#!/bin/bash

# x11vnc option '-noxrecord' added as workaround for crashing bug
# See https://github.com/LibVNC/x11vnc/issues/61
#
# The option is not be needed with latest x11vnc from source, but we don't rely
# on the remote side being up to date.

ssh()
{
    command ssh "$@" 2>&1 | sed 's/^/REMOTE> /'
}

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

share_display()
{
    if [ "$DEBUG" ]
    then
        set -x
    fi

    port=5500
    while fuser -vk $port/tcp
    do
        sleep 0.1
    done
    x11vnc -noxrecord -q -nopw -ncache -ncache_cr -localhost -display "${local_display}" -rfbport "$port" &
    X11VNC=$!
    trap 'if [ ! "$DEBUG" ]; then exec 2>/dev/null; fi; set -- "$X11VNC" "$SSH"; ps hu "$@"; kill "$@"' EXIT

    while ! fuser -v $port/tcp
    do
        [ -e /proc/"$X11VNC" ] || break
        sleep 0.1
    done

    # TODO: spin waiting for port 5500
    ssh -n \
        ${remote_port:+ -p "$remote_port" } \
        "$remote_host" \
        "fuser -vk $port/tcp && sleep 1"
    ssh -n \
        -o ControlPath=none \
        -o ExitOnForwardFailure=yes \
        -R "localhost:$port:localhost:$port" \
        ${remote_port:+ -p "$remote_port" } \
        "$remote_host" \
        "DISPLAY=${remote_display} xvncviewer localhost:$port" 2>&1 &
    SSH=$!
    wait -n
}

if [ "$1" = -r ]
then
    shift
    cmd=share_display
elif [ "$1" = -d ]
then
    shift
    cmd=direct_connection
else
    cmd=direct_connection
fi

remote_host=${1:-blackboard}

case "$remote_host" in
    *:*) remote_port=${remote_host##*:}
         remote_host=${remote_host%:*}
         ;;
    *) remote_port=
       ;;
esac
remote_display=${2:-:0}
local_display=${3:-:0}

$cmd