[Chromoting] Add a helper class to map an OAuth access token to an email address.

remoting/host/gaia_user_email_fetcher.cc

Index: remoting/host/gaia_user_email_fetcher.cc
diff --git a/remoting/host/gaia_user_email_fetcher.cc b/remoting/host/gaia_user_email_fetcher.cc
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+// 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.
+
+#include "remoting/host/gaia_user_email_fetcher.h"
+
+#include "base/json/json_reader.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/values.h"
+#include "googleurl/src/gurl.h"
+#include "net/http/http_status_code.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request_context_getter.h"
+
+namespace {
+const char kOAuth2UserInfoUrl[] =
+    "https://www.googleapis.com/oauth2/v1/userinfo";

[Jamie, 2012/10/02 20:38:35]

This is a different URL to the one we use in the Javascript. Is this a JSON
version of the same thing?

[simonmorris, 2012/10/02 21:50:52]

Yes. This URL is used in google_apis/gaia.

+}  // namespace
+
+namespace remoting {
+
+class GaiaUserEmailFetcher::Core
+    : public base::RefCountedThreadSafe<GaiaUserEmailFetcher::Core>,
+      public net::URLFetcherDelegate {
+ public:
+  Core(net::URLRequestContextGetter* request_context_getter)
+      : request_context_getter_(request_context_getter),
+        delegate_(NULL) {
+  }
+
+  void GetUserEmail(const std::string& oauth_access_token, Delegate* delegate);
+
+  // net::URLFetcherDelegate interface
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
+ private:
+  friend class base::RefCountedThreadSafe<Core>;

[Jamie, 2012/10/02 20:38:35]

Why is the friend declaration needed?

[simonmorris, 2012/10/02 21:50:52]

To let the ref counter delete the ref-counted object.

+
+  virtual ~Core() {}
+
+  void FetchUserInfoAndInvokeCallback();
+  void OnUserInfoFetchComplete(const net::URLRequestStatus& status,
+                               int response_code,
+                               const std::string& response);
+
+  scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
+  GaiaUserEmailFetcher::Delegate* delegate_;
+  scoped_ptr<net::URLFetcher> request_;
+};
+
+void GaiaUserEmailFetcher::Core::GetUserEmail(
+    const std::string& oauth_access_token, Delegate* delegate) {
+  DCHECK(!request_.get()) << "Tried to fetch two things at once!";

[Jamie, 2012/10/02 20:38:35]

This feels like is needs more than just a DCHECK. How about notifying either the
new or the old delegate via a callback?

[simonmorris, 2012/10/02 21:50:52]

It's done this way in GaiaOAuthClient, and the similar routines in
google_apis/gaia.

Run-time notifications don't feel right for a programming error. What should the
new/old delegates do if they get such a notification?

[Jamie, 2012/10/02 22:45:27]

It just ensures that the GetUserEmail/callback pairs line up as the caller
expects. It feels like the right thing to do is throw an exception, but that's
not allowed :) Since existing similar classes work this way, I'm happy to leave
it as-is.

+
+  delegate_ = delegate;
+
+  request_.reset(net::URLFetcher::Create(
+      GURL(kOAuth2UserInfoUrl), net::URLFetcher::GET, this));
+  request_->SetRequestContext(request_context_getter_);
+  request_->AddExtraRequestHeader(
+      "Authorization: OAuth " + oauth_access_token);
+  request_->Start();
+}
+
+void GaiaUserEmailFetcher::Core::OnURLFetchComplete(
+    const net::URLFetcher* source) {
+  std::string response_string;
+  source->GetResponseAsString(&response_string);
+  OnUserInfoFetchComplete(source->GetStatus(),
+                          source->GetResponseCode(),
+                          response_string);
+}
+
+void GaiaUserEmailFetcher::Core::OnUserInfoFetchComplete(
+    const net::URLRequestStatus& status,
+    int response_code,
+    const std::string& response) {
+  request_.reset();

[Jamie, 2012/10/02 20:38:35]

It seems more natural for the reset to happen directly in OnURLFetchComplete,
since that's the callback function.

[simonmorris, 2012/10/02 21:50:52]

Unfortunately, moving the reset to before the OnUserInfoFetchComplete() means
that |source| is mutated, which means the parameters for
OnUserInfoFetchComplete() can't be found.

Again, this is consistent with GaiaOAuthClient.

[Jamie, 2012/10/02 22:45:27]

Well, you could save the status and response code before calling the
sub-function, or just eliminate the sub-function altogether. But consistency is
good, so we can agree to disagree here.

+  std::string email;
+  if (response_code == net::HTTP_OK) {
+    scoped_ptr<Value> response_value(base::JSONReader::Read(response));
+    if (response_value.get()) {
+      base::DictionaryValue* response_dict = NULL;
+      if (response_value->GetAsDictionary(&response_dict)) {
+        response_dict->GetString("email", &email);
+      }
+    }
+  }
+  if (email.empty()) {
+    delegate_->OnNetworkError(response_code);
+  } else {
+    delegate_->OnGetUserEmailResponse(email);
+  }
+}
+
+GaiaUserEmailFetcher::GaiaUserEmailFetcher(
+    net::URLRequestContextGetter* context_getter) {
+  core_ = new Core(context_getter);
+}
+
+GaiaUserEmailFetcher::~GaiaUserEmailFetcher() {
+}
+
+void GaiaUserEmailFetcher::GetUserEmail(
+    const std::string& oauth_access_token,
+    Delegate* delegate) {
+  return core_->GetUserEmail(oauth_access_token, delegate);
+}
+
+}  // namespace remoting