/**
 * Feature flags — provider-neutral interface + an in-memory implementation.
 *
 * Vendor SDKs (LaunchDarkly, Flagsmith, Statsig, GrowthBook, OpenFeature) all
 * expose roughly the same shape: `isEnabled / variation / refresh`. The
 * `FeatureFlagAdapter` interface here is the common-denominator surface, and
 * `fromVendor()` wraps any duck-typed SDK into it without us depending on the
 * SDK package.
 */
export interface FlagContext {
    /** Stable user id when known. Used by sticky bucketing. */
    userId?: string;
    /** Free-form attributes for vendor-side targeting (locale, plan, etc.). */
    attributes?: Record<string, unknown>;
}
export interface FeatureFlagAdapter {
    /** Boolean flag. */
    isEnabled(flag: string, ctx?: FlagContext): boolean;
    /** Multi-variate / typed variation. */
    variation<T>(flag: string, defaultValue: T, ctx?: FlagContext): T;
    /** Optional async refresh (poll vendor, swap manifest). */
    refresh?(): Promise<void>;
    /** Subscribe to flag-set updates. Returns unsubscribe. */
    subscribe?(listener: () => void): () => void;
}
export type InMemoryFlagsValue = boolean | string | number | Record<string, unknown>;
export interface InMemoryFlagsOptions {
    flags?: Record<string, InMemoryFlagsValue>;
    /** Optional per-user override map: userId → { flag → value }. */
    overrides?: Record<string, Record<string, InMemoryFlagsValue>>;
}
export declare class InMemoryFlags implements FeatureFlagAdapter {
    private flags;
    private overrides;
    private listeners;
    constructor(opts?: InMemoryFlagsOptions);
    set(flag: string, value: InMemoryFlagsValue): void;
    setOverride(userId: string, flag: string, value: InMemoryFlagsValue): void;
    clearOverride(userId: string, flag?: string): void;
    replaceAll(flags: Record<string, InMemoryFlagsValue>): void;
    isEnabled(flag: string, ctx?: FlagContext): boolean;
    variation<T>(flag: string, defaultValue: T, ctx?: FlagContext): T;
    subscribe(listener: () => void): () => void;
    private resolve;
    private notify;
}
/**
 * Wrap a vendor SDK client into `FeatureFlagAdapter`. We use a *duck-typed*
 * `client` so JORVEL doesn't take a hard dependency on any vendor package.
 *
 * Expected duck:
 *   - `variation(flag, ctx?, defaultValue?)` returning any
 *   - or `boolVariation(flag, ctx?, defaultValue?)` for the boolean fast path
 *
 * Provide your own `toClientContext` if the SDK takes a custom user shape.
 */
export interface VendorClientLike {
    variation?: (flag: string, ctxOrDefault?: unknown, maybeDefault?: unknown) => unknown;
    boolVariation?: (flag: string, ctxOrDefault?: unknown, maybeDefault?: unknown) => boolean;
}
export interface FromVendorOptions {
    /** Convert JORVEL context to whatever the SDK expects (e.g. `{ kind: 'user', key }`). */
    toClientContext?: (ctx: FlagContext | undefined) => unknown;
}
export declare function fromVendor(client: VendorClientLike, opts?: FromVendorOptions): FeatureFlagAdapter;
export declare function setFeatureFlags(adapter: FeatureFlagAdapter): void;
export declare function getFeatureFlags(): FeatureFlagAdapter | undefined;
/** Convenience — returns `false` when no adapter is registered. */
export declare function isFeatureEnabled(flag: string, ctx?: FlagContext): boolean;
/** Convenience — returns `defaultValue` when no adapter is registered. */
export declare function featureVariation<T>(flag: string, defaultValue: T, ctx?: FlagContext): T;
/** @internal — testing */
export declare function _resetFeatureFlags(): void;
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