node_modules/next/dist/client/components/segment-cache/scheduler.js

"use strict";
Object.defineProperty(exports, "__esModule", {
    value: true
});
0 && (module.exports = {
    cancelPrefetchTask: null,
    isPrefetchTaskDirty: null,
    pingPrefetchTask: null,
    reschedulePrefetchTask: null,
    schedulePrefetchTask: null,
    startRevalidationCooldown: null
});
function _export(target, all) {
    for(var name in all)Object.defineProperty(target, name, {
        enumerable: true,
        get: all[name]
    });
}
_export(exports, {
    cancelPrefetchTask: function() {
        return cancelPrefetchTask;
    },
    isPrefetchTaskDirty: function() {
        return isPrefetchTaskDirty;
    },
    pingPrefetchTask: function() {
        return pingPrefetchTask;
    },
    reschedulePrefetchTask: function() {
        return reschedulePrefetchTask;
    },
    schedulePrefetchTask: function() {
        return schedulePrefetchTask;
    },
    startRevalidationCooldown: function() {
        return startRevalidationCooldown;
    }
});
const _approutertypes = require("../../../shared/lib/app-router-types");
const _matchsegments = require("../match-segments");
const _cache = require("./cache");
const _varypath = require("./vary-path");
const _cachekey = require("./cache-key");
const _types = require("./types");
const _segment = require("../../../shared/lib/segment");
const scheduleMicrotask = typeof queueMicrotask === 'function' ? queueMicrotask : (fn)=>Promise.resolve().then(fn).catch((error)=>setTimeout(()=>{
            throw error;
        }));
const taskHeap = [];
let inProgressRequests = 0;
let sortIdCounter = 0;
let didScheduleMicrotask = false;
// The most recently hovered (or touched, etc) link, i.e. the most recent task
// scheduled at Intent priority. There's only ever a single task at Intent
// priority at a time. We reserve special network bandwidth for this task only.
let mostRecentlyHoveredLink = null;
// CDN cache propagation delay after revalidation (in milliseconds)
const REVALIDATION_COOLDOWN_MS = 300;
// Timeout handle for the revalidation cooldown. When non-null, prefetch
// requests are blocked to allow CDN cache propagation.
let revalidationCooldownTimeoutHandle = null;
function startRevalidationCooldown() {
    // Clear any existing timeout in case multiple revalidations happen
    // in quick succession.
    if (revalidationCooldownTimeoutHandle !== null) {
        clearTimeout(revalidationCooldownTimeoutHandle);
    }
    // Schedule the cooldown to expire after the delay.
    revalidationCooldownTimeoutHandle = setTimeout(()=>{
        revalidationCooldownTimeoutHandle = null;
        // Retry the prefetch queue now that the cooldown has expired.
        ensureWorkIsScheduled();
    }, REVALIDATION_COOLDOWN_MS);
}
function schedulePrefetchTask(key, treeAtTimeOfPrefetch, fetchStrategy, priority, onInvalidate) {
    // Spawn a new prefetch task
    const task = {
        key,
        treeAtTimeOfPrefetch,
        cacheVersion: (0, _cache.getCurrentCacheVersion)(),
        priority,
        phase: 1,
        hasBackgroundWork: false,
        spawnedRuntimePrefetches: null,
        fetchStrategy,
        sortId: sortIdCounter++,
        isCanceled: false,
        onInvalidate,
        _heapIndex: -1
    };
    trackMostRecentlyHoveredLink(task);
    heapPush(taskHeap, task);
    // Schedule an async task to process the queue.
    //
    // The main reason we process the queue in an async task is for batching.
    // It's common for a single JS task/event to trigger multiple prefetches.
    // By deferring to a microtask, we only process the queue once per JS task.
    // If they have different priorities, it also ensures they are processed in
    // the optimal order.
    ensureWorkIsScheduled();
    return task;
}
function cancelPrefetchTask(task) {
    // Remove the prefetch task from the queue. If the task already completed,
    // then this is a no-op.
    //
    // We must also explicitly mark the task as canceled so that a blocked task
    // does not get added back to the queue when it's pinged by the network.
    task.isCanceled = true;
    heapDelete(taskHeap, task);
}
function reschedulePrefetchTask(task, treeAtTimeOfPrefetch, fetchStrategy, priority) {
    // Bump the prefetch task to the top of the queue, as if it were a fresh
    // task. This is essentially the same as canceling the task and scheduling
    // a new one, except it reuses the original object.
    //
    // The primary use case is to increase the priority of a Link-initated
    // prefetch on hover.
    // Un-cancel the task, in case it was previously canceled.
    task.isCanceled = false;
    task.phase = 1;
    // Assign a new sort ID to move it ahead of all other tasks at the same
    // priority level. (Higher sort IDs are processed first.)
    task.sortId = sortIdCounter++;
    task.priority = // If this task is the most recently hovered link, maintain its
    // Intent priority, even if the rescheduled priority is lower.
    task === mostRecentlyHoveredLink ? _types.PrefetchPriority.Intent : priority;
    task.treeAtTimeOfPrefetch = treeAtTimeOfPrefetch;
    task.fetchStrategy = fetchStrategy;
    trackMostRecentlyHoveredLink(task);
    if (task._heapIndex !== -1) {
        // The task is already in the queue.
        heapResift(taskHeap, task);
    } else {
        heapPush(taskHeap, task);
    }
    ensureWorkIsScheduled();
}
function isPrefetchTaskDirty(task, nextUrl, tree) {
    // This is used to quickly bail out of a prefetch task if the result is
    // guaranteed to not have changed since the task was initiated. This is
    // strictly an optimization — theoretically, if it always returned true, no
    // behavior should change because a full prefetch task will effectively
    // perform the same checks.
    const currentCacheVersion = (0, _cache.getCurrentCacheVersion)();
    return task.cacheVersion !== currentCacheVersion || task.treeAtTimeOfPrefetch !== tree || task.key.nextUrl !== nextUrl;
}
function trackMostRecentlyHoveredLink(task) {
    // Track the mostly recently hovered link, i.e. the most recently scheduled
    // task at Intent priority. There must only be one such task at a time.
    if (task.priority === _types.PrefetchPriority.Intent && task !== mostRecentlyHoveredLink) {
        if (mostRecentlyHoveredLink !== null) {
            // Bump the previously hovered link's priority down to Default.
            if (mostRecentlyHoveredLink.priority !== _types.PrefetchPriority.Background) {
                mostRecentlyHoveredLink.priority = _types.PrefetchPriority.Default;
                heapResift(taskHeap, mostRecentlyHoveredLink);
            }
        }
        mostRecentlyHoveredLink = task;
    }
}
function ensureWorkIsScheduled() {
    if (didScheduleMicrotask) {
        // Already scheduled a task to process the queue
        return;
    }
    didScheduleMicrotask = true;
    scheduleMicrotask(processQueueInMicrotask);
}
/**
 * Checks if we've exceeded the maximum number of concurrent prefetch requests,
 * to avoid saturating the browser's internal network queue. This is a
 * cooperative limit — prefetch tasks should check this before issuing
 * new requests.
 *
 * Also checks if we're within the revalidation cooldown window, during which
 * prefetch requests are delayed to allow CDN cache propagation.
 */ function hasNetworkBandwidth(task) {
    // Check if we're within the revalidation cooldown window
    if (revalidationCooldownTimeoutHandle !== null) {
        // We're within the cooldown window. Return false to prevent prefetching.
        // When the cooldown expires, the timeout will call ensureWorkIsScheduled()
        // to retry the queue.
        return false;
    }
    // TODO: Also check if there's an in-progress navigation. We should never
    // add prefetch requests to the network queue if an actual navigation is
    // taking place, to ensure there's sufficient bandwidth for render-blocking
    // data and resources.
    // TODO: Consider reserving some amount of bandwidth for static prefetches.
    if (task.priority === _types.PrefetchPriority.Intent) {
        // The most recently hovered link is allowed to exceed the default limit.
        //
        // The goal is to always have enough bandwidth to start a new prefetch
        // request when hovering over a link.
        //
        // However, because we don't abort in-progress requests, it's still possible
        // we'll run out of bandwidth. When links are hovered in quick succession,
        // there could be multiple hover requests running simultaneously.
        return inProgressRequests < 12;
    }
    // The default limit is lower than the limit for a hovered link.
    return inProgressRequests < 4;
}
function spawnPrefetchSubtask(prefetchSubtask) {
    // When the scheduler spawns an async task, we don't await its result.
    // Instead, the async task writes its result directly into the cache, then
    // pings the scheduler to continue.
    //
    // We process server responses streamingly, so the prefetch subtask will
    // likely resolve before we're finished receiving all the data. The subtask
    // result includes a promise that resolves once the network connection is
    // closed. The scheduler uses this to control network bandwidth by tracking
    // and limiting the number of concurrent requests.
    inProgressRequests++;
    return prefetchSubtask.then((result)=>{
        if (result === null) {
            // The prefetch task errored before it could start processing the
            // network stream. Assume the connection is closed.
            onPrefetchConnectionClosed();
            return null;
        }
        // Wait for the connection to close before freeing up more bandwidth.
        result.closed.then(onPrefetchConnectionClosed);
        return result.value;
    });
}
function onPrefetchConnectionClosed() {
    inProgressRequests--;
    // Notify the scheduler that we have more bandwidth, and can continue
    // processing tasks.
    ensureWorkIsScheduled();
}
function pingPrefetchTask(task) {
    // "Ping" a prefetch that's already in progress to notify it of new data.
    if (// Check if prefetch was canceled.
    task.isCanceled || // Check if prefetch is already queued.
    task._heapIndex !== -1) {
        return;
    }
    // Add the task back to the queue.
    heapPush(taskHeap, task);
    ensureWorkIsScheduled();
}
function processQueueInMicrotask() {
    didScheduleMicrotask = false;
    // We aim to minimize how often we read the current time. Since nearly all
    // functions in the prefetch scheduler are synchronous, we can read the time
    // once and pass it as an argument wherever it's needed.
    const now = Date.now();
    // Process the task queue until we run out of network bandwidth.
    let task = heapPeek(taskHeap);
    while(task !== null && hasNetworkBandwidth(task)){
        task.cacheVersion = (0, _cache.getCurrentCacheVersion)();
        const exitStatus = pingRoute(now, task);
        // These fields are only valid for a single attempt. Reset them after each
        // iteration of the task queue.
        const hasBackgroundWork = task.hasBackgroundWork;
        task.hasBackgroundWork = false;
        task.spawnedRuntimePrefetches = null;
        switch(exitStatus){
            case 0:
                // The task yielded because there are too many requests in progress.
                // Stop processing tasks until we have more bandwidth.
                return;
            case 1:
                // The task is blocked. It needs more data before it can proceed.
                // Keep the task out of the queue until the server responds.
                heapPop(taskHeap);
                // Continue to the next task
                task = heapPeek(taskHeap);
                continue;
            case 2:
                if (task.phase === 1) {
                    // Finished prefetching the route tree. Proceed to prefetching
                    // the segments.
                    task.phase = 0;
                    heapResift(taskHeap, task);
                } else if (hasBackgroundWork) {
                    // The task spawned additional background work. Reschedule the task
                    // at background priority.
                    task.priority = _types.PrefetchPriority.Background;
                    heapResift(taskHeap, task);
                } else {
                    // The prefetch is complete. Continue to the next task.
                    heapPop(taskHeap);
                }
                task = heapPeek(taskHeap);
                continue;
            default:
                exitStatus;
        }
    }
}
/**
 * Check this during a prefetch task to determine if background work can be
 * performed. If so, it evaluates to `true`. Otherwise, it returns `false`,
 * while also scheduling a background task to run later. Usage:
 *
 * @example
 * if (background(task)) {
 *   // Perform background-pri work
 * }
 */ function background(task) {
    if (task.priority === _types.PrefetchPriority.Background) {
        return true;
    }
    task.hasBackgroundWork = true;
    return false;
}
function pingRoute(now, task) {
    const key = task.key;
    const route = (0, _cache.readOrCreateRouteCacheEntry)(now, task, key);
    const exitStatus = pingRootRouteTree(now, task, route);
    if (exitStatus !== 0 && key.search !== '') {
        // If the URL has a non-empty search string, also prefetch the pathname
        // without the search string. We use the searchless route tree as a base for
        // optimistic routing; see requestOptimisticRouteCacheEntry for details.
        //
        // Note that we don't need to prefetch any of the segment data. Just the
        // route tree.
        //
        // TODO: This is a temporary solution; the plan is to replace this by adding
        // a wildcard lookup method to the TupleMap implementation. This is
        // non-trivial to implement because it needs to account for things like
        // fallback route entries, hence this temporary workaround.
        const url = new URL(key.pathname, location.origin);
        const keyWithoutSearch = (0, _cachekey.createCacheKey)(url.href, key.nextUrl);
        const routeWithoutSearch = (0, _cache.readOrCreateRouteCacheEntry)(now, task, keyWithoutSearch);
        switch(routeWithoutSearch.status){
            case _cache.EntryStatus.Empty:
                {
                    if (background(task)) {
                        routeWithoutSearch.status = _cache.EntryStatus.Pending;
                        spawnPrefetchSubtask((0, _cache.fetchRouteOnCacheMiss)(routeWithoutSearch, task, keyWithoutSearch));
                    }
                    break;
                }
            case _cache.EntryStatus.Pending:
            case _cache.EntryStatus.Fulfilled:
            case _cache.EntryStatus.Rejected:
                {
                    break;
                }
            default:
                routeWithoutSearch;
        }
    }
    return exitStatus;
}
function pingRootRouteTree(now, task, route) {
    switch(route.status){
        case _cache.EntryStatus.Empty:
            {
                // Route is not yet cached, and there's no request already in progress.
                // Spawn a task to request the route, load it into the cache, and ping
                // the task to continue.
                // TODO: There are multiple strategies in the <Link> API for prefetching
                // a route. Currently we've only implemented the main one: per-segment,
                // static-data only.
                //
                // There's also `<Link prefetch={true}>`
                // which prefetch both static *and* dynamic data.
                // Similarly, we need to fallback to the old, per-page
                // behavior if PPR is disabled for a route (via the incremental opt-in).
                //
                // Those cases will be handled here.
                spawnPrefetchSubtask((0, _cache.fetchRouteOnCacheMiss)(route, task, task.key));
                // If the request takes longer than a minute, a subsequent request should
                // retry instead of waiting for this one. When the response is received,
                // this value will be replaced by a new value based on the stale time sent
                // from the server.
                // TODO: We should probably also manually abort the fetch task, to reclaim
                // server bandwidth.
                route.staleAt = now + 60 * 1000;
                // Upgrade to Pending so we know there's already a request in progress
                route.status = _cache.EntryStatus.Pending;
            // Intentional fallthrough to the Pending branch
            }
        case _cache.EntryStatus.Pending:
            {
                // Still pending. We can't start prefetching the segments until the route
                // tree has loaded. Add the task to the set of blocked tasks so that it
                // is notified when the route tree is ready.
                const blockedTasks = route.blockedTasks;
                if (blockedTasks === null) {
                    route.blockedTasks = new Set([
                        task
                    ]);
                } else {
                    blockedTasks.add(task);
                }
                return 1;
            }
        case _cache.EntryStatus.Rejected:
            {
                // Route tree failed to load. Treat as a 404.
                return 2;
            }
        case _cache.EntryStatus.Fulfilled:
            {
                if (task.phase !== 0) {
                    // Do not prefetch segment data until we've entered the segment phase.
                    return 2;
                }
                // Recursively fill in the segment tree.
                if (!hasNetworkBandwidth(task)) {
                    // Stop prefetching segments until there's more bandwidth.
                    return 0;
                }
                const tree = route.tree;
                // A task's fetch strategy gets set to `PPR` for any "auto" prefetch.
                // If it turned out that the route isn't PPR-enabled, we need to use `LoadingBoundary` instead.
                // We don't need to do this for runtime prefetches, because those are only available in
                // `cacheComponents`, where every route is PPR.
                const fetchStrategy = task.fetchStrategy === _types.FetchStrategy.PPR ? route.isPPREnabled ? _types.FetchStrategy.PPR : _types.FetchStrategy.LoadingBoundary : task.fetchStrategy;
                switch(fetchStrategy){
                    case _types.FetchStrategy.PPR:
                        {
                            // For Cache Components pages, each segment may be prefetched
                            // statically or using a runtime request, based on various
                            // configurations and heuristics. We'll do this in two passes: first
                            // traverse the tree and perform all the static prefetches.
                            //
                            // Then, if there are any segments that need a runtime request,
                            // do another pass to perform a runtime prefetch.
                            pingStaticHead(now, task, route);
                            const exitStatus = pingSharedPartOfCacheComponentsTree(now, task, route, task.treeAtTimeOfPrefetch, tree);
                            if (exitStatus === 0) {
                                // Child yielded without finishing.
                                return 0;
                            }
                            const spawnedRuntimePrefetches = task.spawnedRuntimePrefetches;
                            if (spawnedRuntimePrefetches !== null) {
                                // During the first pass, we discovered segments that require a
                                // runtime prefetch. Do a second pass to construct a request tree.
                                const spawnedEntries = new Map();
                                pingRuntimeHead(now, task, route, spawnedEntries, _types.FetchStrategy.PPRRuntime);
                                const requestTree = pingRuntimePrefetches(now, task, route, tree, spawnedRuntimePrefetches, spawnedEntries);
                                let needsDynamicRequest = spawnedEntries.size > 0;
                                if (needsDynamicRequest) {
                                    // Perform a dynamic prefetch request and populate the cache with
                                    // the result.
                                    spawnPrefetchSubtask((0, _cache.fetchSegmentPrefetchesUsingDynamicRequest)(task, route, _types.FetchStrategy.PPRRuntime, requestTree, spawnedEntries));
                                }
                            }
                            return 2;
                        }
                    case _types.FetchStrategy.Full:
                    case _types.FetchStrategy.PPRRuntime:
                    case _types.FetchStrategy.LoadingBoundary:
                        {
                            // Prefetch multiple segments using a single dynamic request.
                            // TODO: We can consolidate this branch with previous one by modeling
                            // it as if the first segment in the new tree has runtime prefetching
                            // enabled. Will do this as a follow-up refactor. Might want to remove
                            // the special metatdata case below first. In the meantime, it's not
                            // really that much duplication, just would be nice to remove one of
                            // these codepaths.
                            const spawnedEntries = new Map();
                            pingRuntimeHead(now, task, route, spawnedEntries, fetchStrategy);
                            const dynamicRequestTree = diffRouteTreeAgainstCurrent(now, task, route, task.treeAtTimeOfPrefetch, tree, spawnedEntries, fetchStrategy);
                            let needsDynamicRequest = spawnedEntries.size > 0;
                            if (needsDynamicRequest) {
                                spawnPrefetchSubtask((0, _cache.fetchSegmentPrefetchesUsingDynamicRequest)(task, route, fetchStrategy, dynamicRequestTree, spawnedEntries));
                            }
                            return 2;
                        }
                    default:
                        fetchStrategy;
                }
                break;
            }
        default:
            {
                route;
            }
    }
    return 2;
}
function pingStaticHead(now, task, route) {
    // The Head data for a page (metadata, viewport) is not really a route
    // segment, in the sense that it doesn't appear in the route tree. But we
    // store it in the cache as if it were, using a special key.
    pingStaticSegmentData(now, task, route, (0, _cache.readOrCreateSegmentCacheEntry)(now, _types.FetchStrategy.PPR, route, route.metadata), task.key, route.metadata);
}
function pingRuntimeHead(now, task, route, spawnedEntries, fetchStrategy) {
    pingRouteTreeAndIncludeDynamicData(now, task, route, route.metadata, false, spawnedEntries, // When prefetching the head, there's no difference between Full
    // and LoadingBoundary
    fetchStrategy === _types.FetchStrategy.LoadingBoundary ? _types.FetchStrategy.Full : fetchStrategy);
}
// TODO: Rename dynamic -> runtime throughout this module
function pingSharedPartOfCacheComponentsTree(now, task, route, oldTree, newTree) {
    // When Cache Components is enabled (or PPR, or a fully static route when PPR
    // is disabled; those cases are treated equivalently to Cache Components), we
    // start by prefetching each segment individually. Once we reach the "new"
    // part of the tree — the part that doesn't exist on the current page — we
    // may choose to switch to a runtime prefetch instead, based on the
    // information sent by the server in the route tree.
    //
    // The traversal starts in the "shared" part of the tree. Once we reach the
    // "new" part of the tree, we switch to a different traversal,
    // pingNewPartOfCacheComponentsTree.
    // Prefetch this segment's static data.
    const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task.fetchStrategy, route, newTree);
    pingStaticSegmentData(now, task, route, segment, task.key, newTree);
    // Recursively ping the children.
    const oldTreeChildren = oldTree[1];
    const newTreeChildren = newTree.slots;
    if (newTreeChildren !== null) {
        for(const parallelRouteKey in newTreeChildren){
            if (!hasNetworkBandwidth(task)) {
                // Stop prefetching segments until there's more bandwidth.
                return 0;
            }
            const newTreeChild = newTreeChildren[parallelRouteKey];
            const newTreeChildSegment = newTreeChild.segment;
            const oldTreeChild = oldTreeChildren[parallelRouteKey];
            const oldTreeChildSegment = oldTreeChild?.[0];
            let childExitStatus;
            if (oldTreeChildSegment !== undefined && doesCurrentSegmentMatchCachedSegment(route, newTreeChildSegment, oldTreeChildSegment)) {
                // We're still in the "shared" part of the tree.
                childExitStatus = pingSharedPartOfCacheComponentsTree(now, task, route, oldTreeChild, newTreeChild);
            } else {
                // We've entered the "new" part of the tree. Switch
                // traversal functions.
                childExitStatus = pingNewPartOfCacheComponentsTree(now, task, route, newTreeChild);
            }
            if (childExitStatus === 0) {
                // Child yielded without finishing.
                return 0;
            }
        }
    }
    return 2;
}
function pingNewPartOfCacheComponentsTree(now, task, route, tree) {
    // We're now prefetching in the "new" part of the tree, the part that doesn't
    // exist on the current page. (In other words, we're deeper than the
    // shared layouts.) Segments in here default to being prefetched statically.
    // However, if the server instructs us to, we may switch to a runtime
    // prefetch instead. Traverse the tree and check at each segment.
    if (tree.hasRuntimePrefetch) {
        // This route has a runtime prefetch response. Since we're below the shared
        // layout, everything from this point should be prefetched using a single,
        // combined runtime request, rather than using per-segment static requests.
        // This is true even if some of the child segments are known to be fully
        // static — once we've decided to perform a runtime prefetch, we might as
        // well respond with the static segments in the same roundtrip. (That's how
        // regular navigations work, too.) We'll still skip over segments that are
        // already cached, though.
        //
        // It's the server's responsibility to set a reasonable value of
        // `hasRuntimePrefetch`. Currently it's user-defined, but eventually, the
        // server may send a value of `false` even if the user opts in, if it
        // determines during build that the route is always fully static. There are
        // more optimizations we can do once we implement fallback param
        // tracking, too.
        //
        // Use the task object to collect the segments that need a runtime prefetch.
        // This will signal to the outer task queue that a second traversal is
        // required to construct a request tree.
        if (task.spawnedRuntimePrefetches === null) {
            task.spawnedRuntimePrefetches = new Set([
                tree.requestKey
            ]);
        } else {
            task.spawnedRuntimePrefetches.add(tree.requestKey);
        }
        // Then exit the traversal without prefetching anything further.
        return 2;
    }
    // This segment should not be runtime prefetched. Prefetch its static data.
    const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task.fetchStrategy, route, tree);
    pingStaticSegmentData(now, task, route, segment, task.key, tree);
    if (tree.slots !== null) {
        if (!hasNetworkBandwidth(task)) {
            // Stop prefetching segments until there's more bandwidth.
            return 0;
        }
        // Recursively ping the children.
        for(const parallelRouteKey in tree.slots){
            const childTree = tree.slots[parallelRouteKey];
            const childExitStatus = pingNewPartOfCacheComponentsTree(now, task, route, childTree);
            if (childExitStatus === 0) {
                // Child yielded without finishing.
                return 0;
            }
        }
    }
    // This segment and all its children have finished prefetching.
    return 2;
}
function diffRouteTreeAgainstCurrent(now, task, route, oldTree, newTree, spawnedEntries, fetchStrategy) {
    // This is a single recursive traversal that does multiple things:
    // - Finds the parts of the target route (newTree) that are not part of
    //   of the current page (oldTree) by diffing them, using the same algorithm
    //   as a real navigation.
    // - Constructs a request tree (FlightRouterState) that describes which
    //   segments need to be prefetched and which ones are already cached.
    // - Creates a set of pending cache entries for the segments that need to
    //   be prefetched, so that a subsequent prefetch task does not request the
    //   same segments again.
    const oldTreeChildren = oldTree[1];
    const newTreeChildren = newTree.slots;
    let requestTreeChildren = {};
    if (newTreeChildren !== null) {
        for(const parallelRouteKey in newTreeChildren){
            const newTreeChild = newTreeChildren[parallelRouteKey];
            const newTreeChildSegment = newTreeChild.segment;
            const oldTreeChild = oldTreeChildren[parallelRouteKey];
            const oldTreeChildSegment = oldTreeChild?.[0];
            if (oldTreeChildSegment !== undefined && doesCurrentSegmentMatchCachedSegment(route, newTreeChildSegment, oldTreeChildSegment)) {
                // This segment is already part of the current route. Keep traversing.
                const requestTreeChild = diffRouteTreeAgainstCurrent(now, task, route, oldTreeChild, newTreeChild, spawnedEntries, fetchStrategy);
                requestTreeChildren[parallelRouteKey] = requestTreeChild;
            } else {
                // This segment is not part of the current route. We're entering a
                // part of the tree that we need to prefetch (unless everything is
                // already cached).
                switch(fetchStrategy){
                    case _types.FetchStrategy.LoadingBoundary:
                        {
                            // When PPR is disabled, we can't prefetch per segment. We must
                            // fallback to the old prefetch behavior and send a dynamic request.
                            // Only routes that include a loading boundary can be prefetched in
                            // this way.
                            //
                            // This is simlar to a "full" prefetch, but we're much more
                            // conservative about which segments to include in the request.
                            //
                            // The server will only render up to the first loading boundary
                            // inside new part of the tree. If there's no loading boundary
                            // anywhere in the tree, the server will never return any data, so
                            // we can skip the request.
                            const subtreeHasLoadingBoundary = newTreeChild.hasLoadingBoundary !== _approutertypes.HasLoadingBoundary.SubtreeHasNoLoadingBoundary;
                            const requestTreeChild = subtreeHasLoadingBoundary ? pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, newTreeChild, null, spawnedEntries) : (0, _cache.convertRouteTreeToFlightRouterState)(newTreeChild);
                            requestTreeChildren[parallelRouteKey] = requestTreeChild;
                            break;
                        }
                    case _types.FetchStrategy.PPRRuntime:
                        {
                            // This is a runtime prefetch. Fetch all cacheable data in the tree,
                            // not just the static PPR shell.
                            const requestTreeChild = pingRouteTreeAndIncludeDynamicData(now, task, route, newTreeChild, false, spawnedEntries, fetchStrategy);
                            requestTreeChildren[parallelRouteKey] = requestTreeChild;
                            break;
                        }
                    case _types.FetchStrategy.Full:
                        {
                            // This is a "full" prefetch. Fetch all the data in the tree, both
                            // static and dynamic. We issue roughly the same request that we
                            // would during a real navigation. The goal is that once the
                            // navigation occurs, the router should not have to fetch any
                            // additional data.
                            //
                            // Although the response will include dynamic data, opting into a
                            // Full prefetch — via <Link prefetch={true}> — implicitly
                            // instructs the cache to treat the response as "static", or non-
                            // dynamic, since the whole point is to cache it for
                            // future navigations.
                            //
                            // Construct a tree (currently a FlightRouterState) that represents
                            // which segments need to be prefetched and which ones are already
                            // cached. If the tree is empty, then we can exit. Otherwise, we'll
                            // send the request tree to the server and use the response to
                            // populate the segment cache.
                            const requestTreeChild = pingRouteTreeAndIncludeDynamicData(now, task, route, newTreeChild, false, spawnedEntries, fetchStrategy);
                            requestTreeChildren[parallelRouteKey] = requestTreeChild;
                            break;
                        }
                    default:
                        fetchStrategy;
                }
            }
        }
    }
    const requestTree = [
        newTree.segment,
        requestTreeChildren,
        null,
        null,
        newTree.isRootLayout
    ];
    return requestTree;
}
function pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, tree, refetchMarkerContext, spawnedEntries) {
    // This function is similar to pingRouteTreeAndIncludeDynamicData, except the
    // server is only going to return a minimal loading state — it will stop
    // rendering at the first loading boundary. Whereas a Full prefetch is
    // intentionally aggressive and tries to pretfetch all the data that will be
    // needed for a navigation, a LoadingBoundary prefetch is much more
    // conservative. For example, it will omit from the request tree any segment
    // that is already cached, regardles of whether it's partial or full. By
    // contrast, a Full prefetch will refetch partial segments.
    // "inside-shared-layout" tells the server where to start looking for a
    // loading boundary.
    let refetchMarker = refetchMarkerContext === null ? 'inside-shared-layout' : null;
    const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task.fetchStrategy, route, tree);
    switch(segment.status){
        case _cache.EntryStatus.Empty:
            {
                // This segment is not cached. Add a refetch marker so the server knows
                // to start rendering here.
                // TODO: Instead of a "refetch" marker, we could just omit this subtree's
                // FlightRouterState from the request tree. I think this would probably
                // already work even without any updates to the server. For consistency,
                // though, I'll send the full tree and we'll look into this later as part
                // of a larger redesign of the request protocol.
                // Add the pending cache entry to the result map.
                spawnedEntries.set(tree.requestKey, (0, _cache.upgradeToPendingSegment)(segment, // Set the fetch strategy to LoadingBoundary to indicate that the server
                // might not include it in the pending response. If another route is able
                // to issue a per-segment request, we'll do that in the background.
                _types.FetchStrategy.LoadingBoundary));
                if (refetchMarkerContext !== 'refetch') {
                    refetchMarker = refetchMarkerContext = 'refetch';
                } else {
                // There's already a parent with a refetch marker, so we don't need
                // to add another one.
                }
                break;
            }
        case _cache.EntryStatus.Fulfilled:
            {
                // The segment is already cached.
                const segmentHasLoadingBoundary = tree.hasLoadingBoundary === _approutertypes.HasLoadingBoundary.SegmentHasLoadingBoundary;
                if (segmentHasLoadingBoundary) {
                    // This segment has a loading boundary, which means the server won't
                    // render its children. So there's nothing left to prefetch along this
                    // path. We can bail out.
                    return (0, _cache.convertRouteTreeToFlightRouterState)(tree);
                }
                break;
            }
        case _cache.EntryStatus.Pending:
            {
                break;
            }
        case _cache.EntryStatus.Rejected:
            {
                break;
            }
        default:
            segment;
    }
    const requestTreeChildren = {};
    if (tree.slots !== null) {
        for(const parallelRouteKey in tree.slots){
            const childTree = tree.slots[parallelRouteKey];
            requestTreeChildren[parallelRouteKey] = pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, childTree, refetchMarkerContext, spawnedEntries);
        }
    }
    const requestTree = [
        tree.segment,
        requestTreeChildren,
        null,
        refetchMarker,
        tree.isRootLayout
    ];
    return requestTree;
}
function pingRouteTreeAndIncludeDynamicData(now, task, route, tree, isInsideRefetchingParent, spawnedEntries, fetchStrategy) {
    // The tree we're constructing is the same shape as the tree we're navigating
    // to. But even though this is a "new" tree, some of the individual segments
    // may be cached as a result of other route prefetches.
    //
    // So we need to find the first uncached segment along each path add an
    // explicit "refetch" marker so the server knows where to start rendering.
    // Once the server starts rendering along a path, it keeps rendering the
    // entire subtree.
    const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, // Note that `fetchStrategy` might be different from `task.fetchStrategy`,
    // and we have to use the former here.
    // We can have a task with `FetchStrategy.PPR` where some of its segments are configured to
    // always use runtime prefetching (via `export const prefetch`), and those should check for
    // entries that include search params.
    fetchStrategy, route, tree);
    let spawnedSegment = null;
    switch(segment.status){
        case _cache.EntryStatus.Empty:
            {
                // This segment is not cached. Include it in the request.
                spawnedSegment = (0, _cache.upgradeToPendingSegment)(segment, fetchStrategy);
                break;
            }
        case _cache.EntryStatus.Fulfilled:
            {
                // The segment is already cached.
                if (segment.isPartial && (0, _cache.canNewFetchStrategyProvideMoreContent)(segment.fetchStrategy, fetchStrategy)) {
                    // The cached segment contains dynamic holes, and was prefetched using a less specific strategy than the current one.
                    // This means we're in one of these cases:
                    //   - we have a static prefetch, and we're doing a runtime prefetch
                    //   - we have a static or runtime prefetch, and we're doing a Full prefetch (or a navigation).
                    // In either case, we need to include it in the request to get a more specific (or full) version.
                    spawnedSegment = pingFullSegmentRevalidation(now, route, tree, fetchStrategy);
                }
                break;
            }
        case _cache.EntryStatus.Pending:
        case _cache.EntryStatus.Rejected:
            {
                // There's either another prefetch currently in progress, or the previous
                // attempt failed. If the new strategy can provide more content, fetch it again.
                if ((0, _cache.canNewFetchStrategyProvideMoreContent)(segment.fetchStrategy, fetchStrategy)) {
                    spawnedSegment = pingFullSegmentRevalidation(now, route, tree, fetchStrategy);
                }
                break;
            }
        default:
            segment;
    }
    const requestTreeChildren = {};
    if (tree.slots !== null) {
        for(const parallelRouteKey in tree.slots){
            const childTree = tree.slots[parallelRouteKey];
            requestTreeChildren[parallelRouteKey] = pingRouteTreeAndIncludeDynamicData(now, task, route, childTree, isInsideRefetchingParent || spawnedSegment !== null, spawnedEntries, fetchStrategy);
        }
    }
    if (spawnedSegment !== null) {
        // Add the pending entry to the result map.
        spawnedEntries.set(tree.requestKey, spawnedSegment);
    }
    // Don't bother to add a refetch marker if one is already present in a parent.
    const refetchMarker = !isInsideRefetchingParent && spawnedSegment !== null ? 'refetch' : null;
    const requestTree = [
        tree.segment,
        requestTreeChildren,
        null,
        refetchMarker,
        tree.isRootLayout
    ];
    return requestTree;
}
function pingRuntimePrefetches(now, task, route, tree, spawnedRuntimePrefetches, spawnedEntries) {
    // Construct a request tree (FlightRouterState) for a runtime prefetch. If
    // a segment is part of the runtime prefetch, the tree is constructed by
    // diffing against what's already in the prefetch cache. Otherwise, we send
    // a regular FlightRouterState with no special markers.
    //
    // See pingRouteTreeAndIncludeDynamicData for details.
    if (spawnedRuntimePrefetches.has(tree.requestKey)) {
        // This segment needs a runtime prefetch.
        return pingRouteTreeAndIncludeDynamicData(now, task, route, tree, false, spawnedEntries, _types.FetchStrategy.PPRRuntime);
    }
    let requestTreeChildren = {};
    const slots = tree.slots;
    if (slots !== null) {
        for(const parallelRouteKey in slots){
            const childTree = slots[parallelRouteKey];
            requestTreeChildren[parallelRouteKey] = pingRuntimePrefetches(now, task, route, childTree, spawnedRuntimePrefetches, spawnedEntries);
        }
    }
    // This segment is not part of the runtime prefetch. Clone the base tree.
    const requestTree = [
        tree.segment,
        requestTreeChildren,
        null,
        null
    ];
    return requestTree;
}
function pingStaticSegmentData(now, task, route, segment, routeKey, tree) {
    switch(segment.status){
        case _cache.EntryStatus.Empty:
            // Upgrade to Pending so we know there's already a request in progress
            spawnPrefetchSubtask((0, _cache.fetchSegmentOnCacheMiss)(route, (0, _cache.upgradeToPendingSegment)(segment, _types.FetchStrategy.PPR), routeKey, tree));
            break;
        case _cache.EntryStatus.Pending:
            {
                // There's already a request in progress. Depending on what kind of
                // request it is, we may want to revalidate it.
                switch(segment.fetchStrategy){
                    case _types.FetchStrategy.PPR:
                    case _types.FetchStrategy.PPRRuntime:
                    case _types.FetchStrategy.Full:
                        break;
                    case _types.FetchStrategy.LoadingBoundary:
                        // There's a pending request, but because it's using the old
                        // prefetching strategy, we can't be sure if it will be fulfilled by
                        // the response — it might be inside the loading boundary. Perform
                        // a revalidation, but because it's speculative, wait to do it at
                        // background priority.
                        if (background(task)) {
                            // TODO: Instead of speculatively revalidating, consider including
                            // `hasLoading` in the route tree prefetch response.
                            pingPPRSegmentRevalidation(now, route, routeKey, tree);
                        }
                        break;
                    default:
                        segment.fetchStrategy;
                }
                break;
            }
        case _cache.EntryStatus.Rejected:
            {
                // The existing entry in the cache was rejected. Depending on how it
                // was originally fetched, we may or may not want to revalidate it.
                switch(segment.fetchStrategy){
                    case _types.FetchStrategy.PPR:
                    case _types.FetchStrategy.PPRRuntime:
                    case _types.FetchStrategy.Full:
                        break;
                    case _types.FetchStrategy.LoadingBoundary:
                        // There's a rejected entry, but it was fetched using the loading
                        // boundary strategy. So the reason it wasn't returned by the server
                        // might just be because it was inside a loading boundary. Or because
                        // there was a dynamic rewrite. Revalidate it using the per-
                        // segment strategy.
                        //
                        // Because a rejected segment will definitely prevent the segment (and
                        // all of its children) from rendering, we perform this revalidation
                        // immediately instead of deferring it to a background task.
                        pingPPRSegmentRevalidation(now, route, routeKey, tree);
                        break;
                    default:
                        segment.fetchStrategy;
                }
                break;
            }
        case _cache.EntryStatus.Fulfilled:
            break;
        default:
            segment;
    }
// Segments do not have dependent tasks, so once the prefetch is initiated,
// there's nothing else for us to do (except write the server data into the
// entry, which is handled by `fetchSegmentOnCacheMiss`).
}
function pingPPRSegmentRevalidation(now, route, routeKey, tree) {
    const revalidatingSegment = (0, _cache.readOrCreateRevalidatingSegmentEntry)(now, _types.FetchStrategy.PPR, route, tree);
    switch(revalidatingSegment.status){
        case _cache.EntryStatus.Empty:
            // Spawn a prefetch request and upsert the segment into the cache
            // upon completion.
            upsertSegmentOnCompletion(spawnPrefetchSubtask((0, _cache.fetchSegmentOnCacheMiss)(route, (0, _cache.upgradeToPendingSegment)(revalidatingSegment, _types.FetchStrategy.PPR), routeKey, tree)), (0, _varypath.getSegmentVaryPathForRequest)(_types.FetchStrategy.PPR, tree));
            break;
        case _cache.EntryStatus.Pending:
            break;
        case _cache.EntryStatus.Fulfilled:
        case _cache.EntryStatus.Rejected:
            break;
        default:
            revalidatingSegment;
    }
}
function pingFullSegmentRevalidation(now, route, tree, fetchStrategy) {
    const revalidatingSegment = (0, _cache.readOrCreateRevalidatingSegmentEntry)(now, fetchStrategy, route, tree);
    if (revalidatingSegment.status === _cache.EntryStatus.Empty) {
        // During a Full/PPRRuntime prefetch, a single dynamic request is made for all the
        // segments that we need. So we don't initiate a request here directly. By
        // returning a pending entry from this function, it signals to the caller
        // that this segment should be included in the request that's sent to
        // the server.
        const pendingSegment = (0, _cache.upgradeToPendingSegment)(revalidatingSegment, fetchStrategy);
        upsertSegmentOnCompletion((0, _cache.waitForSegmentCacheEntry)(pendingSegment), (0, _varypath.getSegmentVaryPathForRequest)(fetchStrategy, tree));
        return pendingSegment;
    } else {
        // There's already a revalidation in progress.
        const nonEmptyRevalidatingSegment = revalidatingSegment;
        if ((0, _cache.canNewFetchStrategyProvideMoreContent)(nonEmptyRevalidatingSegment.fetchStrategy, fetchStrategy)) {
            // The existing revalidation was fetched using a less specific strategy.
            // Reset it and start a new revalidation.
            const emptySegment = (0, _cache.overwriteRevalidatingSegmentCacheEntry)(fetchStrategy, route, tree);
            const pendingSegment = (0, _cache.upgradeToPendingSegment)(emptySegment, fetchStrategy);
            upsertSegmentOnCompletion((0, _cache.waitForSegmentCacheEntry)(pendingSegment), (0, _varypath.getSegmentVaryPathForRequest)(fetchStrategy, tree));
            return pendingSegment;
        }
        switch(nonEmptyRevalidatingSegment.status){
            case _cache.EntryStatus.Pending:
                // There's already an in-progress prefetch that includes this segment.
                return null;
            case _cache.EntryStatus.Fulfilled:
            case _cache.EntryStatus.Rejected:
                // A previous revalidation attempt finished, but we chose not to replace
                // the existing entry in the cache. Don't try again until or unless the
                // revalidation entry expires.
                return null;
            default:
                nonEmptyRevalidatingSegment;
                return null;
        }
    }
}
const noop = ()=>{};
function upsertSegmentOnCompletion(promise, varyPath) {
    // Wait for a segment to finish loading, then upsert it into the cache
    promise.then((fulfilled)=>{
        if (fulfilled !== null) {
            // Received new data. Attempt to replace the existing entry in the cache.
            (0, _cache.upsertSegmentEntry)(Date.now(), varyPath, fulfilled);
        }
    }, noop);
}
function doesCurrentSegmentMatchCachedSegment(route, currentSegment, cachedSegment) {
    if (cachedSegment === _segment.PAGE_SEGMENT_KEY) {
        // In the FlightRouterState stored by the router, the page segment has the
        // rendered search params appended to the name of the segment. In the
        // prefetch cache, however, this is stored separately. So, when comparing
        // the router's current FlightRouterState to the cached FlightRouterState,
        // we need to make sure we compare both parts of the segment.
        // TODO: This is not modeled clearly. We use the same type,
        // FlightRouterState, for both the CacheNode tree _and_ the prefetch cache
        // _and_ the server response format, when conceptually those are three
        // different things and treated in different ways. We should encode more of
        // this information into the type design so mistakes are less likely.
        return currentSegment === (0, _segment.addSearchParamsIfPageSegment)(_segment.PAGE_SEGMENT_KEY, Object.fromEntries(new URLSearchParams(route.renderedSearch)));
    }
    // Non-page segments are compared using the same function as the server
    return (0, _matchsegments.matchSegment)(cachedSegment, currentSegment);
}
// -----------------------------------------------------------------------------
// The remainder of the module is a MinHeap implementation. Try not to put any
// logic below here unless it's related to the heap algorithm. We can extract
// this to a separate module if/when we need multiple kinds of heaps.
// -----------------------------------------------------------------------------
function compareQueuePriority(a, b) {
    // Since the queue is a MinHeap, this should return a positive number if b is
    // higher priority than a, and a negative number if a is higher priority
    // than b.
    // `priority` is an integer, where higher numbers are higher priority.
    const priorityDiff = b.priority - a.priority;
    if (priorityDiff !== 0) {
        return priorityDiff;
    }
    // If the priority is the same, check which phase the prefetch is in — is it
    // prefetching the route tree, or the segments? Route trees are prioritized.
    const phaseDiff = b.phase - a.phase;
    if (phaseDiff !== 0) {
        return phaseDiff;
    }
    // Finally, check the insertion order. `sortId` is an incrementing counter
    // assigned to prefetches. We want to process the newest prefetches first.
    return b.sortId - a.sortId;
}
function heapPush(heap, node) {
    const index = heap.length;
    heap.push(node);
    node._heapIndex = index;
    heapSiftUp(heap, node, index);
}
function heapPeek(heap) {
    return heap.length === 0 ? null : heap[0];
}
function heapPop(heap) {
    if (heap.length === 0) {
        return null;
    }
    const first = heap[0];
    first._heapIndex = -1;
    const last = heap.pop();
    if (last !== first) {
        heap[0] = last;
        last._heapIndex = 0;
        heapSiftDown(heap, last, 0);
    }
    return first;
}
function heapDelete(heap, node) {
    const index = node._heapIndex;
    if (index !== -1) {
        node._heapIndex = -1;
        if (heap.length !== 0) {
            const last = heap.pop();
            if (last !== node) {
                heap[index] = last;
                last._heapIndex = index;
                heapSiftDown(heap, last, index);
            }
        }
    }
}
function heapResift(heap, node) {
    const index = node._heapIndex;
    if (index !== -1) {
        if (index === 0) {
            heapSiftDown(heap, node, 0);
        } else {
            const parentIndex = index - 1 >>> 1;
            const parent = heap[parentIndex];
            if (compareQueuePriority(parent, node) > 0) {
                // The parent is larger. Sift up.
                heapSiftUp(heap, node, index);
            } else {
                // The parent is smaller (or equal). Sift down.
                heapSiftDown(heap, node, index);
            }
        }
    }
}
function heapSiftUp(heap, node, i) {
    let index = i;
    while(index > 0){
        const parentIndex = index - 1 >>> 1;
        const parent = heap[parentIndex];
        if (compareQueuePriority(parent, node) > 0) {
            // The parent is larger. Swap positions.
            heap[parentIndex] = node;
            node._heapIndex = parentIndex;
            heap[index] = parent;
            parent._heapIndex = index;
            index = parentIndex;
        } else {
            // The parent is smaller. Exit.
            return;
        }
    }
}
function heapSiftDown(heap, node, i) {
    let index = i;
    const length = heap.length;
    const halfLength = length >>> 1;
    while(index < halfLength){
        const leftIndex = (index + 1) * 2 - 1;
        const left = heap[leftIndex];
        const rightIndex = leftIndex + 1;
        const right = heap[rightIndex];
        // If the left or right node is smaller, swap with the smaller of those.
        if (compareQueuePriority(left, node) < 0) {
            if (rightIndex < length && compareQueuePriority(right, left) < 0) {
                heap[index] = right;
                right._heapIndex = index;
                heap[rightIndex] = node;
                node._heapIndex = rightIndex;
                index = rightIndex;
            } else {
                heap[index] = left;
                left._heapIndex = index;
                heap[leftIndex] = node;
                node._heapIndex = leftIndex;
                index = leftIndex;
            }
        } else if (rightIndex < length && compareQueuePriority(right, node) < 0) {
            heap[index] = right;
            right._heapIndex = index;
            heap[rightIndex] = node;
            node._heapIndex = rightIndex;
            index = rightIndex;
        } else {
            // Neither child is smaller. Exit.
            return;
        }
    }
}

if ((typeof exports.default === 'function' || (typeof exports.default === 'object' && exports.default !== null)) && typeof exports.default.__esModule === 'undefined') {
  Object.defineProperty(exports.default, '__esModule', { value: true });
  Object.assign(exports.default, exports);
  module.exports = exports.default;
}

//# sourceMappingURL=scheduler.js.map