#!/bin/bash

max=20
prefix=$1
unique=$$-$(date +%s | base64)
askpass=./sshpass-${unique}

run_command() {
	DISPLAY=nothing:0 SSH_ASKPASS=${askpass} setsid ssh -oStrictHostKeyChecking=no -t ${superuser}@$1 "$2" 2> /dev/null
}

escape() {
	sed -e 's/\//\\\//g'
}

trim() {
	tr -d $'\r' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'
}


user_regex="^(${prefix}[^:]*)"
users=($(grep -Eo "$user_regex" /etc/shadow))

if [ ${#users[@]} -gt ${max} ]; then
	echo >&2 "Over ${max} users with prefix '${prefix}', please narrow down by using longer prefix."
	echo >&2 "Example: $0 inf5063-g"
	exit 1
fi

read -p "Found ${#users[@]} users starting with prefix '${prefix}', continue [y/N]? " yn
case $yn in
	[Yy]*) ;;
	*) exit 1;;
esac

read -p "Superuser username: " superuser
if [ -z "${superuser}" ]; then
	echo >&2 "Username can not be empty"
	exit 1
fi

read -p "Superuser password: " -s superpass
echo

if [ -z "${superuser}" ] || [ -z "${superpass}" ]; then
	echo >&2 "Username and password can not be empty"
	exit 1
fi

echo "echo ${superpass}" > ${askpass}
chmod +x ${askpass}

hosts=()
while true; do
	read -p "Hostname [empty quits]: " hostname
	case ${hostname} in
		"") break;;
		*) ;;
	esac
	if ! realhost=$(run_command "${hostname}" "hostname"); then
		echo >&2 "Hostname '${hostname}' is unreachable or username+password is wrong"
	else
		hosts+=" ${hostname}"
		if ! mountpoint=$(run_command "${hostname}" "echo ${superpass} | sudo -S grep -E '/mnt/home' /etc/fstab"); then
			run_command "${hostname}" "echo ${superpass} | sudo -S echo \"128.39.36.109:/home /mnt/home\tnfs\tdefaults\t0\t0\" >> /etc/fstab"
		fi
	fi
done

if [ ${#hosts[@]} -lt 1 ]; then
	echo >&2 "No hosts specified, aborting"
	exit 2
fi

for host in ${hosts[@]}; do
	echo "Applying changes on ${host}..."

	for user in ${users[@]}; do
		user_regex="^${user}:*"
		passwd=$(grep -E "${user_regex}" /etc/passwd | sed -e "s,/home/${user},/mnt/home/${user},g" | trim)
		shadow=$(grep -E "${user_regex}" /etc/shadow)
		group=$(grep -E "${user_regex}" /etc/group)

		echo "${user}"

		remote_passwd=`run_command "${host}" "echo ${superpass} | sudo -S grep -E \"${user_regex}\" /etc/passwd 2> /dev/null"`
		remote_passwd=$(echo "${remote_passwd}" | trim)
		if [ -z "${remote_passwd}" ]; then
			run_command "${host}" "echo ${superpass} | sudo -S sh -c 'echo \"${passwd}\" >> /etc/passwd' 2> /dev/null"
		else
			a=$(echo "${remote_passwd}" | escape)
			b=$(echo "${passwd}" | escape)
			run_command "${host}" "echo ${superpass} | sudo -S sed -i 's/${a}/${b}/' /etc/passwd 2> /dev/null"
		fi

		remote_shadow=`run_command "${host}" "echo ${superpass} | sudo -S grep -E \"${user_regex}\" /etc/shadow 2> /dev/null"`
		remote_shadow=$(echo "${remote_shadow}" | trim)
		if [ -z "${remote_shadow}" ]; then
			run_command "${host}" "echo ${superpass} | sudo -S sh -c 'echo \"${shadow}\" >> /etc/shadow' 2> /dev/null"
		else
			a=$(echo "${remote_shadow}" | escape)
			b=$(echo "${shadow}" | escape)
			run_command "${host}" "echo ${superpass} | sudo -S sed -i 's/${a}/${b}/' /etc/shadow 2> /dev/null"
		fi

		remote_group=`run_command "${host}" "echo ${superpass} | sudo -S grep -E \"${user_regex}\" /etc/group 2> /dev/null"`
		remote_group=$(echo "${remote_group}" | trim)
		if [ -z "${remote_group}" ]; then
			run_command "${host}" "echo ${superpass} | sudo -S sh -c 'echo \"${group}\" >> /etc/group' 2> /dev/null"
		else
			a=$(echo "${remote_group}" | escape)
			b=$(echo "${group}" | escape)
			run_command "${host}" "echo ${superpass} | sudo -S sed -i 's/${a}/${b}/' /etc/group 2> /dev/null"
		fi
	done
done

rm -f ${askpass}