import asyncio
import concurrent.futures
import os.path
import subprocess
import sys
import traceback


@asyncio.coroutine
def getcommandoutput(*args):
    # Slight modification of the function getstatusoutput present in:
    # https://docs.python.org/3/library/asyncio-subprocess.html#example
    proc = yield from asyncio.create_subprocess_exec(
        *args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    try:
        stdout, stderr = yield from proc.communicate()
    except:
        proc.kill()
        yield from proc.wait()
        raise

    exitcode = yield from proc.wait()
    return (exitcode, stdout, stderr)


MAX_PROCESSES = 10
ITERATIONS = 10**4

def check_results(done):
    errors = 0
    for future in done:
        try:
            future.result()
        except Exception as e:
            errors += 1
            traceback.print_exc()
    return errors

@asyncio.coroutine
def test():
    running = set()
    errors = 0
    for i in range(ITERATIONS):
        filename = __file__
        if i % 100 == 0:
            print(i)
        while len(running) > MAX_PROCESSES:
            done, pending = yield from asyncio.wait(
                running,
                timeout=1.0,
                return_when=concurrent.futures.FIRST_COMPLETED)
            errors += check_results(done)
            if errors:
                print('errors')
                return
            running = pending
            if not done:
                yield from asyncio.sleep(1.0)
        running.add(getcommandoutput('du', '--bytes', filename))
    done, pending = yield from asyncio.wait(running)
    errors += check_results(done)
    assert errors == 0


if __name__ == '__main__':
    if len(sys.argv) > 1:
        MAX_PROCESSES = int(sys.argv[1])
    if len(sys.argv) > 2:
        ITERATIONS = int(sys.argv[2])
    loop = asyncio.get_event_loop()
    loop.run_until_complete(test())