#!/bin/bash
# Filename:      grml-chroot
# Purpose:       Program to chroot into another system
# Authors:       grml-team (grml.org), (c) Michael Gebetsroither <gebi@grml.org>
# Bug-Reports:   see http://grml.org/bugs/
# License:       This file is licensed under the GPL v2.
################################################################################

PROG_NAME_=$(basename "$0")
DEST_=""
MOUNTED_=""     # all mounted destinations


function die
{
    echo "Error: $*" >&2
    exit 1
}

function printUsage
{
    cat <<EOT
Usage: "$PROG_NAME_" NEWROOT [COMMAND....]

$PROG_NAME_ is a chroot wrapper with proc/sys/pts/dev filesystem handling

EOT
}

function storeMounts
{
    local to_append_="$1"
    if [[ $MOUNTED_ == "" ]]; then
        MOUNTED_="$to_append_"
    else
        MOUNTED_="$MOUNTED_ $to_append_"
    fi
}

function mountit
{
    local type_="$1" # type _or_ src
    local dest_="$2"
    local options_="$3"

    local all_options_=()

    if [[ $options_ == "--bind" ]]; then
        all_options_+=(--bind "$type_")
    else
        all_options_+=(-t "$type_" none)
    fi
    mount "${all_options_[@]}" "${DEST_}/$dest_" && storeMounts "$dest_"
}

function umount_all
{
    local reverse
    reverse=$(echo "$MOUNTED_" | awk '{ for (i=NF; i>1; i--) printf("%s ",$i); print $1; }')
    for i in $reverse; do
        umount "${DEST_}/$i"
    done
}


###
### __MAIN
###

while getopts "h" opt; do
    case "$opt" in
        h) printUsage; exit 0 ;;
        ?) printUsage; exit 64 ;;
    esac
done
shift $((OPTIND - 1))

if (( $# < 1 )); then
    printUsage
    die "Wrong number of arguments."
fi

if ! command -v awk >/dev/null 2>&1 ; then
  die "No awk binary found, required for execution."
fi

DEST_="$1"; shift

if [ ! -d "$DEST_" ]; then
    die "Target chroot does not exist: $DEST_"
fi



if [ -f "$DEST_"/proc/cmdline ] ; then
    echo "Looks like $DEST_ already has filesystems mounted, skipping."
else
    mountit "proc"  "proc"
    mountit "sysfs" "sys"
    mountit "/dev"   "dev"   "--bind"
    mountit "devpts" "dev/pts"
    if [ -d /sys/firmware/efi/efivars ] ; then
      mountit "efivarfs" "sys/firmware/efi/efivars"
    fi
    if [ -d "$DEST_"/run/udev ] && [ -d /run/udev ] ; then
      mountit "/run/udev" "/run/udev" "--bind"
    fi
fi

WROTE_DEBIAN_CHROOT=""
if [ ! -f "$DEST_"/etc/debian_chroot ]; then
    WROTE_DEBIAN_CHROOT="yes"
    echo "Writing /etc/debian_chroot ..."
    cat "$DEST_"/etc/hostname > "$DEST_"/etc/debian_chroot
fi

if (( $# < 1 )); then
    chroot "$DEST_"
    RC=$?
else
    chroot "$DEST_" "$@"
    RC=$?
fi
umount_all

if [ -n "$WROTE_DEBIAN_CHROOT" ]; then
    rm "$DEST_"/etc/debian_chroot
fi

exit $RC