require "requirejs/error"
require "requirejs/rails/view_proxy"

module RequirejsHelper
  # EXPERIMENTAL: Additional priority settings appended to
  # any user-specified priority setting by requirejs_include_tag.
  # Used for JS test suite integration.
  mattr_accessor :_priority
  @@_priority = []

  def requirejs_include_tag(name = nil, &block)
    requirejs = Rails.application.config.requirejs

    if requirejs.loader == :almond
      name = requirejs.module_name_for(requirejs.build_config['modules'][0])
      return almond_include_tag(name, &block)
    end

    html = ""

    once_guard do
      rjs_attributes = {
          src: javascript_path("require")
      }

      rjs_attributes = rjs_attributes.merge(Hash[block.call(controller).map do |key, value|
        ["data-#{key}", value]
      end]) \
        if block

      html.concat(content_tag(:script, "", rjs_attributes))

      unless requirejs.run_config.empty?
        run_config = requirejs.run_config.dup

        unless _priority.empty?
          run_config = run_config.dup
          run_config[:priority] ||= []
          run_config[:priority].concat _priority
        end

        if Rails.application.config.assets.digest
          modules = requirejs.build_config['modules'].map { |m| requirejs.module_name_for m }

          # Generate digestified paths from the modules spec
          paths = {}
          modules.each { |m| paths[m] = javascript_path(m).sub /\.js$/, '' }

          if run_config.has_key? 'paths'
            # Add paths for assets specified by full URL (on a CDN)
            run_config['paths'].each do |k, v|
              paths[k] = v if v.is_a?(Array) || v =~ /^https?:/
            end
          end

          # Override user paths, whose mappings are only relevant in dev mode
          # and in the build_config.
          run_config['paths'] = paths
        end

        run_config['baseUrl'] = base_url(name)

        html.concat(content_tag(:script) do
          script = "require.config(#{run_config.to_json});"

          # Pass an array to `require`, since it's a top-level module about to be loaded asynchronously (see
          # `http://requirejs.org/docs/errors.html#notloaded`).
          script.concat(" require([#{name.dump}]);") \
            if name

          script.html_safe
        end)
      end

      html.html_safe
    end
  end

  def javascript_path(source, options = {})
    if defined?(super)
      super
    else
      view_proxy.javascript_path(source, options)
    end
  end

  def content_tag(name, content_or_options_with_block = nil, options = nil, escape = true, &block)
    if defined?(super) && respond_to?(:output_buffer) && respond_to?(:output_buffer=)
      super
    else
      view_proxy.content_tag(name, content_or_options_with_block, options, escape, &block)
    end
  end

  private

  def once_guard
    if defined?(controller) && controller.requirejs_included
      raise Requirejs::MultipleIncludeError, "Only one requirejs_include_tag allowed per page."
    end

    retval = yield

    controller.requirejs_included = true if defined?(controller)
    retval
  end

  def almond_include_tag(name, &block)
    content_tag(:script, "", src: javascript_path(name))
  end

  def base_url(js_asset)
    js_asset_path = javascript_path(js_asset)
    uri = URI.parse(js_asset_path)
    asset_host = uri.host && js_asset_path.sub(uri.request_uri, '')
    [asset_host, Rails.application.config.relative_url_root, Rails.application.config.assets.prefix].join
  end

  def view_proxy
    @view_proxy ||= Requirejs::Rails::ViewProxy.new
  end
end