#!/bin/bash

LXC_BASE=/var/lib/lxc
LOOP_MAX_PART_PARAM=/sys/module/loop/parameters/max_part
MAX_PART_MIN=4

if [ ! -f $LOOP_MAX_PART_PARAM ] ; then
    echo "ERROR: $LOOP_MAX_PART_PARAM is missing" 1>&2
    echo "       Please load \"loop\" module" 1>&2
    exit 1
fi

LOOP_MAX_PART=$(cat $LOOP_MAX_PART_PARAM)
if [ $LOOP_MAX_PART -le $MAX_PART_MIN ] ; then
    echo "ERROR: set loop.max_part to at least $MAX_PART_MIN" 1>&2
    echo "       either \"modprobe loop max_part=$MAX_PART_MIN\"" 1>&2
    echo "       or \"loop.max_part=$MAX_PART_MIN\" on the kernel cmdline" 1>&2
    exit 1
fi

if [ "$USER" != "root" ] ; then
    echo "ERROR: you must be root to run this script" 1>&2
    exit 1
fi

cleanup()
{
    echo "Cleaning up..."
    if [ "$MOUNTPOINT" != "" ] ; then
        umount "${PART}" 2> /dev/null
        rmdir "${MOUNTPOINT}"
    fi
    if [ "$LONAME" != "" ] ; then
        losetup -d $LONAME
    fi
    exit 1
}

usage()
{
    cat <<!EOF
USage: $1 --name NAME --format FORMAT --label LABEL filename [size]
    --name is the name of the container to clone into an image disk
    --label is the disklabel type (mac, msdos, gpt, ...)
    filename is the name of the disk image
    size is the size of the disk image
!EOF
}

options=$(getopt -o hn:l: -l help,name:,label: -- "$@")
if [ $? -ne 0 ]; then
        usage $(basename $0)
        exit 1
fi
eval set -- "$options"

while true ; do
    case "$1" in
    -n|--name)
        shift
        name=$1
        ;;
    -l|--label)
        shift
        label=$1
        ;;
    -h|--help)
        usage
        exit 1
        ;;
    *)
        break
        ;;
    esac
    shift
done

shift
filename="$1"
shift
size=$1

if [ "$filename" = "" ] ; then
    echo "ERROR: you must provide a disk image name" 1>&2
    exit 1
fi

if [ "$name" = "" ] ; then
    echo "ERROR: you must provide a container name" 1>&2
    exit 1
fi
if [ ! -d "$LXC_BASE/$name/rootfs" ] ; then
    echo "ERROR: container $name does not exist" 1>&2
    exit 1
fi

if [ "$label" = "" ] ; then
    echo "ERROR: you must provide a disklabel (see parted(8))" 1>&2
    exit 1
fi

if [ "$size" = "" ] ; then
    echo "Computing disk size..."
    size=$(du -s "$LXC_BASE/$name/rootfs"| cut -f1)
    # Add 20 %
    size=$(( size * 120 / 100 ))k
    echo "Disk size is $size"
fi

if ! sudo -u $SUDO_USER qemu-img create -f raw "$filename" ${size} ; then
    echo "ERROR: cannot create $filename" 1>&2
    exit 1
fi

if ! sudo -u $SUDO_USER parted "$filename" mklabel "$label" ; then
    echo "ERROR: cannot create label $label in $filename" 1>&2
    exit 1
fi

if [ "$label" = "mac" ] ; then
    sudo -u $SUDO_USER parted --script -a optimal "$filename" \
         mkpart primary ext4 32kiB 100%
else
    sudo -u $SUDO_USER parted --script -a optimal "$filename" \
         mkpart primary ext4 4096B 100%
fi
if [ $? -ne 0 ] ; then
    echo "ERROR: cannot create partition in $filename" 1>&2
    exit 1
fi

trap cleanup SIGTERM SIGINT

LONAME=$(losetup -f --show "$filename")

if [ "$label" = "mac" ] ; then
    PART="${LONAME}p2"
else
    PART="${LONAME}p1"
fi

if ! mkfs -t ext4 "${PART}" > /dev/null ; then
    cleanup
    echo "ERROR: cannot create filesystem in $filename" 1>&2
    exit 1
fi
if ! cd "$LXC_BASE/$name/rootfs" ; then
    cleanup
    echo "ERROR: cannot open $LXC_BASE/$name/rootfs" 1>&2
    exit 1
fi

MOUNTPOINT=$(mktemp -d)

if ! mount "${PART}" "${MOUNTPOINT}" ; then
    cleanup
    echo "ERROR: cannot mount filesystem from $filename" 1>&2
    exit 1
fi

echo "Copying filesystem..."

if ! find . | cpio -pdm --sparse "${MOUNTPOINT}" ; then
    cleanup
    echo "ERROR: cannot copy files from $LXC_BASE/$name/rootfs" 1>&2
    exit 1
fi

cleanup