/**
 * Fixed-ceiling delta reader for realtime vault sync v2.
 *
 * A drain deliberately has two request shapes: its first request has the
 * recipient cursor and later requests have only the opaque page token.  This
 * makes it impossible for the client to accidentally turn a fixed-H drain
 * into a new high-water request while it is following a page chain.  Applying
 * a page (and making its cursor durable) belongs to U54; this module does not
 * persist or advance a cursor itself.
 */
import type { CandidateFetch, CandidateTransportAuthorization } from "./candidate-uploader.js";
export type DeltaOperation = "upsert" | "delete";
export interface DeltaRecord {
    deltaId: string;
    canonicalPath: string;
    operation: DeltaOperation;
    versionId: string | null;
    /** Source facts decide regular-file versus symlink application in U54. */
    source: {
        kind: "regular" | "symlink";
        mode: number;
    } | null;
}
export interface DeltaPage {
    /** Immutable recipient-bound high-water cursor for every page in a drain. */
    untilCursor: string;
    /** A hidden projection page is valid: `deltas` may be empty while this exists. */
    nextPageToken: string | null;
    deltas: readonly DeltaRecord[];
}
export interface DeltaClientOptions {
    apiUrl: string;
    fetchImpl?: CandidateFetch;
    now?: () => number;
    authorizationTimeoutMs?: number;
}
export interface DeltaDrainRequest {
    authorization: CandidateTransportAuthorization;
    scopeHandle: string;
    scopeRevision: string;
    cursor: string;
    /** The server chooses the effective page size; this is merely its bounded request limit. */
    limit: number;
}
export interface DeltaDrainResult {
    untilCursor: string;
    pages: number;
    deltas: number;
}
export declare class DeltaGapError extends Error {
    constructor(message?: string);
}
export declare class CursorRetiredError extends Error {
    constructor(message?: string);
}
/**
 * The V2 reader has no LIST capability or dependency.  Its callback is
 * awaited before another page is requested, so a future durable applier can
 * make every page's effects and cursor durable before the next page arrives.
 */
export declare class DeltaClient {
    private readonly apiUrl;
    private readonly fetchImpl;
    private readonly now;
    private readonly timeoutMs;
    constructor(options: DeltaClientOptions);
    drain(request: DeltaDrainRequest, consume: (page: DeltaPage) => Promise<void>): Promise<DeltaDrainResult>;
    private assertRequest;
    private getPage;
    private assertLease;
    private request;
}
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