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chrome/browser/resources/chromeos/chromevox/cvox2/background/recovery_strategy.js

+// Copyright 2017 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 Defines various strategies for recovering automation nodes.
+ */
+
+goog.provide('AncestryRecoveryStrategy');
+goog.provide('RecoveryStrategy');
+goog.provide('TreePathRecoveryStrategy');
+
+goog.scope(function() {
+var AutomationNode = chrome.automation.AutomationNode;
+var RoleType = chrome.automation.RoleType;
+
+/**
+ * @param {!AutomationNode} node
+ * @constructor
+ */
+RecoveryStrategy = function(node) {
+  /** @private {!AutomationNode} */
+  this.node_ = node;
+};
+
+RecoveryStrategy.prototype = {
+  /** @return {!AutomationNode} */
+  get node() {
+    if (this.requiresRecovery())
+      this.node_ = this.recover() || this.node_;
+
+    return this.node_;
+  },
+
+  /** @return {boolean} */
+  requiresRecovery: function() {
+    return !this.node_ || !this.node_.role;
+  },
+
+  /**
+   * @return {AutomationNode}
+   * @protected
+   */
+  recover: function() {
+    return null;
+  }
+};
+
+/**
+ * A recovery strategy that uses the node's ancestors.
+ * @constructor
+ * @extends {RecoveryStrategy}
+ */
+AncestryRecoveryStrategy = function(node) {
+  RecoveryStrategy.call(this, node);
+
+  /** @type {!Array<AutomationNode>} @private */
+  this.ancestry_ = [];
+  var nodeWalker = node;
+  while (nodeWalker) {
+    this.ancestry_.push(nodeWalker);
+    nodeWalker = nodeWalker.parent;
+    if (nodeWalker && nodeWalker.role == RoleType.WINDOW)
+      break;
+  }
+};
+
+AncestryRecoveryStrategy.prototype = {
+  __proto__: RecoveryStrategy.prototype,
+
+  /** @override */
+  recover: function() {
+    return this.ancestry_[this.getFirstValidNodeIndex_()];
+  },
+
+  /**
+   * @return {number}
+   * @protected
+   */
+  getFirstValidNodeIndex_: function() {
+    for (var i = 0; i < this.ancestry_.length; i++) {
+      var firstValidNode = this.ancestry_[i];
+      if (firstValidNode != null && firstValidNode.role !== undefined &&
+          firstValidNode.root != undefined) {
+        return i;
+      }
+    }
+    return 0;
+  }
+};
+
+/**
+ * A recovery strategy that uses the node's tree path.
+ * @constructor
+ * @extends {AncestryRecoveryStrategy}
+ */
+TreePathRecoveryStrategy = function(node) {
+  AncestryRecoveryStrategy.call(this, node);
+
+  /** @type {!Array<number>} @private */
+  this.recoveryChildIndex_ = [];
+  var nodeWalker = node;
+  while (nodeWalker) {
+    this.recoveryChildIndex_.push(nodeWalker.indexInParent);
+    nodeWalker = nodeWalker.parent;
+    if (nodeWalker && nodeWalker.role == RoleType.WINDOW)
+      break;
+  }
+};
+
+TreePathRecoveryStrategy.prototype = {
+  __proto__: AncestryRecoveryStrategy.prototype,
+
+  /** @override */
+  recover: function() {
+    var index = this.getFirstValidNodeIndex_();
+    if (index == 0)
+      return this.ancestry_[index];
+
+    // Otherwise, attempt to recover.
+    var node = this.ancestry_[index];
+    for (var j = index - 1; j >= 0; j--) {
+      var childIndex = this.recoveryChildIndex_[j];
+      var children = node.children;
+      if (!children[childIndex])
+        return node;
+      node = children[childIndex];
+    }
+    return node;
+  }
+};
+
+});  // goog.scope