#!/bin/sh
# Keeps the instance's own map tiles current (Halkyon Train's ADR 0030, D50): the
# newest of Protomaps' daily builds of the planet, cut to MAP_REGION (`west,south,
# east,north` in degrees; by default Europe's, the box BRouter's segments cover) at
# zooms 0 to 15, into /tiles/europe.pmtiles; again every MAP_REFRESH_DAYS days (30)
# where a newer build has come. The cut is written into /tiles/next/ and moved over
# the old one, so the server never reads half a file; until it is done, the old one
# serves. Both at once take twice a cut's room.
set -eu

builds=https://build-metadata.protomaps.dev/builds.json
region=${MAP_REGION:--25,35,45,75}
days=${MAP_REFRESH_DAYS:-30}
cd /tiles
mkdir -p next

refresh() {
  build=$(curl -fsS "$builds" | grep -o '"key": *"[0-9]\{8\}\.pmtiles"' |
    grep -o '[0-9]\{8\}\.pmtiles' | sort | tail -n 1) || build=
  if [ -z "$build" ]; then
    echo "Protomaps' builds didn't come; the tiles stay as they are." >&2
    return 0
  fi
  if [ -e europe.build ] && [ "$(cat europe.build)" = "$build" ]; then
    echo "The tiles are $build's, the newest."
    return 0
  fi
  rm -f next/europe.pmtiles
  if pmtiles extract "https://build.protomaps.com/$build" next/europe.pmtiles \
    --bbox="$region" --maxzoom=15 --download-threads=4; then
    mv next/europe.pmtiles europe.pmtiles
    echo "$build" >europe.build
    echo "The tiles are $build's now, $(du -h europe.pmtiles | cut -f1)."
  else
    rm -f next/europe.pmtiles
    echo "The cut of $build failed; the tiles stay as they are." >&2
  fi
}

while :; do
  refresh
  sleep $((days * 86400))
done