module NSWTopo::ArcGISRaster

def get_raster(temp_dir)
  raise "no resolution specified for #{@name}" unless Numeric === @mm_per_px
  txt_path = temp_dir / "mosaic.txt"
  vrt_path = temp_dir / "mosaic.vrt"
  service = ArcGIS::Service.new @url
  local_bbox = @map.cutline.bbox
  target_bbox = local_bbox.reproject_to service.projection
  target_resolution = @mm_per_px * Math::sqrt(target_bbox.first.area / local_bbox.first.area)
  raise "not a tiled map or image server: #{@url}" unless tile_info = service["tileInfo"]
  lods = tile_info["lods"]
  origin = tile_info["origin"].values_at "x", "y"
  tile_sizes = tile_info.values_at "cols", "rows"
  lods.sort_by! do |lod|
    -lod["resolution"]
  end
  lod = lods.find do |lod|
    lod["resolution"] < target_resolution
  end || lods.last
  tile_level, tile_resolution = lod.values_at "level", "resolution"
  target_bbox.bounds.zip(origin, tile_sizes).map do |(min, max), origin, tile_size|
    [(min - origin) / tile_resolution / tile_size, (max - origin) / tile_resolution / tile_size]
  end.map do |min, max|
    (min.floor..max.ceil).each_cons(2).to_a
  end.inject(&:product).inject(GeoJSON::Collection.new(projection: service.projection)) do |tiles, (cols, rows)|
    [cols, rows].zip(tile_sizes).map do |indices, tile_size|
      indices.map { |index| index * tile_size * tile_resolution }
    end.transpose.map do |corner|
      corner.zip(origin).map(&:sum)
    end.transpose.then do |bounds|
      ring = bounds.inject(&:product).values_at(0,2,3,1,0)
      ullr = bounds.inject(&:product).values_at(1,2).flatten
      row, col = rows[1].abs, cols[0]
      tiles.add_polygon [ring], ullr: ullr, row: row, col: col
    end
  end.clip(target_bbox.first).then do |tiles|
    tiles.map.with_index do |feature, index|
      row, col, ullr = feature.values_at("row", "col", "ullr")
      rel_path = "tile/#{tile_level}/#{row}/#{col}"
      jpg_path = temp_dir / "#{row}.#{col}" # could be png
      tif_path = temp_dir / "#{row}.#{col}.tif"
      gdal_args = ["-a_srs", service.projection, "-a_ullr", *ullr, "-of", "GTiff", jpg_path, tif_path]
      log_update "%s: retrieving tile %i of %i" % [@name, index + 1, tiles.length]
      service.get(rel_path, blankTile: true) do |response|
        jpg_path.binwrite response.body
      end
      OS.gdal_translate *gdal_args
      tif_path
    end
  end.tap do |tif_paths|
    log_update "%s: mosaicing %s tiles" % [@name, tif_paths.length] if tif_paths.length > 1
    txt_path.write tif_paths.join(?\n)
  end
  OS.gdalbuildvrt "-input_file_list", txt_path, vrt_path
  return vrt_path
end