/**
 * DriverBackedHeadRegistry — IHeadRegistry implemented on top of IHeadRegistryDriver.
 *
 * Holds an in-memory cache for reads (getHead is synchronous per the interface).
 * Every mutation writes only the affected key via the driver (O(1) per write).
 * load() hydrates the cache by listing all keys and reading each one.
 *
 * This replaces both PersistentHeadRegistry (single-JSON-file on disk) and
 * CloudHeadRegistry (single-JSON-blob in cloud), which both did a full
 * serialize-all-heads rewrite on every mutation.
 */
import type { IWriteProof } from '../interfaces/auth/writeProof';
import type { DeferredHeadUpdate, IHeadRegistry } from '../interfaces/storage/headRegistry';
import type { HeadRecord, IHeadRegistryDriver } from '../interfaces/storage/headRegistryDriver';
export declare class DriverBackedHeadRegistry implements IHeadRegistry {
    private readonly heads;
    private readonly timestamps;
    private readonly deferred;
    private readonly changeListeners;
    protected readonly driver: IHeadRegistryDriver;
    constructor(driver: IHeadRegistryDriver);
    private makeKey;
    getHead(dbName: string, collectionName: string): string | undefined;
    setHead(dbName: string, collectionName: string, blockId: string, _writeProof?: IWriteProof): Promise<void>;
    removeHead(dbName: string, collectionName: string, _writeProof?: IWriteProof): 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;
    }>;
}
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