import { routes } from "@lodestar/api";
import { CachedBeaconStateAllForks } from "@lodestar/state-transition";
import { RootHex } from "@lodestar/types";
import { Metrics } from "../../metrics/index.js";
import { BlockStateCache } from "./types.js";
export type FIFOBlockStateCacheOpts = {
    maxBlockStates?: number;
};
/**
 * Given `maxSkipSlots` = 32 and `DEFAULT_EARLIEST_PERMISSIBLE_SLOT_DISTANCE` = 32, lodestar doesn't need to
 * reload states in order to process a gossip block.
 *
 * |-----------------------------------------------|-----------------------------------------------|
 *                 maxSkipSlots                      DEFAULT_EARLIEST_PERMISSIBLE_SLOT_DISTANCE    ^
 *                                                                                             clock slot
 */
export declare const DEFAULT_MAX_BLOCK_STATES = 64;
/**
 * New implementation of BlockStateCache that keeps the most recent n states consistently
 *  - Maintain a linked list (FIFO) with special handling for head state, which is always the first item in the list
 *  - Prune per add() instead of per checkpoint so it only keeps n historical states consistently, prune from tail
 *  - No need to prune per finalized checkpoint
 *
 * Given this block tree with Block 11 as head:
 * ```
         Block 10
           |
     +-----+-----+
     |           |
  Block 11   Block 12
     ^           |
     |           |
    head       Block 13
 * ```
 * The maintained key order would be: 11 -> 13 -> 12 -> 10, and state 10 will be pruned first.
 */
export declare class FIFOBlockStateCache implements BlockStateCache {
    /**
     * Max number of states allowed in the cache
     */
    readonly maxStates: number;
    private readonly cache;
    /**
     * Key order to implement FIFO cache
     */
    private readonly keyOrder;
    private readonly metrics;
    constructor(opts: FIFOBlockStateCacheOpts, { metrics }: {
        metrics?: Metrics | null;
    });
    /**
     * Set a state as head, happens when importing a block and head block is changed.
     */
    setHeadState(item: CachedBeaconStateAllForks | null): void;
    /**
     * Get a seed state for state reload, this could be any states. The goal is to have the same
     * base merkle tree for all BeaconState objects across application.
     * See packages/state-transition/src/util/loadState/loadState.ts for more detail
     */
    getSeedState(): CachedBeaconStateAllForks;
    /**
     * Get a state from this cache given a state root hex.
     */
    get(rootHex: RootHex): CachedBeaconStateAllForks | null;
    /**
     * Add a state to this cache.
     * @param isHead if true, move it to the head of the list. Otherwise add to the 2nd position.
     * In importBlock() steps, normally it'll call add() with isHead = false first. Then call setHeadState() to set the head.
     */
    add(item: CachedBeaconStateAllForks, isHead?: boolean): void;
    get size(): number;
    /**
     * Prune the cache from tail to keep the most recent n states consistently.
     * The tail of the list is the oldest state, in case regen adds back the same state,
     * it should stay next to head so that it won't be pruned right away.
     * The FIFO cache helps with this.
     */
    prune(lastAddedKey: string): void;
    /**
     * No need for this implementation
     * This is only to conform to the old api
     */
    deleteAllBeforeEpoch(): void;
    /**
     * ONLY FOR DEBUGGING PURPOSES. For lodestar debug API.
     */
    clear(): void;
    /** ONLY FOR DEBUGGING PURPOSES. For lodestar debug API */
    dumpSummary(): routes.lodestar.StateCacheItem[];
    getStates(): IterableIterator<CachedBeaconStateAllForks>;
    /**
     * For unit test only.
     */
    dumpKeyOrder(): string[];
}
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