/**
 * Home bootstrap reveal policy.
 *
 * The loading screen owns every wait before the page appears. Phase "account"
 * fetches account, model catalog and the session list; phase "prepare" fetches
 * the starter questions, today's starlanguage and the rectification entry
 * summary in parallel. The page is revealed once every applicable item has
 * settled, or when the prepare budget runs out — never with a spinner inside.
 */

export type BootstrapPhase = "account" | "prepare";

export const BOOTSTRAP_PREPARE_TIMEOUT_MS = 4000;
export const SESSION_PREFETCH_COUNT = 5;

export type BootstrapPrepareState = Readonly<{
  profileComplete: boolean;
  onboardingSettled: boolean;
  dailyStarlanguageApplicable: boolean;
  dailyStarlanguageSettled: boolean;
  entrySummarySettled: boolean;
}>;

export function bootstrapPrepareSettled(state: BootstrapPrepareState): boolean {
  if (!state.entrySummarySettled) return false;
  if (state.profileComplete && !state.onboardingSettled) return false;
  if (state.dailyStarlanguageApplicable && !state.dailyStarlanguageSettled) return false;
  return true;
}

export function bootstrapRevealDelayMs(now: number, prepareStartedAt: number | null, settled: boolean): number {
  if (settled) return 0;
  if (prepareStartedAt === null) return BOOTSTRAP_PREPARE_TIMEOUT_MS;
  return Math.max(0, BOOTSTRAP_PREPARE_TIMEOUT_MS - (now - prepareStartedAt));
}

export function bootstrapLoadingCopy(phase: BootstrapPhase): Readonly<{ title: string; detail: string }> {
  return phase === "prepare"
    ? { title: "正在准备对话", detail: "整理推荐问题、今日星语与对话记录" }
    : { title: "正在载入账户", detail: "同步个人资料与对话记录" };
}

export type PrefetchableSession = Readonly<{
  id: string;
  sessionType: string;
  messagesHydrated?: boolean;
}>;

export function sessionIdsToPrefetch(
  sessions: readonly PrefetchableSession[],
  activeSessionId: string,
  limit = SESSION_PREFETCH_COUNT,
): string[] {
  const ids: string[] = [];
  for (const session of sessions) {
    if (ids.length >= limit) break;
    if (session.id === activeSessionId) continue;
    if (session.messagesHydrated) continue;
    if (session.sessionType !== "consultation") continue;
    ids.push(session.id);
  }
  return ids;
}