// Copyright 2021 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 SHILL_VPN_IPSEC_CONNECTION_H_
#define SHILL_VPN_IPSEC_CONNECTION_H_

#include <memory>
#include <optional>
#include <string>
#include <vector>

#include <base/callback.h>
#include <base/files/file_path.h>
#include <base/files/file_path_watcher.h>
#include <base/files/scoped_temp_dir.h>

#include "shill/certificate_file.h"
#include "shill/mockable.h"
#include "shill/process_manager.h"
#include "shill/service.h"
#include "shill/vpn/vpn_connection.h"
#include "shill/vpn/vpn_util.h"

namespace shill {

// IPsecConnection manages the IPsec connection by starting charon process and
// taking to it via swanctl.
// When connecting, IPsecConnection will do the following steps to initiate the
// IPsec connection:
// - Create a temp dir in `/run/ipsec/` to store all the configuration files;
// - Generate strongswan.conf in the created temp dir;
// - Start charon process which is the IKE daemon;
// - Generate swanctl.conf in the created temp dir;
// - Invoke swanctl to let charon load the configurations in swanctl.conf;
// - Invoke swanctl to initiate the connection;
// TODO(b/165170125): Document temporary files.
class IPsecConnection : public VPNConnection {
 public:
  struct Config {
    // Remote hostname or IP address.
    std::string remote;

    // Fields required when using cert auth.
    std::optional<std::vector<std::string>> ca_cert_pem_strings;
    std::optional<std::string> client_cert_id;
    std::optional<std::string> client_cert_slot;
    std::optional<std::string> client_cert_pin;

    // Field required when using psk auth.
    std::optional<std::string> psk;

    // TODO(b/165170125): Add Xauth fields.
    // TODO(b/165170125): Add tunnel group.

    // Protocol and port on the local/remote side. Should be in form of
    // "proto/port", e.g., "17/1701". For the valid values of proto and port,
    // see https://wiki.strongswan.org/projects/strongswan/wiki/Swanctlconf
    std::string local_proto_port;
    std::string remote_proto_port;
  };

  // This enum is only used internally. It need to be public to be accessible in
  // tests. Each value represents an step in the connect procedure. Also see
  // ScheduleConnectTask().
  enum class ConnectStep {
    kStart,
    kStrongSwanConfigWritten,
    kSwanctlConfigWritten,
    kCharonStarted,
    kSwanctlConfigLoaded,
    kIPsecConnected,
  };

  explicit IPsecConnection(std::unique_ptr<Config> config,
                           std::unique_ptr<Callbacks> callbacks,
                           std::unique_ptr<VPNConnection> l2tp_connection,
                           EventDispatcher* dispatcher,
                           ProcessManager* process_manager);
  ~IPsecConnection();

 private:
  friend class IPsecConnectionUnderTest;

  void OnConnect() override;
  void OnDisconnect() override;

  // Run tasks for connecting in order based on the current |step|.
  mockable void ScheduleConnectTask(ConnectStep step);

  // Tasks scheduled by ScheduleConnectTask(). Each function should call
  // ScheduleConnectTask() (either directly or using a callback) on the task
  // done, or call NoitfyFailure() to indicate a failure.

  // Generates strongswan.conf. On success, this function will trigger
  // |kStrongSwanConfigWritten| step and set |strongswan_conf_path_|.
  void WriteStrongSwanConfig();
  // Starts charon process with minijail. The charon process will create the
  // vici socket file and then listen on it. This function will trigger
  // |kCharonStarted| step after that socket it ready. |charon_pid_| will be set
  // if charon is started successfully.
  void StartCharon();
  // Writes swanctl.conf. On success, this function will trigger
  // |kSwanctlConfigWritten| step and set |swanctl_conf_path_| (and also
  // |server_ca_| and |server_ca_path_| if cert auth is used).
  void WriteSwanctlConfig();
  // Executes `swanctl --load-all`. Trigger |kSwanctlConfigLoaded| on success.
  void SwanctlLoadConfig();
  // Executes `swanctl --initiate`. Trigger |kIPsecConnected| on success.
  void SwanctlInitiateConnection();

  void OnCharonExitedUnexpectedly(int exit_code);
  void OnViciSocketPathEvent(const base::FilePath& path, bool error);

  // Helper functions to run swanctl. RunSwanctl() executes `swanctl` with
  // |args|, and invokes |on_success| if the execution succeeds and the exit
  // code is 0, otherwise invokes NoitfyFailure() with |message_on_failure|.
  void RunSwanctl(const std::vector<std::string>& args,
                  base::OnceClosure on_success,
                  const std::string& message_on_failure);
  void OnSwanctlExited(base::OnceClosure on_success,
                       const std::string& message_on_failure,
                       int exit_code);

  // Callbacks from L2TPConnection.
  void OnL2TPConnected(const std::string& interface_name,
                       int interface_index,
                       const IPConfig::Properties& properties);
  void OnL2TPFailure(Service::ConnectFailure reason);
  void OnL2TPStopped();

  // Stops the charon process if it is running and invokes NotifyStopped().
  void StopCharon();

  std::unique_ptr<Config> config_;
  std::unique_ptr<VPNConnection> l2tp_connection_;

  // Runtime variables.
  base::ScopedTempDir temp_dir_;
  CertificateFile server_ca_;
  base::FilePath server_ca_path_;
  base::FilePath strongswan_conf_path_;
  base::FilePath swanctl_conf_path_;
  pid_t charon_pid_;
  base::FilePath vici_socket_path_;
  std::unique_ptr<base::FilePathWatcher> vici_socket_watcher_;

  // External dependencies.
  ProcessManager* process_manager_;
  std::unique_ptr<VPNUtil> vpn_util_;

  base::WeakPtrFactory<IPsecConnection> weak_factory_{this};
};

}  // namespace shill

#endif  // SHILL_VPN_IPSEC_CONNECTION_H_