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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* @fileoverview Implementation of ScreenContext class: key-value storage for
* values that are shared between C++ and JS sides.
*/
cr.define('login', function() {
function require(condition, message) {
if (!condition) {
throw Error(message);
}
}
function checkKeyIsValid(key) {
var keyType = typeof key;
require(keyType === 'string', 'Invalid type of key: "' + keyType + '".');
}
function checkValueIsValid(value) {
var valueType = typeof value;
require(['string', 'boolean', 'number'].indexOf(valueType) != -1,
'Invalid type of value: "' + valueType + '".');
}
function ScreenContext() {
this.storage_ = {};
this.changes_ = {};
}
ScreenContext.prototype = {
/**
* Returns stored value for |key| or |defaultValue| if key not found in
* storage. Throws Error if key not found and |defaultValue| omitted.
*/
get: function(key, defaultValue) {
checkKeyIsValid(key);
if (this.hasKey(key)) {
return this.storage_[key];
} else if (typeof defaultValue !== 'undefined') {
return defaultValue;
} else {
throw Error('Key "' + key + '" not found.');
}
},
/**
* Sets |value| for |key|. Returns true if call changes state of context,
* false otherwise.
*/
set: function(key, value) {
checkKeyIsValid(key);
checkValueIsValid(value);
if (this.hasKey(key) && this.storage_[key] === value)
return false;
this.changes_[key] = value;
this.storage_[key] = value;
return true;
},
hasKey: function(key) {
checkKeyIsValid(key);
return this.storage_.hasOwnProperty(key);
},
hasChanges: function() {
return Object.keys(this.changes_).length > 0;
},
/**
* Applies |changes| to context. Returns Array of changed keys' names.
*/
applyChanges: function(changes) {
require(!this.hasChanges(), 'Context has changes.');
Object.keys(changes).forEach(function(key) {
checkKeyIsValid(key);
checkValueIsValid(changes[key]);
this.storage_[key] = changes[key];
}, this);
return Object.keys(changes);
},
/**
* Returns changes made on context since previous call.
*/
getChangesAndReset: function() {
var result = this.changes_;
this.changes_ = {};
return result;
}
};
return {
ScreenContext: ScreenContext
};
});
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