/**
 * WikiHistoryService — per-page revision history (who changed what).
 *
 * Before a page is overwritten, superseded, accepted from a proposal, or
 * deleted, its previous content is snapshotted to
 * `<vault>/.wiki-history/<page path>/<ISO>.md` together with the author.
 * That gives multi-writer vaults (several teachers, several agents) an
 * audit trail without depending on the vault living in a git repository.
 * Capped per page; oldest snapshots roll off.
 *
 * @module services/wiki/wiki-history.service
 */
/** One snapshot. */
export interface WikiRevision {
    at: string;
    /** Who made the change that replaced this content. */
    author: string;
    /** `write` | `supersede` | `accept_proposal` | `delete` */
    action: string;
    bytes: number;
    file: string;
}
/**
 * Snapshots prior page content under `.wiki-history/`.
 */
export declare class WikiHistoryService {
    private readonly now;
    private static instance;
    private readonly logger;
    constructor(now?: () => Date);
    static getInstance(): WikiHistoryService;
    /** Test-only reset. */
    static _resetForTesting(): void;
    /**
     * Snapshot the current content of a page before it changes. No-op when
     * the page does not exist yet. Never throws.
     *
     * @param vaultPath - Vault root
     * @param relativePath - Vault-relative page path
     * @param author - Session/user making the change
     * @param action - What is about to happen
     * @returns The revision written, or null
     */
    snapshot(vaultPath: string, relativePath: string, author: string, action: string): Promise<WikiRevision | null>;
    /**
     * List revisions of a page, newest first.
     *
     * @param vaultPath - Vault root
     * @param relativePath - Vault-relative page path
     * @returns Revisions
     */
    list(vaultPath: string, relativePath: string): Promise<WikiRevision[]>;
    /**
     * Read one revision's content (meta line stripped).
     *
     * @param file - Absolute snapshot file (from {@link list})
     * @returns Content
     */
    read(file: string): Promise<string>;
    private historyDir;
    private prune;
}
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