/**
 * idb-storage.ts — Zustand-compatible async storage adapter using IndexedDB.
 *
 * Provides a drop-in replacement for localStorage that uses IndexedDB,
 * bypassing the 5MB storage limit for conversation data.
 *
 * Includes one-time migration from localStorage for the conversation store.
 */

import { openDB, type IDBPDatabase } from 'idb';
import { createLogger } from './logger';

const log = createLogger('IDBStorage');

// ---------------------------------------------------------------------------
// IndexedDB schema
// ---------------------------------------------------------------------------

const DB_NAME = 'zclaw-store';
const DB_VERSION = 1;
const STORE_NAME = 'keyvalue';

// localStorage key that holds existing conversation data
const CONVERSATION_LS_KEY = 'zclaw-conversation-storage';

// ---------------------------------------------------------------------------
// Database singleton
// ---------------------------------------------------------------------------

let dbPromise: Promise<IDBPDatabase> | null = null;

function getDB(): Promise<IDBPDatabase> {
  if (!dbPromise) {
    dbPromise = openDB(DB_NAME, DB_VERSION, {
      upgrade(db) {
        if (!db.objectStoreNames.contains(STORE_NAME)) {
          db.createObjectStore(STORE_NAME);
        }
      },
    });
  }
  return dbPromise;
}

// ---------------------------------------------------------------------------
// One-time migration from localStorage -> IndexedDB
// ---------------------------------------------------------------------------

let migrated = false;

async function migrateFromLocalStorage(): Promise<void> {
  if (migrated) return;
  migrated = true;

  try {
    const db = await getDB();
    // Check if IndexedDB already has data
    const existing = await db.get(STORE_NAME, CONVERSATION_LS_KEY);
    if (existing !== undefined) {
      return; // Already migrated
    }

    // Read from localStorage
    const lsData = localStorage.getItem(CONVERSATION_LS_KEY);
    if (!lsData) return;

    log.info('Migrating conversation data from localStorage to IndexedDB...');
    const parsed = JSON.parse(lsData);

    // Write to IndexedDB
    await db.put(STORE_NAME, parsed, CONVERSATION_LS_KEY);

    // Delete from localStorage to free space
    localStorage.removeItem(CONVERSATION_LS_KEY);
    log.info('Migration complete. localStorage entry removed.');
  } catch (err) {
    log.error('Migration from localStorage failed:', err);
    // Allow retry on next load — don't leave `migrated = true` on failure
    migrated = false;
  }
}

// ---------------------------------------------------------------------------
// Zustand-compatible storage adapter
// ---------------------------------------------------------------------------

/**
 * Create a Zustand persist storage adapter backed by IndexedDB.
 *
 * Usage:
 *   persist(store, { storage: createJSONStorage(() => createIdbStorageAdapter()) })
 */
export function createIdbStorageAdapter() {
  return {
    getItem: async (name: string): Promise<string | null> => {
      // Perform migration on first access for conversation store key
      if (name === CONVERSATION_LS_KEY) {
        await migrateFromLocalStorage();
      }

      try {
        const db = await getDB();
        const value = await db.get(STORE_NAME, name);
        if (value === undefined) {
          return null;
        }
        // Zustand persist expects a JSON string
        return typeof value === 'string' ? value : JSON.stringify(value);
      } catch (err) {
        log.error('IndexedDB getItem failed:', err);
        return null;
      }
    },

    setItem: async (name: string, value: string): Promise<void> => {
      try {
        const db = await getDB();
        const parsed = JSON.parse(value);
        await db.put(STORE_NAME, parsed, name);
      } catch (err) {
        log.error('IndexedDB setItem failed:', err);
      }
    },

    removeItem: async (name: string): Promise<void> => {
      try {
        const db = await getDB();
        await db.delete(STORE_NAME, name);
      } catch (err) {
        log.error('IndexedDB removeItem failed:', err);
      }
    },
  };
}