#!/usr/bin/env python3
import sys
import os
import subprocess
p = os.path.join

mounts = [
	"proc",
	"sys",
	"dev",
	p("dev","pts"),
	"tmp",
	"run"
]

def call(cmd,*args,**kwargs):
	proc = subprocess.Popen(cmd,*args,**kwargs)
	rtn = proc.wait()
	if rtn != 0: raise subprocess.CalledProcessError(rtn,cmd)
	return proc

def callRtn(cmd,*args,**kwargs):
	proc = subprocess.Popen(cmd,*args,**kwargs)
	return proc.wait()

def mountChroot(d):
	for mount in mounts:
		if callRtn(["mountpoint","-q",p(d,mount)]) == 0: continue
		call(["mount","--bind",os.path.sep + mount,p(d,mount)])

def umountChroot(d):
	for mount in reversed(mounts):
		if callRtn(["mountpoint","-q",p(d,mount)]) != 0: continue
		call(["umount","-lR",p(d,mount)])

def chroot(d,cmd):
	mountChroot(d)
	call(["chroot",d] + cmd)

if sys.argv[1] == "-u":
	umountChroot(sys.argv[2])
	sys.exit(0)

chroot(sys.argv[1],sys.argv[2:])