const DB_NAME = 'shine-ui-messages-v1';
const DB_VERSION = 3;
const STORE_MESSAGES = 'messages_by_profile';
const LEGACY_STORE_MESSAGES = 'messages';
const ACTIVE_PROFILE_STORAGE_KEY = 'shine-ui-active-profile-v1';
const LEGACY_SESSION_STORAGE_KEY = 'shine-ui-current-session-v1';

function normalizeOwnerLogin(value) {
  return String(value || '').trim().toLowerCase();
}

function storageKey(ownerLogin, messageKey) {
  const owner = normalizeOwnerLogin(ownerLogin);
  const key = String(messageKey || '').trim();
  return owner && key ? `${owner}|${key}` : '';
}

function migrationOwnerLogin() {
  try {
    const active = normalizeOwnerLogin(localStorage.getItem(ACTIVE_PROFILE_STORAGE_KEY));
    if (active) return active;
    const legacy = JSON.parse(localStorage.getItem(LEGACY_SESSION_STORAGE_KEY) || '{}');
    return normalizeOwnerLogin(legacy?.login);
  } catch {
    return '';
  }
}

function ensureIndexes(store) {
  if (!store.indexNames.contains('by_chat')) store.createIndex('by_chat', 'chatId', { unique: false });
  if (!store.indexNames.contains('by_ts')) store.createIndex('by_ts', 'ts', { unique: false });
  if (!store.indexNames.contains('by_owner')) store.createIndex('by_owner', 'ownerLogin', { unique: false });
}

function openDb() {
  return new Promise((resolve, reject) => {
    const request = indexedDB.open(DB_NAME, DB_VERSION);
    request.onupgradeneeded = () => {
      const db = request.result;
      let store;
      if (!db.objectStoreNames.contains(STORE_MESSAGES)) {
        store = db.createObjectStore(STORE_MESSAGES, { keyPath: 'storageKey' });
      } else {
        store = request.transaction.objectStore(STORE_MESSAGES);
      }
      ensureIndexes(store);

      // Однократная миграция старого single-profile кэша в пространство текущего профиля.
      if (db.objectStoreNames.contains(LEGACY_STORE_MESSAGES)) {
        const owner = migrationOwnerLogin();
        if (owner) {
          const legacy = request.transaction.objectStore(LEGACY_STORE_MESSAGES);
          const cursorReq = legacy.openCursor();
          cursorReq.onsuccess = () => {
            const cursor = cursorReq.result;
            if (!cursor) return;
            const row = cursor.value || {};
            const messageKey = String(row.messageKey || '').trim();
            const rowOwner = normalizeOwnerLogin(row.ownerLogin) || owner;
            const key = storageKey(rowOwner, messageKey);
            if (key) store.put({ ...row, ownerLogin: rowOwner, storageKey: key });
            cursor.continue();
          };
        }
      }
    };
    request.onsuccess = () => resolve(request.result);
    request.onerror = () => reject(request.error || new Error('IndexedDB open failed'));
  });
}

async function withStore(mode, callback) {
  const db = await openDb();
  try {
    return await new Promise((resolve, reject) => {
      const tx = db.transaction(STORE_MESSAGES, mode);
      const store = tx.objectStore(STORE_MESSAGES);
      const result = callback(store, tx);
      tx.oncomplete = () => resolve(result);
      tx.onerror = () => reject(tx.error || new Error('IndexedDB transaction failed'));
      tx.onabort = () => reject(tx.error || new Error('IndexedDB transaction aborted'));
    });
  } finally {
    db.close();
  }
}

export async function putStoredMessage(record) {
  if (!record || !record.messageKey) return;
  const ownerLogin = normalizeOwnerLogin(record.ownerLogin);
  const key = storageKey(ownerLogin, record.messageKey);
  if (!key) return;
  await withStore('readwrite', (store) => {
    store.put({ ...record, ownerLogin, storageKey: key });
  });
}

export async function deleteStoredMessage(messageKey, ownerLogin = '') {
  const key = storageKey(ownerLogin, messageKey);
  if (!key) return;
  await withStore('readwrite', (store) => {
    store.delete(key);
  });
}

export async function listStoredMessages(ownerLogin = '') {
  const owner = normalizeOwnerLogin(ownerLogin);
  if (!owner) return [];
  return withStore('readonly', (store) => new Promise((resolve, reject) => {
    const req = store.index('by_owner').getAll(owner);
    req.onsuccess = () => resolve(Array.isArray(req.result) ? req.result : []);
    req.onerror = () => reject(req.error || new Error('IndexedDB getAll by owner failed'));
  }));
}

export async function clearStoredMessages(ownerLogin = '') {
  const owner = normalizeOwnerLogin(ownerLogin);
  if (!owner) {
    await new Promise((resolve, reject) => {
      const request = indexedDB.deleteDatabase(DB_NAME);
      request.onsuccess = () => resolve();
      request.onerror = () => reject(request.error || new Error('IndexedDB delete failed'));
      request.onblocked = () => reject(new Error('IndexedDB delete blocked'));
    });
    return;
  }
  await withStore('readwrite', (store) => new Promise((resolve, reject) => {
    const index = store.index('by_owner');
    const req = index.openKeyCursor(IDBKeyRange.only(owner));
    req.onsuccess = () => {
      const cursor = req.result;
      if (!cursor) {
        resolve();
        return;
      }
      store.delete(cursor.primaryKey);
      cursor.continue();
    };
    req.onerror = () => reject(req.error || new Error('IndexedDB clear by owner failed'));
  }));
}