minecraftimage/src/main.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"os"
	"os/exec"
	"os/signal"
	"strings"
	"syscall"
	"log"
	"regexp"
	"bytes"

	"github.com/creack/pty"
)

func main() {
	log.Println("\033[32mStarting Server\033[0m")
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, syscall.SIGTERM)

	//get environmental variables
	var minram, maxram, args, stop, jar, regex string
	for _, e := range os.Environ() {
		pair := strings.SplitN(e, "=", 2)
		switch pair[0] {
		case "MIN_MEM":
			minram = "-Xms" + pair[1]
		case "MAX_MEM":
			maxram = "-Xmx" + pair[1]
		case "ARGS":
			args = pair[1]
		case "STOP":
			stop = pair[1]
		case "JAR":
			jar = pair[1]
		case "REGEX":
			regex = pair[1]
		}
	}

	//create command
	var cmdversion *exec.Cmd
	cmdversion = exec.Command("java", "--version")
	var out bytes.Buffer
	cmdversion.Stdout = &out
	cmdversion.Run()
	log.Println(out.String())

	log.Printf("Ram: Min: %s Max: %s Stop: %s Jar: %s\n\r", minram, maxram, stop, jar)

	//check if there is a server jar
	if _, err := os.Stat("/server/"+jar); os.IsNotExist(err) {
		log.Println("\033[31mJar \"" + jar + "\" not found\033[0m")
		os.Exit(1)
	}
	
	var cmd *exec.Cmd
	
	if args == "" {
		cmd = exec.Command("java", minram, maxram, "-jar", jar)
	} else {
		cmd = exec.Command("java", minram, maxram, args, "-jar", jar)
		log.Printf("Args: %s \n\r", args)
	}

	//start server
	cmd.Dir = "/server"
	tty, err := pty.Start(cmd)
	
	if err != nil {
		panic(err)
	
	}

	ln, _ := net.Listen("tcp", ":8081")
	
	//cleanup
	defer func() {
		cmd.Process.Kill()
		cmd.Process.Wait()
		tty.Close()
		ln.Close()
	}()

	// capture sigterm
	go func() {
		sig := <-sigs
		if sig == syscall.SIGTERM {
			fmt.Println("\033[31mStopping server\033[0m")
			tty.WriteString(stop + "\n\r")
		}
	}()

	//accepts command from cmd.go and sends them to the server
	
	go func() {
		//accept connections from clients
		for {
			conn, err := ln.Accept()
			if err != nil {
				continue
			}
			go handleClient(conn, tty)
		}
	}()

	//copy to standard out. If the the is a regex pattern, do output anything that matches
	go func() {
		filter := regexp.MustCompile(regex)
		if(regex != "") {
			scanner := bufio.NewScanner(tty)
			for scanner.Scan() {
				text := scanner.Text()
				if(!filter.MatchString(text)) {
					fmt.Println(text)
				}
			}
		} else { //don't filter
			io.Copy(os.Stdout, tty)
		}
	}()

	//copy stdin
	go func() {
		io.Copy(tty, os.Stdin)
	}()

	cmd.Wait() //wait for server to stop
	tty.Write([]byte("\033[31mServer Stopped\033[0m"))
	os.Exit(0)
}

//take commands from cmd.go and send it to sdtin of the server
func handleClient(conn net.Conn, tty *os.File) {
	defer conn.Close()
	cmd, _ := bufio.NewReader(conn).ReadString('\n')
	tty.Write([]byte(cmd))
}