchTask(key: RouteCacheKey, treeAtTimeOfPrefetch: FlightRouterState, fetchStrategy: PrefetchTaskFetchStrategy, priority: PrefetchPriority, onInvalidate: null | (() => void)): PrefetchTask;
export declare function cancelPrefetchTask(task: PrefetchTask): void;
export declare function reschedulePrefetchTask(task: PrefetchTask, treeAtTimeOfPrefetch: FlightRouterState, fetchStrategy: PrefetchTaskFetchStrategy, priority: PrefetchPriority): void;
export declare function isPrefetchTaskDirty(task: PrefetchTask, nextUrl: string | null, tree: FlightRouterState): boolean;
/**
 * Notify the scheduler that we've received new data for an in-progress
 * prefetch. The corresponding task will be added back to the queue (unless the
 * task has been canceled in the meantime).
 */
export declare function pingPrefetchTask(task: PrefetchTask): void;
export {};