Extract callbacks and validations for Post

Move Post create callbacks to PostCreate
Extract Post validations
Move stripped_length_validator to lib/validators

lib/validators/post_validator.rb

@@ -0,0 +1,56 @@
+class PostValidator < ActiveModel::Validator
+  def validate(record)
+    raw_quality(record)
+    max_mention_validator(record)
+    max_images_validator(record)
+    max_links_validator(record)
+    unique_post_validator(record)
+  end
+
+  def raw_quality(post)
+    sentinel = TextSentinel.body_sentinel(post.raw)
+    post.errors.add(:raw, I18n.t(:is_invalid)) unless sentinel.valid?
+  end
+
+  # Ensure maximum amount of mentions in a post
+  def max_mention_validator(post)
+    if acting_user_is_trusted?(post)
+      add_error_if_count_exceeded(post, :too_many_mentions, post.raw_mentions.size, SiteSetting.max_mentions_per_post)
+    else
+      add_error_if_count_exceeded(post, :too_many_mentions_newuser, post.raw_mentions.size, SiteSetting.newuser_max_mentions_per_post)
+    end
+  end
+
+  # Ensure new users can not put too many images in a post
+  def max_images_validator(post)
+    add_error_if_count_exceeded(post, :too_many_images, post.image_count, SiteSetting.newuser_max_images) unless acting_user_is_trusted?(post)
+  end
+
+  # Ensure new users can not put too many links in a post
+  def max_links_validator(post)
+    add_error_if_count_exceeded(post, :too_many_links, post.link_count, SiteSetting.newuser_max_links) unless acting_user_is_trusted?(post)
+  end
+
+  # Stop us from posting the same thing too quickly
+  def unique_post_validator(post)
+    return if SiteSetting.unique_posts_mins == 0
+    return if post.acting_user.admin? || post.acting_user.moderator?
+
+    # If the post is empty, default to the validates_presence_of
+    return if post.raw.blank?
+
+    if $redis.exists(post.unique_post_key)
+      post.errors.add(:raw, I18n.t(:just_posted_that))
+    end
+  end
+
+  private
+
+  def acting_user_is_trusted?(post)
+    post.acting_user.present? && post.acting_user.has_trust_level?(:basic)
+  end
+
+  def add_error_if_count_exceeded(post, key_for_translation, current_count, max_count)
+    post.errors.add(:base, I18n.t(key_for_translation, count: max_count)) if current_count > max_count
+  end
+end