module Scrivito

  # @api public
  module CmsTagHelper
    VOID_TAGS = %w[area base br col command embed hr img input keygen
        link meta param source track wbr]

    # Returns an HTML block tag containing content from an Obj.
    # Add HTML attributes by passing an attributes hash to options.
    # The helper method is somewhat similar to (and internally uses) http://api.rubyonrails.org/classes/ActionView/Helpers/TagHelper.html#method-i-content_tag.
    #
    # This helper method also renders additional data attributes, which are needed for inplace editing.
    # These attributes are only rendered when appropriate, i.e. not for a regular visitor.
    #
    # @param tag_name [String, Symbol] Name of the html tag (e.g. +:h1+ or +:div+).
    # @param obj_or_widget [BasicObj, BasicWidget] A {BasicObj} or {BasicWidget} from which the +field_name+ is read.
    # @param field_name [String, Symbol] Which field of the Obj should be rendered.
    # @param options [Hash] Additional options, which are passed to +content_tag+. Use them to add HTML attributes to the tag.
    # @param block [Proc] Optional block to render inner HTML. If none given the value of attribute will be rendered instead.
    # @return [String] The rendered html tag
    #
    # @example Renders an <h2> tag containing the text of the +headline+ attribute of +@obj+ and assigns the tag a css class called +very_important+.
    #     <%= cms_tag :h2, @obj, :headline, class: "very_important" %>
    #
    # @example Renders an <h2> tag containing an escaped +headline+.
    #     <%= cms_tag :h2, @obj, :headline do %>
    #       <%= strip_tags @obj.headline %>
    #     <% end %>
    #
    # @api public
    def cms_tag(tag_name, obj_or_widget, field_name, options = {}, &block)
      cms_field_tag = CmsFieldTag.new(
        self, cms_editing_context, obj_or_widget, field_name.to_s
      )

      begin
        field_type = cms_field_tag.field_type
      rescue ScrivitoError => e
        return content_tag(tag_name, '', options)
      end

      options.merge!(cms_field_tag.options)

      if VOID_TAGS.include?(tag_name.to_s)
        tag(tag_name, options)
      else
        inner_html =
          if block_given? && field_type != 'widget'
            capture { yield }
          else
            to_render = cms_field_tag.default_content

            if field_type == 'widget'
              modifications = cms_field_tag.modification_info || []
              rendered_widgets = to_render.each_with_index.map do |widget, index|
                render_widget(widget, modifications[index])
              end

              safe_join(rendered_widgets)
            else
              display_value(to_render)
            end
          end

        content_tag(tag_name, inner_html, options)
      end
    end

    # This is a helper class for {Scrivito::CmsTagHelper#cms_tag_list}.
    # @api public
    class List

      attr_reader :output

      def initialize(template, child_obj, show_sortable_options, modification)
        @template = template
        @child_obj = child_obj
        @show_sortable_options = show_sortable_options
        @modification = modification
      end

      # @param tag_name [String, Symbol] Name of the html tag (e.g. +:div+ or +:span+).
      # @param options [Hash] Additional options, which are passed to +content_tag+. Use them to add HTML attributes to the tag.
      # @return [String] The rendered html tag
      #
      # @example Render a <div> tag containing the text "random content" and assigns the tag a css class called +very_important+.
      #   <%= list.tag :div, class: "very_important" do %>
      #     random content
      #   <% end %>
      # @api public
      def tag(tag_name, options = {}, &block)
        if @output.present?
          raise '"list.tag" can only be called once per iteration!'
        else
          if @show_sortable_options
            options = options.merge({
              'data-scrivito-private-obj-id' => @child_obj.id,
              'data-scrivito-private-obj-description-for-editor' => @child_obj.description_for_editor,
            })

            if @modification == Modification::NEW || @modification == Modification::DELETED
              options['data-scrivito-private-obj-modification'] = @modification
            end
          end

          @output = @template.content_tag(tag_name, options, &block) + "\n"

          nil
        end
      end

    end

    # @param tag_name [String, Symbol] Name of the html tag (e.g. +:h1+ or +:div+).
    # @param obj [BasicObj] A {BasicObj} from which method_name is read.
    # @param method_name [String, Symbol] Which method_name of the Obj should be rendered. Currently only +toclist+ is supported
    # @param options [Hash] Additional options, which are passed to +content_tag+. Use them to add HTML attributes to the tag.
    # @yieldparam [List] list An instance, where +tag+ should be called once.
    # @yieldparam [BasicObj] child Each child of +toclist+
    # @return [String] The rendered html tag
    #
    # @example
    #   <%= cms_tag_list :div, @obj, :toclist, class: "very_important" do |list, child| %>
    #     <%= list.tag :div, class: "also_important" do %>
    #       <%= link_to cms_path(child) do %>
    #         <%= cms_tag :span, child, :title %>
    #       <% end %>
    #     <% end %>
    #   <% end %>
    #
    #   # results for an obj with two children in
    #
    #   <div class="very_important">
    #     <div class="also_important"><a href="/child1"><span>Child 1</span></a></div>
    #     <div class="also_important"><a href="/child2"><span>Child 2</span></a></div>
    #   </div>
    # @api public
    def cms_tag_list(tag_name, obj, method_name, options = {})
      if method_name.to_s == 'toclist'
        items = obj.toclist
      else
        raise "#{method_name} is not (yet) supported. Currently only toclist is supported."
      end

      children_sortable = false

      if inplace_editing_allowed?
        options['data-scrivito-private-obj-description-for-editor'] = obj.description_for_editor
      end

      if obj.has_attribute?(:child_order)
        items = Obj.sort_by_list(items, obj.child_order)
        children_sortable = inplace_editing_allowed?

        if children_sortable
          options = options.merge({
            'data-scrivito-private-child-list-order-obj-id' => obj.id,
          })

          modification = cms_editing_context.comparison.modification_for_attribute(obj,
              :child_order)
          if modification == Modification::EDITED
            options['data-scrivito-private-child-list-modification'] = modification
          end
        end
      end

      inner_html = "\n".html_safe

      items.each do |item|
        item_modification = cms_editing_context.comparison.modification(item)
        list = List.new(self, item, children_sortable, item_modification)

        yield list, item

        inner_html << list.output
      end

      valid_page_classes = Obj.valid_page_classes_beneath(obj.path)

      if inplace_editing_allowed?
        options = options.merge({
          'data-scrivito-private-child-list-path' => obj.path,
          'data-scrivito-private-child-list-allowed-classes' => valid_page_classes.to_json,
        })
      end

      content_tag(tag_name, inner_html, options)
    end

    def render_widget(widget, container_modification = nil)
      options = {}

      if inplace_editing_allowed?
        options['data-scrivito-private-widget-id'] = widget.id
        options['data-scrivito-widget-obj-class'] = widget.obj_class_name

        if has_widget_details_view?(widget)
          options['data-scrivito-private-widget-has-details-view'] = true
        end

        comparison = cms_editing_context.comparison
        options['data-scrivito-private-widget-modification'] =
          if comparison.revision == widget.revision
            if container_modification
              unless widget.in_revision(Workspace.current.revision)
                Modification::DELETED
              end
            end
          else
            comparison.modification(widget)
          end

        options['data-scrivito-private-widget-container-modification'] =
          container_modification
      end

      content_tag(:div, options) do
        render(template: "#{widget.class.to_s.underscore}/show", locals: {widget: widget})
      end
    end

    def has_widget_details_view?(widget)
      details_template_path = "#{widget.obj_class_name.underscore}/details"
      lookup_context.find(details_template_path).present?
    rescue ActionView::MissingTemplate
      false
    end
  end

end