// Copyright 2017 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#ifndef PACKAGER_APP_JOB_MANAGER_H_
#define PACKAGER_APP_JOB_MANAGER_H_

#include <memory>
#include <vector>

#include "packager/base/threading/simple_thread.h"
#include "packager/status.h"

namespace shaka {
namespace media {

class OriginHandler;

// A job is a single line of work that is expected to run in parallel with
// other jobs.
class Job : public base::SimpleThread {
 public:
  Job(const std::string& name, std::shared_ptr<OriginHandler> work);

  // Request that the job stops executing. This is only a request and
  // will not block. If you want to wait for the job to complete, use
  // |wait|.
  void Cancel();

  // Get the current status of the job. If the job failed to initialize
  // or encountered an error during execution this will return the error.
  const Status& status() const { return status_; }

  // If you want to wait for this job to complete, this will return the
  // WaitableEvent you can wait on.
  base::WaitableEvent* wait() { return &wait_; }

 private:
  Job(const Job&) = delete;
  Job& operator=(const Job&) = delete;

  void Run() override;

  std::shared_ptr<OriginHandler> work_;
  Status status_;

  base::WaitableEvent wait_;
};

// Similar to a thread pool, JobManager manages multiple jobs that are expected
// to run in parallel. It can be used to register, run, and stop a batch of
// jobs.
class JobManager {
 public:
  JobManager() = default;

  // Create a new job entry by specifying the origin handler at the top of the
  // chain and a name for the thread. This will only register the job. To start
  // the job, you need to call |RunJobs|.
  void Add(const std::string& name, std::shared_ptr<OriginHandler> handler);

  // Initialize all registered jobs. If any job fails to initialize, this will
  // return the error and it will not be safe to call |RunJobs| as not all jobs
  // will be properly initialized.
  Status InitializeJobs();

  // Run all registered jobs. Before calling this make sure that
  // |InitializedJobs| returned |Status::OK|. This call is blocking and will
  // block until all jobs exit.
  Status RunJobs();

  // Ask all jobs to stop running. This call is non-blocking and can be used to
  // unblock a call to |RunJobs|.
  void CancelJobs();

 private:
  JobManager(const JobManager&) = delete;
  JobManager& operator=(const JobManager&) = delete;

  struct JobEntry {
    std::string name;
    std::shared_ptr<OriginHandler> worker;
  };
  // Stores Job entries for delayed construction of Job object.
  std::vector<JobEntry> job_entries_;
  std::vector<std::unique_ptr<Job>> jobs_;
};

}  // namespace media
}  // namespace shaka

#endif  // PACKAGER_APP_JOB_MANAGER_H_