#!/usr/bin/env bash

# Mount home as an overlay filesystem

# Log stdout & stderr
exec > >(tee -i /tmp/gdm3_postlogin.log) 2>&1

# Treat unset variables as an error when substituting.
set -u

# Exit immediately if a command exits with a non-zero status.
set -e

# Separate tokens on newlines only
IFS='
'

# The value of this parameter is expanded like PS1 and the expanded value is the
# prompt printed before the command line is echoed when the -x option is set
# (see The Set Builtin). The first character of the expanded value is replicated
# multiple times, as necessary, to indicate multiple levels of indirection.
# \D{%F %T} prints date like this : 2019-12-31 23:59:59
PS4='-\D{%F %T} '

# Print commands and their arguments as they are executed.
set -x

# Make sure the mountpoints are free
kill $(lsof -t "$HOME" /mnt) ||:
umount "$HOME" /mnt ||:

if test -e /dev/disk/by-partlabel/01-home; then
	mount -o noatime /dev/disk/by-partlabel/01-home /mnt
else
	# Fails if no local partition is found
	test -e /dev/disk/by-partlabel/01-tmp-home || exit 1

	# We don't care about data consistency since the partition is temporary so disable journaling
	/sbin/mke2fs -t ext4 -O ^has_journal -F /dev/disk/by-partlabel/01-tmp-home
	mount -o noatime,nobarrier /dev/disk/by-partlabel/01-tmp-home /mnt
fi

user_path=/mnt/.01/user
temp_path=/mnt/.01/tmp

mkdir -p "$user_path" "$temp_path"
chown -R "$USER":"$USER" "$user_path" "$temp_path"
mount -t overlay -o lowerdir="$HOME",upperdir="$user_path",workdir="$temp_path" overlay "$HOME"
mkdir -p "$HOME"/.cache
mount -t tmpfs -o size=2G tmpfs "$HOME"/.cache