/**
 * Result of probing a port for an existing bridge server.
 * `null` if nothing healthy responded.
 */
export type PingResult = {
    ok: boolean;
    version: string;
    cwd?: string;
};
/**
 * The action `serve` should take after probing the requested port.
 *
 * - `start`   — no bridge is listening; bind a fresh server on this port.
 * - `reuse`   — a healthy bridge on the same version is already running; do not bind.
 * - `replace` — a healthy bridge on a different version is running; terminate it, then bind.
 */
export type StartActionKind = 'start' | 'reuse' | 'replace';
export type StartAction = {
    kind: StartActionKind;
    reason: string;
};
/**
 * Pure decision function: given the result of probing the target port with a
 * `/api/v1/ping` request, decide whether to start, reuse, or replace.
 *
 * Keeping this pure (no I/O) makes the core singleton policy directly testable
 * without spawning real servers.
 *
 * @param ping     parsed ping payload, or `null` if nothing healthy responded
 * @param version  the current plugin version
 */
export declare function decideStartAction(ping: PingResult | null, version: string): StartAction;
/**
 * Probe a port for a healthy bridge server via `GET /api/v1/ping`.
 * Returns the parsed payload, or `null` when nothing healthy answers
 * (connection refused, timeout, non-2xx, or unparseable body).
 */
export declare function probeBridge(hostname: string, port: number): Promise<PingResult | null>;
/** Test seam: override the runtime dir so pidfile I/O can target a temp dir. */
export declare function setRuntimeDir(dir: string | undefined): void;
/** Stable pidfile path for a given port. */
export declare function pidfilePath(port: number): string;
/** Write `<pid>` for the given port. Best-effort: never throws. */
export declare function writePidfile(port: number, pid?: number): void;
/** Read the pid recorded for a port, or `null` if absent/unreadable/invalid. */
export declare function readPidfile(port: number): number | null;
/** Remove the pidfile for a port. Best-effort: never throws. */
export declare function removePidfile(port: number): void;
/** Whether a pid is alive. Uses signal 0 (no-op probe). */
export declare function isPidAlive(pid: number): boolean;
/**
 * Terminate a previously recorded bridge instance for `port` (SIGTERM).
 * Handles stale pidfiles (pid no longer alive). Returns `true` if a live
 * process was signalled, `false` otherwise.
 */
export declare function terminateRecordedBridge(port: number): boolean;