Remove duplication in code to validate video URL

We were using the same code, and the same regular expressions, in two
places. To do so, we were including a helper inside a model, which is
something we don't usually do.

app/helpers/embed_videos_helper.rb

@@ -1,7 +1,4 @@
 module EmbedVideosHelper
-  VIMEO_REGEX = /vimeo.*(staffpicks\/|channels\/|videos\/|video\/|\/)([^#\&\?]*).*/
-  YOUTUBE_REGEX = /youtu.*(be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/
-
   def embedded_video_code(resource)
     link = resource.video_url
     title = t("proposals.show.embed_video_title", proposal: resource.title)
@@ -12,10 +9,10 @@ module EmbedVideosHelper
     end
 
     if server == "Vimeo"
-      reg_exp = VIMEO_REGEX
+      reg_exp = resource.class::VIMEO_REGEX
       src = "https://player.vimeo.com/video/"
     elsif server == "YouTube"
-      reg_exp = YOUTUBE_REGEX
+      reg_exp = resource.class::YOUTUBE_REGEX
       src = "https://www.youtube.com/embed/"
     end
 
@@ -29,12 +26,4 @@ module EmbedVideosHelper
       ""
     end
   end
-
-  def valid_video_url?
-    return if video_url.blank?
-    return if video_url.match(VIMEO_REGEX)
-    return if video_url.match(YOUTUBE_REGEX)
-
-    errors.add(:video_url, :invalid)
-  end
 end

app/models/concerns/videoable.rb

@@ -0,0 +1,28 @@
+module Videoable
+  extend ActiveSupport::Concern
+
+  included do
+    validate :valid_video_url?
+  end
+
+  VIMEO_REGEX = /vimeo.*(staffpicks\/|channels\/|videos\/|video\/|\/)([^#\&\?]*).*/
+  YOUTUBE_REGEX = /youtu.*(be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/
+
+  def valid_video_url?
+    url = send(video_url_field)
+
+    return if url.blank?
+    return if url.match(VIMEO_REGEX)
+    return if url.match(YOUTUBE_REGEX)
+
+    errors.add(video_url_field, :invalid)
+  end
+
+  def video_url_field
+    if has_attribute?(:video_url)
+      :video_url
+    else
+      :url
+    end
+  end
+end

app/models/poll/question/answer/video.rb

@@ -1,17 +1,6 @@
 class Poll::Question::Answer::Video < ApplicationRecord
   belongs_to :answer, class_name: "Poll::Question::Answer"
-
-  VIMEO_REGEX = /vimeo.*(staffpicks\/|channels\/|videos\/|video\/|\/)([^#\&\?]*).*/
-  YOUTUBE_REGEX = /youtu.*(be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/
+  include Videoable
 
   validates :title, presence: true
-  validate :valid_url?
-
-  def valid_url?
-    return if url.blank?
-    return if url.match(VIMEO_REGEX)
-    return if url.match(YOUTUBE_REGEX)
-
-    errors.add(:url, :invalid)
-  end
 end

app/models/proposal.rb

@@ -14,7 +14,7 @@ class Proposal < ApplicationRecord
   include Mappable
   include Notifiable
   include Documentable
-  include EmbedVideosHelper
+  include Videoable
   include Relationable
   include Milestoneable
   include Randomizable
@@ -59,8 +59,6 @@ class Proposal < ApplicationRecord
 
   validates :terms_of_service, acceptance: { allow_nil: false }, on: :create
 
-  validate :valid_video_url?
-
   before_validation :set_responsible_name
 
   before_save :calculate_hot_score, :calculate_confidence_score