Wiring up a backend that exposes actual content in the frontend.

Content can be fetched for a field and a completely random piece will be returned.  The `render_details` method on the Content model can pass additional information to the frontend rendering code specific to the content type being rendered.

app/controllers/frontend/contents_controller.rb

@@ -0,0 +1,35 @@
+class Frontend::ContentsController < ApplicationController
+  layout false
+
+  before_filter :scope_setup
+
+  def scope_setup
+    @screen = Screen.find(params[:screen_id])
+    @field = Field.find(params[:field_id])
+  end
+
+  def index
+    @content = [Content.first(:offset => rand(Content.count))]
+    @content.each do |c|
+      c.pre_render(@screen, @field)
+    end
+    respond_to do |format|
+      format.json {
+        render :json => @content.to_json(
+          :only => [:name, :id, :duration, :type],
+          :methods => [:render_details]
+        )
+      }
+    end
+  end
+
+  # GET /frontend/1/fields/1/contents/1
+  # Trigger the render function a piece of content and passes all the params
+  # along for processing.  Should send an inline result of the processing.
+  def show
+    @content = Content.find(params[:id])
+    @file = @content.render(params)
+    send_data @file.file_contents, :filename => @file.file_name, :type => @file.file_type, :disposition => 'inline'
+  end
+
+end

app/controllers/frontend/fields_controller.rb

@@ -1,9 +1,3 @@
 class Frontend::FieldsController < ApplicationController
   layout false
-
-  def contents
-    respond_to do |format|
-      format.json { render :json => [] }
-    end
-  end
 end

app/controllers/frontend/screens_controller.rb

@@ -18,6 +18,9 @@ def setup
     else
       # Inject the path into an fake attribute so it gets sent with the setup info.
       @screen.template.path = frontend_screen_template_path(@screen, @screen.template)
+      @screen.template.positions.each do |p|
+        p.field_contents_path = frontend_screen_field_contents_path(@screen, p.field, :format => :json)
+      end
       respond_to do |format|
         format.json {
           render :json => @screen.to_json(
@@ -27,6 +30,7 @@ def setup
                 :include => {
                   :positions => {
                     :except => [:created_at, :updated_at, :template_id],
+                    :methods => [:field_contents_path]
                   },
                 },
                 :only => [:id],

app/helpers/frontend/contents_helper.rb

@@ -0,0 +1,2 @@
+module Frontend::ContentsHelper
+end

app/models/content.rb

@@ -3,7 +3,7 @@ class Content < ActiveRecord::Base
   belongs_to :kind
   has_many :submissions, :dependent => :destroy
   has_many :feeds, :through => :submissions
-  has_many :media, :as => :attachable
+  has_many :media, :as => :attachable, :dependent => :destroy
 
   accepts_nested_attributes_for :media
   accepts_nested_attributes_for :submissions
@@ -23,6 +23,9 @@ class Content < ActiveRecord::Base
   has_many :pending_feeds, :through => :submissions, :source => :feed, :conditions => "submissions.moderation_flag IS NULL"
   has_many :denied_feeds, :through => :submissions, :source => :feed, :conditions => {"submissions.moderation_flag" => false}
 
+  #Magic to let us generate routes
+  delegate :url_helpers, :to => 'Rails.application.routes'
+
   # Determine if content is active based on its start and end times.
   # Content is active if two conditions are met:
   # 1. Start date is before now, or nil.
@@ -52,4 +55,15 @@ def end_time=(_end_time)
     end
   end
 
+
+  # A placeholder for a pre-rendering processing trigger.
+  def pre_render(*arg)
+    true
+  end
+
+  # The additional data required when rendering this content.
+  def render_details
+    {:data => self.data}
+  end
+
 end

app/models/graphic.rb

@@ -38,4 +38,18 @@ def render(options={})
     end
   end
 
+  # Placeholder attributes for rendering.
+  attr_accessor :screen, :field
+
+  # Store the information needed when generating the path to the image.
+  def pre_render(screen, field)
+    self.screen = screen
+    self.field = field
+  end
+
+  # Generate the path to the iamge to be displayed.
+  def render_details
+    {:path => url_helpers.frontend_screen_field_content_path(self.screen, self.field, self)}
+  end
+
 end

app/models/position.rb

@@ -9,6 +9,8 @@ class Position < ActiveRecord::Base
   validates :top, :numericality => {:greater_than_or_equal_to => -1, :less_than_or_equal_to => 1}
   validates :bottom, :numericality => {:greater_than_or_equal_to => -1, :less_than_or_equal_to => 1}
 
+  attr_accessor :field_contents_path
+
   # Compute the width of the position block.
   # A Concerto-1 style attribute, figuring out
   # the total width of the element.

config/routes.rb

@@ -13,9 +13,7 @@
         get :setup
       end
       resources :fields, :only => [] do
-        member do
-          get :contents, :path => 'content'
-        end
+        resources :contents, :only => [:index, :show]
       end
       resources :templates, :only => [:show]
     end

test/functional/frontend/contents_controller_test.rb

@@ -0,0 +1,18 @@
+require 'test_helper'
+
+class Frontend::ContentsControllerTest < ActionController::TestCase
+  include Devise::TestHelpers
+  fixtures :screens
+  fixtures :fields
+  fixtures :contents
+
+  test "should get content for field" do
+    get(:index, {:screen_id => screens(:one).id, :field_id => fields(:one).id, :format => :json})
+    assert_response :success
+    assert_template false
+
+    data = ActiveSupport::JSON.decode(@response.body)
+    assert data.length > 0
+  end
+
+end

test/functional/frontend/fields_controller_test.rb

@@ -3,9 +3,4 @@
 class Frontend::FieldsControllerTest < ActionController::TestCase
   include Devise::TestHelpers
   fixtures :screens, :fields
-
-  test "should get content" do
-    get(:contents, {:screen_id => screens(:one).id, :id => fields(:one).id, :format => :json})
-    assert_response :success
-  end
 end

test/functional/frontend/screens_controller_test.rb

@@ -23,6 +23,9 @@ class Frontend::ScreensControllerTest < ActionController::TestCase
     assert_equal data['template']['positions'].length,
                  screens(:one).template.positions.length
     assert data['template']['path'].length > 0
+    data['template']['positions'].each do |p|
+      assert p['field_contents_path'].length > 0
+    end
   end
 
   test "cannot setup missing screen" do

test/unit/helpers/frontend/contents_helper_test.rb

@@ -0,0 +1,4 @@
+require 'test_helper'
+
+class Frontend::ContentsHelperTest < ActionView::TestCase
+end