# python3
# Copyright 2019 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.
"""Benchmark helpers."""

import datetime
from benchmarks.harness import machine


class Timer:
  """Helper to time runtime of some call.

  Usage:

    with Timer as t:
        # do something.
        t.get_time_in_seconds()
  """

  def __init__(self):
    self._start = datetime.datetime.now()

  def __enter__(self):
    self.start()
    return self

  def start(self):
    """Starts the timer."""
    self._start = datetime.datetime.now()

  def elapsed(self) -> float:
    """Returns the elapsed time in seconds."""
    return (datetime.datetime.now() - self._start).total_seconds()

  def __exit__(self, exception_type, exception_value, exception_traceback):
    pass


def drop_caches(target: machine.Machine):
  """Drops caches on the machine.

  Args:
    target: A machine object.
  """
  target.run("sudo sync")
  target.run("sudo sysctl vm.drop_caches=3")
  target.run("sudo sysctl vm.drop_caches=3")