Implement simplified commercials workflow

It's now possible to simply enter the url of the third party provider to enter a commercial.

app/models/commercial.rb

@@ -1,8 +1,44 @@
 class Commercial < ActiveRecord::Base
+  require 'oembed'
+
   belongs_to :commercialable, polymorphic: true
 
-  validates :commercial_id, presence: true
-  validates :commercial_type, presence: true
+  validates :url, presence: true
+  validates :url, format: URI::regexp(%w(http https))
 
-  validates :commercial_type, inclusion: { in: CONFIG['commercial_types'].values }
+  validate :valid_url
+
+  def self.render_from_url(url)
+    register_provider
+    begin
+      resource = OEmbed::Providers.get(url, maxwidth: 560, maxheight: 315)
+      { html: resource.html.html_safe }
+    rescue StandardError => exception
+      { error: exception.message }
+    end
+  end
+
+  private
+
+  def valid_url
+    result = Commercial.render_from_url(url)
+    if result[:error]
+      errors.add(:base, result[:error])
+    end
+  end
+
+  def self.register_provider
+    speakerdeck = OEmbed::Provider.new('http://speakerdeck.com/oembed.json')
+    speakerdeck << 'https://speakerdeck.com/*'
+    speakerdeck << 'http://speakerdeck.com/*'
+
+    OEmbed::Providers.register(
+        OEmbed::Providers::Youtube,
+        OEmbed::Providers::Vimeo,
+        OEmbed::Providers::Slideshare,
+        OEmbed::Providers::Flickr,
+        OEmbed::Providers::Instagram,
+        speakerdeck
+    )
+  end
 end