1 files changed, 85 insertions, 0 deletions
diff --git a/lib/banzai/object_renderer.rb b/lib/banzai/object_renderer.rb
new file mode 100644
index 00000000000..f0e4f28bf12
--- /dev/null
+++ b/lib/banzai/object_renderer.rb
@@ -0,0 +1,85 @@
+module Banzai
+  # Class for rendering multiple objects (e.g. Note instances) in a single pass.
+  #
+  # Rendered Markdown is stored in an attribute in every object based on the
+  # name of the attribute containing the Markdown. For example, when the
+  # attribute `note` is rendered the HTML is stored in `note_html`.
+  class ObjectRenderer
+    attr_reader :project, :user
+
+    # Make sure to set the appropriate pipeline in the `raw_context` attribute
+    # (e.g. `:note` for Note instances).
+    #
+    # project - A Project to use for rendering and redacting Markdown.
+    # user - The user viewing the Markdown/HTML documents, if any.
+    # context - A Hash containing extra attributes to use in the rendering
+    #           pipeline.
+    def initialize(project, user = nil, raw_context = {})
+      @project = project
+      @user = user
+      @raw_context = raw_context
+    end
+
+    # Renders and redacts an Array of objects.
+    #
+    # objects - The objects to render
+    # attribute - The attribute containing the raw Markdown to render.
+    #
+    # Returns the same input objects.
+    def render(objects, attribute)
+      documents = render_objects(objects, attribute)
+      redacted = redact_documents(documents)
+
+      objects.each_with_index do |object, index|
+        object.__send__("#{attribute}_html=", redacted.fetch(index))
+      end
+
+      objects
+    end
+
+    # Renders the attribute of every given object.
+    def render_objects(objects, attribute)
+      objects.map do |object|
+        render_attribute(object, attribute)
+      end
+    end
+
+    # Redacts the list of documents.
+    #
+    # Returns an Array containing the redacted documents.
+    def redact_documents(documents)
+      redactor = Redactor.new(project, user)
+
+      redactor.redact(documents).map do |document|
+        document.to_html.html_safe
+      end
+    end
+
+    # Returns a Banzai context for the given object and attribute.
+    def context_for(object, attribute)
+      context = base_context.merge(cache_key: [object, attribute])
+
+      if object.respond_to?(:author)
+        context[:author] = object.author
+      end
+
+      context
+    end
+
+    # Renders the attribute of an object.
+    #
+    # Returns a `Nokogiri::HTML::Document`.
+    def render_attribute(object, attribute)
+      context = context_for(object, attribute)
+
+      string = object.__send__(attribute)
+      html = Banzai.render(string, context)
+
+      Banzai::Pipeline[:relative_link].to_document(html, context)
+    end
+
+    def base_context
+      @base_context ||= @raw_context.merge(current_user: user, project: project)
+    end
+  end
+end