/**
 * In-memory key index for O(1) lookups.
 *
 * Maps keys to their location in the data file. This index is
 * rebuilt from the WAL on startup and updated after each write.
 */
import type { Wal } from './wal';
import type { RecordLocation, WalEntry, OpType } from './types';
export interface BuildFromWalResult {
    index: KeyIndex;
    maxSequence: bigint;
}
export declare class KeyIndex {
    private readonly entries;
    private constructor();
    /**
     * Create an empty index.
     */
    static create(): KeyIndex;
    /**
     * Build the index from a WAL by replaying all entries.
     * Also reads keys from the data file since WAL only stores hashes.
     * Returns both the index and the maximum sequence number seen.
     */
    static buildFromWal(wal: Wal, dataPath: string): Promise<BuildFromWalResult>;
    /**
     * Apply a WAL entry to update the index.
     */
    applyEntry(key: string, entry: WalEntry): void;
    /**
     * Apply a location update directly (used after writes).
     */
    apply(key: string, location: RecordLocation, op: OpType): void;
    /**
     * Get the location of a key.
     */
    get(key: string): RecordLocation | undefined;
    /**
     * Check if a key exists.
     */
    has(key: string): boolean;
    /**
     * Delete a key from the index.
     */
    delete(key: string): boolean;
    /**
     * Get all keys in the index.
     */
    keys(): IterableIterator<string>;
    /**
     * Iterate over all entries as [key, location] pairs.
     */
    locations(): IterableIterator<[string, RecordLocation]>;
    /**
     * Get the number of entries in the index.
     */
    count(): number;
}
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