Added HostListApl implementation to connect to legacy directory and GCD.

remoting/webapp/crd/js/combined_host_list_api.js

Index: remoting/webapp/crd/js/combined_host_list_api.js
diff --git a/remoting/webapp/crd/js/combined_host_list_api.js b/remoting/webapp/crd/js/combined_host_list_api.js
new file mode 100644
index 0000000000000000000000000000000000000000..d8a9954c912f5036f4a541cb04a548efa500f7a6
--- /dev/null
+++ b/remoting/webapp/crd/js/combined_host_list_api.js
@@ -0,0 +1,184 @@
+// 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.
+
+/**
+ * @fileoverview
+ * API implementation that combines two other implementations.
+ */
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * Amount of time to wait for GCD results after legacy registry has
+ * returned.
+ */
+var GCD_TIMEOUT_MS = 1000;
+
+/**
+ * @constructor
+ * @param {!remoting.HostListApi} legacyImpl
+ * @param {!remoting.HostListApi} gcdImpl
+ * @implements {remoting.HostListApi}
+ */
+remoting.CombinedHostListApi = function(legacyImpl, gcdImpl) {
+  /** @const {!remoting.HostListApi} */
+  this.legacyImpl_ = legacyImpl;
+
+  /** @const {!remoting.HostListApi} */
+  this.gcdImpl_ = gcdImpl;
+
+  /**
+   * List of host IDs most recently retrieved from |legacyImpl_|.
+   * @type {!Set<string>}
+   */
+  this.legacyIds_ = new Set();
+
+  /**
+   * List of host IDs most recently retrieved |gcdImpl_|.
+   * @type {!Set<string>}
+   */
+  this.gcdIds_ = new Set();
+};
+
+/** @override */
+remoting.CombinedHostListApi.prototype.register = function(
+    hostName, publicKey, hostClientId) {
+  var that = this;
+  // First, register the new host with GCD, which will create a
+  // service account and generate a host ID.
+  return this.gcdImpl_.register(hostName, publicKey, hostClientId).then(
+      function(gcdRegResult) {
+        // After the GCD registration has been created, copy the
+        // registration to the legacy directory so that clients not yet
+        // upgraded to use GCD can see the new host.
+        //
+        // This is an ugly hack for multiple reasons:
+        //
+        // 1. It completely ignores |this.legacyImpl_|, complicating
+        //    unit tests.
+        //
+        // 2. It relies on the fact that, when |hostClientId| is null,
+        //    the legacy directory will "register" a host without
+        //    creating a service account.  This is an obsolete feature
+        //    of the legacy directory that is being revived for a new
+        //    purpose.
+        //
+        // 3. It assumes the device ID generated by GCD is usable as a
+        //    host ID by the legacy directory.  Fortunately both systems
+        //    use UUIDs.
+        return remoting.LegacyHostListApi.registerWithHostId(
+            gcdRegResult.hostId, hostName, publicKey, null).then(
+                function() {
+                  // On success, return the result from GCD, ignoring
+                  // the result returned by the legacy directory.
+                  that.gcdIds_.add(gcdRegResult.hostId);
+                  that.legacyIds_.add(gcdRegResult.hostId);
+                  return gcdRegResult;
+                },
+                function(error) {
+                  console.warn(
+                      'Error copying host GCD host registration ' +
+                      'to legacy directory: ' + error);
+                  throw error;
+                }
+            );
+      });
+};
+
+/** @override */
+remoting.CombinedHostListApi.prototype.get = function() {
+  // Fetch the host list from both directories and merge hosts that
+  // have the same ID.
+  var that = this;
+  var legacyPromise = this.legacyImpl_.get();
+  var gcdPromise = this.gcdImpl_.get();
+  return legacyPromise.then(function(legacyHosts) {
+    // If GCD is too slow, just ignore it and return results from the
+    // legacy directory.
+    /** @type {!Promise<!Array<!remoting.Host>>} */
+    var timeoutPromise = base.Promise.withTimeout(
+        gcdPromise, GCD_TIMEOUT_MS, []);
+    return timeoutPromise.then(function(gcdHosts) {
+      // Combine host information from both directories.  In the case
+      // of conflicting information, prefer information from whichever
+      // directory claims to have newer information.
+
+      var hosts = [];
+      /** @type {!Map<string,!remoting.Host>} */
+      var gcdHostMap = new Map();
+      /** @type {!Map<string,!remoting.Host>} */
+      var legacyHostMap = new Map();
+      gcdHosts.forEach(function(host) {
+        gcdHostMap.set(host.hostId, host);
+      });
+      legacyHosts.forEach(function(host) {
+        legacyHostMap.set(host.hostId, host);
+      });
+      gcdHosts.forEach(function(host) {
+        var legacyHost = legacyHostMap.get(host.hostId);
+        if (!legacyHost || host.updatedTime >= legacyHost.updatedTime) {
+          hosts.push(host);

[kelvinp, 2015/07/20 18:00:51]

Nit: 
After we ensure that either there is no legacy host or the GCD host is more
up-to-date, maybe we can remove the legacy host from the legacyHostMap
immediately and just add all of the legacyHosts from the map at the end?

[John Williams, 2015/07/20 21:43:10]

I rewrote this method for clarity; PTAL.

+        }
+      });
+      legacyHosts.forEach(function(host) {
+        var gcdHost = gcdHostMap.get(host.hostId);
+        if (!gcdHost || host.updatedTime > gcdHost.updatedTime) {
+          hosts.push(host);
+        }
+      });
+      that.legacyIds_ = base.keySet(legacyHostMap);
+      that.gcdIds_ = base.keySet(gcdHostMap);
+      return hosts;
+    });
+  });
+};
+
+/** @override */
+remoting.CombinedHostListApi.prototype.put =
+    function(hostId, hostName, hostPublicKey) {
+  var legacyPromise = Promise.resolve();
+  if (this.legacyIds_.has(hostId)) {
+    legacyPromise = this.legacyImpl_.put(hostId, hostName, hostPublicKey);
+  }
+  var gcdPromise = Promise.resolve();
+  if (this.gcdIds_.has(hostId)) {
+    gcdPromise = this.gcdImpl_.put(hostId, hostName, hostPublicKey);
+  }
+  return legacyPromise.then(function() {
+    // If GCD is too slow, just ignore it and return result from the
+    // legacy directory.
+    return base.Promise.withTimeout(
+        gcdPromise, GCD_TIMEOUT_MS);
+  });
+};
+
+/** @override */
+remoting.CombinedHostListApi.prototype.remove = function(hostId) {
+  var legacyPromise = Promise.resolve();
+  if (this.legacyIds_.has(hostId)) {
+    legacyPromise = this.legacyImpl_.remove(hostId);
+  }
+  var gcdPromise = Promise.resolve();
+  if (this.gcdIds_.has(hostId)) {
+    gcdPromise = this.gcdImpl_.remove(hostId);
+  }
+  return legacyPromise.then(function() {
+    // If GCD is too slow, just ignore it and return result from the
+    // legacy directory.
+    return base.Promise.withTimeout(
+        gcdPromise, GCD_TIMEOUT_MS);
+  });
+};
+
+/** @override */
+remoting.CombinedHostListApi.prototype.getSupportHost = function(supportId) {
+  return this.legacyImpl_.getSupportHost(supportId);
+};
+
+})();