Gemfile

source 'http://rubygems.org'

gem 'rails', '~> 4.1.1'
gem 'microformats2'

schema.rb

ActiveRecord::Schema.define(version: 20160614073723) do
  create_table "comments", force: true do |t|
    t.string   "title",                limit: 50, default: ""
    t.text     "comment"
    t.integer  "commentable_id"
    t.string   "commentable_type"
    t.integer  "user_id"
    t.datetime "created_at",                                        null: false
    t.datetime "updated_at",                                        null: false
    t.string   "comment_author"
    t.string   "comment_author_email"
    t.string   "comment_author_url"
    t.string   "user_agent"
    t.string   "ip_address"
    t.string   "status"
    t.integer  "site_id"
    t.string   "canonical"
    t.string   "comment_type",                    default: "reply"
    t.string   "source"
    t.string   "commenter_avatar_url"
  end

  add_index "comments", ["commentable_id"], name: "index_comments_on_commentable_id", using: :btree
  add_index "comments", ["commentable_type"], name: "index_comments_on_commentable_type", using: :btree
  add_index "comments", ["site_id"], name: "index_comments_on_site_id", using: :btree
  add_index "comments", ["user_id"], name: "index_comments_on_user_id", using: :btree
  
    create_table "sites", force: true do |t|
    t.string "domain",              null: false
    t.string "title",               null: false
  end

  add_index "sites", ["domain"], name: "index_sites_on_domain", using: :btree
  
end

web_mentions_controller.rb

class WebmentionsController < HostedController
  def create
    source_uri = params.require(:source)
    target_uri = params.require(:target)

    if !URI(target_uri).host.match(current_site.subdomain)
      render text: "'target' is not on this site", status: 400
    end

    if source_uri == target_uri
      render text: "'source' and 'target' should not be the same", status: 400
      return
    end

    if source = ensure_source_has_target(source_uri,target_uri)

      site = site_from_uri(target_uri)
      mentioned_model = model_from_uri(site,target_uri)

      if mentioned_model.nil?
        render text: "'target' is not on this site", status: 400
        return
      end

      items = mf2_parse(source,mentioned_model)
      if items.empty?
        render text: "No mf2 h-entry on the source page", status: 400
        return
      end

      if comment = create_mention(source_uri,mentioned_model)
        items.each do |item|
          parse_reply_to(item,comment)
        end
        url = url_for([:hosted, mentioned_model])
        render text: url+"#comment-#{comment.id}", status: 200
        return
      else
        render text: "Error creating mention for #{target_uri}", status: 500
        return
      end
    else
      render text: "'source' does not contain 'target' in it's content", status: 400
      return
    end
  end


  private

  def site_from_uri(uri)
    uri = URI.parse(uri)
    subdomain = uri.host.split(".")[0]
    Site.find_by_domain( "#{subdomain}.subdomain")
  end

  def model_from_uri(site,uri)
    uri = URI.parse(uri)
    path = uri.path

    model, slug = path.split("/")[1..-1]
    site.send(model.pluralize).find(slug)
  end

  def ensure_source_has_target(source_uri,target_uri)
    source = Net::HTTP.get(URI(source_uri))
    replacements = ['http://www.', 'http://', 'https://www.', 'https://']
    replacements.each do |replacement|
      target_uri = target_uri.gsub(replacement,'')
    end

    if !source.downcase.include?(target_uri)
      return false
    else
      return source
    end
  end

  def create_mention(source_uri,mentioned_model)
    mentioned_model.comments.create(
      source: source_uri,
      comment_type: "mention",
      commenter_avatar_url: '',
      comment_author: source_uri,
      comment_author_url: source_uri,
      ip_address: request.env['HTTP_X_FORWARDED_FOR'],
      user_agent: request.env['HTTP_USER_AGENT'],
      status: "pending",
      site: mentioned_model.site,
      comment: "This was mentioned on <a rel=\"nofollow\" href=\"#{source_uri}\">#{source_uri}</a>"
    )
  end

  def parse_like(item,comment)
  end

  def parse_repost(item,comment)
  end

  def parse_favorite(item,comment)

  end

  def parse_bookmark(item,comment)

  end

  def parse_reply_to(item,comment)
    reply_to = item["properties"]["in_reply_to"]
    unless reply_to.nil?
      reply_to.each do |reply|
        if reply["properties"]["url"].present? && reply["properties"]["url"][0] == target_uri
          author = reply["properties"]["author"] || item["properties"]["author"]

          comment = item["properties"]["content"]
          comment_author = author["properties"]["name"]
          comment_author_url = author["properties"]["url"]
          comment_avatar_url = author["properties"]["photo"] || nil

          comment.update_attributes({comment: comment, comment_author: comment_author, comment_author_url: comment_author_url, comment_avatar_url: comment_avatar_url})
        end
      end
    end
  end

  def mf2_parse(source,mentioned_model)
    source_mf2 = Microformats2.parse(source)
    source_mf2 = JSON.parse(source_mf2.to_json)

    source_mf2["items"].select { |a| a["type"][0] == "h-entry"}
  end
end