#!/bin/sh
# The container's entrypoint: runs netwatch-server and nginx side by
# side. TERM or INT stops both, and the container exits 0 if both exit
# cleanly. If either exits on its own, the other is stopped too and the
# container exits non-zero, so the platform restarts it instead of
# leaving it half up.
#
# No set -e: kill and wait return non-zero here in normal operation.
set -u

# PORT is the public port nginx listens on, 8080 when unset or empty.
# nginx would take a value such as localhost or unix:/tmp/x.sock as an
# address and start anyway, so anything but digits stops the container
# here, before either process starts.
export PORT="${PORT:-8080}"
case "$PORT" in
    *[!0-9]*)
        echo "entrypoint: PORT must be a port number, not '$PORT'" >&2
        exit 1
        ;;
esac

# A stop signal is only noted here; the loop below acts on it.
stop_requested=""
trap 'stop_requested=yes' TERM INT

# netwatch-server runs as the netwatch user and listens on loopback
# only, on a port other than the public one; nginx.conf proxies to this
# address. The netwatch user has no login shell, hence -s /bin/sh.
# busybox su replaces itself with the command instead of staying on as
# its parent, so $! is the server's own PID.
BIND_ADDRESS=127.0.0.1 PORT=8081 \
    su -s /bin/sh netwatch -c 'exec netwatch-server' &
backend=$!

# nginx starts through the nginx image's own entrypoint, which applies
# the image's start-up configuration and then replaces itself with
# nginx. Part of that start-up configuration renders nginx.conf into
# conf.d with nginx listening on PORT. NGINX_ENVSUBST_FILTER limits
# that rendering to PORT: a variable nginx itself uses, such as $uri,
# would otherwise be replaced by an environment variable of the same
# name.
NGINX_ENVSUBST_FILTER='^PORT$' \
    /docker-entrypoint.sh nginx -g 'daemon off;' &
nginx=$!

running() {
    kill -0 "$1" 2>/dev/null
}

# POSIX sh cannot wait for whichever of two children exits first, so
# look once a second. The shell collects a child that has exited while
# it runs sleep, and running() is false for that child from then on.
while [ -z "$stop_requested" ] && running "$backend" && running "$nginx"; do
    sleep 1
done

# Stop both, then wait until neither is left.
kill -TERM "$backend" "$nginx" 2>/dev/null
while running "$backend" || running "$nginx"; do
    sleep 1
done

wait "$backend"
backend_status=$?
wait "$nginx"
nginx_status=$?
echo "entrypoint: netwatch-server exited $backend_status," \
    "nginx exited $nginx_status"

# Success is a requested stop that both processes exited cleanly from.
if [ -n "$stop_requested" ] && [ "$backend_status" -eq 0 ] &&
    [ "$nginx_status" -eq 0 ]; then
    exit 0
fi
exit 1