Sw precaching

lib/idb-helper.js

@@ -19,123 +19,139 @@ import idb from 'idb';
  * A wrapper to store for an IDB connection to a particular ObjectStore.
  *
  * @private
- * @class
  */
-function IDBHelper(name, version, storeName) {
-  if (name == undefined || version == undefined || storeName == undefined) {
-    throw Error('name, version, storeName must be passed to the constructor.');
+class IDBHelper {
+  constructor(name, version, storeName) {
+    if (name == undefined || version == undefined || storeName == undefined) {
+      throw Error('name, version, storeName must be passed to the ' +
+        'constructor.');
+    }
+
+    this._name = name;
+    this._version = version;
+    this._storeName = storeName;
   }
 
-  this._name = name;
-  this._version = version;
-  this._storeName = storeName;
-}
+  /**
+   * Returns a promise that resolves with an open connection to IndexedDB,
+   * either existing or newly opened.
+   *
+   * @private
+   * @return {Promise<DB>}
+   */
+  _getDb() {
+    if (this._dbPromise) {
+      return this._dbPromise;
+    }
+    console.log('-------------> Opening DB');
+    this._dbPromise = idb.open(this._name, this._version, (upgradeDB) => {
+      upgradeDB.createObjectStore(this._storeName);
+    })
+    .then((db) => {
+      return db;
+    });
 
-/**
- * Returns a promise that resolves with an open connection to IndexedDB, either
- * existing or newly opened.
- *
- * @private
- * @return {Promise<DB>}
- */
-IDBHelper.prototype._getDb = function() {
-  if (this._db) {
-    return Promise.resolve(this._db);
+    return this._dbPromise;
   }
 
-  return idb.open(this._name, this._version, (upgradeDB) => {
-    upgradeDB.createObjectStore(this._storeName);
-  }).then((db) => {
-    this._db = db;
-    return db;
-  });
-};
+  close() {
+    if (!this._dbPromise) {
+      return;
+    }
+    console.log('----------------> Closing DB');
+    return this._dbPromise
+    .then((db) => {
+      db.close();
+      this._dbPromise = null;
+    });
+  }
 
-/**
- * Wrapper on top of the idb wrapper, which simplifies saving the key/value
- * pair to the object store.
- * Returns a Promise that fulfills when the transaction completes.
- *
- * @private
- * @param {String} key
- * @param {Object} value
- * @return {Promise<T>}
- */
-IDBHelper.prototype.put = function(key, value) {
-  return this._getDb().then((db) => {
-    const tx = db.transaction(this._storeName, 'readwrite');
-    const objectStore = tx.objectStore(this._storeName);
-    objectStore.put(value, key);
-    return tx.complete;
-  });
-};
+  /**
+   * Wrapper on top of the idb wrapper, which simplifies saving the key/value
+   * pair to the object store.
+   * Returns a Promise that fulfills when the transaction completes.
+   *
+   * @private
+   * @param {String} key
+   * @param {Object} value
+   * @return {Promise<T>}
+   */
+  put(key, value) {
+    return this._getDb().then((db) => {
+      const tx = db.transaction(this._storeName, 'readwrite');
+      const objectStore = tx.objectStore(this._storeName);
+      objectStore.put(value, key);
+      return tx.complete;
+    });
+  }
 
-/**
- * Wrapper on top of the idb wrapper, which simplifies deleting an entry
- * from the object store.
- * Returns a Promise that fulfills when the transaction completes.
- *
- * @private
- * @param {String} key
- * @return {Promise<T>}
- */
-IDBHelper.prototype.delete = function(key) {
-  return this._getDb().then((db) => {
-    const tx = db.transaction(this._storeName, 'readwrite');
-    const objectStore = tx.objectStore(this._storeName);
-    objectStore.delete(key);
-    return tx.complete;
-  });
-};
+  /**
+   * Wrapper on top of the idb wrapper, which simplifies deleting an entry
+   * from the object store.
+   * Returns a Promise that fulfills when the transaction completes.
+   *
+   * @private
+   * @param {String} key
+   * @return {Promise<T>}
+   */
+  delete(key) {
+    return this._getDb().then((db) => {
+      const tx = db.transaction(this._storeName, 'readwrite');
+      const objectStore = tx.objectStore(this._storeName);
+      objectStore.delete(key);
+      return tx.complete;
+    });
+  }
 
-/**
- * Wrapper on top of the idb wrapper, which simplifies getting a key's value
- * from the object store.
- * Returns a promise that fulfills with the value.
- *
- * @private
- * @param {String} key
- * @return {Promise<Object>}
- */
-IDBHelper.prototype.get = function(key) {
-  return this._getDb().then((db) => {
-    return db.transaction(this._storeName)
-      .objectStore(this._storeName)
-      .get(key);
-  });
-};
+  /**
+   * Wrapper on top of the idb wrapper, which simplifies getting a key's value
+   * from the object store.
+   * Returns a promise that fulfills with the value.
+   *
+   * @private
+   * @param {String} key
+   * @return {Promise<Object>}
+   */
+  get(key) {
+    return this._getDb().then((db) => {
+      return db.transaction(this._storeName)
+        .objectStore(this._storeName)
+        .get(key);
+    });
+  }
 
-/**
- * Wrapper on top of the idb wrapper, which simplifies getting all the values
- * in an object store.
- * Returns a promise that fulfills with all the values.
- *
- * @private
- * @return {Promise<Array<Object>>}
- */
-IDBHelper.prototype.getAllValues = function() {
-  return this._getDb().then((db) => {
-    return db.transaction(this._storeName)
-      .objectStore(this._storeName)
-      .getAll();
-  });
-};
+  /**
+   * Wrapper on top of the idb wrapper, which simplifies getting all the values
+   * in an object store.
+   * Returns a promise that fulfills with all the values.
+   *
+   * @private
+   * @return {Promise<Array<Object>>}
+   */
+  getAllValues() {
+    return this._getDb().then((db) => {
+      return db.transaction(this._storeName)
+        .objectStore(this._storeName)
+        .getAll();
+    });
+  }
 
-/**
- * Wrapper on top of the idb wrapper, which simplifies getting all the keys
- * in an object store.
- * Returns a promise that fulfills with all the keys.
- *
- * @private
- * @param {String} storeName
- * @return {Promise<Array<Object>>}
- */
-IDBHelper.prototype.getAllKeys = function() {
-  return this._getDb().then((db) => {
-    return db.transaction(this._storeName)
-      .objectStore(this._storeName)
-      .getAllKeys();
-  });
-};
+  /**
+   * Wrapper on top of the idb wrapper, which simplifies getting all the keys
+   * in an object store.
+   * Returns a promise that fulfills with all the keys.
+   *
+   * @private
+   * @param {String} storeName
+   * @return {Promise<Array<Object>>}
+   */
+  getAllKeys() {
+    return this._getDb().then((db) => {
+      return db.transaction(this._storeName)
+        .objectStore(this._storeName)
+        .getAllKeys();
+    });
+  }
+}
 
 export default IDBHelper;