import type { RealTime } from "@deadhead/sim";

/** The server's only source of "now" (decision 0.5.18), so tests can control time. */
export type Clock = () => RealTime;

export const systemClock: Clock = () => Date.now();

/**
 * A clock that runs ahead of (or behind) its base clock by an adjustable offset.
 * The test-only clock-offset endpoint moves it; production never does (Step 7.2).
 */
export interface OffsetClock {
  now: Clock;
  offsetMs(): number;
  setOffset(ms: number): void;
  /** Converts a time on this clock to the base clock, e.g. for pg-boss timers. */
  toBase(time: RealTime): RealTime;
}

export function createOffsetClock(base: Clock): OffsetClock {
  let offset = 0;
  return {
    now: () => base() + offset,
    offsetMs: () => offset,
    setOffset: (ms) => {
      offset = ms;
    },
    toBase: (time) => time - offset,
  };
}