#!/usr/bin/env python3
# vim: expandtab ft=python ts=4 sw=4 sts=4:
import os
import sys
import subprocess
import signal
import time
import atexit
import argparse
from threading import Thread
###############################################################################
# Exit codes and prints helpers
verbose_level = 0


def __print_message__(message, file=sys.stdout, notime=False):
    if notime:
        print(message, file=file)
    else:
        print('[' + time.strftime('%H:%M:%S') + '] ' + message, file=file)


def info(message, minverbose=0, notime=False):
    "Prints message to stdout if minverbose >= verbose_level"
    if verbose_level >= minverbose:
        __print_message__(message, notime=notime)


def warning(message, minverbose=-1, notime=False):
    "Prints message to stderr if minverbose >= verbose_level"
    if verbose_level >= minverbose:
        __print_message__(message, file=sys.stderr, notime=notime)


def error(message, minverbose=-2, errcode=-1, notime=False):
    "Prints message to stderr if minverbose >= verbose_level"
    if verbose_level >= minverbose:
        __print_message__(message, file=sys.stderr, notime=notime)
    sys.exit(errcode)

###############################################################################

__STATUSSTRINGS__ = {
    0: "Not running",
    1: "Starting",
    2: "Running",
    3: "Stopping",
    }

__INPUTPIPE__ = 'input_pipe'
__STATUSFILE__ = 'status'
__PLAYERSFILE__ = 'players'
__PIDFILE__ = 'server.pid'


class MCServer:
    "Minecraft server wrapper class"
    def __init__(self, command, statusfile=False, playersfile=False):
        self.players = set()
        self.status = 0
        self.process = None
        self.command = command
        self.statusfile = statusfile
        self.plaersfile = playersfile
        info("Server wrapper initializing")
        if os.path.isfile(__PIDFILE__):
            with open(__PIDFILE__) as file:
                lpid = int(file.readline())
            try:
                os.kill(lpid, 0)
            except OSError:
                warning("Detected forced termination of previous server "
                        "wrapper instance.")
            else:
                error("Another wrapper is running with given identifier.",
                      -1, 1)
        try:
            os.mkfifo(__INPUTPIPE__, 0o640)
        except FileExistsError:
            pass
        if statusfile:
            with open(__STATUSFILE__, 'w') as file:
                file.write(__STATUSSTRINGS__[0] + '\n')
        if playersfile:
            open(__PLAYERSFILE__, 'w')
        self.inputthread = Thread(target=self.__input_thread__,
                                  daemon=True)
        self.outputhread = Thread(target=self.__output_thread__,
                                  daemon=True)

    def clean(self):
        "Cleans files generated by wrapper"
        info("Server wrapper clean.")
        try:
            os.remove(__INPUTPIPE__)
        except FileNotFoundError:
            pass
        try:
            os.path.isfile(__PIDFILE__)
        except FileNotFoundError:
            pass
        try:
            os.remove(__STATUSFILE__)
        except FileNotFoundError:
            pass
        try:
            os.remove(__STATUSFILE__)
        except FileNotFoundError:
            pass

    def execstart(self):
        "Start execution of Minecraft server and hold until its exits"
        self.start()
        self.process.wait()

    def start(self):
        "Start Minecraft server"
        self.process = subprocess.Popen(
            self.command, stdin=subprocess.PIPE,
            stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
            start_new_session=False)
        with open(__PIDFILE__, "w") as file:
            file.write(str(self.process.pid))
        self.status = 1
        if self.statusfile:
            with open(__STATUSFILE__, 'w') as file:
                file.write(__STATUSSTRINGS__[1] + '\n')
        if not self.inputthread.is_alive():
            self.inputthread.start()
        if not self.outputhread.is_alive():
            self.outputhread.start()

    def stop(self):
        "Sends /stop command to Minecraft server"
        if self.running():
            self.process.stdin.write(bytes(
                "/stop\n", sys.getdefaultencoding()))
            self.process.stdin.flush()

    def running(self):
        "Returns True if mc server is running. Othervise False."
        return bool(self.status)

    def write_to_terminal(self, text):
        "Write to server terminal. If server not running it does nothing"
        if self.status == 2:
            info("Input: " + text, 1)
            self.process.stdin.write(bytes(text, sys.getdefaultencoding()))
            self.process.stdin.flush()
            return True
        else:
            return False

    def __user_join__(self, username):
        info("User '" + username + "' joined server.")
        self.players.add(username)
        if self.plaersfile:
            with open(__PLAYERSFILE__, 'a') as file:
                file.write(username + '\n')

    def __user_leave__(self, username):
        info("User '" + username + "' left server.")
        self.players.remove(username)
        if self.plaersfile:
            with open(__PLAYERSFILE__, 'w') as file:
                file.writelines(self.players)
                if self.players:
                    file.write('\n')

    def __parse_line__(self, line):
        if ': Done' in line:
            info("Server start.")
            self.status = 2
            if self.statusfile:
                with open(__STATUSFILE__, 'w') as file:
                    file.write(__STATUSSTRINGS__[2] + '\n')
        elif ': Stopping the server' in line:
            info("Server stop.")
            self.status = 3
            if self.statusfile:
                with open(__STATUSFILE__, 'w') as file:
                    file.write(__STATUSSTRINGS__[3] + '\n')
        elif 'logged in with entity id' in line:
            name = line[len('[00:00:00] [Server thread/INFO]: '):]
            name = name[:name.index('[')]
            self.__user_join__(name)
        elif 'left the game' in line:
            name = line[len('[00:00:00] [Server thread/INFO]: '):]
            name = name[:name.index(' ')]
            self.__user_leave__(name)

    def __output_thread__(self):
        for linen in self.process.stdout:
            line = linen.decode(sys.getdefaultencoding())
            info(line.rstrip(), 2, notime=True)
            self.__parse_line__(line.rstrip())
        if self.statusfile:
            with open(__STATUSFILE__, 'w') as file:
                file.write(__STATUSSTRINGS__[0] + '\n')

    def __input_thread__(self):
        with open(__INPUTPIPE__, 'r') as pipe:
            while True:
                line = pipe.readline().rstrip()
                if line:
                    self.write_to_terminal(line + "\n")
                else:
                    time.sleep(3)

###############################################################################
mcserver = None


def __wrapper_atexit__():
    "This is called when wrapper is exiting"
    mcserver.clean()


def __wrapper_toexit__():
    "This function is called when system signalizes that mcwrapper should exit"
    mcserver.stop()


def __signal_term__(_signo, _stack_frame):
    __wrapper_toexit__()


__HELP_DESC__ = """
    This script is executing Minecraft server and reads its output. From output
    is extracted server status and list of online players. And standard input
    can be accessed by fifo file.
    """


def main():
    "Main function"
    global verbose_level
    parser = argparse.ArgumentParser(description=__HELP_DESC__)
    parser.add_argument('--verbose', '-v', action='count', default=0,
                        help="Increase verbose level of output")
    parser.add_argument('--quiet', '-q', action='count', default=0,
                        help="Decrease verbose level of output")
    parser.add_argument('--status-file', '-s', action='store_true',
                        help="Outputs server status to file \"status\"")
    parser.add_argument('--players-file', '-p', action='store_true',
                        help="""Outputs list of online players to file
                        \"players\" """)
    parser.add_argument('command', nargs=argparse.REMAINDER,
                        help="""Command to be executed to start Minecraft
                        server.""")
    args = parser.parse_args()

    verbose_level = args.verbose - args.quiet
    command = args.command
    sfile = args.status_file
    pfile = args.players_file

    if not command:
        parser.print_help()
    if 'nogui' not in command:
        command.append('nogui')

    global mcserver
    mcserver = MCServer(command, pfile, sfile)
    signal.signal(signal.SIGTERM, __signal_term__)
    signal.signal(signal.SIGINT, __signal_term__)
    atexit.register(__wrapper_atexit__)

    mcserver.execstart()

if __name__ == '__main__':
    main()