import concurrent.futures
import tempfile
import os
import shutil
import subprocess


def task(kind):
    dirname = tempfile.mkdtemp()
    f_w =  open(os.path.join(dirname, "stdout.txt"), "w")

    if kind == "subprocess_devnull":
        with subprocess.Popen("dir", shell=True, stdout=subprocess.DEVNULL):
            pass
    elif kind == "subprocess_noredirect":
        with subprocess.Popen("dir > NUL", shell=True):
            pass
    elif kind == "subprocess_redirfile":
        with subprocess.Popen("dir", shell=True, stdout=f_w):
            pass
    elif kind == "nosubprocess":
        print("Starting", file=f_w)
        import time
        time.sleep(0.1)
        print("Stop", file=f_w)
    else:
        raise ValueError("invalid value {}".format(kind))

    f_w.close()

    shutil.rmtree(dirname)


def execute_tasks(N, parallel, kind):
    results = []
    def task_done(f):
        if f.exception() is None:
            results.append(True)
        else:
            #print(f.exception())
            results.append(f.exception())

    threadpool = concurrent.futures.ThreadPoolExecutor(max_workers=parallel)
    for i in range(N):
        threadpool.submit(task, kind).add_done_callback(task_done)

    threadpool.shutdown()
    errors = [r for r in results if r is not True]
    print(FMTSTRING.format(kind, parallel, "OK" if len(errors) == 0 else "{} errors".format(len(errors))))


import platform
print("Platform:", platform.platform())
print()
FMTSTRING = "{:25} {:<10} {:10}"
print(FMTSTRING.format(*"task_type #threads result".split()))


execute_tasks(10, 2, "subprocess_redirfile")
execute_tasks(10, 1, "subprocess_redirfile")
execute_tasks(10, 2, "subprocess_devnull")
execute_tasks(10, 1, "subprocess_devnull")
execute_tasks(10, 2, "subprocess_noredirect")
execute_tasks(10, 1, "subprocess_noredirect")
execute_tasks(10, 2, "nosubprocess")
execute_tasks(10, 1, "nosubprocess")