/**
 * Locking and id allocation for a project's tickets folder
 * (specs/2026-09-28-project-tickets.md §2 "Concurrency").
 *
 * Two layers, because writers live in more than one process (the backend,
 * a `crewly tickets migrate` run, a second backend on the same machine):
 * - an in-process operation lock keyed on the folder, so concurrent async
 *   callers in one process queue up instead of polling the lockfile;
 * - a lockfile created with `O_EXCL` (`wx`), so other processes wait too. A
 *   lockfile older than {@link PROJECT_TICKET_CONSTANTS.LOCK_STALE_MS} was left
 *   by a crashed writer and is taken over.
 *
 * @module services/project-tickets/ticket-folder-lock
 */
/** Counter file shape. */
export interface TicketCounter {
    prefix: string;
    next: number;
}
/**
 * Run `fn` while holding the folder's in-process and cross-process locks.
 * Creates the folder (and its own `.gitignore` for the lock and temp files)
 * when missing.
 *
 * @param dir - Absolute tickets folder
 * @param fn - Critical section
 * @returns Whatever `fn` returns
 * @throws When the lock cannot be taken, or whatever `fn` throws
 *
 * @example
 * ```typescript
 * await withTicketFolderLock(dir, async () => writeTicket(...));
 * ```
 */
export declare function withTicketFolderLock<T>(dir: string, fn: () => Promise<T>): Promise<T>;
/**
 * Derive a ticket id prefix from a project name: up to four letters/digits,
 * preferring word initials for multi-word names.
 *
 * @param projectName - Project display name
 * @returns Uppercase prefix (never empty)
 *
 * @example
 * ```typescript
 * derivePrefix('crewly');           // 'CREW'
 * derivePrefix('Steam Fun Portal'); // 'SFP'
 * ```
 */
export declare function derivePrefix(projectName: string): string;
/**
 * Read the counter file (missing or corrupt → null).
 *
 * @param dir - Tickets folder
 * @returns Counter, or null
 */
export declare function readCounter(dir: string): Promise<TicketCounter | null>;
/**
 * Allocate the next ticket id. MUST be called while holding
 * {@link withTicketFolderLock} for the same folder.
 *
 * Takes `max(counter.next, highest used + 1)` so ids that arrive through a
 * git merge are never reused, then advances the counter.
 *
 * @param dir - Tickets folder
 * @param projectName - Used to derive the prefix the first time
 * @returns The new id, e.g. `CREW-13`
 */
export declare function allocateTicketId(dir: string, projectName: string): Promise<string>;
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