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..cbc1be84d7a940d3daa68c5d02950bb8aaff3e11
--- /dev/null
+++ b/remoting/webapp/crd/js/combined_host_list_api.js
@@ -0,0 +1,209 @@
+// 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 act as if it had returned an empty
+    // result set.
+    /** @type {!Promise<!Array<!remoting.Host>>} */
+    var timeoutPromise = base.Promise.withTimeout(
+        gcdPromise, GCD_TIMEOUT_MS, []);
+
+    // Combine host information from both directories.  In the case of
+    // conflicting information, prefer information from whichever
+    // directory claims to have newer information.
+    return timeoutPromise.then(function(gcdHosts) {
+      // First, for each directory, build a mapping from host ID to
+      // host data, and collect a set of host IDs present in the
+      // directory.
+      /** @type {!Map<string,!remoting.Host>} */
+      var gcdHostMap = new Map();

[kelvinp, 2015/07/20 22:46:18]

Would the following be simpler?

var hostMap = new Map();

// Initialize the map with gcd host.
gcdHosts.forEach(function(host) {
  hostMap.set(host.hostId, host);
});

// Dedupe it against the legacy hosts.
legacyHosts.forEach(function(legacyHost) {
 var gcdHost = hostMap.get(legacyHost.hostId);
 if (gcdHost) {
    // The host is in both maps.
    if (gcdHost.updatedTime >= legacyHost.updatedTime) {
      hostMap.set(legacyHost.hostId, gcdHost);      
    } else {
      hostMap.set(legacyHost.hostId, legacyHost);
    }
 }
});

var hosts = [];
hostMap.forEach(function(host) {
  hosts.push(host);
});

[John Williams, 2015/07/21 04:54:55]

That's not quite right, but I incorporated something similar.

+      /** @type {!Map<string,!remoting.Host>} */
+      var legacyHostMap = new Map();
+      that.gcdIds_ = new Set();
+      that.legacyIds_ = new Set();
+      gcdHosts.forEach(function(host) {
+        that.gcdIds_.add(host.hostId);
+        gcdHostMap.set(host.hostId, host);
+      });
+      legacyHosts.forEach(function(host) {
+        that.legacyIds_.add(host.hostId);
+        legacyHostMap.set(host.hostId, host);
+      });
+
+      // Trim the host maps such that each host exists in only a
+      // single map.  We iterate over |that.gcdIds_| instead of
+      // |gcdHosts| to avoid any potential issues with modifying a map
+      // while iterating over it.
+      that.gcdIds_.forEach(function(hostId) {
+        var gcdHost = gcdHostMap.get(hostId);
+        console.assert(gcdHost);
+        var legacyHost = legacyHostMap.get(hostId);
+        if (legacyHost) {
+          // The host is in both maps.
+          if (gcdHost.updatedTime >= legacyHost.updatedTime) {
+            legacyHostMap.delete(hostId);
+          } else {
+            gcdHostMap.delete(hostId);
+          }
+        }
+      });
+
+      // Build a combined list of hosts, preserving the original
+      // ordering as much as possible.
+      var hosts = [];
+      gcdHosts.forEach(function(host) {
+        if (gcdHostMap.has(host.hostId)) {
+          hosts.push(host);
+        }
+      });
+      legacyHosts.forEach(function(host) {
+        if (legacyHostMap.has(host.hostId)) {
+          hosts.push(host);
+        }
+      });
+
+      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);
+};
+
+})();