middleman/middleman-core/lib/middleman-core/extensions/asset_host.rb

class Middleman::Extensions::AssetHost < ::Middleman::Extension
  option :host, nil, 'The asset host to use or a Proc to determine asset host', required: true
  option :exts, nil, 'List of extensions that get cache busters strings appended to them.'
  option :sources, %w(.css .htm .html .js .php .xhtml), 'List of extensions that are searched for bustable assets.'
  option :ignore, [], 'Regexes of filenames to skip adding query strings to'
  option :rewrite_ignore, [], 'Regexes of filenames to skip processing for host rewrites'

  Contract ResourceList => ResourceList
  def manipulate_resource_list(resources)
    resources.each do |r|
      next unless r.destination_path.end_with?('/', *options.sources)
      next if Array(options.rewrite_ignore || []).any? do |i|
        ::Middleman::Util.path_match(i, "/#{r.destination_path}")
      end

      r.filters << ::Middleman::InlineURLRewriter.new(:asset_host,
                                                      app,
                                                      r,
                                                      after_filter: :asset_hash,
                                                      url_extensions: options.exts || app.config[:asset_extensions],
                                                      ignore: options.ignore,
                                                      proc: method(:rewrite_url))
    end
  end

  Contract String, Or[String, Pathname], Any => String
  def rewrite_url(asset_path, dirpath, _request_path)
    uri = ::Middleman::Util.parse_uri(asset_path)
    relative_path = uri.path[0..0] != '/'

    full_asset_path = if relative_path
      dirpath.join(asset_path).to_s
    else
      asset_path
    end

    asset_prefix = if options[:host].is_a?(Proc)
      options[:host].call(full_asset_path)
    elsif options[:host].is_a?(String)
      options[:host]
    end

    File.join(asset_prefix, full_asset_path)
  end
  memoize :rewrite_url
end