#!/usr/bin/env bash
# author: joe.zheng
# version: 23.12.08

set -e

BASE=0
COUNT=2
IMAGE="vm-base.img"
FORCE="n"
DRY_RUN="n"

FORMAT="qcow2"
VM_PREFIX="vm-"
IMG_SUFFIX=".img"

function usage() {
  local self=`basename $0`
  local version="$(sed -n '1,4s/# version: \(.*\)/\1/p' $0)"

  cat <<EOF
Usage: $self [-b <base>] [-f] [-n] [-h] [<count>] [<image>]
  Clone VM disk image from the base one to save storage

  -b <base>:  base index of the VM, default: $BASE
  -f:         overwrite image forcibly, default: $FORCE
  -n:         dry run, print out information only, default: $DRY_RUN
  -h:         print the usage message

  <count>:    number of VMs, default: $COUNT
  <image>:    the base image, default: $IMAGE

  We assume the index of the VM is consecutive, e.g.: if the  base index is 0,
  the 2 images will be named ${VM_PREFIX}0${IMG_SUFFIX} and ${VM_PREFIX}1${IMG_SUFFIX}

Examples:
  # Check information before actual execution
  $self -n

  # Replicate $COUNT disk images from $IMAGE
  $self

  # Replicate $COUNT disk images from $IMAGE, overwrite images if already exist
  $self -f

  # Replicate 2 disk images from base.img, the output is vm-10.img and vm-11.img
  $self -b 10 2 base.img

Version: $version
EOF

}

while getopts ":b:fhn" opt
do
  case $opt in
    b ) BASE=$OPTARG;;
    f ) FORCE=y;;
    n ) DRY_RUN=y;;
    h ) usage && exit;;
    * ) usage && exit 1;;
  esac
done

shift $((OPTIND-1))

COUNT=${1:-$COUNT}
IMAGE=${2:-$IMAGE}

if [[ ! -e $IMAGE ]]; then
  echo "can't find $IMAGE"
  exit 1
fi

for ((i=BASE; i<BASE+COUNT; i++)); do
  dest="$VM_PREFIX${i}$IMG_SUFFIX"

  if [[ $FORCE != 'y' && -e $dest ]]; then
    echo "$dest already exits, quit"
    exit 1
  fi

  echo "clone $IMAGE to $dest, format: $FORMAT"
  if [[ $DRY_RUN != "y" ]]; then
    qemu-img create -f $FORMAT -F $FORMAT -b $IMAGE $dest
    echo "$dest is created"
  fi
done