Refactor print preview web ui

chrome/browser/resources/print_preview/data/ticket_items/ticket_item.js

+// Copyright (c) 2012 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.
+
+cr.define('print_preview.ticket_items', function() {
+  'use strict';
+
+  /**
+   * An object that represents a user modifiable item in a print ticket. Each
+   * ticket item has a value which can be set by the user. Ticket items can also
+   * be unavailable for modifying if the print destination doesn't support it or
+   * if other ticket item constraints are not met.
+   * @constructor
+   */
+  function TicketItem() {
+    /**
+     * Backing store of the print ticket item.
+     * @type {Object}
+     * @private
+     */
+    this.value_ = null;
+
+    /**
+     * A cache of whether the ticket item's value is valid.
+     * @type {?boolean}
+     * @private
+     */
+    this.isValid_ = null;
+  };
+
+  TicketItem.prototype = {
+    /**
+     * Determines whether a given value is valid for the ticket item.
+     * @param {Object} value The value to check for validity.
+     * @return {boolean} Whether the given value is valid for the ticket item.
+     */
+    wouldValueBeValid: function(value) {
+      throw Error('Abstract method not overriden');
+    },
+
+    /**
+     * @return {boolean} Whether the print destination capability is available.
+     */
+    isCapabilityAvailable: function() {
+      throw Error('Abstract method not overriden');
+    },
+
+    /** @return {object} The value of the ticket item. */
+    getValue: function() {
+      if (this.isCapabilityAvailable()) {
+        if (this.value_ == null) {
+          return this.getDefaultValueInternal();
+        } else {
+          return this.value_;
+        }
+      } else {
+        return this.getCapabilityNotAvailableValueInternal();
+      }
+    },
+
+    /** @return {boolean} Whether the ticket item was modified by the user. */
+    isUserEdited: function() {
+      return this.value_ != null;
+    },
+
+    /** @return {boolean} Whether the ticket item's value is valid. */
+    isValid: function() {
+      if (!this.isUserEdited()) {
+        return true;
+      }
+      if (this.isValid_ == null) {
+        this.isValid_ = this.wouldValueBeValid(this.value_);
+      }
+      return this.isValid_;
+    },
+
+    /** @param {object} Value to set as the value of the ticket item. */
+    updateValue: function(value) {
+      this.value_ = value;
+      this.isValid_ = null;
+    },
+
+    /**
+     * @return {object} Default value of the ticket item if no value was set by
+     *     the user.
+     * @protected
+     */
+    getDefaultValueInternal: function() {
+      throw Error('Abstract method not overriden');
+    },
+
+    /**
+     * @return {object} Default value of the ticket item if the capability is
+     *     not available.
+     * @protected
+     */
+    getCapabilityNotAvailableValueInternal: function() {
+      throw Error('Abstract method not overriden');
+    }
+  };
+
+  // Export
+  return {
+    TicketItem: TicketItem
+  };
+});