discourse/app/models/topic_link.rb

require 'uri'
require_dependency 'slug'

class TopicLink < ActiveRecord::Base
  belongs_to :topic
  belongs_to :user
  belongs_to :post
  belongs_to :link_topic, class_name: 'Topic'
  belongs_to :link_post, class_name: 'Post'

  validates_presence_of :url

  validates_length_of :url, maximum: 500

  validates_uniqueness_of :url, scope: [:topic_id, :post_id]

  has_many :topic_link_clicks, dependent: :destroy

  validate :link_to_self

  after_commit :crawl_link_title

  # Make sure a topic can't link to itself
  def link_to_self
    errors.add(:base, "can't link to the same topic") if (topic_id == link_topic_id)
  end

  def self.topic_map(guardian, topic_id)

    # Sam: complicated reports are really hard in AR
    builder = SqlBuilder.new("SELECT ftl.url,
                     COALESCE(ft.title, ftl.title) AS title,
                     ftl.link_topic_id,
                     ftl.reflection,
                     ftl.internal,
                     ftl.domain,
                     MIN(ftl.user_id) AS user_id,
                     SUM(clicks) AS clicks
              FROM topic_links AS ftl
              LEFT JOIN topics AS ft ON ftl.link_topic_id = ft.id
              LEFT JOIN categories AS c ON c.id = ft.category_id
              /*where*/
              GROUP BY ftl.url, ft.title, ftl.title, ftl.link_topic_id, ftl.reflection, ftl.internal, ftl.domain
              ORDER BY clicks DESC")

    builder.where('ftl.topic_id = :topic_id', topic_id: topic_id)
    builder.where('ft.deleted_at IS NULL')

    builder.secure_category(guardian.secure_category_ids)

    builder.exec.to_a

  end

  def self.counts_for(guardian,topic, posts)
    return {} if posts.blank?

    # Sam: I don't know how to write this cleanly in AR,
    #   in particular the securing logic is tricky and would fallback to SQL anyway
    builder = SqlBuilder.new("SELECT
                      l.post_id,
                      l.url,
                      l.clicks,
                      COALESCE(t.title, l.title) AS title,
                      l.internal,
                      l.reflection,
                      l.domain
              FROM topic_links l
              LEFT JOIN topics t ON t.id = l.link_topic_id
              LEFT JOIN categories AS c ON c.id = t.category_id
              /*where*/
              ORDER BY reflection ASC, clicks DESC")

    builder.where('t.deleted_at IS NULL')

    # not certain if pluck is right, cause it may interfere with caching
    builder.where('l.post_id IN (:post_ids)', post_ids: posts.map(&:id))
    builder.secure_category(guardian.secure_category_ids)

    builder.map_exec(OpenStruct).each_with_object({}) do |l,result|
      result[l.post_id] ||= []
      result[l.post_id] << {url: l.url,
                            clicks: l.clicks,
                            title: l.title,
                            internal: l.internal,
                            reflection: l.reflection}
    end
  end

  # Extract any urls in body
  def self.extract_from(post)
    return unless post.present?

    added_urls = []
    TopicLink.transaction do

      added_urls = []
      reflected_urls = []

      PrettyText
        .extract_links(post.cooked)
        .map{|u| [u, URI.parse(u)] rescue nil}
        .reject{|u,p| p.nil?}
        .uniq{|u,p| u}
        .each do |url, parsed|
        begin

          internal = false
          topic_id = nil
          post_number = nil

          if Discourse.store.has_been_uploaded?(url)
            internal = Discourse.store.internal?
          elsif parsed.host == Discourse.current_hostname || !parsed.host
            internal = true

            route = Rails.application.routes.recognize_path(parsed.path)

            # We aren't interested in tracking internal links to users
            next if route[:controller] == 'users'

            topic_id = route[:topic_id]
            post_number = route[:post_number] || 1

            # Store the canonical URL
            topic = Topic.where(id: topic_id).first

            if topic.present?
              url = "#{Discourse.base_url}#{topic.relative_url}"
              url << "/#{post_number}" if post_number.to_i > 1
            end

          end

          # Skip linking to ourselves
          next if topic_id == post.topic_id

          reflected_post = nil
          if post_number && topic_id
            reflected_post = Post.where(topic_id: topic_id, post_number: post_number.to_i).first
          end

          added_urls << url
          TopicLink.create(post_id: post.id,
                           user_id: post.user_id,
                           topic_id: post.topic_id,
                           url: url,
                           domain: parsed.host || Discourse.current_hostname,
                           internal: internal,
                           link_topic_id: topic_id,
                           link_post_id: reflected_post.try(:id))

          # Create the reflection if we can
          if topic_id.present?
            topic = Topic.where(id: topic_id).first

            if topic && post.topic && post.topic.archetype != 'private_message' && topic.archetype != 'private_message'

              prefix = Discourse.base_url

              reflected_url = "#{prefix}#{post.topic.relative_url(post.post_number)}"

              reflected_urls << reflected_url
              TopicLink.create(user_id: post.user_id,
                                     topic_id: topic_id,
                                     post_id: reflected_post.try(:id),
                                     url: reflected_url,
                                     domain: Discourse.current_hostname,
                                     reflection: true,
                                     internal: true,
                                     link_topic_id: post.topic_id,
                                     link_post_id: post.id)
            end
          end

        rescue URI::InvalidURIError
          # if the URI is invalid, don't store it.
        rescue ActionController::RoutingError
          # If we can't find the route, no big deal
        end
      end

      # Remove links that aren't there anymore
      if added_urls.present?
        TopicLink.delete_all ["(url not in (:urls)) AND (post_id = :post_id)", urls: added_urls, post_id: post.id]
        TopicLink.delete_all ["(url not in (:urls)) AND (link_post_id = :post_id)", urls: reflected_urls, post_id: post.id]
      else
        TopicLink.delete_all ["post_id = :post_id OR link_post_id = :post_id", post_id: post.id]
      end
    end
  end

  # Crawl a link's title after it's saved
  def crawl_link_title
    Jobs.enqueue(:crawl_topic_link, topic_link_id: id)
  end
end

# == Schema Information
#
# Table name: topic_links
#
#  id            :integer          not null, primary key
#  topic_id      :integer          not null
#  post_id       :integer
#  user_id       :integer          not null
#  url           :string(500)      not null
#  domain        :string(100)      not null
#  internal      :boolean          default(FALSE), not null
#  link_topic_id :integer
#  created_at    :datetime         not null
#  updated_at    :datetime         not null
#  reflection    :boolean          default(FALSE)
#  clicks        :integer          default(0), not null
#  link_post_id  :integer
#  title         :string(255)
#  crawled_at    :datetime
#
# Indexes
#
#  index_forum_thread_links_on_forum_thread_id                      (topic_id)
#  index_forum_thread_links_on_forum_thread_id_and_post_id_and_url  (topic_id,post_id,url) UNIQUE
#