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gaia/apps/keyboard/js/shared/promise_storage.js

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+'use strict';
+
+/* global Promise */
+
+(function(exports) {
+
+/**
+ * PromiseStorage wraps IndexedDB into simple key-value storage.
+ *
+ * It exposes simple Promise interfaces at the expenses of hiding powerful stuff
+ * of IndexedDB. For example, there is no interface here for you to iterate
+ * all the available items.
+ *
+ * Note that due to the nature of Promises, this library does not support
+ * read-modify-write operation; you simply cannot chain a get() and a set() for
+ * that safely. For more discussion please read
+ *
+ * http://lists.w3.org/Archives/Public/public-webapps/2013AprJun/0217.html
+ *
+ * (We might get around this if we implement PromiseStorage#update here.)
+ *
+ */
+var PromiseStorage = function(name) {
+  this.name = name;
+
+  if (typeof this.name !== 'string' || this.name === '') {
+    throw new Error('PromiseStorage: Need a storage name.');
+  }
+
+  this._openPromise = null;
+};
+
+// Version and the single object store name is considered internal to
+// the implementation of PromiseStorage. We should try to upgrade the
+// old storage should we encounter one.
+PromiseStorage.prototype.DB_VERSION = 1;
+PromiseStorage.prototype.STORE_NAME = 'keyvaluepairs';
+
+PromiseStorage.prototype.start = function() {
+  return this._getDatabase().catch(function(e) {
+    this._openPromise = null;
+
+    throw e;
+  }.bind(this));
+};
+
+PromiseStorage.prototype.stop = function() {
+  if (!this._openPromise) {
+    return Promise.resolve();
+  }
+
+  return this._getDatabase().then(function(db) {
+    db.close();
+
+    this._openPromise = null;
+  });
+};
+
+PromiseStorage.prototype._getDatabase = function() {
+  if (this._openPromise) {
+    return this._openPromise;
+  }
+
+  var p = new Promise(function(resolve, reject) {
+    var req = window.indexedDB.open(this.name, this.DB_VERSION);
+    req.onerror = function() {
+      reject(req.error);
+    };
+    req.onsuccess = function(evt) {
+      resolve(req.result);
+    };
+    req.onupgradeneeded = function(evt) {
+      var db = req.result;
+      if (evt.oldVersion < 1) {
+        db.createObjectStore(this.STORE_NAME);
+      }
+      // ... put next database upgrade here.
+      // See http://www.w3.org/TR/IndexedDB/#introduction
+      // on how upgradeneeded should be handled.
+    }.bind(this);
+  }.bind(this));
+
+  this._openPromise = p;
+  return p;
+};
+
+// Get transaction of the type and execute callback with that tranaction
+// in the same function loop.
+// callback should return a promise, to be chained on the returned promise.
+PromiseStorage.prototype._getTxn = function(type, callback) {
+  return this._getDatabase().then(function(db) {
+    var txn = db.transaction(this.STORE_NAME, type);
+    return callback(txn);
+  }.bind(this));
+};
+
+PromiseStorage.prototype.getItems = function(names) {
+  return this._getTxn('readonly', function(txn) {
+    var store = txn.objectStore(this.STORE_NAME);
+    var reqPromises = names.map(function(name) {
+      return new Promise(function(resolve, reject) {
+        var req = store.get(name);
+        req.onerror = function(e) {
+          reject(req.error);
+        };
+        req.onsuccess = function() {
+          resolve(req.result);
+        };
+      });
+    }, this);
+
+    return new Promise(function(resolve) {
+      txn.oncomplete = function() {
+        resolve(Promise.all(reqPromises));
+      };
+    });
+  }.bind(this)).catch(function(e) {
+    e && console.error(e);
+
+    return Promise.reject(e);
+  });
+};
+
+PromiseStorage.prototype.getItem = function(name) {
+  return this._getTxn('readonly', function(txn) {
+    return new Promise(function(resolve, reject) {
+      var req = txn.objectStore(this.STORE_NAME).get(name);
+      req.onerror = function(e) {
+        reject(req.error);
+      };
+      txn.oncomplete = function() {
+        resolve(req.result);
+      };
+    }.bind(this));
+  }.bind(this)).catch(function(e) {
+    e && console.error(e);
+
+    return Promise.reject(e);
+  });
+};
+
+PromiseStorage.prototype.setItem = function(name, data) {
+  return this._getTxn('readwrite', function(txn) {
+    return new Promise(function(resolve, reject) {
+      var store = txn.objectStore(this.STORE_NAME);
+      var req = store.put(data, name);
+      req.onerror = function(e) {
+        reject(req.error);
+      };
+      txn.oncomplete = function() {
+        resolve(req.result);
+      };
+    }.bind(this));
+  }.bind(this)).catch(function(e) {
+    e && console.error(e);
+
+    return Promise.reject(e);
+  });
+};
+
+// items is a object mapping from name to data.
+PromiseStorage.prototype.setItems = function(items) {
+  return this._getTxn('readwrite', function(txn) {
+    var store = txn.objectStore(this.STORE_NAME);
+    var reqPromises = Object.keys(items).map(function(name) {
+      var data = items[name];
+      return new Promise(function(resolve, reject) {
+        var req = store.put(data, name);
+        req.onerror = function(e) {
+          reject(req.error);
+        };
+        req.onsuccess = function() {
+          resolve(req.result);
+        };
+      });
+    }, this);
+
+    return new Promise(function(resolve) {
+      txn.oncomplete = function() {
+        resolve(Promise.all(reqPromises));
+      };
+    });
+  }.bind(this)).catch(function(e) {
+    e && console.error(e);
+
+    return Promise.reject(e);
+  });
+};
+
+PromiseStorage.prototype.deleteItem = function(name) {
+  return this._getTxn('readwrite', function(txn) {
+    return new Promise(function(resolve, reject) {
+      var req = txn.objectStore(this.STORE_NAME).delete(name);
+      req.onerror = function(e) {
+        reject(req.error);
+      };
+      txn.oncomplete = function() {
+        resolve();
+      };
+    }.bind(this));
+  }.bind(this)).catch(function(e) {
+    e && console.error(e);
+
+    return Promise.reject(e);
+  });
+};
+
+exports.PromiseStorage = PromiseStorage;
+
+}(window));