#!/bin/sh

error() { echo "$@" 1>&2; }
Usage() {
    cat <<EOF
Usage: ${0##*/} release

   release is like 'xenial' or 'artful'.

    - Downloads an image from cloud-image.ubuntu.com
    - converts it to raw format (from qcow2)
    - creates a -proposed image using the original as a qcow2 backing.
      - updates cloud-init inside.
EOF
}

sstream_check() {
   local kpath="/usr/share/keyrings/ubuntu-cloudimage-keyring.gpg"
   command -v sstream-query >/dev/null 2>&1 || return
   if [ -f "$f" ]; then
      KEYRING="--keyring=$kpath"
   else
      # is it in the default keyring?
      local fprint="4A3CE3CD565D7EB5C810E2B97FF3F408476CF100"
      command -v gpg >/dev/null 2>&1 &&
         gpg --list-public-keys | grep -q "$fprint" &&
         KEYRING="" && return 0
   fi
   return 1
}
sstream_get_image() {
   local rel="$1" output="$2" ftype="${3:-disk1.img}"
   local url="http://cloud-images.ubuntu.com/daily/"
   local arch="amd64"
   local ofmt="%(release)s %(version_name)s %(ftype)s %(sha256)s %(item_url)s"
   local out=""
   out=$(sstream-query ${KEYRING:+"--keyring=${KEYRING}"} \
      --max=1 "--output-format=$ofmt" \
      "$url" "datatype=image-downloads" \
      "ftype=$ftype" "release=$rel" arch="$arch") ||
      { error "sstream-query failed."; return 1; }
   local rrel version ftype sha256 url sha256r
   set -- $out
   [ $# -eq 5 ] || {
      error "too many fields returned in query (multiple results?): $out";
      return 1;
   }
   rrel="$1"; version="$2"; ftype="$3"; sha256="$4"; url="$5"
   error "Downloading $rel/$version/$ftype from $url."
   wget --progress=dot:mega "$url" -O "$output.tmp" &&
      out=$(sha256sum "$output.tmp") && sha256r="${out%  *}" || {
         rm -f "$output.tmp"
         error "download failed: $url"
         return 1
      }
   [ "${sha256r}" = "$sha256" ] || {
      rm -f "$output.tmp"
      error "hashsum mismatch (found=$sha256r expected=$sha256)"
      return 1
   }
   mv "$output.tmp" "$output"
}

rel="$1"
[ "$1" = "-h" -o "$1" = "--help" ] && { Usage; exit 0; }
[ -n "$rel" ] || { Usage 1>&2; error "Must give release"; exit 1; }

arch="amd64"
burl="http://cloud-images.ubuntu.com/daily/server"
fname=$rel-server-cloudimg-amd64.img
ofname="$fname"
case "$rel" in
    precise|trusty|xenial) ofname="$rel-server-cloudimg-amd64-disk1.img";;
esac

pfname="${fname%.img}-proposed.img"
raw="${fname%.img}.raw"
if [ ! -f "$fname" ]; then
   if sstream_check; then
      error "getting image via simplestreams."
      sstream_get_image "$rel" "$fname" || exit
   else
      wget "$burl/$rel/current/$ofname" -O "$fname.tmp" &&
          mv "$fname.tmp" "$fname" || exit
   fi
   rm -f "$raw"
fi
if [ ! -f "$raw" ]; then
   qemu-img convert -O raw "$fname" "$raw.tmp" &&
       mv "$raw.tmp" "$raw" || exit
   rm -f "$pfname"
fi
if [ ! -f "$pfname" ]; then
    qemu-img create -f qcow2 -b "$raw" "$pfname.tmp" || break
    sudo mount-image-callback --system-resolvconf "$pfname.tmp" -- \
        mchroot sh -ec '
            r=$(lsb_release -sc)
            m="http://archive.ubuntu.com/ubuntu"
            plist="/etc/apt/sources.list.d/proposed.list"
            echo "deb $m $r-proposed main" > "$plist"
            apt-get update -q
            DEBIAN_FRONTEND=noninteractive apt-get -qy install cloud-init
        ' </dev/null || exit
    mv $pfname.tmp $pfname
    echo "wrote $pfname"
else
    echo "re-used $pfname"
fi

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