#!/usr/bin/env bash
set -euo pipefail

# Start a headless X server, a lightweight desktop, x11vnc and noVNC proxy.
# Runs as the container user (configured via devcontainer.json remoteUser).

VNC_PASS=${VNC_PASSWORD:-devpass}
VNC_DIR="$HOME/.vnc"
mkdir -p "$VNC_DIR"

if [ ! -f "$VNC_DIR/passwd" ]; then
  echo "Creating VNC password"
  x11vnc -storepasswd "$VNC_PASS" "$VNC_DIR/passwd"
fi

# Prefer using an existing X server (host) when available. Set USE_EXISTING_DISPLAY=true
# to force using the existing DISPLAY; otherwise, if a host DISPLAY is propagated into the
# container (via devcontainer runArgs / mounts), prefer that instead of starting Xvfb.
if [ "${USE_EXISTING_DISPLAY:-}" = "true" ] || { [ -n "${DISPLAY:-}" ] && [ -d "/tmp/.X11-unix" ]; }; then
  echo "Using existing X server on ${DISPLAY:-<unset>} (X11 forwarding to host)"
  export USE_EXISTING_DISPLAY=true
else
  echo "Prefer Xvfb — starting Xvfb :1"
  if command -v Xvfb >/dev/null 2>&1; then
    # Define virtual screen size once; will try to confirm at runtime
    # using xdpyinfo and fall back to these values if xdpyinfo isn't available.
    SCREEN_W=1280
    SCREEN_H=800
    # Use a slightly taller virtual screen so desktop panels/toolbars
    # don't cause the noVNC client to show an unexpected area below
    # the visible display; use variables so we can clip x11vnc to
    # exactly the same region and avoid framebuffer artifacts.
    Xvfb :1 -screen 0 "${SCREEN_W}x${SCREEN_H}x24" >/tmp/xvfb.log 2>&1 &
    export DISPLAY=:1
  else
    echo "Warning: Xvfb not available; expecting an X server on DISPLAY"
  fi
fi

sleep 1

echo "Starting desktop session (xfce)"
# startxfce4 backgrounds itself; if not available fall back to openbox
if command -v startxfce4 >/dev/null 2>&1; then
  startxfce4 >/tmp/xfce4.log 2>&1 &
else
  if command -v openbox-session >/dev/null 2>&1; then
    openbox-session >/tmp/openbox.log 2>&1 &
  fi
fi

sleep 1

echo "Starting x11vnc on ${DISPLAY:-:1}"
  if [ "${USE_EXISTING_DISPLAY:-}" != "true" ]; then
  # Query the actual display size (xdpyinfo) to compute a precise clip region
  # and avoid sending framebuffer rows outside the visible desktop. Disable
  # client-side caching which can sometimes produce visual artifacts.
  GEOM=""
  if command -v xdpyinfo >/dev/null 2>&1; then
    GEOM=$(xdpyinfo -display "${DISPLAY:-:1}" 2>/dev/null | awk '/dimensions:/ {print $2}') || true
  fi
  if [ -n "$GEOM" ]; then
    # GEOM looks like WxH (e.g. 1280x800)
    W=${GEOM%x*}
    H=${GEOM#*x}
  else
    W=${SCREEN_W}
    H=${SCREEN_H}
  fi
  echo "Starting x11vnc with clip ${W}x${H}+0+0 (display ${DISPLAY:-:1})"
  x11vnc -display "${DISPLAY:-:1}" -rfbauth "$VNC_DIR/passwd" -forever -shared -rfbport 5900 -clip ${W}x${H}+0+0 -bg || true
else
  echo "USE_EXISTING_DISPLAY=true — skipping x11vnc (display forwarded to host)"
fi

sleep 1

# Locate noVNC installation. Prefer /opt/noVNC, then workspace/noVNC.
NOVNC_DIR=""
if [ -d /opt/noVNC ]; then
  NOVNC_DIR="/opt/noVNC"
elif [ -d "$PWD/noVNC" ]; then
  NOVNC_DIR="$PWD/noVNC"
  # Ensure it's available under /opt for tools that expect it there
  if [ ! -e /opt/noVNC ]; then
    mkdir -p /opt
    ln -s "$NOVNC_DIR" /opt/noVNC || true
  fi
fi

# Start the noVNC proxy only when we are running an internal VNC server on port 5900
if [ -n "$NOVNC_DIR" ] && [ "${USE_EXISTING_DISPLAY:-}" != "true" ]; then
  echo "Found noVNC at $NOVNC_DIR"
  # If a wrapper exists in the devcontainer, install it into the noVNC web
  # root so we can set localStorage defaults (e.g. prefer local scaling)
  WRAPPER="${SCRIPT_DIR:-$(pwd)}/novnc/vnc-wrapper.html"
  if [ -f "$WRAPPER" ]; then
    # Backup original vnc.html once and replace with wrapper
    if [ -f "$NOVNC_DIR/vnc.html" ] && [ ! -f "$NOVNC_DIR/vnc.orig.html" ]; then
      echo "Backing up original noVNC vnc.html to vnc.orig.html and installing wrapper"
      cp "$NOVNC_DIR/vnc.html" "$NOVNC_DIR/vnc.orig.html" || true
      cp "$WRAPPER" "$NOVNC_DIR/vnc.html" || true
    fi
  fi
  echo "Waiting for VNC server on localhost:5900..."
  ATTEMPTS=0
  until ss -ltnp | grep -q ':5900' || [ $ATTEMPTS -ge 10 ]; do
    ATTEMPTS=$((ATTEMPTS+1))
    sleep 1
  done

  if ss -ltnp | grep -q ':5900'; then
    # If port 6080 is already bound, report the owner and skip starting a new proxy.
    if ss -ltnp | grep -q ':6080'; then
      echo "Port 6080 already in use. Current listener:"
      ss -ltnp | egrep ':6080' || true
      echo "Skipping starting another noVNC proxy to avoid address-in-use errors."
    else
      echo "Starting noVNC proxy on port 6080"
      # Prefer the bundled novnc_proxy script; pass explicit --web and bind address
      NOVNC_PROXY="$NOVNC_DIR/utils/novnc_proxy"
      if [ -x "$NOVNC_PROXY" ]; then
        nohup "$NOVNC_PROXY" --vnc localhost:5900 --listen 0.0.0.0:6080 --web "$NOVNC_DIR" >/tmp/novnc.log 2>&1 &
      else
        nohup python3 "$NOVNC_DIR/utils/novnc_proxy" --vnc localhost:5900 --listen 0.0.0.0:6080 --web "$NOVNC_DIR" >/tmp/novnc.log 2>&1 &
      fi
    fi
  else
    echo "VNC server not listening on :5900, skipping noVNC startup. See logs for details."
  fi
else
  if [ "${USE_EXISTING_DISPLAY:-}" = "true" ]; then
    echo "Using host X11 forwarding; skipping noVNC/websockify startup."
  fi
fi

echo "VNC service started. Connect to :5900 or open http://<host>:6080/vnc.html"