"""Demonstrate POSIX thread safety problems with the subprocess module."""

from __future__ import print_function
import subprocess
import sys
import threading
import time


class Result(object):

  def __init__(self, name, value, expected):
    self.name = name
    self.value = value
    self.expected = expected

  def Print(self):
    print('  {}\t= {}, expected {} {}'.format(
        self.name, self.value, self.expected,
        '*** MISMATCH ***' if self.value != self.expected else ''))


def TestPopen(popen):
  """Test a particular 'Popen' method, and print results.

  Args:
    popen: (callable) the Popen method to test (ex subproccess.Popen).
  """
  start_time = time.time()
  results = []

  subproc = popen(['/bin/sleep', '60'])
  results.append(Result('r0', subproc.returncode, None))

  def Interrupt():
    """Kill the subprocess, and capture returncode."""
    # should be None because process hasn't exited yet
    results.append(Result('ri0', subproc.returncode, None))

    # kill the subproc, and wait for the result
    subproc.kill()
    subproc.wait()

    # should be -9 because subproc was killed
    results.append(Result('ri1', subproc.returncode, -9))

    # another wait() should be a no-op, because subproc has already finished
    subproc.wait()

    # should still be -9 because subproc was killed
    results.append(Result('ri2', subproc.returncode, -9))

  # start a separate thread to run Interrupt after a 1 second delay
  t = threading.Timer(1, Interrupt)
  t.start()

  results.append(Result('r1', subproc.returncode, None))

  # wait for subproc to finish; it will be killed before
  # successfully finishing, when Interrupt fires
  subproc.wait()

  # should be -9 because subproc was killed
  results.append(Result('r2', subproc.returncode, -9))

  # another wait() should be a no-op because subproc has already finished
  subproc.wait()

  # should still be -9 because subproc was killed
  results.append(Result('r3', subproc.returncode, -9))

  t.join()

  print('Results with %r:' % popen)

  for r in results:
    r.Print()

  print('elapsed = %f seconds' % (time.time() - start_time))


def main():
  print('sys.version = %s' % sys.version)
  print('--------')
  TestPopen(subprocess.Popen)


if __name__ == '__main__':
  main()