#!/bin/sh

direct_connection()
{
    port=$((5900 + local_display))
    ssh -o ControlPath=none -n \
        -L $port:localhost:$port "$remote_host" "x11vnc -nopw -ncache -ncache_cr -localhost -display ${remote_display}" &
    pid=$!
    sleep 1 # surrender race
    xvncviewer -encodings "copyrect tight zrle hextile" localhost:0
    kill $pid
}

quietly()
{
    "$@" >/dev/null 2>&1
}

reverse_connection()
{
    port=5500
    xvncviewer -fullscreen -encodings "copyrect tight zrle hextile" -listen &
    pid=$!
    quietly ssh -o ControlPath=none \
                -R $port:localhost:$port "$remote_host" \
                "x11vnc -q -nopw -localhost -display ${remote_display} -coe localhost:$port -rfbport 0"
    kill $pid
}

share_display()
{
    set -x
    port=5500
    fuser -vk $port/tcp
    ssh -o ControlPath=none \
        -o ExitOnForwardFailure=yes \
        -f \
        -L $port:localhost:$port "$remote_host" \
        "fuser -vk $port/tcp; DISPLAY=${remote_display} xvncviewer -fullscreen -encodings 'copyrect tight zrle hextile' -listen"
    trap "fuser -vk $port/tcp" INT
    sleep 1
    x11vnc -q -nopw -localhost -display ${local_display} -coe localhost:$port -rfbport 0
}

if [ "$1" = -r ]
then
    shift
    cmd=share_display
else
    cmd=reverse_connection
fi

remote_host=${1:-blackboard}
remote_display=${2:-:0}
local_display=${3:-:0}

$cmd