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promise_storage.js
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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;
this._supportsIndexedDB = !!window.indexedDB;
if (!this._supportsIndexedDB) {
console.warn('PromiseStorage: IndexedDB is unsupported');
}
};
// 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;
}
if (!this._supportsIndexedDB) {
return Promise.resolve();
}
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) {
if (!this._supportsIndexedDB) {
console.warn(
'PromiseStorage: IndexedDB is unsupported, unable to operate');
return Promise.resolve();
}
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));