export interface RequestDeadline {
  readonly signal: AbortSignal;
  remainingMs(): number;
  dispose(): void;
}

/**
 * Convert an adapter-provided absolute epoch deadline into one abort signal.
 * The absolute form survives JSON-RPC transport time and prevents every stage
 * from accidentally receiving a fresh timeout budget.
 */
export function createRequestDeadline(
  deadlineAt: number,
  now: () => number = Date.now,
): RequestDeadline {
  const controller = new AbortController();
  const remainingMs = (): number => Math.max(0, deadlineAt - now());
  const initialRemaining = remainingMs();
  let timer: ReturnType<typeof setTimeout> | null = null;

  if (!Number.isFinite(deadlineAt) || initialRemaining <= 0) {
    controller.abort(new DOMException("request deadline exceeded", "TimeoutError"));
  } else {
    timer = setTimeout(() => {
      controller.abort(new DOMException("request deadline exceeded", "TimeoutError"));
    }, initialRemaining);
  }

  return {
    signal: controller.signal,
    remainingMs,
    dispose(): void {
      if (timer) clearTimeout(timer);
      timer = null;
    },
  };
}