import type { LoggerWrapper } from "./ConfigCatLogger";
import { ProjectConfig } from "./ProjectConfig";
/** Defines the interface used by the ConfigCat SDK to store and retrieve downloaded config data. */
export interface IConfigCatCache {
    /**
     * Stores a data item into the cache.
     * @param key A string identifying the data item.
     * @param value The data item to cache.
     */
    set(key: string, value: string): Promise<void> | void;
    /**
     * Retrieves a data item from the cache.
     * @param key A string identifying the value.
     * @returns The cached data item or `null` or `undefined` if there is none.
     */
    get(key: string): Promise<string | null | undefined> | string | null | undefined;
}
/** @remarks Unchanged config is returned as is, changed config is wrapped in an array so we can distinguish between the two cases. */
export declare type CacheSyncResult = ProjectConfig | [changedConfig: ProjectConfig];
export interface IConfigCache {
    set(key: string, config: ProjectConfig): Promise<void> | void;
    get(key: string): Promise<CacheSyncResult> | CacheSyncResult;
    getInMemory(): ProjectConfig;
}
export declare class InMemoryConfigCache implements IConfigCache {
    private cachedConfig;
    set(_key: string, config: ProjectConfig): void;
    get(_key: string): ProjectConfig;
    getInMemory(): ProjectConfig;
}
export declare class ExternalConfigCache implements IConfigCache {
    private readonly cache;
    private readonly logger;
    private cachedConfig;
    private cachedSerializedConfig;
    constructor(cache: IConfigCatCache, logger: LoggerWrapper);
    set(key: string, config: ProjectConfig): Promise<void>;
    private updateCachedConfig;
    get(key: string): Promise<CacheSyncResult> | CacheSyncResult;
    getInMemory(): ProjectConfig;
}
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