malice

export const ENGINE_CHANNEL = 'malice-engine';

export type HelloAction = 'ignore' | 'yield' | 'announce';

interface BuildStamp {

  seconds: number;

  tag: string;

}

function parseBuild(build: string): BuildStamp | null {

  const match = /^(\d+)-(.+)$/.exec(build);

  return match ? { seconds: Number(match[1]), tag: match[2] } : null;

}

/** Positive when `a` is newer than `b`, null when either is not a build id. */

export function compareBuilds(a: string, b: string): number | null {

  const left = parseBuild(a);

  const right = parseBuild(b);

  if (!left || !right) return null;

  if (left.seconds !== right.seconds) return left.seconds - right.seconds;

  return left.tag < right.tag ? -1 : left.tag > right.tag ? 1 : 0;

}

/**

 * What a worker of build `own` does on hearing a hello from build `other`.

 * A newer peer wins the store lock, so the worker yields. An older peer is

 * told to yield by repeating our own hello, which it will judge the same way.

 */

export function helloAction(own: string, other: string): HelloAction {

  const order = compareBuilds(other, own);

  if (order === null || order === 0) return 'ignore';

  return order > 0 ? 'yield' : 'announce';

}

export const RELOAD_GUARD_MS = 60_000;

/** A superseded tab reloads itself once, so a shell stuck on the old build cannot loop. */

export function mayAutoReload(now: number, lastReload: number | null): boolean {

  return lastReload === null || now - lastReload >= RELOAD_GUARD_MS;

}

export function retryDelay(attempt: number): number {

  return Math.min(1000 * 2 ** attempt, 8000);

}