#!/bin/ksh93

# Usage: see $0 -h

typeset -r VERSION='1.0' FPROG=${.sh.file} PROG=${FPROG##*/} SDIR=${FPROG%/*}

function showUsage {
    [[ -n $1 ]] && X='-?' ||  X='--man'
    getopts -a ${PROG} "${ print ${USAGE} ; }" OPT $X
}

function doMain {
	typeset -Ai HSEEN ASEEN
	typeset A LINE HNAME H
	integer N
	
	[[ -z $1 || ! -r "$1" ]] && showUsage 1 && exit 1

	# sort on timestamp, newest first
	sort -k3nr $1 | \
	while read LINE ; do
		A=( ${LINE} )
	
		# EA\tIP\tTIMESTAMP\tHOSTNAME\tINTERFACE
		(( ${#A[@]} == 5 )) || continue
	
		# ignore comments and for "backward compat" entries with unresolved
		# hostname, i.e. raw IP
		[[ ${A:0:1} == '#' || ${A[3]} =~ \.[0-9][0-9]*$ ]] && continue
	
		# make unique: take into account only the 1st, most recent ea seen 
		(( ASEEN["$A"] )) && continue
		ASEEN["$A"]=1
	
		# append '-ip' to DECnet entry hostnames
		[[ ${A:0:7} == 'aa:0:4:' ]] && A[3]+='-ip'
	
		# append -old[N] suffix to duped hostnames
		HNAME="${A[3]}"
		if (( HSEEN["${HNAME}"] )); then
			H="${A[3]}-old"
			N=0
			while (( HSEEN["$H"] )); do
				(( N++ ))
				H="${A[3]}-old$N"
			done
			A[3]="$H"
		fi
		HSEEN["${A[3]}"]=1
		print "${A[0]}\t${A[3]}"
	done | sort		# sort by ethernet address
}

USAGE="[-?${VERSION}"' ]
[-copyright?Copyright (c) 2016 Jens Elkner. All rights reserved.]
[-license?CDDL 1.0]
[+NAME?'"${PROG}"' - ethers(4) generator]
[+DESCRIPTION?This script prints out entries of the arpwatch database \afile\a (usually \b/var/arpwatch/arp.dat\b) in \bethers\b(4) format. Only the most recent, resolvable entries are taken into account, so it is normal, that the number of entries in the produced output and the database file differ.]
[h:help?Print this help and exit.]
[F:functions?Print a list of all functions available.]
[T:trace]:[functionList?A comma separated list of functions of this script to trace (convinience for troubleshooting).]
[+SEE ALSO?\barpwatch\b(1M).]
\n\n\afile\a
'
X="${ print ${USAGE} ; }"
while getopts "${X}" OPT ; do
	case ${OPT} in
		h) showUsage ; exit 0 ;;
		T)	if [[ ${OPTARG} == 'ALL' ]]; then
				typeset -ft ${ typeset +f ; }
			else
				typeset -ft ${OPTARG//,/ }
			fi
			;;
		F) typeset +f && exit 0 ;;
		*) showUsage 1 ; exit 1 ;;
	esac
done
X=$((OPTIND-1))
shift $X && OPTIND=1
unset X

doMain "$@"