#!/usr/bin/env bash
 set -e
 
 mkimg="$(basename "$0")"
 
 usage() {
 	echo >&2 "usage: $mkimg [-d dir] [-t tag] script [script-args]"
 	echo >&2 "   ie: $mkimg -t someuser/debian debootstrap --variant=minbase jessie"

 	echo >&2 "       $mkimg -t someuser/ubuntu debootstrap --include=ubuntu-minimal --components=main,universe trusty"

 	echo >&2 "       $mkimg -t someuser/busybox busybox-static"
 	echo >&2 "       $mkimg -t someuser/centos:5 rinse --distribution centos-5"

 	echo >&2 "       $mkimg -t someuser/mageia:4 mageia-urpmi --version=4"
 	echo >&2 "       $mkimg -t someuser/mageia:4 mageia-urpmi --version=4 --mirror=http://somemirror/"

 	exit 1
 }
 
 scriptDir="$(dirname "$(readlink -f "$BASH_SOURCE")")/mkimage"
 
 optTemp=$(getopt --options '+d:t:h' --longoptions 'dir:,tag:,help' --name "$mkimg" -- "$@")
 eval set -- "$optTemp"
 unset optTemp
 
 dir=
 tag=
 while true; do
 	case "$1" in
 		-d|--dir) dir="$2" ; shift 2 ;;
 		-t|--tag) tag="$2" ; shift 2 ;;
 		-h|--help) usage ;;
 		--) shift ; break ;;
 	esac
 done
 
 script="$1"
 [ "$script" ] || usage
 shift
 
 if [ ! -x "$scriptDir/$script" ]; then
 	echo >&2 "error: $script does not exist or is not executable"
 	echo >&2 "  see $scriptDir for possible scripts"
 	exit 1
 fi
 
 # don't mistake common scripts like .febootstrap-minimize as image-creators
 if [[ "$script" == .* ]]; then
 	echo >&2 "error: $script is a script helper, not a script"
 	echo >&2 "  see $scriptDir for possible scripts"
 	exit 1
 fi
 
 delDir=
 if [ -z "$dir" ]; then

 	dir="$(mktemp -d ${TMPDIR:-/var/tmp}/docker-mkimage.XXXXXXXXXX)"

 	delDir=1
 fi
 
 rootfsDir="$dir/rootfs"
 ( set -x; mkdir -p "$rootfsDir" )
 
 # pass all remaining arguments to $script
 "$scriptDir/$script" "$rootfsDir" "$@"
 
 # Docker mounts tmpfs at /dev and procfs at /proc so we can remove them
 rm -rf "$rootfsDir/dev" "$rootfsDir/proc"
 mkdir -p "$rootfsDir/dev" "$rootfsDir/proc"
 
 # make sure /etc/resolv.conf has something useful in it
 mkdir -p "$rootfsDir/etc"
 cat > "$rootfsDir/etc/resolv.conf" <<'EOF'
 nameserver 8.8.8.8
 nameserver 8.8.4.4
 EOF
 
 tarFile="$dir/rootfs.tar.xz"
 touch "$tarFile"
 
 (
 	set -x
 	tar --numeric-owner -caf "$tarFile" -C "$rootfsDir" --transform='s,^./,,' .
 )
 
 echo >&2 "+ cat > '$dir/Dockerfile'"
 cat > "$dir/Dockerfile" <<'EOF'
 FROM scratch
 ADD rootfs.tar.xz /
 EOF
 
 # if our generated image has a decent shell, let's set a default command
 for shell in /bin/bash /usr/bin/fish /usr/bin/zsh /bin/sh; do
 	if [ -x "$rootfsDir/$shell" ]; then
 		( set -x; echo 'CMD ["'"$shell"'"]' >> "$dir/Dockerfile" )
 		break
 	fi
 done
 
 ( set -x; rm -rf "$rootfsDir" )
 
 if [ "$tag" ]; then
 	( set -x; docker build -t "$tag" "$dir" )
 elif [ "$delDir" ]; then
 	# if we didn't specify a tag and we're going to delete our dir, let's just build an untagged image so that we did _something_
 	( set -x; docker build "$dir" )
 fi
 
 if [ "$delDir" ]; then
 	( set -x; rm -rf "$dir" )
 fi