#!/bin/sh

set -e

if [ ! -n "$1" ]; then
    echo "usage: $(basename $0) <chroot target> <commands>"
    exit 0
fi

# if this is running on an interactive
# terminal (as opposed to in a script), if tput is installed, and if tput
# knows some color codes, then set the color values.
if [ -t 1 ] && [ "$(tput colors 2>/dev/null || echo 0)" -ge 8 ]; then
	_clr="$(tput sgr0)"
	_red="$(tput setaf 1)"
fi

err() {
    echo "$_red[ERR]$_clr $@" >&2
    exit 1
}

tgt="$1"
shift

[ -d "$tgt" ] || err "no such directory as '$tgt'"

[ "$(stat -Lt "$tgt")" != "$(stat -Lt "/")" ] \
|| err "chroot target points to /! did something go wrong? exiting."

# if the user already did some of the necessary prep, don't mess with it.
[ -e "$tgt/proc" ] || export _proc="skip"
[ -e "$tgt/dev" ] || export _dev="skip"
[ -e "$tgt/sys" ] || export _sys="skip"
[ -e "$tgt/tmp" ] || export _tmp="skip"

[ -z "$_proc" ] || { mkdir "$tgt/proc" && mount -n -t proc proc "$tgt/proc"; }
[ -z "$_dev" ] || { mkdir "$tgt/dev" && mount -o bind /dev "$tgt/dev"; }
[ -z "$_sys" ] || { mkdir "$tgt/sys" && mount -n -t sysfs sys "$tgt/sys"; }
[ -z "$_tmp" ] || { mkdir "$tgt/tmp" && mount -n -t tmpfs tmpfs "$tgt/tmp"; }

cleanup() {
	[ -z "$_tmp" ] || { umount "$tgt/tmp" && rmdir "$tgt/tmp"; }
	[ -z "$_sys" ] || { umount "$tgt/sys" && rmdir "$tgt/sys"; }
	[ -z "$_dev" ] || { umount "$tgt/dev" && rmdir "$tgt/dev"; }
	[ -z "$_proc" ] || { umount "$tgt/proc" && rmdir "$tgt/proc"; }
}
trap cleanup EXIT INT HUP

cd -- "$tgt"
chroot . sh -c "$@"
cd - >/dev/null