discourse/lib/post_creator.rb

# Responsible for creating posts and topics
#
require_dependency 'rate_limiter'
require_dependency 'topic_creator'
require_dependency 'post_jobs_enqueuer'
require_dependency 'distributed_mutex'

class PostCreator

  attr_reader :errors, :opts

  # Acceptable options:
  #
  #   raw                     - raw text of post
  #   image_sizes             - We can pass a list of the sizes of images in the post as a shortcut.
  #   invalidate_oneboxes     - Whether to force invalidation of oneboxes in this post
  #   acting_user             - The user performing the action might be different than the user
  #                             who is the post "author." For example when copying posts to a new
  #                             topic.
  #   created_at              - Post creation time (optional)
  #   auto_track              - Automatically track this topic if needed (default true)
  #   custom_fields           - Custom fields to be added to the post, Hash (default nil)
  #
  #   When replying to a topic:
  #     topic_id              - topic we're replying to
  #     reply_to_post_number  - post number we're replying to
  #
  #   When creating a topic:
  #     title                 - New topic title
  #     archetype             - Topic archetype
  #     category              - Category to assign to topic
  #     target_usernames      - comma delimited list of usernames for membership (private message)
  #     target_group_names    - comma delimited list of groups for membership (private message)
  #     meta_data             - Topic meta data hash
  #     cooking_options       - Options for rendering the text
  #
  def initialize(user, opts)
    # TODO: we should reload user in case it is tainted, should take in a user_id as opposed to user
    # If we don't do this we introduce a rather risky dependency
    @user = user
    @opts = opts || {}
    @spam = false
  end

  # True if the post was considered spam
  def spam?
    @spam
  end

  def guardian
    @guardian ||= Guardian.new(@user)
  end

  def create
    @topic = nil
    @post = nil

    transaction do
      setup_topic
      setup_post
      rollback_if_host_spam_detected
      save_post
      extract_links
      store_unique_post_key
      track_topic
      update_topic_stats
      update_user_counts
      create_embedded_topic

      ensure_in_allowed_users if guardian.is_staff?
      @post.advance_draft_sequence
      @post.save_reply_relationships
    end

    if @post && @post.errors.empty?
      publish
      PostAlerter.post_created(@post) unless @opts[:import_mode]

      track_latest_on_category
      enqueue_jobs
      BadgeGranter.queue_badge_grant(Badge::Trigger::PostRevision, post: @post)
    end

    if @post || @spam
      handle_spam unless @opts[:import_mode]
    end

    @post
  end

  def self.create(user, opts)
    PostCreator.new(user, opts).create
  end

  def self.before_create_tasks(post)
    set_reply_user_id(post)

    post.word_count = post.raw.scan(/\w+/).size
    post.post_number ||= Topic.next_post_number(post.topic_id, post.reply_to_post_number.present?)

    cooking_options = post.cooking_options || {}
    cooking_options[:topic_id] = post.topic_id

    post.cooked ||= post.cook(post.raw, cooking_options)
    post.sort_order = post.post_number
    DiscourseEvent.trigger(:before_create_post, post)
    post.last_version_at ||= Time.now
  end

  def self.set_reply_user_id(post)
    return unless post.reply_to_post_number.present?

    post.reply_to_user_id ||= Post.select(:user_id).find_by(topic_id: post.topic_id, post_number: post.reply_to_post_number).try(:user_id)
  end

  protected

  def transaction(&blk)
    Post.transaction do
      if new_topic?
        blk.call
      else
        # we need to ensure post_number is monotonically increasing with no gaps
        # so we serialize creation to avoid needing rollbacks
        DistributedMutex.synchronize("topic_id_#{@opts[:topic_id]}", &blk)
      end
    end
  end

  # You can supply an `embed_url` for a post to set up the embedded relationship.
  # This is used by the wp-discourse plugin to associate a remote post with a
  # discourse post.
  def create_embedded_topic
    return unless @opts[:embed_url].present?
    TopicEmbed.create!(topic_id: @post.topic_id, post_id: @post.id, embed_url: @opts[:embed_url])
  end

  def handle_spam
    if @spam
      GroupMessage.create( Group[:moderators].name,
                           :spam_post_blocked,
                           { user: @user,
                             limit_once_per: 24.hours,
                             message_params: {domains: @post.linked_hosts.keys.join(', ')} } )
    elsif @post && !@post.errors.present? && !@opts[:skip_validations]
      SpamRulesEnforcer.enforce!(@post)
    end
  end

  def track_latest_on_category
    return unless @post && @post.errors.count == 0 && @topic && @topic.category_id

    Category.where(id: @topic.category_id).update_all(latest_post_id: @post.id)
    Category.where(id: @topic.category_id).update_all(latest_topic_id: @topic.id) if @post.post_number == 1
  end

  def ensure_in_allowed_users
    return unless @topic.private_message?

    unless @topic.topic_allowed_users.where(user_id: @user.id).exists?
      @topic.topic_allowed_users.create!(user_id: @user.id)
    end
  end

  private

  def setup_topic
    if new_topic?
      topic_creator = TopicCreator.new(@user, guardian, @opts)

      begin
        topic = topic_creator.create
        @errors = topic_creator.errors
      rescue ActiveRecord::Rollback => ex
        # In the event of a rollback, grab the errors from the topic
        @errors = topic_creator.errors
        raise ex
      end
    else
      topic = Topic.find_by(id: @opts[:topic_id])
      guardian.ensure_can_create!(Post, topic)
    end
    @topic = topic
  end

  def update_topic_stats
    # Update attributes on the topic - featured users and last posted.
    attrs = {last_posted_at: @post.created_at, last_post_user_id: @post.user_id}
    attrs[:bumped_at] = @post.created_at unless @post.no_bump
    attrs[:word_count] = (@topic.word_count || 0) + @post.word_count
    attrs[:excerpt] = @post.excerpt(220, strip_links: true) if new_topic?
    @topic.update_attributes(attrs)
  end

  def setup_post
    post = @topic.posts.new(raw: @opts[:raw],
                            user: @user,
                            reply_to_post_number: @opts[:reply_to_post_number])

    # Attributes we pass through to the post instance if present
    [:post_type, :no_bump, :cooking_options, :image_sizes, :acting_user, :invalidate_oneboxes, :cook_method].each do |a|
      post.send("#{a}=", @opts[a]) if @opts[a].present?
    end

    post.extract_quoted_post_numbers
    post.created_at = Time.zone.parse(@opts[:created_at].to_s) if @opts[:created_at].present?

    if fields = @opts[:custom_fields]
      post.custom_fields = fields
    end

    @post = post
  end

  def rollback_if_host_spam_detected
    return if @opts[:skip_validations]
    if @post.has_host_spam?
      @post.errors.add(:base, I18n.t(:spamming_host))
      @errors = @post.errors
      @spam = true
      raise ActiveRecord::Rollback.new
    end
  end

  def save_post
    unless @post.save(validate: !@opts[:skip_validations])
      @errors = @post.errors
      raise ActiveRecord::Rollback.new
    end
  end

  def store_unique_post_key
    @post.store_unique_post_key
  end

  def update_user_counts
    @user.create_user_stat if @user.user_stat.nil?

    if @user.user_stat.first_post_created_at.nil?
      @user.user_stat.first_post_created_at = @post.created_at
    end

    @user.user_stat.post_count += 1
    @user.user_stat.topic_count += 1 if @post.post_number == 1

    # We don't count replies to your own topics
    if !@opts[:import_mode] && @user.id != @topic.user_id
      @user.user_stat.update_topic_reply_count
    end

    @user.user_stat.save!

    @user.last_posted_at = @post.created_at
    @user.save!
  end

  def publish
    return if @opts[:import_mode]
    return unless @post.post_number > 1

    MessageBus.publish("/topic/#{@post.topic_id}",{
                    id: @post.id,
                    created_at: @post.created_at,
                    user: BasicUserSerializer.new(@post.user).as_json(root: false),
                    post_number: @post.post_number
                  },
                  group_ids: @topic.secure_group_ids
    )
  end

  def extract_links
    TopicLink.extract_from(@post)
    QuotedPost.extract_from(@post)
  end

  def track_topic
    return if @opts[:auto_track] == false

    TopicUser.change(@post.user.id,
                     @post.topic.id,
                     posted: true,
                     last_read_post_number: @post.post_number,
                     seen_post_count: @post.post_number)


    # assume it took us 5 seconds of reading time to make a post
    PostTiming.record_timing(topic_id: @post.topic_id,
                             user_id: @post.user_id,
                             post_number: @post.post_number,
                             msecs: 5000)


    TopicUser.auto_track(@user.id, @topic.id, TopicUser.notification_reasons[:created_post])
  end

  def enqueue_jobs
    return unless @post && !@post.errors.present?
    PostJobsEnqueuer.new(@post, @topic, new_topic?, {import_mode: @opts[:import_mode]}).enqueue_jobs
  end

  def new_topic?
    @opts[:topic_id].blank?
  end

end