/*
 * IndexedDB operations module. Provides typed helpers for reading and writing to
 * the browser-side database. All functions depend on `state.db` being set during
 * initialization.
 *
 * Changes from the original monolithic app.js:
 * - A5: `dbTransaction()` wraps multi-store operations in a single IndexedDB
 *   transaction so related writes (e.g. delete report + delete attachments) are
 *   atomic and won't leave orphaned records on mid-operation failure.
 */

import { state } from './state.js';
import {
  DB_NAME,
  DB_VERSION,
  STORE_TEMPLATES,
  STORE_LOOKUPS,
  STORE_CONFIG,
  STORE_REPORTS,
  STORE_ATTACHMENTS,
  STORE_SETTINGS
} from './constants.js';

/* ── Database bootstrap ─────────────────────────────────────────────────── */

export function openDatabase() {
  return new Promise((resolve, reject) => {
    const request = indexedDB.open(DB_NAME, DB_VERSION);

    request.onerror = () => reject(request.error);
    request.onsuccess = () => resolve(request.result);
    request.onupgradeneeded = (event) => {
      const db = request.result;

      if (!db.objectStoreNames.contains(STORE_TEMPLATES)) {
        db.createObjectStore(STORE_TEMPLATES, { keyPath: 'cacheKey' });
      }

      if (!db.objectStoreNames.contains(STORE_LOOKUPS)) {
        db.createObjectStore(STORE_LOOKUPS, { keyPath: 'code' });
      }

      if (!db.objectStoreNames.contains(STORE_CONFIG)) {
        db.createObjectStore(STORE_CONFIG, { keyPath: 'key' });
      }

      if (!db.objectStoreNames.contains(STORE_REPORTS)) {
        db.createObjectStore(STORE_REPORTS, { keyPath: 'id' });
      }

      if (!db.objectStoreNames.contains(STORE_ATTACHMENTS)) {
        const store = db.createObjectStore(STORE_ATTACHMENTS, { keyPath: 'id' });
        store.createIndex('byReportId', 'reportId', { unique: false });
      }

      if (!db.objectStoreNames.contains(STORE_SETTINGS)) {
        db.createObjectStore(STORE_SETTINGS, { keyPath: 'key' });
      }
    };
  });
}

/* ── Single-store helpers ───────────────────────────────────────────────── */

export function dbGetAll(storeName) {
  return executeStoreRequest(storeName, 'readonly', (store) => store.getAll());
}

export function dbGet(storeName, key) {
  return executeStoreRequest(storeName, 'readonly', (store) => store.get(key));
}

export function dbPut(storeName, value) {
  return executeStoreRequest(storeName, 'readwrite', (store) => store.put(value));
}

export function dbDelete(storeName, key) {
  return executeStoreRequest(storeName, 'readwrite', (store) => store.delete(key));
}

export function dbGetAllByIndex(storeName, indexName, key) {
  return executeStoreRequest(storeName, 'readonly', (store) => {
    return store.index(indexName).getAll(IDBKeyRange.only(key));
  });
}

function executeStoreRequest(storeName, mode, callback) {
  return new Promise((resolve, reject) => {
    const transaction = state.db.transaction(storeName, mode);
    const store = transaction.objectStore(storeName);
    const request = callback(store);

    request.onsuccess = () => resolve(request.result);
    request.onerror = () => reject(request.error);
  });
}

/* ── Multi-store transaction (A5) ───────────────────────────────────────── */

/*
 * Wraps multiple writes across different object stores in a single IndexedDB
 * transaction. The callback receives a helper that returns a store by name.
 * All writes either commit together or roll back as a unit.
 *
 * Example:
 *   await dbTransaction([STORE_REPORTS, STORE_ATTACHMENTS], 'readwrite', (getStore) => {
 *     getStore(STORE_REPORTS).delete(reportId);
 *     getStore(STORE_ATTACHMENTS).delete(attachmentId);
 *   });
 */
export function dbTransaction(storeNames, mode, callback) {
  return new Promise((resolve, reject) => {
    const tx = state.db.transaction(storeNames, mode);

    tx.oncomplete = () => resolve();
    tx.onerror = () => reject(tx.error);
    tx.onabort = () => reject(tx.error || new Error('Transaction aborted'));

    const getStore = (name) => tx.objectStore(name);
    callback(getStore);
  });
}

/* ── Settings helpers ───────────────────────────────────────────────────── */

export async function saveSetting(key, value) {
  await dbPut(STORE_SETTINGS, { key, value });
}

export async function loadSetting(key) {
  const record = await dbGet(STORE_SETTINGS, key);
  return record?.value;
}