#!/bin/bash
PROGNAME=${0##*/}

main()
{
    #  Defaults for options
    SSH_OPTS=
    WM_DECORATIONS_HEIGHT=49
    START_SERVER_FLAG=true
    START_VIEWER_FLAG=true
    DFLT_REMOTE_GEOMETRY=1920x1200

    #  Process options
    while [ $# -ge 1 ]; do
        case $1 in
            --ssh-opts=*)              SSH_OPTS=${1#*=} ;;
            --wm-decorations-height=*) WM_DECORATIONS_HEIGHT=${1#*=} ;;
            --no-viewer)               START_VIEWER_FLAG=false ;;
            --)                        shift; break ;;
            -*)                        usage ;;
            *)                         break ;;
        esac
        shift
    done

    #  Process arguments
    [ $# = 2 ] || usage
    USER_AT_HOST=$1
    VNC_DISPLAY_NO=$2

    #  Sanity checks and derivations
    [ "X$(setsid ssh $SSH_OPTS -n $USER_AT_HOST echo OK 2>&1)" = XOK ] || error "$USER_AT_HOST: no ssh access (has the local key file been added to the remote user's authorized_keys file?)"
    if check_x_connection; then
        LOCAL_GEOMETRY=$(xwininfo -root | sed -n 's/^  -geometry \(.*\)+0+0/\1/p')
        [[ $LOCAL_GEOMETRY =~ ([0-9]+)x([0-9]+) ]]
        REMOTE_GEOMETRY=${BASH_REMATCH[1]}x$((${BASH_REMATCH[2]}-$WM_DECORATIONS_HEIGHT))
    else
        warning "can't query local display size; defaulting to $DFLT_REMOTE_GEOMETRY ..."
        REMOTE_GEOMETRY=$DFLT_REMOTE_GEOMETRY
    fi

    debug 10 "main: creating xstartup ..."
    ssh $SSH_OPTS $USER_AT_HOST "mkdir -p ~/.vnc; cat > ~/.vnc/xstartup; chmod 755 ~/.vnc/xstartup" <<EOF
#!/bin/bash
#  This script was created by $PROGNAME on $(date).
exec env -i /bin/sh -c "export PATH=\$PATH
                        export DISPLAY=\$DISPLAY
                        export HOME=\$HOME
                        export LOGNAME=\$LOGNAME
                        export USER=\$USER
			. ~/.profile
                        exec /usr/bin/xfce4-session"
EOF
    #  clean up old remote password files (there's no opportunity after it's been used).
    debug 10 "main: cleaning up old remote password files ..."
    ssh $SSH_OPTS $USER_AT_HOST -n "rm -f /tmp/$PROGNAME.*.remote-passwd"
    debug 10 "main: creating password ..."
    echo xxxxxxx | vncpasswd -f > /tmp/$PROGNAME.$$.local-passwd
    debug 10 "main: copying password to remote ..."
    scp -q $SSH_OPTS /tmp/$PROGNAME.$$.local-passwd $USER_AT_HOST:/tmp/$PROGNAME.$$.remote-passwd
    debug 10 "main: running vncserver ..."
    ssh $SSH_OPTS $USER_AT_HOST -n "vncserver $VNC_DISPLAY_NO -geometry $REMOTE_GEOMETRY -rfbauth /tmp/$PROGNAME.$$.remote-passwd"
    ! $START_VIEWER_FLAG || vncviewer -passwd /tmp/$PROGNAME.$$.local-passwd ${USER_AT_HOST#*@}$VNC_DISPLAY_NO
    debug 10 "main: cleaning up old local password files ..."
    rm -f /tmp/$PROGNAME.*.local-passwd
}

check_x_connection()
{
    xlsclients > /dev/null 2>&1
}

usage()
{
    {
        echo "Usage: $PROGNAME [<user>@]<host>"
    } >&2
    exit 1
}
    
error() 
{ 
    if check_x_connection; then
        gxmessage -geometry 400x100 -wrap "ERROR: $1"
    else
        echo "$PROGNAME: ERROR: $1" >&2
    fi
    exit 1
}

debug() { echo "$PROGNAME: DEBUG[$1]: $2" >&2; }

main "$@"