#!/bin/sh
# Docker entrypoint for PX4 SITL containers.
#
# On Docker Desktop (macOS/Windows), host.docker.internal resolves to the
# host machine. We detect this and configure MAVLink + DDS to send to the
# host IP instead of localhost (which stays inside the container VM).
#
# On Linux with --network host, host.docker.internal does not resolve and
# PX4 defaults work without modification.

set -e

# Detect install prefix (SIH uses /opt/px4, Gazebo uses /opt/px4-gazebo)
if [ -d /opt/px4-gazebo ]; then
    PX4_PREFIX=/opt/px4-gazebo
else
    PX4_PREFIX=/opt/px4
fi

# Resolve host.docker.internal to an IPv4 address. mavlink and uxrce_dds_client
# only parse IPv4, and on Docker Desktop for Windows the default `getent hosts`
# lookup can return an IPv6 ULA first, which both modules then reject.
DOCKER_HOST_IP=$(getent ahostsv4 host.docker.internal 2>/dev/null | awk '/STREAM/ {print $1; exit}')

if [ -n "$DOCKER_HOST_IP" ]; then
    # MAVLink: replace default target (127.0.0.1) with the Docker host IP
    sed -i "s/mavlink start -x -u/mavlink start -x -t $DOCKER_HOST_IP -u/g" \
        "$PX4_PREFIX/etc/init.d-posix/px4-rc.mavlink"

    # DDS: point uXRCE-DDS client at the host
    sed -i "s|uxrce_dds_client start -t udp|uxrce_dds_client start -t udp -h $DOCKER_HOST_IP|" \
        "$PX4_PREFIX/etc/init.d-posix/rcS"
fi

exec "$PX4_PREFIX/bin/px4" "$@"