// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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 __WINDOWS__
#include <unistd.h> // For pid_t.
#endif // __WINDOWS__

#include <deque>

#include <process/clock.hpp>

#include <stout/foreach.hpp>
#include <stout/os.hpp>

#include <stout/os/pstree.hpp>

#include "usage/usage.hpp"

namespace mesos {
namespace internal {

Try<ResourceStatistics> usage(pid_t pid, bool mem, bool cpus)
{
  Try<os::ProcessTree> pstree = os::pstree(pid);

  if (pstree.isError()) {
    return Error("Failed to get usage: " + pstree.error());
  }

  ResourceStatistics statistics;

  // The timestamp is the only required field.
  statistics.set_timestamp(process::Clock::now().secs());

  std::deque<os::ProcessTree> trees;
  trees.push_back(pstree.get());

  while (!trees.empty()) {
    const os::ProcessTree& tree = trees.front();

    if (mem) {
      if (tree.process.rss.isSome()) {
        statistics.set_mem_rss_bytes(
            statistics.mem_rss_bytes() + tree.process.rss->bytes());
      }
    }

    // We only show utime and stime when both are available, otherwise
    // we're exposing a partial view of the CPU times.
    if (cpus) {
      if (tree.process.utime.isSome() && tree.process.stime.isSome()) {
        statistics.set_cpus_user_time_secs(
            statistics.cpus_user_time_secs() + tree.process.utime->secs());

        statistics.set_cpus_system_time_secs(
            statistics.cpus_system_time_secs() + tree.process.stime->secs());
      }
    }

    foreach (const os::ProcessTree& child, tree.children) {
      trees.push_back(child);
    }

    trees.pop_front();
  }

  return statistics;
}

} // namespace internal {
} // namespace mesos {