#!/bin/sh

# simple script to set up a new vserver guest

# test the first argument against the remaining ones, return success on a match
isin() {
	local	_a=$1 _b

	shift
	for _b; do
		[ "$_a" = "$_b" ] && return 0
	done
	return 1
}

# remove all occurrences of first argument from list formed by
# the remaining arguments
rmel() {
	local	_a=$1 _b

	shift
	for _b; do
		[ "$_a" != "$_b" ] && echo -n "$_b "
	done
}

# Issue a read into the global variable $resp. 
_ask() {
	local _redo=0

	read resp
	case "$resp" in
	!)	echo "Type 'exit' to return to setup."
		sh
		_redo=1
		;;
	!*)	eval "${resp#?}"
		_redo=1
		;;
	esac
	return $_redo
}

# Ask for user input.
#
#    $1    = the question to ask the user
#    $2    = the default answer
#
# Save the user input (or the default) in $resp.
#
# Allow the user to escape to shells ('!') or execute commands
# ('!foo') before entering the input.
ask() {
	local _question=$1 _default=$2

	while :; do
		echo -n "$_question "
		[ -z "$_default" ] || echo -n "[$_default] "
		_ask && : ${resp:=$_default} && break
	done
}

# Ask for user input until a non-empty reply is entered.
#
#    $1    = the question to ask the user
#    $2    = the default answer
#
# Save the user input (or the default) in $resp.
ask_until() {
	resp=
	while [ -z "$resp" ] ; do
		ask "$1" "$2"
	done
}

# Ask for the user to select one value from a list, or 'done'.
#
# $1 = name of the list items (disk, cd, etc.)
# $2 = question to ask
# $3 = list of valid choices
# $4 = default choice, if it is not specified use the first item in $3
#
# N.B.! $3 and $4 will be "expanded" using eval, so be sure to escape them
#       if they contain spooky stuff
#
# At exit $resp holds selected item, or 'done'
ask_which() {
	local _name=$1 _query=$2 _list=$3 _def=$4 _dynlist _dyndef

	while :; do
		# Put both lines in ask prompt, rather than use a
		# separate 'echo' to ensure the entire question is
		# re-ask'ed after a '!' or '!foo' shell escape.
		eval "_dynlist=\"$_list\""
		eval "_dyndef=\"$_def\""

		# Clean away whitespace and determine the default
		set -o noglob
		set -- $_dyndef; _dyndef="$1"
		set -- $_dynlist; _dynlist="$*"
		set +o noglob
		[ $# -lt 1 ] && resp=done && return

		: ${_dyndef:=$1}
		echo "Available ${_name}s are: $_dynlist."
		echo -n "Which one $_query? (or 'done') "
		[ -n "$_dyndef" ] && echo -n "[$_dyndef] "
		_ask || continue
		[ -z "$resp" ] && resp="$_dyndef"

		# Quote $resp to prevent user from confusing isin() by
		# entering something like 'a a'.
		isin "$resp" $_dynlist done && break
		echo "'$resp' is not a valid choice."
	done
}

# Ask for user input until a non-empty reply is entered.
#
#    $1    = the question to ask the user
#    $2    = the default answer
#
# Save the user input (or the default) in $resp.
ask_until() {
	resp=
	while [ -z "$resp" ] ; do
		ask "$1" "$2"
	done
}

# http://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names
valid_hostname() {
        # check length
        if [ $(echo "$1" | wc -c) -gt 63 ]; then
                echo "Hostname '$1' is too long."
                return 1
        fi
        # check that it only contains valid chars
        if ! [ -z "$(echo $1 | sed 's/[0-9a-z-]//g')" ]; then
                echo "Hostname must only contain letters (a-z), digits (0-9) or -"
                return 1
        fi
        # must not start with -
        case "$1" in
                -*) echo "Hostname must not start with a '-'"; return 1;;
        esac
        return 0
}

# return last ipv4 address and mask
#
# $1 = interface
#
last_ipv4_addr_mask() {
	local _iface=$1
	ip addr show dev $_iface | awk '$1 == "inet" {print $2}' | tail -n1
}

valid_ip() {
	[ "$1" ] || return 0
        ipcalc -s $1
}

# ask for hostname
# 
# $1 = default
#
# retrusn hostname in global var $resp
#
ask_hostname() {
	while true; do
		ask "Hostname for new vserver:" $1
		if [ -d /etc/vservers/$resp ]; then
			echo "/etc/vservers/$resp already exist"
			continue
		fi
		if [ -d /vservers/$resp ]; then
			echo "/vservers/$resp already exist"
			continue
		fi
		valid_hostname $resp && break
	done
}

ask_ifaceopts() {
	# get ip address(es)
	resp=
	local ifaceopts= _def= _iface=
	local ifaces=$(ip addr | awk -F: '$1 ~ /^[0-9]/ {printf "%s" $2} END {printf "\n"}')
	local last_iface=$(echo $ifaces | sed 's/.* //')
	while [ "$resp" != "done" ]; do
		if [ -z "$ifaces" ] || [ "$ifaces" = "lo " ] || [ -n "$ifaceopts" ]; then
			_def="done"
		else
			_def=$(echo $ifaces | sed 's/.* //')
		fi
		ask_which "network interface" "to use for $_hostname" \
			"$ifaces" $_def
		[ "$resp" = "done" ] && break

		_iface=$resp
		ifaces=$(rmel $_iface $ifaces)
		# suggested ip by last digit + 1
		_last_ip_mask=$(last_ipv4_addr_mask $_iface)
		_last_ip=${_last_ip_mask%/*}
		_last_ip_digit=${_last_ip##*.}
		_ip=${_last_ip%.*}.$((($_last_ip_digit + 1) % 256))
		_mask=${_last_ip_mask#*/}
		while true; do
			ask "Enter IP address/mask for $_iface:" $_ip/$_mask
			valid_ip $resp && break
			echo "$resp is not a valid IPv4 address/mask"
		done
		_ip_mask=$resp
		ifaceopts="$ifaceopts --interface $_iface:$_ip_mask"

		# suggest context from last digit in first ip address
		if [ -z "$_context" ]; then
			_ip=${_ip_mask%/*}
			_last_digit=${_ip##*.}
			_context=$((10000 + $_last_digit))
		fi
	done
	resp="$ifaceopts"
}

ask_context() {
	# get context id
	while true; do
		ask "Enter context id for $_hostname:" $_context
		if echo "$resp" | egrep -q "[0-9]+"; then
			[ $resp -ge 0 ] && [ $resp -lt 65535 ] && break
		fi
		echo "Context id must be a 0-65534 number"
	done
}

ask_template() {
	local temp
	# get template
	while true; do
		ask "Enter template file (or empty for generate a new):" \
			$_template
		if [ -z "$resp" ] || [ -r "$resp" ]; then
			break
		fi
		echo "Can not read $resp"
	done
	temp=$resp
	if [ -z "$temp" ]; then
		temp=/vservers/template.tar.gz
		echo -n "Generating template..."
		if setup-vs-template -q -o $temp; then
			echo "ok"
		else
			echo "Failed to create template"
			exit 1
		fi
	fi
	resp=$temp
}

usage() {
	echo "Usage: ${0##*/} [-h] [HOSTNAME...]"
	exit 1
}

while getopts "h" opt; do
	case "$opt" in
		h) usage;;
		?) usage;;
	esac
done

shift $(($OPTIND - 1))

if [ "$(whoami)" != "root" ]; then
	echo "Need to be root. Sorry."
	exit 1
fi

while true; do
	ask_hostname $1
	_hostname=$resp

	ask_ifaceopts
	_ifaceopts=$resp

	ask_context
	_context=$resp

	ask_template
	_template=$resp

	vserver $_hostname build \
		--hostname $_hostname \
		$_ifaceopts \
		--context $_context \
		-m template -- -t "$_template" -d alpine \
		&& cp /etc/resolv.conf /vservers/$_hostname/etc/ \
		&& cp /etc/apk/repositories /vservers/$_hostname/etc/apk/ \
		|| exit 1
	
	shift
	[ $# -le 0 ] && exit 0
done