#!/bin/sh

gdir=".git"
if [ ! -d ${gdir} ] ; then
	echo "Run this is in the root of the git tree"
	exit 1
fi

revmap() {
	find ${gdir}/svn/$1/ '(' -name '.rev_map.*' -a '!' -name '*.bak' ')' -print
}

decode() {
	xxd -c24 < $1
}
encode() {
	xxd -c24 -r
}

get_branch() {
	branch=${1:-trunk}
	if [ ! -d ${gdir}/svn/${branch} ] ; then
		echo "Branch ${branch} not in ${gdir}/svn/"
		exit 1
	fi

	map=$(revmap ${branch})

	cur_rev=$(printf '%i' 0x$(decode $map | tail -n1 | awk '{print $3}'))
}

show() {
	get_branch "$@"
	echo "${branch}: at rev ${cur_rev}"
	exit 0
}

reset() {
	get_branch "$@"
	new_rev=$2
	if [ -z "$new_rev" ] || [ "$new_rev" -gt "$cur_rev" ] ; then
		echo "${branch}: invalid rev '$new_rev' (at $cur_rev)"
		exit 1
	fi

	printf "really reset $branch to $new_rev ? [y/N] "
	read ans
	case ${ans} in
		[yY]) ;;
		*) exit 1;;
	esac

	hex0=$(printf '%04x' $(( new_rev % 0x10000 )) )
	hex1=$(printf '%04x' $(( new_rev / 0x10000 )) )
	cp $map $map.bak
	decode $map.bak \
		| sed -n "1,/^[^:]*: $hex1 $hex0/p" \
		| encode \
		> $map

	show ${branch}
	echo "don't forget to reset manually ref/remotes/${branch}"
}

usage() {
	echo "Unknown op '$op'"
	exit 1
}

branch=
op=$1
shift
case $op in
	-s) show "$@";;
	-r) reset "$@";;
	*) usage;;
esac