/**
 * In-memory HeadRegistry implementation.
 *
 * Preserves the existing HeadRegistry behavior (pure in-memory, no disk I/O)
 * while conforming to the IHeadRegistry interface. Mutating methods return
 * resolved Promises for interface compatibility with persistent implementations.
 *
 * Use `createIsolated()` for test scenarios that need an independent registry.
 */
import type { DeferredHeadUpdate, IHeadRegistry } from '../interfaces/storage/headRegistry';
import type { HeadRecord } from '../interfaces/storage/headRegistryDriver';
export declare class InMemoryHeadRegistry implements IHeadRegistry {
    private readonly heads;
    private readonly timestamps;
    private readonly deferred;
    private readonly changeListeners;
    private makeKey;
    getHead(dbName: string, collectionName: string): string | undefined;
    setHead(dbName: string, collectionName: string, blockId: string): Promise<void>;
    removeHead(dbName: string, collectionName: string): Promise<void>;
    clear(): Promise<void>;
    load(): Promise<void>;
    getAllHeads(): Map<string, string>;
    getHeadTimestamp(dbName: string, collectionName: string): Date | undefined;
    mergeHeadUpdate(dbName: string, collectionName: string, blockId: string, timestamp: Date): Promise<boolean>;
    private notifyHeadChange;
    onHeadChange(dbName: string, collectionName: string, callback: (blockId: string) => void): () => void;
    deferHeadUpdate(dbName: string, collectionName: string, blockId: string, timestamp: Date): Promise<void>;
    applyDeferredUpdates(blockId: string): Promise<number>;
    getDeferredUpdates(): DeferredHeadUpdate[];
    exportSnapshot(): ReadonlyMap<string, HeadRecord>;
    mergeSnapshot(snapshot: Iterable<readonly [string, HeadRecord]>): Promise<{
        merged: number;
        skipped: number;
    }>;
    /**
     * Factory method that creates an independent InMemoryHeadRegistry instance.
     * Useful for tests that need isolated state.
     */
    static createIsolated(): InMemoryHeadRegistry;
}
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