#!/usr/bin/env python

import argparse
import sys
import syslog
import subprocess


def get_command_result(command):
    """Executes command and return the exit code, stdout and stderr.

    Args:
        command: A string contains the command to be executed.

    Returns:
        An integer contains the exit code.
        A string contains the output of stdout.
        A string contains the output of stderr.
    """
    command_stdout = ""
    command_stderr = ""

    try:
        proc_instance = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                                         shell=True, universal_newlines=True)
        command_stdout, command_stderr = proc_instance.communicate()
        if proc_instance.returncode != 0:
            return 1, command_stdout.strip(), command_stderr.strip()
    except (OSError, ValueError) as err:
        return 2, command_stdout.strip(), err

    return 0, command_stdout.strip(), command_stderr.strip()


def reset_failed_flag(service_name):
    """Reset the failed status of a service.

    Args:
        service_name: Name of the service.

    Returns:
        None
    """
    reset_failed_command = "sudo systemctl reset-failed {}.service".format(service_name)

    syslog.syslog(syslog.LOG_INFO, "Resetting failed status of service '{}' ..."
                  .format(service_name))

    exit_code, command_stdout, command_stderr = get_command_result(reset_failed_command)
    if exit_code == 0:
        syslog.syslog(syslog.LOG_INFO, "Succeeded to reset failed status of service '{}.service'."
                      .format(service_name))
    else:
        syslog.syslog(syslog.LOG_ERR, "Failed to reset failed status of service '{}'. Error: {}"
                      .format(service_name, command_stderr))


def restart_service(service_name):
    """Reset the failed status of a service and then restart it.

    Args:
        service_name: Name of specified service.

    Returns:
        None.
    """
    restart_command = "sudo systemctl restart {}.service".format(service_name)

    reset_failed_flag(service_name)

    syslog.syslog(syslog.LOG_INFO, "Restarting service '{}' ...".format(service_name))
    exit_code, command_stdout, command_stderr = get_command_result(restart_command)
    if exit_code != 0:
        syslog.syslog(syslog.LOG_ERR, "Failed to restart the service '{}'. Error: {}"
                      .format(service_name, command_stderr))


def main():
    parser = argparse.ArgumentParser(description="Restart a specific service",
                                     usage="/usr/bin/restart_service <service_name>")
    parser.add_argument("service_name", help="service name")
    args = parser.parse_args()

    restart_service(args.service_name)


if __name__ == "__main__":
    main()