Refactor CryptAuth component to be more testable.

components/proximity_auth/cryptauth/cryptauth_access_token_fetcher.cc

+// Copyright 2014 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 "components/proximity_auth/cryptauth/cryptauth_access_token_fetcher.h"
+
+#include "base/callback.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+
+namespace proximity_auth {
+
+namespace {
+
+// Implementation of CryptAuthAccessTokenFetcher fetching an access token for a
+// given account using the provided OAuth2TokenService.
+class CryptAuthAccessTokenFetcherImpl : public CryptAuthAccessTokenFetcher,
+                                        public OAuth2TokenService::Consumer {
+ public:
+  // |token_service| is not owned, and must outlive this object.
+  CryptAuthAccessTokenFetcherImpl(OAuth2TokenService* token_service,
+                                  const std::string& account_id);
+  ~CryptAuthAccessTokenFetcherImpl() override;
+
+  // CryptAuthAccessTokenFetcher:
+  void FetchAccessToken(const AccessTokenCallback& callback) override;
+
+ private:
+  // OAuth2TokenService::Consumer:
+  void OnGetTokenSuccess(const OAuth2TokenService::Request* request,
+                         const std::string& access_token,
+                         const base::Time& expiration_time) override;
+  void OnGetTokenFailure(const OAuth2TokenService::Request* request,
+                         const GoogleServiceAuthError& error) override;
+
+  // System service that caches and fetches tokens for a given account.
+  // Not owned.
+  OAuth2TokenService* token_service_;
+
+  // The account id for whom to mint the token.
+  std::string account_id_;
+
+  // True if FetchAccessToken() has been called.
+  bool fetch_started_;
+
+  // Stores the request from |token_service_| to mint the token.
+  scoped_ptr<OAuth2TokenService::Request> token_request_;
+
+  // Callback to invoke when the token fetch succeeds or fails.
+  AccessTokenCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(CryptAuthAccessTokenFetcherImpl);
+};

[Ilya Sherman, 2015/04/06 18:53:33]

I rather preferred having this as a separate file.  Why did you fold it into the
anonymous namespace here?

[Tim Song, 2015/04/06 23:21:17]

Done.

+
+// Returns the set of OAuth2 scopes that CryptAuth uses.
+OAuth2TokenService::ScopeSet GetScopes() {
+  OAuth2TokenService::ScopeSet scopes;
+  scopes.insert("https://www.googleapis.com/auth/cryptauth");
+  return scopes;
+}

[Ilya Sherman, 2015/04/06 18:53:33]

nit: Please move this either above or below the class declaration+definition.

[Tim Song, 2015/04/06 23:21:17]

Moved definitions to another file.

+
+CryptAuthAccessTokenFetcherImpl::CryptAuthAccessTokenFetcherImpl(
+    OAuth2TokenService* token_service,
+    const std::string& account_id)
+    : OAuth2TokenService::Consumer("cryptauth_account_token_fetcher"),
+      token_service_(token_service),
+      account_id_(account_id),
+      fetch_started_(false) {
+}
+
+CryptAuthAccessTokenFetcherImpl::~CryptAuthAccessTokenFetcherImpl() {
+}
+
+void CryptAuthAccessTokenFetcherImpl::FetchAccessToken(
+    const AccessTokenCallback& callback) {
+  if (fetch_started_) {
+    LOG(WARNING) << "Create an instance for each token fetched. Do not reuse.";
+    callback.Run(std::string());
+    return;
+  }
+
+  fetch_started_ = true;
+  callback_ = callback;
+  // This request will return a cached result if it is available, saving a
+  // network round trip every time we fetch the access token.
+  token_request_ = token_service_->StartRequest(account_id_, GetScopes(), this);
+}
+
+void CryptAuthAccessTokenFetcherImpl::OnGetTokenSuccess(
+    const OAuth2TokenService::Request* request,
+    const std::string& access_token,
+    const base::Time& expiration_time) {
+  callback_.Run(access_token);
+}
+
+void CryptAuthAccessTokenFetcherImpl::OnGetTokenFailure(
+    const OAuth2TokenService::Request* request,
+    const GoogleServiceAuthError& error) {
+  callback_.Run(std::string());
+}
+
+}  // namespace
+
+// static.
+scoped_ptr<CryptAuthAccessTokenFetcher>
+CryptAuthAccessTokenFetcher::CreateDefault(OAuth2TokenService* token_service,
+                                           const std::string& account_id) {
+  return make_scoped_ptr(
+      new CryptAuthAccessTokenFetcherImpl(token_service, account_id));
+}
+
+}  // namespace proximity_auth