#!/usr/bin/env bash

# Script to handle automatic snapshotting and restoring of test machines.
# This script should be run early in the startup process to see if the
# user wants to continue/create a session or to delete an existing
# session and start over fresh.

set -e
[ $EUID == 0 ] || exec sudo "$0" "$@"

# If a snapshot is being merged, wait until the process completes
# since we're not allowed to make some kinds of changes until then.
ROOT_DEV=$(mount | awk '/ on \/ /{print $1}')
while true; do
	ROOT_DATA=$(lvs --noheadings --aligned --separator "$(echo -e '\t')" $ROOT_DEV | tr -d ' ')
	if [[ -n "$(echo "$ROOT_DATA" | cut -f7)" ]]; then
		echo "Restoring snapshot, please wait..."
		sleep 5
	else
		break
	fi
done
ROOT_VG=$(echo "$ROOT_DATA" | cut -f2)

# If a snapshot is present, ask if they want to continue their session.
# If they don't, see if they want to delete the snapshot to start
# fresh instead.
SNAP_PREFIX="wacsnap"
SNAP_LIST=$(lvs --noheadings --select "lv_name=~$SNAP_PREFIX" --aligned --separator "$(echo -e '\t')" | tr -d ' ')
while [[ -n "$SNAP_LIST" ]]; do
	echo "Previous snapshots(s) detected:"
	echo $(echo "$SNAP_LIST" | cut -f1)

	LV=$(echo "$SNAP_LIST" | cut -f1 | head -n1)
	VG=$(echo "$SNAP_LIST" | cut -f2 | head -n1)

	while true; do
		read -p "Do you want to continue your last session (Y/N)? " CONTINUE
		case $CONTINUE in
		[Yy]*)
			echo "Continuing last session."
			exit;;
		[Nn]*)
			break;;
		esac
	done

	while true; do
		read -p "Delete current session (Y/N)? " DELETE
		case $DELETE in
		[Yy]*)
			lvconvert --merge ${VG}/${LV}
			read -p "Press enter to reboot." FOO
			reboot;;
		[Nn]*)
			break;;
		esac
	done
	echo
	echo
done

# Create a temporary snapshot just in case the user takes a long
# time to decide if they want to start a new session or to enter
# maintainence mode. We don't want changes made while this prompt
# is waiting to be committed to the base system...
SIZE=$(echo "$ROOT_DATA" | cut -f4)
lvcreate --snapshot --name $SNAP_PREFIX --size $SIZE $ROOT_DEV

# Ask if the user wants to start a new session or if they
# are performing system maintainence (e.g. installing updates).
# Delete temp snapshot and exit if performing system maintainence.
while true; do
	read -p "Start new session? (Y/N) " STARTNEW
	case $STARTNEW in
	[Yy]*)
		break;;
	[Nn]*)
		echo "Entering maintainence mode. Enter 'Y' if asked to remove the '${SNAP_PREFIX}' volume."
		lvremove ${ROOT_VG}/${SNAP_PREFIX}
		exit;;
	esac
done

# Ask user for their name and a one-word note. Rename the snapshot
# with this information so that in future reboots we know what is
# going on with this machine.
read -p "What is your name (e.g ping)? " USER
read -p "One-word session note (e.g. test-the-thing)? " NOTE
lvrename ${ROOT_VG}/${SNAP_PREFIX} ${SNAP_PREFIX}_${USER}_${NOTE}