# This function performs host completion based on ssh's known_hosts files,
# defaulting to standard host completion if they don't exist.
# Arguments:  -a             Use aliases
#             -c             Use `:' suffix
#             -F configfile  Use `configfile' for configuration settings
_known_hosts()
{
	local configfile cur curd ocur user suffix aliases global_kh user_kh hosts i host
	local -a kh khd config

	COMPREPLY=()
	cur=`_get_cword`
	ocur=$cur

	local OPTIND=1
	while getopts "acF:" flag "$@"; do 
	    case $flag in
		a) aliases='yes' ;;
		c) suffix=':' ;;
		F) configfile="$OPTARG" ;;
	    esac
	done

	[[ $cur == *@* ]] && user=${cur%@*}@ && cur=${cur#*@}
	kh=()

	# ssh config files
	if [ -n "$configfile" ]; then
	    [ -r "$configfile" ] && 
		config=( "${config[@]}" "$configfile" )
	else
	    [ -r /etc/ssh/ssh_config ] &&
		config=( "${config[@]}" "/etc/ssh/ssh_config" )
	    [ -r "${HOME}/.ssh/config" ] &&
		config=( "${config[@]}" "${HOME}/.ssh/config" )
	    [ -r "${HOME}/.ssh2/config" ] &&
		config=( "${config[@]}" "${HOME}/.ssh2/config" );
	fi

	if [ ${#config[@]} -gt 0 ]; then
	    # expand path (if present) to global known hosts file
	    global_kh=$( eval echo "$( sed -ne 's/^[ \t]*[Gg][Ll][Oo][Bb][Aa][Ll][Kk][Nn][Oo][Ww][Nn][Hh][Oo][Ss][Tt][Ss][Ff][Ii][Ll][Ee]['"$'\t '"']*\(.*\)$/\1/p' "${config[@]}" )" )
	    # expand path (if present) to user known hosts file
	    user_kh=$( eval echo "$( sed -ne 's/^[ \t]*[Uu][Ss][Ee][Rr][Kk][Nn][Oo][Ww][Nn][Hh][Oo][Ss][Tt][Ss][Ff][Ii][Ll][Ee]['"$'\t '"']*\(.*\)$/\1/p' "${config[@]}" )" )
	fi

	# Global known_hosts files
	[ -r "$global_kh" ] &&
		kh=( "${kh[@]}" "$global_kh" )
	if [ -z "$configfile" ]; then
	    [ -r /etc/ssh/ssh_known_hosts ] &&
		kh=( "${kh[@]}" /etc/ssh/ssh_known_hosts )
	    [ -r /etc/ssh/ssh_known_hosts2 ] &&
		kh=( "${kh[@]}" /etc/ssh/ssh_known_hosts2 )
	    [ -r /etc/known_hosts ] &&
		kh=( "${kh[@]}" /etc/known_hosts )
	    [ -r /etc/known_hosts2 ] &&
		kh=( "${kh[@]}" /etc/known_hosts2 )
	    [ -d /etc/ssh2/knownhosts ] &&
		khd=( "${khd[@]}" /etc/ssh2/knownhosts/*pub )
	fi

	# User known_hosts files
	[ -r "$user_kh" ] &&
		kh=( "${kh[@]}" "$user_kh" )
	if [ -z "$configfile" ]; then
	    [ -r ~/.ssh/known_hosts ] &&
		kh=( "${kh[@]}" ~/.ssh/known_hosts )
	    [ -r ~/.ssh/known_hosts2 ] &&
		kh=( "${kh[@]}" ~/.ssh/known_hosts2 )
	    [ -d ~/.ssh2/hostkeys ] &&
		khd=( "${khd[@]}" ~/.ssh2/hostkeys/*pub )
	fi

	# If we have known_hosts files to use
	if [ ${#kh[@]} -gt 0 -o ${#khd[@]} -gt 0 -o -n "$configfile" ]; then
	    # Escape slashes and dots in paths for awk
	    cur=${cur//\//\\\/}
	    cur=${cur//\./\\\.}
	    curd=$cur

	    if [[ "$cur" == [0-9]*.* ]]; then
		# Digits followed by a dot - just search for that
		cur="^$cur.*"
	    elif [[ "$cur" == [0-9]* ]]; then
		# Digits followed by no dot - search for digits followed
		# by a dot
		cur="^$cur.*\."
	    elif [ -z "$cur" ]; then
		# A blank - search for a dot or an alpha character
		cur="[a-z.]"
	    else
		cur="^$cur"
	    fi

	    if [ ${#kh[@]} -gt 0 ]; then

		# FS needs to look for a comma separated list
		COMPREPLY=( $( awk 'BEGIN {FS=","}
				/^[^|]/ {for (i=1; i<=2; ++i) { \
				       gsub(" .*$", "", $i); \
				       if ($i ~ /'$cur'/) {print $i} \
				}}' "${kh[@]}" 2>/dev/null ) )
	    fi
	    if [ ${#khd[@]} -gt 0 ]; then
		# Needs to look for files called
		# .../.ssh2/key_22_<hostname>.pub
		# dont fork any processes, because in a cluster environment,
		# there can be hundreds of hostkeys
		for i in "${khd[@]}" ; do
		    if [[ "$i" == *key_22_$curd*.pub ]] && [ -r "$i" ] ; then
			host=${i/#*key_22_/}
			host=${host/%.pub/}
			COMPREPLY=( "${COMPREPLY[@]}" $host )
		    fi
		done
	    fi
	    # append any available aliases from config files
	    if [ ${#config[@]} -gt 0 ] && [ -n "$aliases" ]; then
	    local host_aliases=$( sed -ne 's/^[ \t]*[Hh][Oo][Ss][Tt]\([Nn][Aa][Mm][Ee]\)\?['"$'\t '"']\+\([^#*?]*\)\(#.*\)\?$/\2/p' "${config[@]}" )
	    hosts=$( compgen -W "$host_aliases" -- $ocur )
		COMPREPLY=( "${COMPREPLY[@]}" $hosts )
	    fi
	    
	    # Now add results of normal hostname completion
	    COMPREPLY=( "${COMPREPLY[@]}" $( compgen -A hostname -- $ocur ) )

	    # apply suffix
	    for (( i=0; i < ${#COMPREPLY[@]}; i++ )); do
		COMPREPLY[i]=$user${COMPREPLY[i]}$suffix
	    done
	elif [ -z "$configfile" ]; then
	    # Just do normal hostname completion
	    COMPREPLY=( $( compgen -A hostname -S "$suffix" -- $cur ) )
	fi

	return 0
} # _known_hosts()