#!/bin/sh
# Serves Photon on the database in /data/current (Halkyon Train's ADR 0030, D50), once
# data.sh has brought one; and where data.sh has made a newer one (/data/next/ready),
# stops Photon, puts the new one in the old one's place and starts it again: a
# minute or two without search, once a month. Looked at every minute, which also
# starts a Photon that stopped (killed for memory) again. PHOTON_HEAP is Java's
# heap (6g).
set -eu

cd /data
heap=${PHOTON_HEAP:-6g}
pid=

start() {
  java "-Xmx$heap" -jar /app/photon.jar serve -data-dir /data/current \
    -listen-ip 0.0.0.0 -listen-port 2322 -max-results 20 &
  pid=$!
}

stop() {
  if [ -n "$pid" ]; then
    kill "$pid" 2>/dev/null || true
    wait "$pid" 2>/dev/null || true
    pid=
  fi
}
trap 'stop; exit 0' TERM INT

swap() {
  [ -e next/ready ] || return 1
  rm -f next/ready
  rm -rf old
  if [ -d current ]; then mv current old; fi
  mkdir current
  mv next/photon_data current/photon_data
  mv next/fetched fetched
  rm -rf old
}

while [ ! -d current/photon_data ] && ! swap; do
  echo "No database yet; data.sh brings one."
  sleep 600 &
  wait $! || true
done
start
while :; do
  sleep 60 &
  wait $! || true
  if [ -e next/ready ]; then
    stop
    swap
    start
    echo "Photon serves the new database."
  elif ! kill -0 "$pid" 2>/dev/null; then
    echo "Photon stopped; started again." >&2
    start
  fi
done