index.html.erb

t_for :webpage_title do -%>
	<%= @webpage.title if @webpage %>
<%- end -%>

<%= display_html_content(@contents) unless @contents.nil? %>

migrations

class CreateContents < ActiveRecord::Migration
  def self.up
    create_table :contents do |t|
      t.text :data
      t.integer :layout_order
      t.integer :element_id
      t.integer :webpage_id 
      t.integer :parent_id
     
      t.timestamps
    end
  end

  def self.down
    drop_table :contents
  end
end

class CreateElements < ActiveRecord::Migration
  def self.up
    create_table :elements do |t|
      t.string :markup
      t.text :style
      
      t.timestamps
    end
  end

  def self.down
    drop_table :elements
  end
end

Models

class Webpage < ActiveRecord::Base
  belongs_to :dropdown
  has_many :contents, :order => "parent_id, layout_order"
end

class Content < ActiveRecord::Base
  belongs_to :element
  belongs_to :webpage
end

class Element < ActiveRecord::Base
  has_many :contents
end

rake task to build example data

task :db_initialize => :environment do
  
# ------------------- 

# 1
  e = Element.new
  e.markup = "p"
  e.style = "color: red;"
  e.save!

# 2  
  e = Element.new
  e.markup = "h2"
  e.style = "text-align: center;"
  e.save!
  
# 3
  e = Element.new
  e.markup = "li"
  e.style = "text-align: right; list-style-type: disc;"
  e.save!
  
# 4
  e = Element.new  
  e.markup = "div"
  e.style = "float: left; border: 1px solid red; width: 48%;"
  e.save!
  
# 5  
  e = Element.new  
  e.markup = "div"
  e.style = "float: right; border: 1px solid blue;"
  e.save!
  
# 6
  e = Element.new  
  e.markup = "div"
  e.style = "width: 50%; text-align: center; border: 1px solid teal;"
  e.save!

# 7
  e = Element.new
  e.markup = "ul"
  e.style = "border: 1px solid green;"
  e.save!

#8
  e = Element.new
  e.markup = "div"
  e.style = "background: #9d10ff; margin: 5px; padding: 15%; float: left; border: 1px solid #333;"
  e.save!
  
#  ------------------- 

  
  #red div
  c = Content.new
  c.element_id = 4
  c.webpage_id = 1
  c.layout_order = 1
  c.parent_id = nil
  c.data = nil
  c.save!

  left_div = c.id
  
  #red div
  c = Content.new
  c.element_id = 4
  c.webpage_id = 1
  c.layout_order = 2
  c.parent_id = nil
  c.data = nil
  c.save!

  left2_div = c.id

  #p
  c = Content.new
  c.element_id = 1
  c.webpage_id = 1
  c.layout_order = 2
  c.parent_id = left_div
  c.data = "I should be a 2nd paragraph in the left div"
  c.save

  #p
  c = Content.new
  c.element_id = 1
  c.webpage_id = 1
  c.layout_order = 1
  c.parent_id = left_div
  c.data = "I am a paragraph, meant to be in the left div"
  c.save


  #purple box
  c = Content.new
  c.element_id = 8
  c.webpage_id = 1
  c.layout_order = 3
  c.parent_id = left2_div
  c.save!

  purple = c.id

  #ul
  c = Content.new
  c.element_id = 7
  c.webpage_id = 1
  c.layout_order = 1
  c.parent_id = purple
  c.save!

  ul_id = c.id

  num = 0
  5.times do
    num += 1
    c = Content.new
    c.element_id = 3
    c.webpage_id = 1
    c.layout_order = num
    c.parent_id = ul_id
    c.data = "inside purple item number#{num}"
    c.save!
  end
  
end

end

webpages_controller

class WebpagesController < ApplicationController
  # GET /webpages
  # GET /webpages.xml
  def index
    @webpage = Webpage.find_by_id(params[:page])
    @contents = @webpage.contents unless @webpage.nil?
    
    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @webpages }
    end
  end
end

webpages_helper

module WebpagesHelper
  def display_html_content(contents)
 
  $completed_elements = []
 
    contents.map do |c|

      unless $completed_elements.include?(c.id)
        get_nested_elements(c, contents) 
      end

    end
    
  end
  
  def get_nested_elements(c, contents)
   
    nested_items = contents.find_all_by_parent_id(c.id)

    content_tag c.element.markup, :style => c.element.style do

      nested = c.data.nil? ? "" : c.data
      
      unless nested_items.blank?
        nested_items.map do |n|
          nested += get_nested_elements(n, contents)
        end
      end
      
      $completed_elements << c.id
      
      nested

    end
    
  end
end