google_apis/gaia/oauth2_token_service.cc - platform/external/chromium_org - Git at Google

 // Copyright 2013 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 "google_apis/gaia/oauth2_token_service.h"

 #include <vector>

 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
 #include "base/stl_util.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "google_apis/gaia/gaia_urls.h"
 #include "google_apis/gaia/google_service_auth_error.h"
 #include "google_apis/gaia/oauth2_access_token_consumer.h"
 #include "google_apis/gaia/oauth2_access_token_fetcher.h"
 #include "net/url_request/url_request_context_getter.h"

 int OAuth2TokenService::max_fetch_retry_num_ = 5;

 OAuth2TokenService::RequestImpl::RequestImpl(
     OAuth2TokenService::Consumer* consumer)
     : consumer_(consumer) {
 }

 OAuth2TokenService::RequestImpl::~RequestImpl() {
   DCHECK(CalledOnValidThread());
 }

 void OAuth2TokenService::RequestImpl::InformConsumer(
     const GoogleServiceAuthError& error,
     const std::string& access_token,
     const base::Time& expiration_date) {
   DCHECK(CalledOnValidThread());
   if (error.state() == GoogleServiceAuthError::NONE)
     consumer_->OnGetTokenSuccess(this, access_token, expiration_date);
   else
     consumer_->OnGetTokenFailure(this, error);
 }

 // Class that fetches OAuth2 access tokens for given scopes and refresh token.
 //
 // It aims to meet OAuth2TokenService's requirements on token fetching. Retry
 // mechanism is used to handle failures.
 //
 // To use this class, call CreateAndStart() to create and start a Fetcher.
 //
 // The Fetcher will call back the service by calling
 // OAuth2TokenService::OnFetchComplete() when it completes fetching, if it is
 // not destructed before it completes fetching; if the Fetcher is destructed
 // before it completes fetching, the service will never be called back. The
 // Fetcher destructs itself after calling back the service when finishes
 // fetching.
 //
 // Requests that are waiting for the fetching results of this Fetcher can be
 // added to the Fetcher by calling
 // OAuth2TokenService::Fetcher::AddWaitingRequest() before the Fetcher completes
 // fetching.
 //
 // The waiting requests are taken as weak pointers and they can be deleted. The
 // waiting requests will be called back with fetching results if they are not
 // deleted
 // - when the Fetcher completes fetching, if the Fetcher is not destructed
 //   before it completes fetching, or
 // - when the Fetcher is destructed if the Fetcher is destructed before it
 //   completes fetching (in this case, the waiting requests will be called back
 //   with error).
 class OAuth2TokenService::Fetcher : public OAuth2AccessTokenConsumer {
  public:
   // Creates a Fetcher and starts fetching an OAuth2 access token for
   // |refresh_token| and |scopes| in the request context obtained by |getter|.
   // The given |oauth2_token_service| will be informed when fetching is done.
   static Fetcher* CreateAndStart(OAuth2TokenService* oauth2_token_service,
                                  net::URLRequestContextGetter* getter,
                                  const std::string& chrome_client_id,
                                  const std::string& chrome_client_secret,
                                  const std::string& refresh_token,
                                  const OAuth2TokenService::ScopeSet& scopes,
                                  base::WeakPtr<RequestImpl> waiting_request);
   virtual ~Fetcher();

   // Add a request that is waiting for the result of this Fetcher.
   void AddWaitingRequest(base::WeakPtr<RequestImpl> waiting_request);

   void Cancel();

   const OAuth2TokenService::ScopeSet& GetScopeSet() const;
   const std::string& GetRefreshToken() const;

   // The error result from this fetcher.
   const GoogleServiceAuthError& error() const { return error_; }

  protected:
    // OAuth2AccessTokenConsumer
   virtual void OnGetTokenSuccess(const std::string& access_token,
                                  const base::Time& expiration_date) OVERRIDE;
   virtual void OnGetTokenFailure(const GoogleServiceAuthError& error) OVERRIDE;

  private:
   Fetcher(OAuth2TokenService* oauth2_token_service,
           net::URLRequestContextGetter* getter,
           const std::string& chrome_client_id,
           const std::string& chrome_client_secret,
           const std::string& refresh_token,
           const OAuth2TokenService::ScopeSet& scopes,
           base::WeakPtr<RequestImpl> waiting_request);
   void Start();
   void InformWaitingRequests();
   void InformWaitingRequestsAndDelete();
   static bool ShouldRetry(const GoogleServiceAuthError& error);
   int64 ComputeExponentialBackOffMilliseconds(int retry_num);

   // |oauth2_token_service_| remains valid for the life of this Fetcher, since
   // this Fetcher is destructed in the dtor of the OAuth2TokenService or is
   // scheduled for deletion at the end of OnGetTokenFailure/OnGetTokenSuccess
   // (whichever comes first).
   OAuth2TokenService* const oauth2_token_service_;
   scoped_refptr<net::URLRequestContextGetter> getter_;
   const std::string refresh_token_;
   const OAuth2TokenService::ScopeSet scopes_;
   std::vector<base::WeakPtr<RequestImpl> > waiting_requests_;

   int retry_number_;
   base::OneShotTimer<OAuth2TokenService::Fetcher> retry_timer_;
   scoped_ptr<OAuth2AccessTokenFetcher> fetcher_;

   // Variables that store fetch results.
   // Initialized to be GoogleServiceAuthError::SERVICE_UNAVAILABLE to handle
   // destruction.
   GoogleServiceAuthError error_;
   std::string access_token_;
   base::Time expiration_date_;
   // OAuth2 client id and secret.
   std::string chrome_client_id_;
   std::string chrome_client_secret_;

   DISALLOW_COPY_AND_ASSIGN(Fetcher);
 };

 // static
 OAuth2TokenService::Fetcher* OAuth2TokenService::Fetcher::CreateAndStart(
     OAuth2TokenService* oauth2_token_service,
     net::URLRequestContextGetter* getter,
     const std::string& chrome_client_id,
     const std::string& chrome_client_secret,
     const std::string& refresh_token,
     const OAuth2TokenService::ScopeSet& scopes,
     base::WeakPtr<RequestImpl> waiting_request) {
   OAuth2TokenService::Fetcher* fetcher = new Fetcher(
       oauth2_token_service,
       getter,
       chrome_client_id,
       chrome_client_secret,
       refresh_token,
       scopes,
       waiting_request);
   fetcher->Start();
   return fetcher;
 }

 OAuth2TokenService::Fetcher::Fetcher(
     OAuth2TokenService* oauth2_token_service,
     net::URLRequestContextGetter* getter,
     const std::string& chrome_client_id,
     const std::string& chrome_client_secret,
     const std::string& refresh_token,
     const OAuth2TokenService::ScopeSet& scopes,
     base::WeakPtr<RequestImpl> waiting_request)
     : oauth2_token_service_(oauth2_token_service),
       getter_(getter),
       refresh_token_(refresh_token),
       scopes_(scopes),
       retry_number_(0),
       error_(GoogleServiceAuthError::SERVICE_UNAVAILABLE),
       chrome_client_id_(chrome_client_id),
       chrome_client_secret_(chrome_client_secret) {
   DCHECK(oauth2_token_service_);
   DCHECK(getter_.get());
   DCHECK(refresh_token_.length());
   waiting_requests_.push_back(waiting_request);
 }

 OAuth2TokenService::Fetcher::~Fetcher() {
   // Inform the waiting requests if it has not done so.
   if (waiting_requests_.size())
     InformWaitingRequests();
 }

 void OAuth2TokenService::Fetcher::Start() {
   fetcher_.reset(new OAuth2AccessTokenFetcher(this, getter_.get()));
   fetcher_->Start(chrome_client_id_,
                   chrome_client_secret_,
                   refresh_token_,
                   std::vector<std::string>(scopes_.begin(), scopes_.end()));
   retry_timer_.Stop();
 }

 void OAuth2TokenService::Fetcher::OnGetTokenSuccess(
     const std::string& access_token,
     const base::Time& expiration_date) {
   fetcher_.reset();

   // Fetch completes.
   error_ = GoogleServiceAuthError::AuthErrorNone();
   access_token_ = access_token;
   expiration_date_ = expiration_date;

   // Subclasses may override this method to skip caching in some cases, but
   // we still inform all waiting Consumers of a successful token fetch below.
   // This is intentional -- some consumers may need the token for cleanup
   // tasks. https://chromiumcodereview.appspot.com/11312124/
   oauth2_token_service_->RegisterCacheEntry(refresh_token_,
                                             scopes_,
                                             access_token_,
                                             expiration_date_);
   InformWaitingRequestsAndDelete();
 }

 void OAuth2TokenService::Fetcher::OnGetTokenFailure(
     const GoogleServiceAuthError& error) {
   fetcher_.reset();

   if (ShouldRetry(error) && retry_number_ < max_fetch_retry_num_) {
     int64 backoff = ComputeExponentialBackOffMilliseconds(retry_number_);
     ++retry_number_;
     retry_timer_.Stop();
     retry_timer_.Start(FROM_HERE,
                        base::TimeDelta::FromMilliseconds(backoff),
                        this,
                        &OAuth2TokenService::Fetcher::Start);
     return;
   }

   error_ = error;
   InformWaitingRequestsAndDelete();
 }

 // Returns an exponential backoff in milliseconds including randomness less than
 // 1000 ms when retrying fetching an OAuth2 access token.
 int64 OAuth2TokenService::Fetcher::ComputeExponentialBackOffMilliseconds(
     int retry_num) {
   DCHECK(retry_num < max_fetch_retry_num_);
   int64 exponential_backoff_in_seconds = 1 << retry_num;
   // Returns a backoff with randomness < 1000ms
   return (exponential_backoff_in_seconds + base::RandDouble()) * 1000;
 }

 // static
 bool OAuth2TokenService::Fetcher::ShouldRetry(
     const GoogleServiceAuthError& error) {
   GoogleServiceAuthError::State error_state = error.state();
   return error_state == GoogleServiceAuthError::CONNECTION_FAILED ||
          error_state == GoogleServiceAuthError::REQUEST_CANCELED ||
          error_state == GoogleServiceAuthError::SERVICE_UNAVAILABLE;
 }

 void OAuth2TokenService::Fetcher::InformWaitingRequests() {
   std::vector<base::WeakPtr<RequestImpl> >::const_iterator iter =
       waiting_requests_.begin();
   for (; iter != waiting_requests_.end(); ++iter) {
     base::WeakPtr<RequestImpl> waiting_request = *iter;
     if (waiting_request.get())
       waiting_request->InformConsumer(error_, access_token_, expiration_date_);
   }
   waiting_requests_.clear();
 }

 void OAuth2TokenService::Fetcher::InformWaitingRequestsAndDelete() {
   // Deregisters itself from the service to prevent more waiting requests to
   // be added when it calls back the waiting requests.
   oauth2_token_service_->OnFetchComplete(this);
   InformWaitingRequests();
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }

 void OAuth2TokenService::Fetcher::AddWaitingRequest(
     base::WeakPtr<OAuth2TokenService::RequestImpl> waiting_request) {
   waiting_requests_.push_back(waiting_request);
 }

 void OAuth2TokenService::Fetcher::Cancel() {
   fetcher_.reset();
   retry_timer_.Stop();
   error_ = GoogleServiceAuthError(GoogleServiceAuthError::REQUEST_CANCELED);
   InformWaitingRequestsAndDelete();
 }

 const OAuth2TokenService::ScopeSet& OAuth2TokenService::Fetcher::GetScopeSet()
     const {
   return scopes_;
 }

 const std::string& OAuth2TokenService::Fetcher::GetRefreshToken() const {
   return refresh_token_;
 }

 OAuth2TokenService::Request::Request() {
 }

 OAuth2TokenService::Request::~Request() {
 }

 OAuth2TokenService::Consumer::Consumer() {
 }

 OAuth2TokenService::Consumer::~Consumer() {
 }

 OAuth2TokenService::OAuth2TokenService() {
 }

 OAuth2TokenService::~OAuth2TokenService() {
   // Release all the pending fetchers.
   STLDeleteContainerPairSecondPointers(
       pending_fetchers_.begin(), pending_fetchers_.end());
 }

 void OAuth2TokenService::AddObserver(Observer* observer) {
   observer_list_.AddObserver(observer);
 }

 void OAuth2TokenService::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }

 bool OAuth2TokenService::RefreshTokenIsAvailable() {
   return !GetRefreshToken().empty();
 }

 scoped_ptr<OAuth2TokenService::Request> OAuth2TokenService::StartRequest(
     const OAuth2TokenService::ScopeSet& scopes,
     OAuth2TokenService::Consumer* consumer) {
   return StartRequestForClientWithContext(
       GetRequestContext(),
       GaiaUrls::GetInstance()->oauth2_chrome_client_id(),
       GaiaUrls::GetInstance()->oauth2_chrome_client_secret(),
       scopes,
       consumer);
 }

 scoped_ptr<OAuth2TokenService::Request>
 OAuth2TokenService::StartRequestForClient(
     const std::string& client_id,
     const std::string& client_secret,
     const OAuth2TokenService::ScopeSet& scopes,
     OAuth2TokenService::Consumer* consumer) {
   return StartRequestForClientWithContext(
       GetRequestContext(),
       client_id,
       client_secret,
       scopes,
       consumer);
 }

 scoped_ptr<OAuth2TokenService::Request>
 OAuth2TokenService::StartRequestWithContext(
     net::URLRequestContextGetter* getter,
     const ScopeSet& scopes,
     Consumer* consumer) {
   return StartRequestForClientWithContext(
       getter,
       GaiaUrls::GetInstance()->oauth2_chrome_client_id(),
       GaiaUrls::GetInstance()->oauth2_chrome_client_secret(),
       scopes,
       consumer);
 }

 scoped_ptr<OAuth2TokenService::Request>
 OAuth2TokenService::StartRequestForClientWithContext(
     net::URLRequestContextGetter* getter,
     const std::string& client_id,
     const std::string& client_secret,
     const ScopeSet& scopes,
     Consumer* consumer) {
   DCHECK(CalledOnValidThread());

   scoped_ptr<RequestImpl> request(new RequestImpl(consumer));

   if (!RefreshTokenIsAvailable()) {
     base::MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
         &RequestImpl::InformConsumer,
         request->AsWeakPtr(),
         GoogleServiceAuthError(GoogleServiceAuthError::USER_NOT_SIGNED_UP),
         std::string(),
         base::Time()));
     return request.PassAs<Request>();
   }

   if (HasCacheEntry(scopes)) {
     StartCacheLookupRequest(request.get(), scopes, consumer);
   } else {
     FetchOAuth2Token(request.get(),
                      getter,
                      client_id,
                      client_secret,
                      scopes);
   }
   return request.PassAs<Request>();
 }

 void OAuth2TokenService::FetchOAuth2Token(RequestImpl* request,
                                           net::URLRequestContextGetter* getter,
                                           const std::string& client_id,
                                           const std::string& client_secret,
                                           const ScopeSet& scopes) {
   std::string refresh_token = GetRefreshToken();

   // If there is already a pending fetcher for |scopes| and |refresh_token|,
   // simply register this |request| for those results rather than starting
   // a new fetcher.
   FetchParameters fetch_parameters = std::make_pair(refresh_token, scopes);
   std::map<FetchParameters, Fetcher*>::iterator iter =
       pending_fetchers_.find(fetch_parameters);
   if (iter != pending_fetchers_.end()) {
     iter->second->AddWaitingRequest(request->AsWeakPtr());
     return;
   }

   pending_fetchers_[fetch_parameters] =
       Fetcher::CreateAndStart(this,
                               getter,
                               client_id,
                               client_secret,
                               refresh_token,
                               scopes,
                               request->AsWeakPtr());
 }

 void OAuth2TokenService::StartCacheLookupRequest(
     RequestImpl* request,
     const OAuth2TokenService::ScopeSet& scopes,
     OAuth2TokenService::Consumer* consumer) {
   CHECK(HasCacheEntry(scopes));
   const CacheEntry* cache_entry = GetCacheEntry(scopes);
   base::MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
       &RequestImpl::InformConsumer,
       request->AsWeakPtr(),
       GoogleServiceAuthError(GoogleServiceAuthError::NONE),
       cache_entry->access_token,
       cache_entry->expiration_date));
 }

 void OAuth2TokenService::InvalidateToken(const ScopeSet& scopes,
                                          const std::string& invalid_token) {
   DCHECK(CalledOnValidThread());
   RemoveCacheEntry(scopes, invalid_token);
 }

 void OAuth2TokenService::OnFetchComplete(Fetcher* fetcher) {
   DCHECK(CalledOnValidThread());

   // Update the auth error state so auth errors are appropriately communicated
   // to the user.
   UpdateAuthError(fetcher->error());

   // Note |fetcher| is recorded in |pending_fetcher_| mapped to its refresh
   // token and scope set. This is guaranteed as follows; here a Fetcher is said
   // to be uncompleted if it has not finished calling back
   // OAuth2TokenService::OnFetchComplete().
   //
   // (1) All the live Fetchers are created by this service.
   //     This is because (1) all the live Fetchers are created by a live
   //     service, as all the fetchers created by a service are destructed in the
   //     service's dtor.
   //
   // (2) All the uncompleted Fetchers created by this service are recorded in
   //     |pending_fetchers_|.
   //     This is because (1) all the created Fetchers are added to
   //     |pending_fetchers_| (in method StartRequest()) and (2) method
   //     OnFetchComplete() is the only place where a Fetcher is erased from
   //     |pending_fetchers_|. Note no Fetcher is erased in method
   //     StartRequest().
   //
   // (3) Each of the Fetchers recorded in |pending_fetchers_| is mapped to its
   //     refresh token and ScopeSet. This is guaranteed by Fetcher creation in
   //     method StartRequest().
   //
   // When this method is called, |fetcher| is alive and uncompleted.
   // By (1), |fetcher| is created by this service.
   // Then by (2), |fetcher| is recorded in |pending_fetchers_|.
   // Then by (3), |fetcher_| is mapped to its refresh token and ScopeSet.
   std::map<FetchParameters, Fetcher*>::iterator iter =
     pending_fetchers_.find(std::make_pair(
         fetcher->GetRefreshToken(), fetcher->GetScopeSet()));
   DCHECK(iter != pending_fetchers_.end());
   DCHECK_EQ(fetcher, iter->second);
   pending_fetchers_.erase(iter);
 }

 bool OAuth2TokenService::HasCacheEntry(
     const OAuth2TokenService::ScopeSet& scopes) {
   const CacheEntry* cache_entry = GetCacheEntry(scopes);
   return cache_entry && cache_entry->access_token.length();
 }

 const OAuth2TokenService::CacheEntry* OAuth2TokenService::GetCacheEntry(
     const OAuth2TokenService::ScopeSet& scopes) {
   DCHECK(CalledOnValidThread());
   TokenCache::iterator token_iterator = token_cache_.find(scopes);
   if (token_iterator == token_cache_.end())
     return NULL;
   if (token_iterator->second.expiration_date <= base::Time::Now()) {
     token_cache_.erase(token_iterator);
     return NULL;
   }
   return &token_iterator->second;
 }

 bool OAuth2TokenService::RemoveCacheEntry(
     const OAuth2TokenService::ScopeSet& scopes,
     const std::string& token_to_remove) {
   DCHECK(CalledOnValidThread());
   TokenCache::iterator token_iterator = token_cache_.find(scopes);
   if (token_iterator != token_cache_.end() &&
       token_iterator->second.access_token == token_to_remove) {
     token_cache_.erase(token_iterator);
     return true;
   }
   return false;
 }

 void OAuth2TokenService::RegisterCacheEntry(
     const std::string& refresh_token,
     const OAuth2TokenService::ScopeSet& scopes,
     const std::string& access_token,
     const base::Time& expiration_date) {
   DCHECK(CalledOnValidThread());

   CacheEntry& token = token_cache_[scopes];
   token.access_token = access_token;
   token.expiration_date = expiration_date;
 }

 void OAuth2TokenService::UpdateAuthError(const GoogleServiceAuthError& error) {
   // Default implementation does nothing.
 }

 void OAuth2TokenService::ClearCache() {
   DCHECK(CalledOnValidThread());
   token_cache_.clear();
 }

 void OAuth2TokenService::CancelAllRequests() {
   std::vector<Fetcher*> fetchers_to_cancel;
   for (std::map<FetchParameters, Fetcher*>::iterator iter =
            pending_fetchers_.begin();
        iter != pending_fetchers_.end();
        ++iter) {
     fetchers_to_cancel.push_back(iter->second);
   }
   CancelFetchers(fetchers_to_cancel);
 }

 void OAuth2TokenService::CancelRequestsForToken(
     const std::string& refresh_token) {
   std::vector<Fetcher*> fetchers_to_cancel;
   for (std::map<FetchParameters, Fetcher*>::iterator iter =
            pending_fetchers_.begin();
        iter != pending_fetchers_.end();
        ++iter) {
     if (iter->first.first == refresh_token)
       fetchers_to_cancel.push_back(iter->second);
   }
   CancelFetchers(fetchers_to_cancel);
 }

 void OAuth2TokenService::CancelFetchers(
     std::vector<Fetcher*> fetchers_to_cancel) {
   for (std::vector<OAuth2TokenService::Fetcher*>::iterator iter =
            fetchers_to_cancel.begin();
        iter != fetchers_to_cancel.end();
        ++iter) {
     (*iter)->Cancel();
   }
 }

 void OAuth2TokenService::FireRefreshTokenAvailable(
     const std::string& account_id) {
   FOR_EACH_OBSERVER(Observer, observer_list_,
                     OnRefreshTokenAvailable(account_id));
 }

 void OAuth2TokenService::FireRefreshTokenRevoked(
     const std::string& account_id) {
   FOR_EACH_OBSERVER(Observer, observer_list_,
                     OnRefreshTokenRevoked(account_id));
 }

 void OAuth2TokenService::FireRefreshTokensLoaded() {
   FOR_EACH_OBSERVER(Observer, observer_list_, OnRefreshTokensLoaded());
 }

 void OAuth2TokenService::FireRefreshTokensCleared() {
   FOR_EACH_OBSERVER(Observer, observer_list_, OnRefreshTokensCleared());
 }

 int OAuth2TokenService::cache_size_for_testing() const {
   return token_cache_.size();
 }

 void OAuth2TokenService::set_max_authorization_token_fetch_retries_for_testing(
     int max_retries) {
   DCHECK(CalledOnValidThread());
   max_fetch_retry_num_ = max_retries;
 }
	// Copyright 2013 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 "google_apis/gaia/oauth2_token_service.h"

	#include <vector>

	#include "base/bind.h"
	#include "base/memory/weak_ptr.h"
	#include "base/message_loop/message_loop.h"
	#include "base/rand_util.h"
	#include "base/stl_util.h"
	#include "base/time/time.h"
	#include "base/timer/timer.h"
	#include "google_apis/gaia/gaia_urls.h"
	#include "google_apis/gaia/google_service_auth_error.h"
	#include "google_apis/gaia/oauth2_access_token_consumer.h"
	#include "google_apis/gaia/oauth2_access_token_fetcher.h"
	#include "net/url_request/url_request_context_getter.h"

	int OAuth2TokenService::max_fetch_retry_num_ = 5;

	OAuth2TokenService::RequestImpl::RequestImpl(
	OAuth2TokenService::Consumer* consumer)
	: consumer_(consumer) {
	}

	OAuth2TokenService::RequestImpl::~RequestImpl() {
	DCHECK(CalledOnValidThread());
	}

	void OAuth2TokenService::RequestImpl::InformConsumer(
	const GoogleServiceAuthError& error,
	const std::string& access_token,
	const base::Time& expiration_date) {
	DCHECK(CalledOnValidThread());
	if (error.state() == GoogleServiceAuthError::NONE)
	consumer_->OnGetTokenSuccess(this, access_token, expiration_date);
	else
	consumer_->OnGetTokenFailure(this, error);
	}

	// Class that fetches OAuth2 access tokens for given scopes and refresh token.
	//
	// It aims to meet OAuth2TokenService's requirements on token fetching. Retry
	// mechanism is used to handle failures.
	//
	// To use this class, call CreateAndStart() to create and start a Fetcher.
	//
	// The Fetcher will call back the service by calling
	// OAuth2TokenService::OnFetchComplete() when it completes fetching, if it is
	// not destructed before it completes fetching; if the Fetcher is destructed
	// before it completes fetching, the service will never be called back. The
	// Fetcher destructs itself after calling back the service when finishes
	// fetching.
	//
	// Requests that are waiting for the fetching results of this Fetcher can be
	// added to the Fetcher by calling
	// OAuth2TokenService::Fetcher::AddWaitingRequest() before the Fetcher completes
	// fetching.
	//
	// The waiting requests are taken as weak pointers and they can be deleted. The
	// waiting requests will be called back with fetching results if they are not
	// deleted
	// - when the Fetcher completes fetching, if the Fetcher is not destructed
	// before it completes fetching, or
	// - when the Fetcher is destructed if the Fetcher is destructed before it
	// completes fetching (in this case, the waiting requests will be called back
	// with error).
	class OAuth2TokenService::Fetcher : public OAuth2AccessTokenConsumer {
	public:
	// Creates a Fetcher and starts fetching an OAuth2 access token for
	// \|refresh_token\| and \|scopes\| in the request context obtained by \|getter\|.
	// The given \|oauth2_token_service\| will be informed when fetching is done.
	static Fetcher* CreateAndStart(OAuth2TokenService* oauth2_token_service,
	net::URLRequestContextGetter* getter,
	const std::string& chrome_client_id,
	const std::string& chrome_client_secret,
	const std::string& refresh_token,
	const OAuth2TokenService::ScopeSet& scopes,
	base::WeakPtr<RequestImpl> waiting_request);
	virtual ~Fetcher();

	// Add a request that is waiting for the result of this Fetcher.
	void AddWaitingRequest(base::WeakPtr<RequestImpl> waiting_request);

	void Cancel();

	const OAuth2TokenService::ScopeSet& GetScopeSet() const;
	const std::string& GetRefreshToken() const;

	// The error result from this fetcher.
	const GoogleServiceAuthError& error() const { return error_; }

	protected:
	// OAuth2AccessTokenConsumer
	virtual void OnGetTokenSuccess(const std::string& access_token,
	const base::Time& expiration_date) OVERRIDE;
	virtual void OnGetTokenFailure(const GoogleServiceAuthError& error) OVERRIDE;

	private:
	Fetcher(OAuth2TokenService* oauth2_token_service,
	net::URLRequestContextGetter* getter,
	const std::string& chrome_client_id,
	const std::string& chrome_client_secret,
	const std::string& refresh_token,
	const OAuth2TokenService::ScopeSet& scopes,
	base::WeakPtr<RequestImpl> waiting_request);
	void Start();
	void InformWaitingRequests();
	void InformWaitingRequestsAndDelete();
	static bool ShouldRetry(const GoogleServiceAuthError& error);
	int64 ComputeExponentialBackOffMilliseconds(int retry_num);

	// \|oauth2_token_service_\| remains valid for the life of this Fetcher, since
	// this Fetcher is destructed in the dtor of the OAuth2TokenService or is
	// scheduled for deletion at the end of OnGetTokenFailure/OnGetTokenSuccess
	// (whichever comes first).
	OAuth2TokenService* const oauth2_token_service_;
	scoped_refptr<net::URLRequestContextGetter> getter_;
	const std::string refresh_token_;
	const OAuth2TokenService::ScopeSet scopes_;
	std::vector<base::WeakPtr<RequestImpl> > waiting_requests_;

	int retry_number_;
	base::OneShotTimer<OAuth2TokenService::Fetcher> retry_timer_;
	scoped_ptr<OAuth2AccessTokenFetcher> fetcher_;

	// Variables that store fetch results.
	// Initialized to be GoogleServiceAuthError::SERVICE_UNAVAILABLE to handle
	// destruction.
	GoogleServiceAuthError error_;
	std::string access_token_;
	base::Time expiration_date_;
	// OAuth2 client id and secret.
	std::string chrome_client_id_;
	std::string chrome_client_secret_;

	DISALLOW_COPY_AND_ASSIGN(Fetcher);
	};

	// static
	OAuth2TokenService::Fetcher* OAuth2TokenService::Fetcher::CreateAndStart(
	OAuth2TokenService* oauth2_token_service,
	net::URLRequestContextGetter* getter,
	const std::string& chrome_client_id,
	const std::string& chrome_client_secret,
	const std::string& refresh_token,
	const OAuth2TokenService::ScopeSet& scopes,
	base::WeakPtr<RequestImpl> waiting_request) {
	OAuth2TokenService::Fetcher* fetcher = new Fetcher(
	oauth2_token_service,
	getter,
	chrome_client_id,
	chrome_client_secret,
	refresh_token,
	scopes,
	waiting_request);
	fetcher->Start();
	return fetcher;
	}

	OAuth2TokenService::Fetcher::Fetcher(
	OAuth2TokenService* oauth2_token_service,
	net::URLRequestContextGetter* getter,
	const std::string& chrome_client_id,
	const std::string& chrome_client_secret,
	const std::string& refresh_token,
	const OAuth2TokenService::ScopeSet& scopes,
	base::WeakPtr<RequestImpl> waiting_request)
	: oauth2_token_service_(oauth2_token_service),
	getter_(getter),
	refresh_token_(refresh_token),
	scopes_(scopes),
	retry_number_(0),
	error_(GoogleServiceAuthError::SERVICE_UNAVAILABLE),
	chrome_client_id_(chrome_client_id),
	chrome_client_secret_(chrome_client_secret) {
	DCHECK(oauth2_token_service_);
	DCHECK(getter_.get());
	DCHECK(refresh_token_.length());
	waiting_requests_.push_back(waiting_request);
	}

	OAuth2TokenService::Fetcher::~Fetcher() {
	// Inform the waiting requests if it has not done so.
	if (waiting_requests_.size())
	InformWaitingRequests();
	}

	void OAuth2TokenService::Fetcher::Start() {
	fetcher_.reset(new OAuth2AccessTokenFetcher(this, getter_.get()));
	fetcher_->Start(chrome_client_id_,
	chrome_client_secret_,
	refresh_token_,
	std::vector<std::string>(scopes_.begin(), scopes_.end()));
	retry_timer_.Stop();
	}

	void OAuth2TokenService::Fetcher::OnGetTokenSuccess(
	const std::string& access_token,
	const base::Time& expiration_date) {
	fetcher_.reset();

	// Fetch completes.
	error_ = GoogleServiceAuthError::AuthErrorNone();
	access_token_ = access_token;
	expiration_date_ = expiration_date;

	// Subclasses may override this method to skip caching in some cases, but
	// we still inform all waiting Consumers of a successful token fetch below.
	// This is intentional -- some consumers may need the token for cleanup
	// tasks. https://chromiumcodereview.appspot.com/11312124/
	oauth2_token_service_->RegisterCacheEntry(refresh_token_,
	scopes_,
	access_token_,
	expiration_date_);
	InformWaitingRequestsAndDelete();
	}

	void OAuth2TokenService::Fetcher::OnGetTokenFailure(
	const GoogleServiceAuthError& error) {
	fetcher_.reset();

	if (ShouldRetry(error) && retry_number_ < max_fetch_retry_num_) {
	int64 backoff = ComputeExponentialBackOffMilliseconds(retry_number_);
	++retry_number_;
	retry_timer_.Stop();
	retry_timer_.Start(FROM_HERE,
	base::TimeDelta::FromMilliseconds(backoff),
	this,
	&OAuth2TokenService::Fetcher::Start);
	return;
	}

	error_ = error;
	InformWaitingRequestsAndDelete();
	}

	// Returns an exponential backoff in milliseconds including randomness less than
	// 1000 ms when retrying fetching an OAuth2 access token.
	int64 OAuth2TokenService::Fetcher::ComputeExponentialBackOffMilliseconds(
	int retry_num) {
	DCHECK(retry_num < max_fetch_retry_num_);
	int64 exponential_backoff_in_seconds = 1 << retry_num;
	// Returns a backoff with randomness < 1000ms
	return (exponential_backoff_in_seconds + base::RandDouble()) * 1000;
	}

	// static
	bool OAuth2TokenService::Fetcher::ShouldRetry(
	const GoogleServiceAuthError& error) {
	GoogleServiceAuthError::State error_state = error.state();
	return error_state == GoogleServiceAuthError::CONNECTION_FAILED \|\|
	error_state == GoogleServiceAuthError::REQUEST_CANCELED \|\|
	error_state == GoogleServiceAuthError::SERVICE_UNAVAILABLE;
	}

	void OAuth2TokenService::Fetcher::InformWaitingRequests() {
	std::vector<base::WeakPtr<RequestImpl> >::const_iterator iter =
	waiting_requests_.begin();
	for (; iter != waiting_requests_.end(); ++iter) {
	base::WeakPtr<RequestImpl> waiting_request = *iter;
	if (waiting_request.get())
	waiting_request->InformConsumer(error_, access_token_, expiration_date_);
	}
	waiting_requests_.clear();
	}

	void OAuth2TokenService::Fetcher::InformWaitingRequestsAndDelete() {
	// Deregisters itself from the service to prevent more waiting requests to
	// be added when it calls back the waiting requests.
	oauth2_token_service_->OnFetchComplete(this);
	InformWaitingRequests();
	base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
	}

	void OAuth2TokenService::Fetcher::AddWaitingRequest(
	base::WeakPtr<OAuth2TokenService::RequestImpl> waiting_request) {
	waiting_requests_.push_back(waiting_request);
	}

	void OAuth2TokenService::Fetcher::Cancel() {
	fetcher_.reset();
	retry_timer_.Stop();
	error_ = GoogleServiceAuthError(GoogleServiceAuthError::REQUEST_CANCELED);
	InformWaitingRequestsAndDelete();
	}

	const OAuth2TokenService::ScopeSet& OAuth2TokenService::Fetcher::GetScopeSet()
	const {
	return scopes_;
	}

	const std::string& OAuth2TokenService::Fetcher::GetRefreshToken() const {
	return refresh_token_;
	}

	OAuth2TokenService::Request::Request() {
	}

	OAuth2TokenService::Request::~Request() {
	}

	OAuth2TokenService::Consumer::Consumer() {
	}

	OAuth2TokenService::Consumer::~Consumer() {
	}

	OAuth2TokenService::OAuth2TokenService() {
	}

	OAuth2TokenService::~OAuth2TokenService() {
	// Release all the pending fetchers.
	STLDeleteContainerPairSecondPointers(
	pending_fetchers_.begin(), pending_fetchers_.end());
	}

	void OAuth2TokenService::AddObserver(Observer* observer) {
	observer_list_.AddObserver(observer);
	}

	void OAuth2TokenService::RemoveObserver(Observer* observer) {
	observer_list_.RemoveObserver(observer);
	}

	bool OAuth2TokenService::RefreshTokenIsAvailable() {
	return !GetRefreshToken().empty();
	}

	scoped_ptr<OAuth2TokenService::Request> OAuth2TokenService::StartRequest(
	const OAuth2TokenService::ScopeSet& scopes,
	OAuth2TokenService::Consumer* consumer) {
	return StartRequestForClientWithContext(
	GetRequestContext(),
	GaiaUrls::GetInstance()->oauth2_chrome_client_id(),
	GaiaUrls::GetInstance()->oauth2_chrome_client_secret(),
	scopes,
	consumer);
	}

	scoped_ptr<OAuth2TokenService::Request>
	OAuth2TokenService::StartRequestForClient(
	const std::string& client_id,
	const std::string& client_secret,
	const OAuth2TokenService::ScopeSet& scopes,
	OAuth2TokenService::Consumer* consumer) {
	return StartRequestForClientWithContext(
	GetRequestContext(),
	client_id,
	client_secret,
	scopes,
	consumer);
	}

	scoped_ptr<OAuth2TokenService::Request>
	OAuth2TokenService::StartRequestWithContext(
	net::URLRequestContextGetter* getter,
	const ScopeSet& scopes,
	Consumer* consumer) {
	return StartRequestForClientWithContext(
	getter,
	GaiaUrls::GetInstance()->oauth2_chrome_client_id(),
	GaiaUrls::GetInstance()->oauth2_chrome_client_secret(),
	scopes,
	consumer);
	}

	scoped_ptr<OAuth2TokenService::Request>
	OAuth2TokenService::StartRequestForClientWithContext(
	net::URLRequestContextGetter* getter,
	const std::string& client_id,
	const std::string& client_secret,
	const ScopeSet& scopes,
	Consumer* consumer) {
	DCHECK(CalledOnValidThread());

	scoped_ptr<RequestImpl> request(new RequestImpl(consumer));

	if (!RefreshTokenIsAvailable()) {
	base::MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
	&RequestImpl::InformConsumer,
	request->AsWeakPtr(),
	GoogleServiceAuthError(GoogleServiceAuthError::USER_NOT_SIGNED_UP),
	std::string(),
	base::Time()));
	return request.PassAs<Request>();
	}

	if (HasCacheEntry(scopes)) {
	StartCacheLookupRequest(request.get(), scopes, consumer);
	} else {
	FetchOAuth2Token(request.get(),
	getter,
	client_id,
	client_secret,
	scopes);
	}
	return request.PassAs<Request>();
	}

	void OAuth2TokenService::FetchOAuth2Token(RequestImpl* request,
	net::URLRequestContextGetter* getter,
	const std::string& client_id,
	const std::string& client_secret,
	const ScopeSet& scopes) {
	std::string refresh_token = GetRefreshToken();

	// If there is already a pending fetcher for \|scopes\| and \|refresh_token\|,
	// simply register this \|request\| for those results rather than starting
	// a new fetcher.
	FetchParameters fetch_parameters = std::make_pair(refresh_token, scopes);
	std::map<FetchParameters, Fetcher*>::iterator iter =
	pending_fetchers_.find(fetch_parameters);
	if (iter != pending_fetchers_.end()) {
	iter->second->AddWaitingRequest(request->AsWeakPtr());
	return;
	}

	pending_fetchers_[fetch_parameters] =
	Fetcher::CreateAndStart(this,
	getter,
	client_id,
	client_secret,
	refresh_token,
	scopes,
	request->AsWeakPtr());
	}

	void OAuth2TokenService::StartCacheLookupRequest(
	RequestImpl* request,
	const OAuth2TokenService::ScopeSet& scopes,
	OAuth2TokenService::Consumer* consumer) {
	CHECK(HasCacheEntry(scopes));
	const CacheEntry* cache_entry = GetCacheEntry(scopes);
	base::MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
	&RequestImpl::InformConsumer,
	request->AsWeakPtr(),
	GoogleServiceAuthError(GoogleServiceAuthError::NONE),
	cache_entry->access_token,
	cache_entry->expiration_date));
	}

	void OAuth2TokenService::InvalidateToken(const ScopeSet& scopes,
	const std::string& invalid_token) {
	DCHECK(CalledOnValidThread());
	RemoveCacheEntry(scopes, invalid_token);
	}

	void OAuth2TokenService::OnFetchComplete(Fetcher* fetcher) {
	DCHECK(CalledOnValidThread());

	// Update the auth error state so auth errors are appropriately communicated
	// to the user.
	UpdateAuthError(fetcher->error());

	// Note \|fetcher\| is recorded in \|pending_fetcher_\| mapped to its refresh
	// token and scope set. This is guaranteed as follows; here a Fetcher is said
	// to be uncompleted if it has not finished calling back
	// OAuth2TokenService::OnFetchComplete().
	//
	// (1) All the live Fetchers are created by this service.
	// This is because (1) all the live Fetchers are created by a live
	// service, as all the fetchers created by a service are destructed in the
	// service's dtor.
	//
	// (2) All the uncompleted Fetchers created by this service are recorded in
	// \|pending_fetchers_\|.
	// This is because (1) all the created Fetchers are added to
	// \|pending_fetchers_\| (in method StartRequest()) and (2) method
	// OnFetchComplete() is the only place where a Fetcher is erased from
	// \|pending_fetchers_\|. Note no Fetcher is erased in method
	// StartRequest().
	//
	// (3) Each of the Fetchers recorded in \|pending_fetchers_\| is mapped to its
	// refresh token and ScopeSet. This is guaranteed by Fetcher creation in
	// method StartRequest().
	//
	// When this method is called, \|fetcher\| is alive and uncompleted.
	// By (1), \|fetcher\| is created by this service.
	// Then by (2), \|fetcher\| is recorded in \|pending_fetchers_\|.
	// Then by (3), \|fetcher_\| is mapped to its refresh token and ScopeSet.
	std::map<FetchParameters, Fetcher*>::iterator iter =
	pending_fetchers_.find(std::make_pair(
	fetcher->GetRefreshToken(), fetcher->GetScopeSet()));
	DCHECK(iter != pending_fetchers_.end());
	DCHECK_EQ(fetcher, iter->second);
	pending_fetchers_.erase(iter);
	}

	bool OAuth2TokenService::HasCacheEntry(
	const OAuth2TokenService::ScopeSet& scopes) {
	const CacheEntry* cache_entry = GetCacheEntry(scopes);
	return cache_entry && cache_entry->access_token.length();
	}

	const OAuth2TokenService::CacheEntry* OAuth2TokenService::GetCacheEntry(
	const OAuth2TokenService::ScopeSet& scopes) {
	DCHECK(CalledOnValidThread());
	TokenCache::iterator token_iterator = token_cache_.find(scopes);
	if (token_iterator == token_cache_.end())
	return NULL;
	if (token_iterator->second.expiration_date <= base::Time::Now()) {
	token_cache_.erase(token_iterator);
	return NULL;
	}
	return &token_iterator->second;
	}

	bool OAuth2TokenService::RemoveCacheEntry(
	const OAuth2TokenService::ScopeSet& scopes,
	const std::string& token_to_remove) {
	DCHECK(CalledOnValidThread());
	TokenCache::iterator token_iterator = token_cache_.find(scopes);
	if (token_iterator != token_cache_.end() &&
	token_iterator->second.access_token == token_to_remove) {
	token_cache_.erase(token_iterator);
	return true;
	}
	return false;
	}

	void OAuth2TokenService::RegisterCacheEntry(
	const std::string& refresh_token,
	const OAuth2TokenService::ScopeSet& scopes,
	const std::string& access_token,
	const base::Time& expiration_date) {
	DCHECK(CalledOnValidThread());

	CacheEntry& token = token_cache_[scopes];
	token.access_token = access_token;
	token.expiration_date = expiration_date;
	}

	void OAuth2TokenService::UpdateAuthError(const GoogleServiceAuthError& error) {
	// Default implementation does nothing.
	}

	void OAuth2TokenService::ClearCache() {
	DCHECK(CalledOnValidThread());
	token_cache_.clear();
	}

	void OAuth2TokenService::CancelAllRequests() {
	std::vector<Fetcher*> fetchers_to_cancel;
	for (std::map<FetchParameters, Fetcher*>::iterator iter =
	pending_fetchers_.begin();
	iter != pending_fetchers_.end();
	++iter) {
	fetchers_to_cancel.push_back(iter->second);
	}
	CancelFetchers(fetchers_to_cancel);
	}

	void OAuth2TokenService::CancelRequestsForToken(
	const std::string& refresh_token) {
	std::vector<Fetcher*> fetchers_to_cancel;
	for (std::map<FetchParameters, Fetcher*>::iterator iter =
	pending_fetchers_.begin();
	iter != pending_fetchers_.end();
	++iter) {
	if (iter->first.first == refresh_token)
	fetchers_to_cancel.push_back(iter->second);
	}
	CancelFetchers(fetchers_to_cancel);
	}

	void OAuth2TokenService::CancelFetchers(
	std::vector<Fetcher*> fetchers_to_cancel) {
	for (std::vector<OAuth2TokenService::Fetcher*>::iterator iter =
	fetchers_to_cancel.begin();
	iter != fetchers_to_cancel.end();
	++iter) {
	(*iter)->Cancel();
	}
	}

	void OAuth2TokenService::FireRefreshTokenAvailable(
	const std::string& account_id) {
	FOR_EACH_OBSERVER(Observer, observer_list_,
	OnRefreshTokenAvailable(account_id));
	}

	void OAuth2TokenService::FireRefreshTokenRevoked(
	const std::string& account_id) {
	FOR_EACH_OBSERVER(Observer, observer_list_,
	OnRefreshTokenRevoked(account_id));
	}

	void OAuth2TokenService::FireRefreshTokensLoaded() {
	FOR_EACH_OBSERVER(Observer, observer_list_, OnRefreshTokensLoaded());
	}

	void OAuth2TokenService::FireRefreshTokensCleared() {
	FOR_EACH_OBSERVER(Observer, observer_list_, OnRefreshTokensCleared());
	}

	int OAuth2TokenService::cache_size_for_testing() const {
	return token_cache_.size();
	}

	void OAuth2TokenService::set_max_authorization_token_fetch_retries_for_testing(
	int max_retries) {
	DCHECK(CalledOnValidThread());
	max_fetch_retry_num_ = max_retries;
	}