"""Automatic minecraft server runner used and maintained for myself; see constants for configuration. Dynamically uses spigot/paper jars placed in same dir"""

from __future__ import print_function
import os
import sys
import time
import signal

"""The possible beginnings of filenames for server jars"""
STARTJAR = ["spigot-", "paper-"]

"""Default ram to provide in MB if none is provided in args"""
DEFAULT_RAM_MB = 3072

"""Seconds to wait to restart server from crash"""
RESTART_COOLDOWN = 12

# util error-printing
def eprint(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)

# ctrl+c signal handling
def signal_handler(sig, frame):
    print("Exiting runner gracefully")
    sys.exit(0)
signal.signal(signal.SIGINT, signal_handler)

# dynamic config values found
ram = DEFAULT_RAM_MB if len(sys.argv) < 2 else int(sys.argv[1])
path = None

# get path corrosponding to STARTJAR
for (_, _, files) in os.walk("."):
    for filename in files:
        if len([filename for x in STARTJAR if filename.startswith(x)]) != 0:
            path = filename
            break

    break

# error if path isnt found
if path == None:
    eprint(f"No filename found beginning with '{STARTJAR}' in local dir")
    sys.exit(1)

# server loop
count = 0
while True:
    # start server msg
    if count == 0:
        print("Starting server for the first time..")
    else:
        eprint(f"Restarting crashed server (#{count})")

    # run server
    os.system(f"java -Xmx{ram}m -jar {path}")

    # on crash
    eprint(f"Server crashed, restarting in {RESTART_COOLDOWN} second(s)")
    count += 1
    time.sleep(RESTART_COOLDOWN)