frontend/src/utils/tabSession.ts

const SESSION_PREFIX = "masters_toolkit_tab_session_v2:";
const MAX_SESSION_CHARS = 850_000;
const SAVE_DEBOUNCE_MS = 220;
const saveTimers = new Map<string, number>();
const pendingSerialized = new Map<string, string>();

export function loadTabSession<T>(tabKey: string): T | null {
  if (typeof window === "undefined") return null;
  try {
    const raw = window.localStorage.getItem(`${SESSION_PREFIX}${tabKey}`);
    if (!raw) return null;
    return JSON.parse(raw) as T;
  } catch {
    return null;
  }
}

export function saveTabSession<T>(tabKey: string, value: T): boolean {
  if (typeof window === "undefined") return false;
  try {
    const serialized = JSON.stringify(value);
    if (serialized.length > MAX_SESSION_CHARS) return false;
    window.localStorage.setItem(`${SESSION_PREFIX}${tabKey}`, serialized);
    return true;
  } catch {
    return false;
  }
}

export function saveTabSessionDebounced<T>(tabKey: string, value: T, debounceMs = SAVE_DEBOUNCE_MS): void {
  if (typeof window === "undefined") return;
  try {
    const serialized = JSON.stringify(value);
    if (serialized.length > MAX_SESSION_CHARS) return;
    pendingSerialized.set(tabKey, serialized);
    const prev = saveTimers.get(tabKey);
    if (typeof prev === "number") window.clearTimeout(prev);
    const t = window.setTimeout(() => {
      const payload = pendingSerialized.get(tabKey);
      if (!payload) return;
      try {
        window.localStorage.setItem(`${SESSION_PREFIX}${tabKey}`, payload);
      } catch {
        // ignore
      } finally {
        pendingSerialized.delete(tabKey);
        saveTimers.delete(tabKey);
      }
    }, Math.max(80, debounceMs));
    saveTimers.set(tabKey, t);
  } catch {
    // ignore
  }
}

export function clearTabSession(tabKey: string): void {
  if (typeof window === "undefined") return;
  try {
    const pending = saveTimers.get(tabKey);
    if (typeof pending === "number") {
      window.clearTimeout(pending);
      saveTimers.delete(tabKey);
    }
    pendingSerialized.delete(tabKey);
    window.localStorage.removeItem(`${SESSION_PREFIX}${tabKey}`);
  } catch {
    // ignore
  }
}