#!/usr/bin/env bash
set -euo pipefail

builder_image=""
debian_release=""
debian_snapshot=""
packages_file=""
guest_agent=""
guest_init=""
agent_service=""
workdir=""
output=""

while [[ $# -gt 0 ]]; do
  case "$1" in
    --builder-image) builder_image="$2"; shift 2 ;;
    --debian-release) debian_release="$2"; shift 2 ;;
    --debian-snapshot) debian_snapshot="$2"; shift 2 ;;
    --packages-file) packages_file="$2"; shift 2 ;;
    --guest-agent) guest_agent="$2"; shift 2 ;;
    --guest-init) guest_init="$2"; shift 2 ;;
    --agent-service) agent_service="$2"; shift 2 ;;
    --workdir) workdir="$2"; shift 2 ;;
    --output) output="$2"; shift 2 ;;
    *) echo "unknown arg: $1" >&2; exit 1 ;;
  esac
done

: "${builder_image:?missing --builder-image}"
: "${debian_release:?missing --debian-release}"
: "${debian_snapshot:?missing --debian-snapshot}"
: "${packages_file:?missing --packages-file}"
: "${guest_agent:?missing --guest-agent}"
: "${guest_init:?missing --guest-init}"
: "${agent_service:?missing --agent-service}"
: "${workdir:?missing --workdir}"
: "${output:?missing --output}"

rm -rf "$workdir"
mkdir -p "$workdir/in" "$workdir/out" "$(dirname "$output")"
workdir="$(cd "$workdir" && pwd)"
output_dir="$(cd "$(dirname "$output")" && pwd)"
output="$output_dir/$(basename "$output")"
cp "$packages_file" "$workdir/in/packages.txt"
cp "$guest_agent" "$workdir/in/pyro_guest_agent.py"
cp "$guest_init" "$workdir/in/pyro-init"
cp "$agent_service" "$workdir/in/pyro-guest-agent.service"

container_script="$workdir/build-rootfs-container.sh"
cat > "$container_script" <<'SCRIPT'
#!/usr/bin/env bash
set -euo pipefail
export DEBIAN_FRONTEND=noninteractive
apt-get update
apt-get install -y --no-install-recommends ca-certificates debootstrap e2fsprogs systemd-container

mirror="http://snapshot.debian.org/archive/debian/${DEBIAN_SNAPSHOT}/"
packages_csv="$(paste -sd, /work/in/packages.txt)"
rootfs_dir="/work/rootfs"
rm -rf "$rootfs_dir"
mkdir -p "$rootfs_dir"

debootstrap \
  --arch=amd64 \
  --variant=minbase \
  --include="$packages_csv" \
  --no-check-gpg \
  "$DEBIAN_RELEASE" \
  "$rootfs_dir" \
  "$mirror"

cat > "$rootfs_dir/etc/apt/sources.list" <<APT
 deb [check-valid-until=no] http://snapshot.debian.org/archive/debian/${DEBIAN_SNAPSHOT}/ ${DEBIAN_RELEASE} main
 deb [check-valid-until=no] http://snapshot.debian.org/archive/debian-security/${DEBIAN_SNAPSHOT}/ ${DEBIAN_RELEASE}-security main
APT

mkdir -p "$rootfs_dir/opt/pyro/bin" "$rootfs_dir/etc/systemd/system/multi-user.target.wants"
install -m 0755 /work/in/pyro_guest_agent.py "$rootfs_dir/opt/pyro/bin/pyro_guest_agent.py"
install -m 0755 /work/in/pyro-init "$rootfs_dir/opt/pyro/bin/pyro-init"
install -m 0644 /work/in/pyro-guest-agent.service "$rootfs_dir/etc/systemd/system/pyro-guest-agent.service"
ln -sf /etc/systemd/system/pyro-guest-agent.service \
  "$rootfs_dir/etc/systemd/system/multi-user.target.wants/pyro-guest-agent.service"
ln -sf /opt/pyro/bin/pyro-init "$rootfs_dir/sbin/init"
printf '127.0.0.1 localhost\n' > "$rootfs_dir/etc/hosts"
truncate -s 2G /work/out/rootfs.ext4
mkfs.ext4 -F -d "$rootfs_dir" /work/out/rootfs.ext4 >/dev/null
SCRIPT
chmod +x "$container_script"

docker run --rm \
  -e DEBIAN_RELEASE="$debian_release" \
  -e DEBIAN_SNAPSHOT="$debian_snapshot" \
  -v "$workdir:/work" \
  "$builder_image" \
  /work/build-rootfs-container.sh

cp "$workdir/out/rootfs.ext4" "$output"