module Opal::Sprockets::AssetsHelper
  # Bootstraps modules loaded by sprockets on `Opal.modules` marking any
  # non-Opal asset as already loaded.
  #
  # @example
  #
  #   Opal::Sprockets.load_asset('application')
  #
  # @example Will output the following JavaScript:
  #
  #   Opal.loaded("jquery.self", "yet_another_carousel.self");
  #   Opal.require("opal", "application");
  #
  # @param name [String] The logical name of the main asset to be loaded (without extension)
  #
  # @return [String] JavaScript code
  def load_asset(*names)
    if names.last.is_a?(::Sprockets::Environment)
      unless @load_asset_warning_displayed
        @load_asset_warning_displayed = true
        warn "Passing a sprockets environment to Opal::Sprockets.load_asset no more needed.\n  #{caller(1, 3).join("\n  ")}"
      end
      names.pop
    end

    names = names.map { |name| name.sub(/(\.(js|rb|opal))*\z/, '') }
    stubbed = ::Opal::Config.stubbed_files.to_a

    loaded = 'typeof(OpalLoaded) === "undefined" ? [] : OpalLoaded'
    loaded = "#{stubbed.to_json}.concat(#{loaded})" if stubbed.any?

    [
      "Opal.loaded(#{loaded});",
      *names.map { |name| "Opal.require(#{name.to_json});" }
    ].join("\n")
  end

  # Mark an asset as already loaded.
  # This is useful for requiring JavaScript files which are not managed by Opal's laoding system.
  #
  # @param [String] name The "logical name" of the asset
  # @return [String] JavaScript code
  def loaded_asset(name)
    %{if (typeof(OpalLoaded) === 'undefined') OpalLoaded = []; OpalLoaded.push(#{name.to_json});}
  end

  # Generate a `<script>` tag for Opal assets.
  #
  # @param [String] name     The logical name of the asset to be loaded (without extension)
  # @param [Hash]   options  The options about sprockets
  # @option options [Sprockets::Environment] :sprockets  The sprockets instance
  # @option options [String]                 :prefix     The prefix String at which is mounted Sprockets, e.g. '/assets'
  # @option options [Boolean]                :debug      Wether to enable debug mode along with sourcemaps support
  #
  # @return a string of HTML code containing `<script>` tags.
  def javascript_include_tag(name, options = {})
    sprockets = options.fetch(:sprockets)
    prefix    = options.fetch(:prefix)
    debug     = options.fetch(:debug)

    # Avoid double slashes
    prefix = prefix.chop if prefix.end_with? '/'

    asset = sprockets[name, accept: "application/javascript", pipeline: debug ? :debug : nil]
    raise "Cannot find asset: #{name}" if asset.nil?
    scripts = []

    if debug
      scripts << %{<script src="#{prefix}/#{asset.digest_path}"></script>}
    else
      scripts << %{<script src="#{prefix}/#{name}.js"></script>}
    end

    scripts << %{<script>#{load_asset('opal', name)}</script>}

    scripts.join "\n"
  end
end