/**
 * Lifecycle vocabulary and timing calculators shared by the durable task
 * ledger and its diagnostics/metrics consumers.
 *
 * The `op:queued:`/`op:inflight:`/`op:resolved:`/`op:dead-letter:` record
 * shapes and type guards this module once exported alongside these
 * calculators are gone: WFT-22 replaced the key scheme with the durable
 * task ledger (`task-ledger.ts`), and WFT-24 migrated `get-task-diagnostics.ts`
 * (the last production reader of those legacy shapes) onto the ledger.
 * What remains is still load-bearing: `TaskLifecycleFields` and
 * `TaskRequeueReason` back the ledger's own record types, and the
 * queue-latency, execution-latency, and heartbeat-staleness calculators
 * back `task-metrics.ts` and the ledger diagnostics.
 *
 * @module task-state
 */
/** Why a task was requeued before another dispatch attempt. */
export type TaskRequeueReason = 'visibility-timeout' | 'worker-disconnect';
/** Lifecycle evidence persisted with task records for diagnostics. */
export interface TaskLifecycleFields {
    /** First time this operation entered a task queue. */
    firstQueuedAt?: number | undefined;
    /** Most recent time this operation entered a task queue. */
    lastQueuedAt?: number | undefined;
    /** Most recent time this operation was dispatched to a worker. */
    lastDispatchedAt?: number | undefined;
    /** Time this operation started executing on a worker when knowable. */
    startedAt?: number | undefined;
    /** Time this operation reached a terminal task state. */
    completedAt?: number | undefined;
    /** Most recent worker heartbeat observed for this operation. */
    lastHeartbeatAt?: number | undefined;
    /** Number of retry attempts after the original attempt. */
    retryCount?: number | undefined;
    /** Number of times visibility/disconnect handling moved this task back to queued. */
    requeueCount?: number | undefined;
    /** Most recent reason this task moved back to queued. */
    lastRequeueReason?: TaskRequeueReason | undefined;
}
/**
 * The subset of {@link TaskLifecycleFields} the queue-latency, execution-latency,
 * and heartbeat-staleness calculations actually read. Deliberately narrower
 * than `TaskLifecycleFields` so these calculations also accept the durable
 * remote task ledger's records (`RemoteTaskLeased`, `RemoteTaskQueued` —
 * WFT-22), which carry the same timing fields but a free-text
 * `lastRequeueReason` rather than the fixed {@link TaskRequeueReason} enum.
 */
export type TaskTimingFields = Readonly<{
    lastQueuedAt?: number | undefined;
    lastDispatchedAt?: number | undefined;
    startedAt?: number | undefined;
    lastHeartbeatAt?: number | undefined;
}>;
export declare function calculateQueueLatencyMs(record: TaskTimingFields): number | undefined;
export declare function calculateExecutionLatencyMs(record: TaskTimingFields, completedAt: number): number | undefined;
export declare function calculateHeartbeatAgeMs(record: TaskTimingFields & {
    deadline?: number | undefined;
}, currentTime: number): number | undefined;
export declare function isHeartbeatStale(record: TaskTimingFields & {
    deadline?: number | undefined;
}, currentTime: number, staleAfterMs: number): boolean;