// State, den der Service-Worker per postMessage befüllt. Die App
// spiegelt den Sync-Fortschritt im SyncIndicator.
export type SyncState =
  | { kind: 'idle' }
  | { kind: 'syncing'; current: number; total: number }
  | { kind: 'error'; message: string };

export type SWMessage =
  | { type: 'sync-start'; total: number }
  | { type: 'sync-progress'; current: number; total: number }
  | { type: 'sync-done'; lastSynced: number }
  | { type: 'sync-error'; message: string };

const STORAGE_KEY = 'kochwas.sw.lastSynced';

function loadLastSynced(): number | null {
  if (typeof localStorage === 'undefined') return null;
  const raw = localStorage.getItem(STORAGE_KEY);
  if (!raw) return null;
  const n = Number(raw);
  return Number.isFinite(n) ? n : null;
}

function saveLastSynced(ts: number): void {
  if (typeof localStorage === 'undefined') return;
  localStorage.setItem(STORAGE_KEY, String(ts));
}

class SyncStatusStore {
  state = $state<SyncState>({ kind: 'idle' });
  lastSynced = $state<number | null>(loadLastSynced());

  handle(msg: SWMessage): void {
    switch (msg.type) {
      case 'sync-start':
        this.state = { kind: 'syncing', current: 0, total: msg.total };
        break;
      case 'sync-progress':
        this.state = { kind: 'syncing', current: msg.current, total: msg.total };
        break;
      case 'sync-done':
        this.state = { kind: 'idle' };
        this.lastSynced = msg.lastSynced;
        saveLastSynced(msg.lastSynced);
        break;
      case 'sync-error':
        this.state = { kind: 'error', message: msg.message };
        break;
    }
  }
}

export const syncStatus = new SyncStatusStore();