// public/js/admin/cacheSync.js

function mapById(arr) {
  const map = new Map();

  for (const item of arr || []) {
    if (item && item.id != null) {
      map.set(String(item.id), item);
    }
  }

  return map;
}

function readLocalArray(cacheKey) {
  try {
    const raw = localStorage.getItem(cacheKey);
    const arr = raw ? JSON.parse(raw) : [];

    return Array.isArray(arr) ? arr : [];
  } catch (err) {
    console.warn(`[AdminCacheSync] errore lettura ${cacheKey}:`, err.message);
    return [];
  }
}

function writeLocalArray(cacheKey, arr) {
  const safeArr = Array.isArray(arr) ? arr : [];
  localStorage.setItem(cacheKey, JSON.stringify(safeArr));
}

function removeItemFromLocalCache(cacheKey, id) {
  if (id == null) {
    return {
      ok: false,
      reason: "missing id",
      cacheKey
    };
  }

  const arr = readLocalArray(cacheKey);
  const before = arr.length;

  const next = arr.filter(item => String(item.id) !== String(id));

  writeLocalArray(cacheKey, next);

  return {
    ok: true,
    cacheKey,
    id,
    before,
    after: next.length,
    removed: before - next.length
  };
}

function removePhotoFromCache(id) {
  return removeItemFromLocalCache("photosCache", id);
}

function removeActivityFromCache(id) {
  return removeItemFromLocalCache("activitiesCache", id);
}

async function progressiveSyncPhotosCacheFromAdmin() {
  const lastSync = localStorage.getItem("lastSyncPhotos");
  const localPhotos = readLocalArray("photosCache");

  // Se non ho cache o lastSync, faccio full load foto
  if (!lastSync || localPhotos.length === 0) {
    const photos = await apiGet("/photos");

    writeLocalArray("photosCache", photos);
    localStorage.setItem("lastSyncPhotos", new Date().toISOString());

    return {
      mode: "photos",
      type: "full",
      count: Array.isArray(photos) ? photos.length : 0
    };
  }

  const changed = await apiGet(
    `/photos/changes?since=${encodeURIComponent(lastSync)}`
  );

  const hardDeletedRes = await apiGet(
    `/photos/deleted_hard?since=${encodeURIComponent(lastSync)}`
  );

  const hardDeleted = hardDeletedRes.deleted || [];
  const map = mapById(localPhotos);

  for (const p of changed || []) {
    if (p && p.id != null) {
      map.set(String(p.id), p);
    }
  }

  for (const d of hardDeleted || []) {
    if (d && d.id != null) {
      map.delete(String(d.id));
    }
  }

  const merged = Array.from(map.values());

  writeLocalArray("photosCache", merged);
  localStorage.setItem("lastSyncPhotos", new Date().toISOString());

  return {
    mode: "photos",
    type: "progressive",
    changed: Array.isArray(changed) ? changed.length : 0,
    hardDeleted: hardDeleted.length,
    count: merged.length
  };
}

async function progressiveSyncActivitiesCacheFromAdmin() {
  const lastSync = localStorage.getItem("lastSyncActivities");
  const localActivities = readLocalArray("activitiesCache");

  // Se non ho cache o lastSync, faccio full load attività
  if (!lastSync || localActivities.length === 0) {
    const activities = await apiGet("/activities");

    writeLocalArray("activitiesCache", activities);
    localStorage.setItem("lastSyncActivities", new Date().toISOString());

    return {
      mode: "activities",
      type: "full",
      count: Array.isArray(activities) ? activities.length : 0
    };
  }

  const changed = await apiGet(
    `/activities/changes?since=${encodeURIComponent(lastSync)}`
  );

  const hardDeletedRes = await apiGet(
    `/activities/deleted_hard?since=${encodeURIComponent(lastSync)}`
  );

  const hardDeleted = hardDeletedRes.deleted || [];
  const map = mapById(localActivities);

  for (const a of changed || []) {
    if (a && a.id != null) {
      map.set(String(a.id), a);
    }
  }

  for (const d of hardDeleted || []) {
    if (d && d.id != null) {
      map.delete(String(d.id));
    }
  }

  const merged = Array.from(map.values());

  writeLocalArray("activitiesCache", merged);
  localStorage.setItem("lastSyncActivities", new Date().toISOString());

  return {
    mode: "activities",
    type: "progressive",
    changed: Array.isArray(changed) ? changed.length : 0,
    hardDeleted: hardDeleted.length,
    count: merged.length
  };
}

// Export globale per uso negli altri file admin
window.AdminCacheSync = {
  progressiveSyncPhotosCacheFromAdmin,
  progressiveSyncActivitiesCacheFromAdmin,
  removePhotoFromCache,
  removeActivityFromCache
};