nix-home

#!/bin/sh

performLink="true"
op=""

if [ $# -eq 0 ]; then
	op="--set"
fi

for i in "$@"
do
case $i in
	--version)
		echo "0.3.1";
		exit
	;;
	# we only really need to list options which disable linking. Everything else
	# is passed directly to nix-env
	--list-generations)
		performLink="false"
	;;
	--delete-generations)
		performLink="false"
	;;
	--help)
		nix-env --help
		exit
	;;
esac
done

if [ ! -e $HOME/default.nix ]; then
	echo "No $HOME/default.nix file found, refusing to run"
	exit -1
fi

# TODO: we may want to complain if default.nix is a symlink. It can be a symlink but has some relative
# path issues.

# The trailing / is important for find to work properly
OLDOLDROOT=/var/run/user/$UID/current-home/
OLDROOT=$HOME/.nix-home/
ROOT=/nix/var/nix/profiles/per-user/$USER/nix-home/

function fail() {
	echo "Failed to run"
	rm $TMPFILE
	exit 255
}

prefix=$ROOT
TMPFILE=`mktemp -u --suffix=nixhome`

if [ "$performLink" == "true" ]; then

	# enumerate over every file in current-home, store in TMPFILE
	touch $TMPFILE

	# 0.1.x
	if [ -e $OLDOLDROOT ]; then
		find $OLDOLDROOT -type f >> $TMPFILE
		find $OLDOLDROOT -type l >> $TMPFILE
	fi

	# 0.2.x
	if [ -e $OLDROOT ]; then
		find $OLDROOT -type f >> $TMPFILE
		find $OLDROOT -type l >> $TMPFILE
	fi

	# 0.3.x and beyond
	if [ -e $ROOT ]; then
		find $ROOT -type f >> $TMPFILE
		find $ROOT -type l >> $TMPFILE
	fi
fi

if [ "x_$PRINTCMDS" == "x_true" ]; then
	echo "nix-env -I NIXHOME -p $ROOT -f $HOME $op $@ || fail"
fi

# run the actual command
nix-env -I NIXHOME -p $ROOT -f $HOME $op $@ || fail

# quit if we have skipped linking
if [ "$performLink" != "true" ]; then
	exit
fi

# link all symlinks in the overlay to $HOME
for x in `find $ROOT -type l`; do
	dest=${x#$prefix}

	if [ ! -h "$HOME/$dest" ]; then
		if [ -f "$HOME/$dest" ]; then
			echo "$dest is a regular file refusing to overwrite with link"
		elif [ -d "$HOME/$dest" ]; then
			echo "$dest is a regular directory, refusing to overwrite with link"
		else
			# dest does not exist
			echo "linking $x to $dest"
			mkdir -p `dirname $HOME/$dest`
			ln -sf $x -t `dirname $HOME/$dest`
		fi
	else
		# dest file or dir is a symbolic link
		originalFile=$(readlink $HOME/$dest) # ensure the existing link goes to a nix-home file, otherwise ignore it.
		case $originalFile in
			$OLDOLDROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			$OLDROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			$ROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			*)
				echo "$dest is a symlink to a non nix-home file, refusing to overwrite with link"
			;;
		esac
	fi
done

# link all the regular files in the overlay to $HOME
for x in `find $ROOT -type f`; do
	dest=${x#$prefix}

	if [ ! -h "$HOME/$dest" ]; then
		if [ -f "$HOME/$dest" ]; then
			echo "$dest is a regular file refusing to overwrite with link"
		elif [ -d "$HOME/$dest" ]; then
			echo "$dest is a regular directory, refusing to overwrite with link"
		else
			# dest does not exist
			echo "linking $x to $dest"
			mkdir -p `dirname $HOME/$dest`
			ln -sf $x -t `dirname $HOME/$dest`
		fi
	else
		# dest file or dir is a symbolic link
		originalFile=$(readlink $HOME/$dest)
		case $originalFile in
			$OLDOLDROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			$OLDROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			$ROOT*)
				echo "linking $x to $dest"
				mkdir -p `dirname $HOME/$dest`
				ln -sf $x -t `dirname $HOME/$dest`
			;;
			*)
				echo "$dest is a symlink to a non nix-home file, refusing to overwrite with link"
			;;
		esac
	fi
done

# iterate over all files in TMPFILE
for x in `cat $TMPFILE`; do
	if [ ! -e $x ]; then
		echo "$x does not exist in new home"
		dest=${x#$prefix}

		if [ -h "$HOME/$dest" ]; then
			echo "unlinking $HOME/$dest"
			rm $HOME/$dest
		else
			echo "$HOME/$dest is not a symbolic link, skipping"
		fi
	fi
done

# cleanup
rm $TMPFILE