#!/bin/bash
#@file    addtodhcp
#@brief   Append a "host" section for each defined computer to the DHCP configuration file.
#@usage   addtodhcp [-f FILE] [-r] [-e] [ {LABNAME|COMPUTERNAME} ...]
#@param   -f, --file FILE   DHCP configuration file (/etc/dhcp/dhcpd.conf, by default)
#@param   -r, --restart     restart DHCP service
#@param   -e, --exam        assign to alternative network ("exam mode" from Universidad de Sevilla)
#@param   LABNAME           only add computers defined in this lab
#@param   COMPUTERNAME      only add a single computer data
#@version 1.1.1b - Initial version.
#@author  Ramón M. Gómez - ETSII Univ. Sevilla
#@date    2020-02-03


# Variables.
PROG="$(basename "$0")"
OPENGNSYS=${OPENGNSYS:-"/opt/opengnsys"}
SERVERCONF=$OPENGNSYS/etc/ogserver.cfg
DHCPCONF=/etc/dhcp/dhcpd.conf
DHCPCONFBCK="$DHCPCONF-$(date +"%Y%m%d")"

source $OPENGNSYS/lib/ogfunctions.sh || exit 1

# Show help or version number.
[ "$*" == "help" ] && help
[ "$*" == "version" ] && version
# Error control.
[ "$USER" != "root" ] && raiseError access "Need to be root"
source $SERVERCONF 2>/dev/null || raiseError access "Cannot read OpenGnsys Server configuration file"

# Processing parameters.
opts=$(getopt -n "$PROG" -l exam,file:,restart -o 'ef:r' -- "$@" ) || raiseError usage
set -- $opts
while [ "$1" ]; do
    case "$1" in
        -e|--exam)
            EXAM=1
            shift ;;
        -f|--file)
            eval DHCPCONF=$2
            shift 2 ;;
        -r|--restart)
            RESTART=1
            shift ;;
        --)
            shift; break ;;
    esac
done
RESOURCES="$*"
[ -f $DHCPCONF ] || raiseError access "Cannot access DHCP configuration file"
grep -q "^[ 	]*\bsubnet\b" $DHCPCONF || raiseError access "Cannot detect any \"group\" clauses in DHCP configuration file"
grep -q "^[ 	]*\bgroup\b" $DHCPCONF && raiseError access "Cannot modify DHCP configuration file with \"group\" clauses"

[ "$*" ] && WHEREEXPR="WHERE $(sed -e "s/\('[^']*'\)/nombreaula=\1 OR nombreordenador=\1 OR/g" <<< "$*")"
WHEREEXPR="${WHEREEXPR% OR}"

# Looking for data.
SEDEXPR=""
while read -pe NAME IP MAC ROUTER LAB; do
    [ "$LAB" ] || break
    if [ "$EXAM" ]; then
        IP="${IP/10.1./192.168.}"
        ROUTER="${ROUTER/10.1./192.168.}"
    fi
    # Check if router is defined.
    if ! grep -Eq "routers[[:space:]]+$ROUTER" $DHCPCONF; then
        raiseError notfound "Router \"$ROUTER\" not defined in DHCP configuration file"
    fi
    # Find any "host" clause.
    SEDEXPR+="/\bhost $NAME\b/"
    if ! grep -Eq "host[[:space:]]+$NAME[[:space:]]*}" $DHCPCONF; then
        SEDEXPR+=",/}/"
    fi
    if [ "$LAB" != "$LABBCK" ]; then
        NEWLAB="\\\n"
	LABBCK="$LAB"
    else
        NEWLAB=""
    fi
    # Delete the found "host" clause and add a new one.
    SEDEXPR+="d
/^[[:space:]]*option[[:space:]]+routers[[:space:]]+\b$ROUTER\b/a ${NEWLAB}host $NAME { hardware ethernet $MAC; fixed-address $IP; }  # $LAB
"
done <<<$(dbexec "
SELECT nombreordenador, ip, 
       CONCAT_WS('', SUBSTR(mac, 1, 2), ':', SUBSTR(mac, 3, 2), ':', SUBSTR(mac, 5, 2), ':',
                     SUBSTR(mac, 7, 2), ':', SUBSTR(mac, 9, 2), ':', SUBSTR(mac, 11, 2)),
       ordenadores.router, nombreaula
  FROM ordenadores
  JOIN aulas USING (idaula)
 $WHEREEXPR
 ORDER BY nombreaula ASC, idordenador ASC;" 2>/dev/null)

# Edit DHCP configuration file.
[ "$SEDEXPR" ] || raiseError notfound "$RESOURCES"
cp -a $DHCPCONF $DHCPCONFBCK || raiseError access "Cannot back-up DHCP configuration file"
sed -i -re "$SEDEXPR" $DHCPCONF
# Delete duplicate empty lines.
perl -0777pi -e "s/\n{3,}/\n\n/g" $DHCPCONF
# Restart the service, if needed.
[ "$RESTART" ] && restart isc-dhcp-server