Files.app: Add model classes to manage cache states of new MetadataCache.

ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_item.js

Index: ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_item.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_item.js b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_item.js
new file mode 100644
index 0000000000000000000000000000000000000000..707d405fd29dca5946c4d51c0696c1b98e3c3e54
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+++ b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_item.js
@@ -0,0 +1,128 @@
+// Copyright 2015 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.
+
+/**
+ * Cache of metadata for a FileEntry.
+ * @constructor
+ * @struct
+ */
+function MetadataCacheItem() {
+  /**
+   * Map of property name and MetadataCacheItemProperty.
+   * @private {!Object<string, !MetadataCacheItemProperty>}
+   * @const
+   */
+  this.properties_ = {};
+}
+
+/**
+ * Marks invalidated properies as loading and returns property names that are
+ * need to be loaded.
+ * @param {number} requestId
+ * @param {!Array<string>} names
+ * @return {!Array<string>} Load requested names.
+ */
+MetadataCacheItem.prototype.startRequests = function(requestId, names) {
+  var loadRequested = [];
+  for (var i = 0; i < names.length; i++) {
+    var name = names[i];
+    // Check if the property needs to be updated.
+    if (this.properties_[name] &&
+        this.properties_[name].state !==
+        MetadataCacheItemPropertyState.INVALIDATED) {
+      continue;
+    }
+    if (!this.properties_[name])
+      this.properties_[name] = new MetadataCacheItemProperty();
+    this.properties_[name].requestId = requestId;
+    this.properties_[name].state = MetadataCacheItemPropertyState.LOADING;
+    loadRequested.push(name);
+  }
+  return loadRequested;
+};
+
+/**
+ * Feeds the result of startRequests.
+ * @param {number} requestId Request ID passed when calling startRequests.
+ * @param {!Object} object Map of property name and value.
+ * @return {boolean} Whether at least one property is updated or not.
+ */
+MetadataCacheItem.prototype.storeProperties = function(requestId, object) {
+  var changed = false;
+  for (var name in object) {
+    if (!this.properties_[name])
+      this.properties_[name] = new MetadataCacheItemProperty();
+    if (requestId < this.properties_[name].requestId)
+      continue;
+    changed = true;
+    this.properties_[name].requestId = requestId;
+    this.properties_[name].value = object[name];
+    this.properties_[name].state = MetadataCacheItemPropertyState.FULFILLED;
+  }
+  return changed;
+};
+
+/**
+ * Marks the caches of all properties in the item as invalidates and forces to
+ * reload at the next time of startRequests.
+ * @param {number} requestId Request ID of the invalidation request. This must
+ *     be larger than other requets ID passed to the item before.
+ */
+MetadataCacheItem.prototype.invalidate = function(requestId) {
+  for (var name in this.properties_) {
+    assert(this.properties_[name].requestId < requestId);
+    this.properties_[name].requestId = requestId;
+    this.properties_[name].state = MetadataCacheItemPropertyState.INVALIDATED;
+  }
+};
+
+/**
+ * Obtains property for entries and names.
+ * Note that it returns invalidated properties also.
+ * @param {!Array<string>} names
+ * @return {!Object}
+ */
+MetadataCacheItem.prototype.get = function(names) {
+  var result = {};
+  for (var i = 0; i < names.length; i++) {
+    var name = names[i];
+    if (this.properties_[name])
+      result[name] = this.properties_[name].value;
+  }
+  return result;
+};
+
+/**
+ * @enum {string}
+ */
+var MetadataCacheItemPropertyState = {
+  INVALIDATED: 'invalidated',
+  LOADING: 'loading',
+  FULFILLED: 'fulfilled'
+};
+
+/**
+ * Cache of metadata for a property.
+ * @constructor
+ * @struct
+ */
+function MetadataCacheItemProperty() {
+  /**
+   * Cached value of property.
+   * @public {*}
+   */
+  this.value = null;
+
+  /**
+   * Last request ID.
+   * @public {number}
+   */
+  this.requestId = -1;
+
+  /**
+   * Cache state of the property.
+   * @public {MetadataCacheItemPropertyState}
+   */
+  this.state = MetadataCacheItemPropertyState.INVALIDATED;
+}