/**
 * @license Angular v18.1.0-next.1
 * (c) 2010-2024 Google LLC. https://angular.io/
 * License: MIT
 */

/**
 * The default equality function used for `signal` and `computed`, which uses referential equality.
 */
function defaultEquals(a, b) {
    return Object.is(a, b);
}

/**
 * The currently active consumer `ReactiveNode`, if running code in a reactive context.
 *
 * Change this via `setActiveConsumer`.
 */
let activeConsumer = null;
let inNotificationPhase = false;
/**
 * Global epoch counter. Incremented whenever a source signal is set.
 */
let epoch = 1;
/**
 * Symbol used to tell `Signal`s apart from other functions.
 *
 * This can be used to auto-unwrap signals in various cases, or to auto-wrap non-signal values.
 */
const SIGNAL = /* @__PURE__ */ Symbol('SIGNAL');
function setActiveConsumer(consumer) {
    const prev = activeConsumer;
    activeConsumer = consumer;
    return prev;
}
function getActiveConsumer() {
    return activeConsumer;
}
function isInNotificationPhase() {
    return inNotificationPhase;
}
function isReactive(value) {
    return value[SIGNAL] !== undefined;
}
const REACTIVE_NODE = {
    version: 0,
    lastCleanEpoch: 0,
    dirty: false,
    producerNode: undefined,
    producerLastReadVersion: undefined,
    producerIndexOfThis: undefined,
    nextProducerIndex: 0,
    liveConsumerNode: undefined,
    liveConsumerIndexOfThis: undefined,
    consumerAllowSignalWrites: false,
    consumerIsAlwaysLive: false,
    producerMustRecompute: () => false,
    producerRecomputeValue: () => { },
    consumerMarkedDirty: () => { },
    consumerOnSignalRead: () => { },
};
/**
 * Called by implementations when a producer's signal is read.
 */
function producerAccessed(node) {
    if (inNotificationPhase) {
        throw new Error(typeof ngDevMode !== 'undefined' && ngDevMode
            ? `Assertion error: signal read during notification phase`
            : '');
    }
    if (activeConsumer === null) {
        // Accessed outside of a reactive context, so nothing to record.
        return;
    }
    activeConsumer.consumerOnSignalRead(node);
    // This producer is the `idx`th dependency of `activeConsumer`.
    const idx = activeConsumer.nextProducerIndex++;
    assertConsumerNode(activeConsumer);
    if (idx < activeConsumer.producerNode.length && activeConsumer.producerNode[idx] !== node) {
        // There's been a change in producers since the last execution of `activeConsumer`.
        // `activeConsumer.producerNode[idx]` holds a stale dependency which will be be removed and
        // replaced with `this`.
        //
        // If `activeConsumer` isn't live, then this is a no-op, since we can replace the producer in
        // `activeConsumer.producerNode` directly. However, if `activeConsumer` is live, then we need
        // to remove it from the stale producer's `liveConsumer`s.
        if (consumerIsLive(activeConsumer)) {
            const staleProducer = activeConsumer.producerNode[idx];
            producerRemoveLiveConsumerAtIndex(staleProducer, activeConsumer.producerIndexOfThis[idx]);
            // At this point, the only record of `staleProducer` is the reference at
            // `activeConsumer.producerNode[idx]` which will be overwritten below.
        }
    }
    if (activeConsumer.producerNode[idx] !== node) {
        // We're a new dependency of the consumer (at `idx`).
        activeConsumer.producerNode[idx] = node;
        // If the active consumer is live, then add it as a live consumer. If not, then use 0 as a
        // placeholder value.
        activeConsumer.producerIndexOfThis[idx] = consumerIsLive(activeConsumer)
            ? producerAddLiveConsumer(node, activeConsumer, idx)
            : 0;
    }
    activeConsumer.producerLastReadVersion[idx] = node.version;
}
/**
 * Increment the global epoch counter.
 *
 * Called by source producers (that is, not computeds) whenever their values change.
 */
function producerIncrementEpoch() {
    epoch++;
}
/**
 * Ensure this producer's `version` is up-to-date.
 */
function producerUpdateValueVersion(node) {
    if (consumerIsLive(node) && !node.dirty) {
        // A live consumer will be marked dirty by producers, so a clean state means that its version
        // is guaranteed to be up-to-date.
        return;
    }
    if (!node.dirty && node.lastCleanEpoch === epoch) {
        // Even non-live consumers can skip polling if they previously found themselves to be clean at
        // the current epoch, since their dependencies could not possibly have changed (such a change
        // would've increased the epoch).
        return;
    }
    if (!node.producerMustRecompute(node) && !consumerPollProducersForChange(node)) {
        // None of our producers report a change since the last time they were read, so no
        // recomputation of our value is necessary, and we can consider ourselves clean.
        node.dirty = false;
        node.lastCleanEpoch = epoch;
        return;
    }
    node.producerRecomputeValue(node);
    // After recomputing the value, we're no longer dirty.
    node.dirty = false;
    node.lastCleanEpoch = epoch;
}
/**
 * Propagate a dirty notification to live consumers of this producer.
 */
function producerNotifyConsumers(node) {
    if (node.liveConsumerNode === undefined) {
        return;
    }
    // Prevent signal reads when we're updating the graph
    const prev = inNotificationPhase;
    inNotificationPhase = true;
    try {
        for (const consumer of node.liveConsumerNode) {
            if (!consumer.dirty) {
                consumerMarkDirty(consumer);
            }
        }
    }
    finally {
        inNotificationPhase = prev;
    }
}
/**
 * Whether this `ReactiveNode` in its producer capacity is currently allowed to initiate updates,
 * based on the current consumer context.
 */
function producerUpdatesAllowed() {
    return activeConsumer?.consumerAllowSignalWrites !== false;
}
function consumerMarkDirty(node) {
    node.dirty = true;
    producerNotifyConsumers(node);
    node.consumerMarkedDirty?.(node);
}
/**
 * Prepare this consumer to run a computation in its reactive context.
 *
 * Must be called by subclasses which represent reactive computations, before those computations
 * begin.
 */
function consumerBeforeComputation(node) {
    node && (node.nextProducerIndex = 0);
    return setActiveConsumer(node);
}
/**
 * Finalize this consumer's state after a reactive computation has run.
 *
 * Must be called by subclasses which represent reactive computations, after those computations
 * have finished.
 */
function consumerAfterComputation(node, prevConsumer) {
    setActiveConsumer(prevConsumer);
    if (!node ||
        node.producerNode === undefined ||
        node.producerIndexOfThis === undefined ||
        node.producerLastReadVersion === undefined) {
        return;
    }
    if (consumerIsLive(node)) {
        // For live consumers, we need to remove the producer -> consumer edge for any stale producers
        // which weren't dependencies after the recomputation.
        for (let i = node.nextProducerIndex; i < node.producerNode.length; i++) {
            producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
        }
    }
    // Truncate the producer tracking arrays.
    // Perf note: this is essentially truncating the length to `node.nextProducerIndex`, but
    // benchmarking has shown that individual pop operations are faster.
    while (node.producerNode.length > node.nextProducerIndex) {
        node.producerNode.pop();
        node.producerLastReadVersion.pop();
        node.producerIndexOfThis.pop();
    }
}
/**
 * Determine whether this consumer has any dependencies which have changed since the last time
 * they were read.
 */
function consumerPollProducersForChange(node) {
    assertConsumerNode(node);
    // Poll producers for change.
    for (let i = 0; i < node.producerNode.length; i++) {
        const producer = node.producerNode[i];
        const seenVersion = node.producerLastReadVersion[i];
        // First check the versions. A mismatch means that the producer's value is known to have
        // changed since the last time we read it.
        if (seenVersion !== producer.version) {
            return true;
        }
        // The producer's version is the same as the last time we read it, but it might itself be
        // stale. Force the producer to recompute its version (calculating a new value if necessary).
        producerUpdateValueVersion(producer);
        // Now when we do this check, `producer.version` is guaranteed to be up to date, so if the
        // versions still match then it has not changed since the last time we read it.
        if (seenVersion !== producer.version) {
            return true;
        }
    }
    return false;
}
/**
 * Disconnect this consumer from the graph.
 */
function consumerDestroy(node) {
    assertConsumerNode(node);
    if (consumerIsLive(node)) {
        // Drop all connections from the graph to this node.
        for (let i = 0; i < node.producerNode.length; i++) {
            producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
        }
    }
    // Truncate all the arrays to drop all connection from this node to the graph.
    node.producerNode.length =
        node.producerLastReadVersion.length =
            node.producerIndexOfThis.length =
                0;
    if (node.liveConsumerNode) {
        node.liveConsumerNode.length = node.liveConsumerIndexOfThis.length = 0;
    }
}
/**
 * Add `consumer` as a live consumer of this node.
 *
 * Note that this operation is potentially transitive. If this node becomes live, then it becomes
 * a live consumer of all of its current producers.
 */
function producerAddLiveConsumer(node, consumer, indexOfThis) {
    assertProducerNode(node);
    if (node.liveConsumerNode.length === 0 && isConsumerNode(node)) {
        // When going from 0 to 1 live consumers, we become a live consumer to our producers.
        for (let i = 0; i < node.producerNode.length; i++) {
            node.producerIndexOfThis[i] = producerAddLiveConsumer(node.producerNode[i], node, i);
        }
    }
    node.liveConsumerIndexOfThis.push(indexOfThis);
    return node.liveConsumerNode.push(consumer) - 1;
}
/**
 * Remove the live consumer at `idx`.
 */
function producerRemoveLiveConsumerAtIndex(node, idx) {
    assertProducerNode(node);
    if (typeof ngDevMode !== 'undefined' && ngDevMode && idx >= node.liveConsumerNode.length) {
        throw new Error(`Assertion error: active consumer index ${idx} is out of bounds of ${node.liveConsumerNode.length} consumers)`);
    }
    if (node.liveConsumerNode.length === 1 && isConsumerNode(node)) {
        // When removing the last live consumer, we will no longer be live. We need to remove
        // ourselves from our producers' tracking (which may cause consumer-producers to lose
        // liveness as well).
        for (let i = 0; i < node.producerNode.length; i++) {
            producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
        }
    }
    // Move the last value of `liveConsumers` into `idx`. Note that if there's only a single
    // live consumer, this is a no-op.
    const lastIdx = node.liveConsumerNode.length - 1;
    node.liveConsumerNode[idx] = node.liveConsumerNode[lastIdx];
    node.liveConsumerIndexOfThis[idx] = node.liveConsumerIndexOfThis[lastIdx];
    // Truncate the array.
    node.liveConsumerNode.length--;
    node.liveConsumerIndexOfThis.length--;
    // If the index is still valid, then we need to fix the index pointer from the producer to this
    // consumer, and update it from `lastIdx` to `idx` (accounting for the move above).
    if (idx < node.liveConsumerNode.length) {
        const idxProducer = node.liveConsumerIndexOfThis[idx];
        const consumer = node.liveConsumerNode[idx];
        assertConsumerNode(consumer);
        consumer.producerIndexOfThis[idxProducer] = idx;
    }
}
function consumerIsLive(node) {
    return node.consumerIsAlwaysLive || (node?.liveConsumerNode?.length ?? 0) > 0;
}
function assertConsumerNode(node) {
    node.producerNode ??= [];
    node.producerIndexOfThis ??= [];
    node.producerLastReadVersion ??= [];
}
function assertProducerNode(node) {
    node.liveConsumerNode ??= [];
    node.liveConsumerIndexOfThis ??= [];
}
function isConsumerNode(node) {
    return node.producerNode !== undefined;
}

/**
 * Create a computed signal which derives a reactive value from an expression.
 */
function createComputed(computation) {
    const node = Object.create(COMPUTED_NODE);
    node.computation = computation;
    const computed = () => {
        // Check if the value needs updating before returning it.
        producerUpdateValueVersion(node);
        // Record that someone looked at this signal.
        producerAccessed(node);
        if (node.value === ERRORED) {
            throw node.error;
        }
        return node.value;
    };
    computed[SIGNAL] = node;
    return computed;
}
/**
 * A dedicated symbol used before a computed value has been calculated for the first time.
 * Explicitly typed as `any` so we can use it as signal's value.
 */
const UNSET = /* @__PURE__ */ Symbol('UNSET');
/**
 * A dedicated symbol used in place of a computed signal value to indicate that a given computation
 * is in progress. Used to detect cycles in computation chains.
 * Explicitly typed as `any` so we can use it as signal's value.
 */
const COMPUTING = /* @__PURE__ */ Symbol('COMPUTING');
/**
 * A dedicated symbol used in place of a computed signal value to indicate that a given computation
 * failed. The thrown error is cached until the computation gets dirty again.
 * Explicitly typed as `any` so we can use it as signal's value.
 */
const ERRORED = /* @__PURE__ */ Symbol('ERRORED');
// Note: Using an IIFE here to ensure that the spread assignment is not considered
// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.
// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.
const COMPUTED_NODE = /* @__PURE__ */ (() => {
    return {
        ...REACTIVE_NODE,
        value: UNSET,
        dirty: true,
        error: null,
        equal: defaultEquals,
        producerMustRecompute(node) {
            // Force a recomputation if there's no current value, or if the current value is in the
            // process of being calculated (which should throw an error).
            return node.value === UNSET || node.value === COMPUTING;
        },
        producerRecomputeValue(node) {
            if (node.value === COMPUTING) {
                // Our computation somehow led to a cyclic read of itself.
                throw new Error('Detected cycle in computations.');
            }
            const oldValue = node.value;
            node.value = COMPUTING;
            const prevConsumer = consumerBeforeComputation(node);
            let newValue;
            try {
                newValue = node.computation();
            }
            catch (err) {
                newValue = ERRORED;
                node.error = err;
            }
            finally {
                consumerAfterComputation(node, prevConsumer);
            }
            if (oldValue !== UNSET &&
                oldValue !== ERRORED &&
                newValue !== ERRORED &&
                node.equal(oldValue, newValue)) {
                // No change to `valueVersion` - old and new values are
                // semantically equivalent.
                node.value = oldValue;
                return;
            }
            node.value = newValue;
            node.version++;
        },
    };
})();

function defaultThrowError() {
    throw new Error();
}
let throwInvalidWriteToSignalErrorFn = defaultThrowError;
function throwInvalidWriteToSignalError() {
    throwInvalidWriteToSignalErrorFn();
}
function setThrowInvalidWriteToSignalError(fn) {
    throwInvalidWriteToSignalErrorFn = fn;
}

/**
 * If set, called after `WritableSignal`s are updated.
 *
 * This hook can be used to achieve various effects, such as running effects synchronously as part
 * of setting a signal.
 */
let postSignalSetFn = null;
/**
 * Create a `Signal` that can be set or updated directly.
 */
function createSignal(initialValue) {
    const node = Object.create(SIGNAL_NODE);
    node.value = initialValue;
    const getter = (() => {
        producerAccessed(node);
        return node.value;
    });
    getter[SIGNAL] = node;
    return getter;
}
function setPostSignalSetFn(fn) {
    const prev = postSignalSetFn;
    postSignalSetFn = fn;
    return prev;
}
function signalGetFn() {
    producerAccessed(this);
    return this.value;
}
function signalSetFn(node, newValue) {
    if (!producerUpdatesAllowed()) {
        throwInvalidWriteToSignalError();
    }
    if (!node.equal(node.value, newValue)) {
        node.value = newValue;
        signalValueChanged(node);
    }
}
function signalUpdateFn(node, updater) {
    if (!producerUpdatesAllowed()) {
        throwInvalidWriteToSignalError();
    }
    signalSetFn(node, updater(node.value));
}
// Note: Using an IIFE here to ensure that the spread assignment is not considered
// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.
// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.
const SIGNAL_NODE = /* @__PURE__ */ (() => {
    return {
        ...REACTIVE_NODE,
        equal: defaultEquals,
        value: undefined,
    };
})();
function signalValueChanged(node) {
    node.version++;
    producerIncrementEpoch();
    producerNotifyConsumers(node);
    postSignalSetFn?.();
}

function createWatch(fn, schedule, allowSignalWrites) {
    const node = Object.create(WATCH_NODE);
    if (allowSignalWrites) {
        node.consumerAllowSignalWrites = true;
    }
    node.fn = fn;
    node.schedule = schedule;
    const registerOnCleanup = (cleanupFn) => {
        node.cleanupFn = cleanupFn;
    };
    function isWatchNodeDestroyed(node) {
        return node.fn === null && node.schedule === null;
    }
    function destroyWatchNode(node) {
        if (!isWatchNodeDestroyed(node)) {
            consumerDestroy(node); // disconnect watcher from the reactive graph
            node.cleanupFn();
            // nullify references to the integration functions to mark node as destroyed
            node.fn = null;
            node.schedule = null;
            node.cleanupFn = NOOP_CLEANUP_FN;
        }
    }
    const run = () => {
        if (node.fn === null) {
            // trying to run a destroyed watch is noop
            return;
        }
        if (isInNotificationPhase()) {
            throw new Error(`Schedulers cannot synchronously execute watches while scheduling.`);
        }
        node.dirty = false;
        if (node.hasRun && !consumerPollProducersForChange(node)) {
            return;
        }
        node.hasRun = true;
        const prevConsumer = consumerBeforeComputation(node);
        try {
            node.cleanupFn();
            node.cleanupFn = NOOP_CLEANUP_FN;
            node.fn(registerOnCleanup);
        }
        finally {
            consumerAfterComputation(node, prevConsumer);
        }
    };
    node.ref = {
        notify: () => consumerMarkDirty(node),
        run,
        cleanup: () => node.cleanupFn(),
        destroy: () => destroyWatchNode(node),
        [SIGNAL]: node,
    };
    return node.ref;
}
const NOOP_CLEANUP_FN = () => { };
// Note: Using an IIFE here to ensure that the spread assignment is not considered
// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.
// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.
const WATCH_NODE = /* @__PURE__ */ (() => {
    return {
        ...REACTIVE_NODE,
        consumerIsAlwaysLive: true,
        consumerAllowSignalWrites: false,
        consumerMarkedDirty: (node) => {
            if (node.schedule !== null) {
                node.schedule(node.ref);
            }
        },
        hasRun: false,
        cleanupFn: NOOP_CLEANUP_FN,
    };
})();

function setAlternateWeakRefImpl(impl) {
    // TODO: remove this function
}

export { REACTIVE_NODE, SIGNAL, SIGNAL_NODE, consumerAfterComputation, consumerBeforeComputation, consumerDestroy, consumerMarkDirty, consumerPollProducersForChange, createComputed, createSignal, createWatch, defaultEquals, getActiveConsumer, isInNotificationPhase, isReactive, producerAccessed, producerNotifyConsumers, producerUpdateValueVersion, producerUpdatesAllowed, setActiveConsumer, setAlternateWeakRefImpl, setPostSignalSetFn, setThrowInvalidWriteToSignalError, signalSetFn, signalUpdateFn };
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