/*
 * Copyright 2022 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef CDC_STREAM_SESSION_MANAGER_H_
#define CDC_STREAM_SESSION_MANAGER_H_

#include <memory>
#include <unordered_map>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/synchronization/mutex.h"
#include "cdc_stream/session_config.h"
#include "metrics/metrics.h"

namespace cdc_ft {

class MultiSession;
class ProcessFactory;
struct SessionTarget;

// Adds logic around MultiSession to start and stop streaming sessions. Makes
// sure that some invariants are maintained, like no two streaming sessions
// exist to the same target user@host:dir.
class SessionManager {
 public:
  SessionManager(SessionConfig cfg, ProcessFactory* process_factory,
                 metrics::MetricsService* metrics_service);
  ~SessionManager();

  // Starts a new session or reuses an existing one.
  // |instance_id| is a unique id for the remote instance and mount directory,
  // e.g. user@host:mount_dir.
  // |src_dir| is the local directory to stream.
  // |target| identifies the remote target and how to connect to it.
  // |project_id| is the project that owns the instance. Stadia only.
  // |organization_id| is organization that contains the instance. Stadia only.
  // Populates |multi_session| and |metrics_status| on success.
  absl::Status StartSession(const std::string& instance_id,
                            const std::string& src_dir,
                            const SessionTarget& target,
                            const std::string& project_id,
                            const std::string& organization_id,
                            MultiSession** multi_session,
                            metrics::SessionStartStatus* metrics_status)
      ABSL_LOCKS_EXCLUDED(sessions_mutex_);

  // Stops all sessions that match the given |instance_id_filter|.
  // The filter may contain Windows-style wildcards like * and ?.
  // Matching is case-sensitive.
  // Returns a NotFound error if no session exists.
  absl::Status StopSession(const std::string& instance_id_filter)
      ABSL_LOCKS_EXCLUDED(sessions_mutex_);

  // Shuts down all existing MultiSessions.
  absl::Status Shutdown() ABSL_LOCKS_EXCLUDED(sessions_mutex_);

 private:
  // Stops the session for the given |instance_id|. Returns a NotFound error if
  // no session exists.
  absl::Status StopSessionInternal(const std::string& instance_id)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);

  // Returns the MultiSession for the given workstation directory |src_dir| or
  // nullptr if it does not exist.
  MultiSession* GetMultiSession(const std::string& src_dir)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);

  // Gets an existing MultiSession or creates a new one for the given
  // workstation directory |src_dir|.
  absl::StatusOr<MultiSession*> GetOrCreateMultiSession(
      const std::string& src_dir)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);

  // Sets session start status for a metrics event.
  void SetSessionStartStatus(metrics::DeveloperLogEvent* evt,
                             absl::Status absl_status,
                             metrics::SessionStartStatus status) const;

  const SessionConfig cfg_;
  ProcessFactory* const process_factory_;
  metrics::MetricsService* const metrics_service_;

  absl::Mutex sessions_mutex_;
  using SessionMap =
      std::unordered_map<std::string, std::unique_ptr<MultiSession>>;
  SessionMap sessions_ ABSL_GUARDED_BY(sessions_mutex_);
};

}  // namespace cdc_ft

#endif  // CDC_STREAM_SESSION_MANAGER_H_