#!/bin/sh
 
 set -e
 
 [ $(id -u) -eq 0 ] || {
 	printf >&2 '%s requires root\n' "$0"
 	exit 1
 }
 
 usage() {
 	printf >&2 '%s: [-r release] [-m mirror] [-s]\n' "$0"
 	exit 1
 }
 
 tmp() {

 	TMP=$(mktemp -d ${TMPDIR:-/var/tmp}/alpine-docker-XXXXXXXXXX)
 	ROOTFS=$(mktemp -d ${TMPDIR:-/var/tmp}/alpine-docker-rootfs-XXXXXXXXXX)

 	trap "rm -rf $TMP $ROOTFS" EXIT TERM INT
 }
 
 apkv() {

 	curl -sSL $REPO/$ARCH/APKINDEX.tar.gz | tar -Oxz |

 		grep '^P:apk-tools-static$' -A1 | tail -n1 | cut -d: -f2
 }
 
 getapk() {

 	curl -sSL $REPO/$ARCH/apk-tools-static-$(apkv).apk |

 		tar -xz -C $TMP sbin/apk.static
 }
 
 mkbase() {
 	$TMP/sbin/apk.static --repository $REPO --update-cache --allow-untrusted \
 		--root $ROOTFS --initdb add alpine-base
 }
 
 conf() {
 	printf '%s\n' $REPO > $ROOTFS/etc/apk/repositories
 }
 
 pack() {
 	local id
 	id=$(tar --numeric-owner -C $ROOTFS -c . | docker import - alpine:$REL)
 
 	docker tag $id alpine:latest
 	docker run -i -t alpine printf 'alpine:%s with id=%s created!\n' $REL $id
 }
 
 save() {
 	[ $SAVE -eq 1 ] || return
 
 	tar --numeric-owner -C $ROOTFS -c . | xz > rootfs.tar.xz
 }
 
 while getopts "hr:m:s" opt; do
 	case $opt in
 		r)
 			REL=$OPTARG
 			;;
 		m)
 			MIRROR=$OPTARG
 			;;
 		s)
 			SAVE=1
 			;;
 		*)
 			usage
 			;;
 	esac
 done
 
 REL=${REL:-edge}
 MIRROR=${MIRROR:-http://nl.alpinelinux.org/alpine}
 SAVE=${SAVE:-0}
 REPO=$MIRROR/$REL/main

 ARCH=${ARCH:-$(uname -m)}

 
 tmp
 getapk
 mkbase
 conf
 pack
 save