import logging
import tempfile
import subprocess

class Result(object):

    def __init__(self, rc, stdout, stderr, cmd):
        self.rc = rc
        self.stdout = stdout
        self.stderr = stderr
        self.cmd= cmd

    def __str__(self):
        cutoff = 128
        if len(self.stdout) > cutoff:
            self.stdout = self.stdout[:cutoff] + '...'
        if len(self.stderr) > cutoff:
            self.stderr = self.stderr[:cutoff] + '...'

        return "Result: cmd=%(cmd)s -> " \
               "rc=%(rc)s, stdout=%(stdout)s, stderr=%(stderr)s" % {k: repr(self.__dict__[k]) for k in self.__dict__}

def run(cmd, shell=True, large_buffer=False):
    logging.info("run: '%s' on <localhost>..." % cmd)

    # subprocess.PIPE is a fixed size (64K) buffer,
    # process will be hanging if stdout exceeds this limit.
    if large_buffer:
        stdout = tempfile.TemporaryFile()
        stderr = tempfile.TemporaryFile()
    else:
        stdout = subprocess.PIPE
        stderr = subprocess.PIPE

    child = subprocess.Popen(
        cmd,
        shell=shell,
        stdout=stdout,
        stderr=stderr,
        close_fds=False
    )

    child.wait()
    rc = child.returncode
    if large_buffer:
        stdout.seek(0)
        stderr.seek(0)
        out = stdout.read()
        err = stderr.read()
        stdout.close()
        stderr.close()
    else:
        out = child.stdout.read()
        err = child.stderr.read()


    r = Result(rc, out, err, cmd)
    logging.debug(str(r))
    if r.rc != 0:
        logging.warning("Non-zero return code!!! %s" % r)
        logging.debug(r.stdout)
        logging.debug(r.stderr)
    return r

# cmd = "for i in {1..10000}; do echo 'hello world\n'; done"
cmd = "sh -c \"for i in {1..10000}; do echo 'hello world\n'; done\""
# 1. Without using tempfile, the process is hanging.
# r = run(cmd)
# print r

# 2. Using tempfile works.
r = run(cmd, large_buffer=True)
print r