// Copyright (c) 2012 The Chromium OS 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 LOGIN_MANAGER_SESSION_MANAGER_SERVICE_H_
#define LOGIN_MANAGER_SESSION_MANAGER_SERVICE_H_

#include <string>
#include <vector>

#include <base/callback.h>
#include <base/files/file_path.h>
#include <base/macros.h>
#include <base/memory/ref_counted.h>
#include <base/memory/scoped_ptr.h>
#include <base/time/time.h>
#include <brillo/asynchronous_signal_handler.h>
#include <chromeos/dbus/service_constants.h>
#include <dbus/bus.h>
#include <dbus/message.h>

#include "login_manager/child_exit_handler.h"
#include "login_manager/job_manager.h"
#include "login_manager/key_generator.h"
#include "login_manager/liveness_checker.h"
#include "login_manager/process_manager_service_interface.h"
#include "login_manager/server_backed_state_key_generator.h"
#include "login_manager/session_manager_interface.h"

struct signalfd_siginfo;

class MessageLoop;

namespace dbus {
class ExportedObject;
class ObjectProxy;
}  // namespace dbus

namespace login_manager {

class BrowserJobInterface;
class DBusSignalEmitterInterface;
class LoginMetrics;
class NssUtil;
class SessionManagerDBusAdaptor;
class SystemUtils;

// Provides methods for running the browser, watching its progress, and
// restarting it if need be.
//
// Once the browser is run, it will be restarted perpetually, UNLESS
// |magic_chrome_file| exists, or this process receives a termination signal.
// Also provides a wrapper that exports SessionManagerImpl methods via
// D-Bus.
//
// ::g_type_init() must be called before this class is used.
class SessionManagerService
    : public base::RefCountedThreadSafe<SessionManagerService>,
      public JobManagerInterface,
      public ProcessManagerServiceInterface {
 public:
  enum ExitCode {
    SUCCESS = 0,
    CRASH_WHILE_RESTART_DISABLED = 1,
    CHILD_EXITING_TOO_FAST = 2,
    MUST_WIPE_DEVICE = 3,
  };

  // Path to flag file indicating that a user has logged in since last boot.
  static const char kLoggedInFlag[];

  // Path to magic file that will trigger device wiping on next boot.
  static const char kResetFile[];

  // Constants for setting the ARC instance cgroup state.
  static const char kFrozen[];
  static const char kThawed[];

  // If you want to call any of these setters, you should do so before calling
  // any other methods on this class.
  class TestApi {
   public:
    void set_systemutils(SystemUtils* utils) {
      session_manager_service_->system_ = utils;
    }
    void set_login_metrics(LoginMetrics* metrics) {
      session_manager_service_->login_metrics_ = metrics;
    }
    void set_liveness_checker(LivenessChecker* checker) {
      session_manager_service_->liveness_checker_.reset(checker);
    }
    void set_session_manager(SessionManagerInterface* impl) {
      session_manager_service_->impl_.reset(impl);
    }
    // Sets whether the the manager exits when a child finishes.
    void set_exit_on_child_done(bool do_exit) {
      session_manager_service_->exit_on_child_done_ = do_exit;
    }

    // Sets up powerd and arc cgroup freezer state location
    // for testing ARC functionality.
    void set_powerd_object_proxy(dbus::ObjectProxy* proxy) {
      session_manager_service_->powerd_dbus_proxy_ = proxy;
    }
    void set_arc_cgroup_freezer_state_path(base::FilePath path) {
      session_manager_service_->arc_cgroup_freezer_state_path_ = path;
    }
    void set_suspend_delay_id(int id) {
      session_manager_service_->suspend_delay_id_ = id;
    }

    // Executes the CleanupChildren() method on the manager.
    void CleanupChildren(int timeout_sec) {
      session_manager_service_->CleanupChildren(
          base::TimeDelta::FromSeconds(timeout_sec));
    }

    // Cause handling of faked-out exit of a child process.
    void ScheduleChildExit(pid_t pid, int status);

    // Trigger and handle SessionManagerImpl initialization.
    bool InitializeImpl() { return session_manager_service_->InitializeImpl(); }

    // Fake messages from powerd.
    void Suspend(dbus::Signal* signal) {
      return session_manager_service_->HandleSuspendImminent(signal);
    }
    void Resume() {
      return session_manager_service_->HandleSuspendDone(nullptr);
    }

   private:
    friend class SessionManagerService;
    explicit TestApi(SessionManagerService* session_manager_service)
        : session_manager_service_(session_manager_service) {}
    SessionManagerService* session_manager_service_;
  };

  SessionManagerService(scoped_ptr<BrowserJobInterface> child_job,
                        uid_t uid,
                        int kill_timeout,
                        bool enable_browser_abort_on_hang,
                        base::TimeDelta hang_detection_interval,
                        LoginMetrics* metrics,
                        SystemUtils* system);
  virtual ~SessionManagerService();

  // TestApi exposes internal routines for testing purposes.
  TestApi test_api() { return TestApi(this); }

  bool Initialize();

  // Tears down objects set up during Initialize(), cleans up child processes,
  // and announces that the user session has stopped over DBus.
  void Finalize();

  ExitCode exit_code() { return exit_code_; }

  // Implementing ProcessManagerServiceInterface
  void ScheduleShutdown() override;
  void RunBrowser() override;
  void AbortBrowser(int signal, const std::string& message) override;
  void RestartBrowserWithArgs(const std::vector<std::string>& args,
                              bool args_are_extra) override;
  void SetBrowserSessionForUser(const std::string& username,
                                const std::string& userhash) override;
  void SetFlagsForUser(const std::string& username,
                       const std::vector<std::string>& flags) override;
  bool IsBrowser(pid_t pid) override;

  // Implementation of JobManagerInterface.
  // Actually just an alias for IsBrowser
  bool IsManagedJob(pid_t pid) override;
  // Re-runs the browser, unless one of the following is true:
  //  The screen is supposed to be locked,
  //  UI shutdown is in progress,
  //  The child indicates that it should not run anymore, or
  //  ShouldRunBrowser() indicates the browser should not run anymore.
  void HandleExit(const siginfo_t& info) override;
  // Request that browser_ exit.
  void RequestJobExit() override;
  // Ensure that browser_ is gone.
  void EnsureJobExit(base::TimeDelta timeout) override;

  // Set all changed signal handlers back to the default behavior.
  // This _must_ be async signal safe. No library calls or malloc'ing allowed.
  static void RevertHandlers();

 private:
  static const int kKillTimeoutCollectChrome;
  static const char kCollectChromeFile[];

  // |data| is a SessionManagerService*.
  static DBusHandlerResult FilterMessage(DBusConnection* conn,
                                         DBusMessage* message,
                                         void* data);

  // Set up any necessary signal handlers.
  void SetUpHandlers();

  // Returns appropriate child-killing timeout, depending on flag file state.
  base::TimeDelta GetKillTimeout();

  // Initializes policy subsystems which, among other things, finds and
  // validates the stored policy signing key if one is present.
  // A corrupted policy key means that the device needs to have its data wiped.
  // We trigger a reboot and then wipe (most of) the stateful partition.
  bool InitializeImpl();

  // Initializes connection to DBus system bus, and creates proxies to talk
  // to other needed services. Failure is fatal.
  void InitializeDBus();

  // Initializes suspend delays with powerd and registers callbacks for
  // suspend and resume.
  void InitializeSuspendDelays();

  // Takes ownership of the Session Manager's well-known service name.
  // Failure is fatal.
  void TakeDBusServiceOwnership();

  // Tears down DBus connection. Failure is fatal.
  void ShutDownDBus();

  // Tell us that, if we want, we can cause a graceful exit from MessageLoop.
  void AllowGracefulExitOrRunForever();

  // Sets the proccess' exit code immediately and posts a QuitClosure to the
  // main event loop.
  void SetExitAndScheduleShutdown(ExitCode code);

  // Terminate all children, with increasing prejudice.
  void CleanupChildren(base::TimeDelta timeout);

  // Callback when receiving a termination signal.
  bool OnTerminationSignal(const struct signalfd_siginfo& info);

  // Helper for making powerd calls.
  bool CallPowerdMethod(const std::string& method_name,
                        const google::protobuf::MessageLite& request,
                        google::protobuf::MessageLite* reply_out);

  // Sets up suspend delay with powerd.
  void SetUpSuspendHandler();

  // Callbacks for suspend/resume.
  void HandleSuspendImminent(dbus::Signal* signal);
  void HandleSuspendDone(dbus::Signal* signal);

  // Sets the ARC instance cgroup state. Can be used to freeze or thaw
  // the instance.
  void SetArcCgroupState(const std::string& state);

  scoped_ptr<BrowserJobInterface> browser_;
  bool exit_on_child_done_;
  const base::TimeDelta kill_timeout_;

  scoped_refptr<dbus::Bus> bus_;
  const std::string match_rule_;
  dbus::ExportedObject* session_manager_dbus_object_;  // Owned by bus_;
  dbus::ObjectProxy* powerd_dbus_proxy_;  // Owned by bus_.

  // ARC instance related. |arc_cgroup_freezer_state_path_| is the path
  // to the sysfs file that controls whether the instance's processes
  // are frozen. |suspend_delay_id_| needs to be passed back to powerd
  // after we are done freezing the instance to let it know we're ready
  // to suspend.
  base::FilePath arc_cgroup_freezer_state_path_;
  int suspend_delay_id_;

  LoginMetrics* login_metrics_;  // Owned by the caller.
  SystemUtils* system_;  // Owned by the caller.

  scoped_ptr<NssUtil> nss_;
  KeyGenerator key_gen_;
  ServerBackedStateKeyGenerator state_key_generator_;
  scoped_ptr<DBusSignalEmitterInterface> dbus_emitter_;
  scoped_ptr<LivenessChecker> liveness_checker_;
  const bool enable_browser_abort_on_hang_;
  const base::TimeDelta liveness_checking_interval_;

  // Holds pointers to nss_, key_gen_, this. Shares system_, login_metrics_.
  scoped_ptr<SessionManagerInterface> impl_;
  scoped_ptr<SessionManagerDBusAdaptor> adaptor_;

  brillo::AsynchronousSignalHandler signal_handler_;
  ChildExitHandler child_exit_handler_;
  bool shutting_down_;
  bool shutdown_already_;
  ExitCode exit_code_;

  DISALLOW_COPY_AND_ASSIGN(SessionManagerService);
};
}  // namespace login_manager

#endif  // LOGIN_MANAGER_SESSION_MANAGER_SERVICE_H_