#!/bin/sh
set -e
fail () { echo >&2 "$0: $*"; exit 1; }

case "$#.$1" in
2.edit|2.done)	mode="$1"; arg="$2" ;;
3.gitfetchinfo)	mode="$1"; arg="$2"; remote="$3" ;;
?.-*)	fail "no options understood"			;;
*)	fail "usage:
    tartree-edit edit|done DIRECTORY|TARBALL
    tartree-edit gitfetchinfo DIRECTORY|TARBALL REMOTE"	;;
esac

case "$arg" in
*.tar)		base=${arg%.tar}			;;
*.edit)		base=${arg%.edit}			;;
*)		base=${arg}				;;
esac

tryat_pre () {
	local b="$1"
	rm -rf "$b.tmp"
	if test -f "$b.tar" && test -f "$b.edit"; then
		echo "$b.edit exists, deleting possibly-obsolete $b.tar"
		rm "$b.tar"
	fi
}

tryat_edit () {
	local b="$1"
	if test -d "$b.edit"; then
		echo "$b.edit already exists"
		exit 0
	fi
	if test -f "$b.tar"; then
		mkdir "$b.tmp"
		(set -e; cd "$b.tmp"; tar xf "$b.tar")
		mv "$b.tmp" "$b.edit"
		rm "$b.tar"
		echo "$b.edit ready"
		exit 0
	fi
}

gitfetchinfo_perhaps_commit () {
	local m="$1"
	set +e
	git diff --cached --quiet --exit-code HEAD
	local rc=$?
	set -e
	case "$rc" in
	0)   return ;;
	1)   git commit --allow-empty --author='tartree-edit <>' -m "$m" ;;
	*)   fail "git diff failed ($rc)" ;;
	esac
}

tryat_gitfetchinfo () {
	local wd=$(pwd)
	case "$wd" in
	*.edit) fail "bad idea to run gitfetchinfo into a .edit tree!" ;;
	esac
	local play=.git/tartree-edit-work
	rm -rf $play
	mkdir $play
	if test -d "$b.edit"; then
		cp -a "$b.edit"/. "$play"/.
	else
		exec 3<"$b.tar"
		tar -C $play -f - <&3 -x
		exec 3<&-
	fi
	local innerwd=$play/*
	git remote remove "$remote" 2>/dev/null ||:
	git remote add "$remote" $innerwd
	git fetch --no-tags -p "$remote" \
		+"HEAD:refs/remotes/$remote/HEAD"
	cd $innerwd
	git checkout -b WORKTREE
	gitfetchinfo_perhaps_commit INDEX
	git add -Af .
	gitfetchinfo_perhaps_commit WORKTREE
	cd ../../..
	git fetch --no-tags "$remote" --refmap \
		+"refs/*:refs/remotes/$remote/*" \
		+"refs/*:refs/remotes/$remote/*"
	exit 0
}

tryat_done () {
	local b="$1"
	if test -d "$b.edit"; then
		(set -e; cd "$b.edit"; tar cf "$b.tmp" *)
		mv "$b.tmp" "$b.tar"
		mv "$b.edit" "$b.tmp"
		rm -rf "$b.tmp"
		echo "$b.tar regenerated"
		exit 0
	fi
	if test -f "$b.tar"; then
		echo "$b.tar already exists and $b.edit doesn't"
		exit 0
	fi
}

tryat () {
	local b="$1"
	if ! test -f "$b.tar" && ! test -d "$b.edit"; then
		return
	fi
	tryat_pre "$b"
	tryat_$mode "$b"
	fail "unexpected situation in $b.*"
}

case "$arg" in
/*)		tryat "$base"
		;;
*)
		pwd=`pwd`
		tryat "$pwd/$base"
		tryat "$pwd/git-srcs/$base"
		tryat "$pwd/tests/git-srcs/$base"
		fail "could not find $base..."
		;;
esac