// Copyright (c) 2010 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.

#ifndef CHROME_BROWSER_POLICY_DEVICE_TOKEN_FETCHER_H_
#define CHROME_BROWSER_POLICY_DEVICE_TOKEN_FETCHER_H_
#pragma once

#include <string>

#include "base/file_path.h"
#include "base/ref_counted.h"
#include "base/waitable_event.h"
#include "chrome/browser/policy/device_management_backend.h"
#include "chrome/common/notification_observer.h"
#include "chrome/common/notification_registrar.h"

namespace policy {

namespace em = enterprise_management;

// Fetches the device token that can be used for policy requests with the device
// management server, either from disk if it already has been successfully
// requested, otherwise from the device management server. An instance of the
// fetcher is shared as a singleton by all users of the device management token
// to ensure they all get the same token.
class DeviceTokenFetcher
    : public NotificationObserver,
      public DeviceManagementBackend::DeviceRegisterResponseDelegate,
      public base::RefCountedThreadSafe<DeviceTokenFetcher> {
 public:
  // Requests to the device management server are sent through |backend|, which
  // is passed in explicitly to simplify mocking of the backend for unit
  // testing. The fetcher uses the directory in |token_dir| in which to store
  // the device token once it's retrieved from the server. Should only be called
  // by unit tests.
  DeviceTokenFetcher(DeviceManagementBackend* backend,
                     const FilePath& token_path);
  virtual ~DeviceTokenFetcher() {}

  // NotificationObserver method overrides:
  virtual void Observe(NotificationType type,
                       const NotificationSource& source,
                       const NotificationDetails& details);

  // DeviceManagementBackend::DeviceRegisterResponseDelegate method overrides:
  virtual void HandleRegisterResponse(
      const em::DeviceRegisterResponse& response);
  virtual void OnError(DeviceManagementBackend::ErrorCode code);

  // Called by subscribers of the device management token to indicate that they
  // will need the token in the future. Must be called on the UI thread.
  void StartFetching();

  // Returns true if there is a pending token request to the device management
  // server.
  bool IsTokenPending();

  // Returns the device management token for this device, blocking until
  // outstanding requests to the device management server are satisfied.  In the
  // case that the token could not be fetched, an empty string is returned.
  std::string GetDeviceToken();

  // True if the fetcher has a valid AuthToken for the device management server.
  bool HasAuthToken() const { return !auth_token_.empty(); }

  // True if the device token has been fetched and is valid.
  bool IsTokenValid() const;

 private:
  friend class DeviceTokenFetcherTest;

  // The different states that the fetcher can be in during the process of
  // getting the device token.
  enum FetcherState {
    kStateNotStarted,
    kStateLoadDeviceTokenFromDisk,
    kStateReadyToRequestDeviceTokenFromServer,
    kStateRequestingDeviceTokenFromServer,
    kStateHasDeviceToken,
    kStateFailure
  };

  // Moves the fetcher into a new state. If the fetcher has the device token
  // or is moving into the failure state, callers waiting on WaitForToken
  // are unblocked.
  void SetState(FetcherState state);

  // Returns the full path to the file that persists the device manager token.
  void GetDeviceTokenPath(FilePath* token_path) const;

  // Tries to load the device token from disk. Must be called on the FILE
  // thread.
  void AttemptTokenLoadFromDisk();

  // Called if it's not possible to load the device token from disk.  Sets the
  // fetcher in a state that's ready to register the device with the device
  // management server and receive the device token in return. If the AuthToken
  // for the device management server is available, initiate the server
  // request.
  void MakeReadyToRequestDeviceToken();

  // Issues a registration request to the server if both the fetcher is in the
  // ready-to-request state and the device management server AuthToken is
  // available.
  void SendServerRequestIfPossible();

  // Saves the device management token to disk once it has been retrieved from
  // the server. Must be called on the FILE thread.
  static void WriteDeviceTokenToDisk(const FilePath& path,
                                     const std::string& token);

  // Returns the device ID used to register the device with the device
  // management server and generate the device token.
  static std::string GetDeviceID();

  FilePath token_path_;
  DeviceManagementBackend* backend_;  // weak
  FetcherState state_;
  std::string device_token_;

  // Contains the AuthToken for the device management server. Empty if the
  // AuthToken hasn't been issued yet or that was an error getting the
  // AuthToken.
  std::string auth_token_;

  // An event that is signaled only once the device token has been fetched
  // or it has been determined that there was an error during fetching.
  base::WaitableEvent device_token_load_complete_event_;

  // Registers the fetcher for notification of successful Gaia logins.
  NotificationRegistrar registrar_;
};

}  // namespace policy

#endif  // CHROME_BROWSER_POLICY_DEVICE_TOKEN_FETCHER_H_