#!/bin/bash
# This script is public domain

COMM_FILE="/tmp/minecraft.not-a-socket"
CONFIG_PATH="/home/minecraft/server"
SERVER_JAR="/home/minecraft/server/minecraft_server.jar"
MEMORY_MAX="1024M"
MEMORY_MIN="128M"
PID_FILE="/tmp/minecraft.pid"
JAVA="$(which java)"

function start_server
{
    server_status > /dev/null && echo "Server already running." && exit 1

    # Prepare the path for server launch
    if mkdir -p "$CONFIG_PATH" && cd "$CONFIG_PATH" && > "$COMM_FILE"
    then
        # Pipe the contents of $COMM_FILE into the server every 250ms
        tail -fs 0.25 "$COMM_FILE" | \
            $JAVA -Xms$MEMORY_MIN -Xmx$MEMORY_MAX -jar "$SERVER_JAR" nogui \
            > /dev/null 2>&1 &

        # Save the PID the disown the tail and java thread
        PID="$!"
        echo "$PID" > "$PID_FILE"
        disown "$PID"
    fi

    server_status
    return "$?"
}

function stop_server
{
    server_status > /dev/null || { echo "Server not running" && exit 1; }

    # Send "stop" to the server console
    communicate stop

    # Kill off any tail commands reading from the communication file
    TAILS="$(ps ao comm,pid,args | \
        awk "/^tail.*$(basename $COMM_FILE)\$/ {print \$2}")"
    kill $TAILS > /dev/null 2>&1

    echo -n "Waiting on server to stop..."
    while server_status > /dev/null
    do
        echo -n "."
        sleep 1
    done
    echo " Done."
}

function communicate
{
    if server_status > /dev/null
    then
        # Save the last line from the server log
        LAST_LINE="$(tail -n1 "$CONFIG_PATH/server.log")"

        # Echo the message to the $COMM_FILE
        echo $* >> "$COMM_FILE"

        # Sleep for a moment, then print all new dat written to the server log
        usleep 250000 > /dev/null 2>&1 || sleep 1
        fgrep -A100000 "$LAST_LINE" "$CONFIG_PATH/server.log" | tail -n +2
        return 0
    fi

    echo "Unable to communicate with server."
    return 1
}

function server_status
{
    PID="$(cat "$PID_FILE" 2> /dev/null)"
    if kill -0 "$PID" > /dev/null 2>&1
    then
        echo "Server PID is $PID."
        return 0
    fi

    echo "Server is not running."
    return 1
}

case "$1" in
    start)
        start_server
        ;;
    stop)
        stop_server
        ;;
    restart)
        stop_server
        start_server
        ;;
    status)
        server_status
        ;;
    send)
        shift
        communicate $*
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|status|send MESSAGE}"
        exit 1
        ;;
esac
exit