#
# How a post is deleted is affected by who is performing the action.
# this class contains the logic to delete it.
#
class PostDestroyer

  def self.destroy_old_hidden_posts
    Post.where(deleted_at: nil, hidden: true)
      .where("hidden_at < ?", 30.days.ago)
      .find_each do |post|
      PostDestroyer.new(Discourse.system_user, post).destroy
    end
  end

  def self.destroy_stubs
    context = I18n.t('remove_posts_deleted_by_author')

    # exclude deleted topics and posts that are actively flagged
    Post.where(deleted_at: nil, user_deleted: true)
      .where("NOT EXISTS (
            SELECT 1 FROM topics t
            WHERE t.deleted_at IS NOT NULL AND
                  t.id = posts.topic_id
        )")
      .where("updated_at < ? AND post_number > 1", SiteSetting.delete_removed_posts_after.hours.ago)
      .where("NOT EXISTS (
                  SELECT 1
                  FROM post_actions pa
                  WHERE pa.post_id = posts.id
                    AND pa.deleted_at IS NULL
                    AND pa.deferred_at IS NULL
                    AND pa.post_action_type_id IN (?)
              )", PostActionType.notify_flag_type_ids)
      .find_each do |post|

      PostDestroyer.new(Discourse.system_user, post, context: context).destroy
    end
  end

  def initialize(user, post, opts = {})
    @user = user
    @post = post
    @topic = post.topic if post
    @opts = opts
  end

  def destroy
    payload = WebHook.generate_payload(:post, @post)
    topic = @post.topic

    if @post.is_first_post? && topic
      topic_view = TopicView.new(topic.id, Discourse.system_user)
      topic_payload = WebHook.generate_payload(:topic, topic_view, WebHookTopicViewSerializer)
    end

    delete_removed_posts_after = @opts[:delete_removed_posts_after] || SiteSetting.delete_removed_posts_after

    if @user.staff? || delete_removed_posts_after < 1
      perform_delete
    elsif @user.id == @post.user_id
      mark_for_deletion(delete_removed_posts_after)
    end
    DiscourseEvent.trigger(:post_destroyed, @post, @opts, @user)
    WebHook.enqueue_hooks(:post, :post_destroyed,
      id: @post.id,
      category_id: @post&.topic&.category_id,
      payload: payload
    )

    if @post.is_first_post? && @post.topic
      DiscourseEvent.trigger(:topic_destroyed, @post.topic, @user)
      WebHook.enqueue_hooks(:topic, :topic_destroyed,
        id: topic.id,
        category_id: topic&.category_id,
        payload: topic_payload
      )
    end
  end

  def recover
    if @user.staff? && @post.deleted_at
      staff_recovered
    elsif @user.staff? || @user.id == @post.user_id
      user_recovered
    end
    topic = Topic.with_deleted.find @post.topic_id
    topic.recover! if @post.is_first_post?
    topic.update_statistics
    recover_user_actions
    DiscourseEvent.trigger(:post_recovered, @post, @opts, @user)
    if @post.is_first_post?
      DiscourseEvent.trigger(:topic_recovered, topic, @user)
      StaffActionLogger.new(@user).log_topic_delete_recover(topic, "recover_topic", @opts.slice(:context)) if @user.id != @post.user_id
    end
  end

  def staff_recovered
    @post.recover!

    if @post.topic && !@post.topic.private_message?
      if author = @post.user
        if @post.is_first_post?
          author.user_stat.topic_count += 1
        else
          author.user_stat.post_count += 1
        end
        author.user_stat.save!
      end

      if @post.is_first_post?
        # Update stats of all people who replied
        counts = Post.where(post_type: Post.types[:regular], topic_id: @post.topic_id).where('post_number > 1').group(:user_id).count
        counts.each do |user_id, count|
          if user_stat = UserStat.where(user_id: user_id).first
            user_stat.update_attributes(post_count: user_stat.post_count + count)
          end
        end
      end
    end

    @post.publish_change_to_clients! :recovered
    TopicTrackingState.publish_recover(@post.topic) if @post.topic && @post.is_first_post?
  end

  # When a post is properly deleted. Well, it's still soft deleted, but it will no longer
  # show up in the topic
  def perform_delete
    Post.transaction do
      @post.trash!(@user)
      if @post.topic
        make_previous_post_the_last_one
        clear_user_posted_flag
        Topic.reset_highest(@post.topic_id)
      end
      trash_public_post_actions
      agree_with_flags
      trash_user_actions
      @post.update_flagged_posts_count
      remove_associated_replies
      remove_associated_notifications
      if @post.topic && @post.is_first_post?
        StaffActionLogger.new(@user).log_topic_delete_recover(@post.topic, "delete_topic", @opts.slice(:context)) if @user.id != @post.user_id
        @post.topic.trash!(@user)
      elsif @user.id != @post.user_id
        StaffActionLogger.new(@user).log_post_deletion(@post, @opts.slice(:context))
      end
      update_associated_category_latest_topic
      update_user_counts
      TopicUser.update_post_action_cache(post_id: @post.id)
    end

    feature_users_in_the_topic if @post.topic
    @post.publish_change_to_clients! :deleted if @post.topic
    TopicTrackingState.publish_delete(@post.topic) if @post.topic && @post.post_number == 1
  end

  # When a user 'deletes' their own post. We just change the text.
  def mark_for_deletion(delete_removed_posts_after = SiteSetting.delete_removed_posts_after)
    I18n.with_locale(SiteSetting.default_locale) do

      # don't call revise from within transaction, high risk of deadlock
      @post.revise(@user,
        { raw: I18n.t('js.post.deleted_by_author', count: delete_removed_posts_after) },
        force_new_version: true
      )

      Post.transaction do
        @post.update_column(:user_deleted, true)
        @post.update_flagged_posts_count
        @post.topic_links.each(&:destroy)
      end
    end
  end

  def user_recovered
    Post.transaction do
      @post.update_column(:user_deleted, false)
      @post.skip_unique_check = true
      @post.update_flagged_posts_count
    end

    # has internal transactions, if we nest then there are some very high risk deadlocks
    last_revision = @post.revisions.last
    @post.revise(@user, { raw: last_revision.modifications["raw"][0] }, force_new_version: true) if last_revision.present?
  end

  private

  def make_previous_post_the_last_one
    last_post = Post.where("topic_id = ? and id <> ?", @post.topic_id, @post.id).order('created_at desc').limit(1).first
    if last_post.present? && @post.topic.present?
      topic = @post.topic
      topic.last_posted_at = last_post.created_at
      topic.last_post_user_id = last_post.user_id
      topic.highest_post_number = last_post.post_number
      topic.save!(validate: false)
    end
  end

  def clear_user_posted_flag
    unless Post.exists?(["topic_id = ? and user_id = ? and id <> ?", @post.topic_id, @post.user_id, @post.id])
      TopicUser.where(topic_id: @post.topic_id, user_id: @post.user_id).update_all 'posted = false'
    end
  end

  def feature_users_in_the_topic
    Jobs.enqueue(:feature_topic_users, topic_id: @post.topic_id)
  end

  def trash_public_post_actions
    if public_post_actions = PostAction.publics.where(post_id: @post.id)
      public_post_actions.each { |pa| pa.trash!(@user) }

      @post.custom_fields["deleted_public_actions"] = public_post_actions.ids
      @post.save_custom_fields

      f = PostActionType.public_types.map { |k, _| ["#{k}_count", 0] }
      Post.with_deleted.where(id: @post.id).update_all(Hash[*f.flatten])
    end
  end

  def agree_with_flags
    if @post.has_active_flag? && @user.id > 0 && @user.staff?
      Jobs.enqueue(
        :send_system_message,
        user_id: @post.user.id,
        message_type: :flags_agreed_and_post_deleted,
        message_options: {
          url: @post.url,
          flag_reason: I18n.t(
            "flag_reasons.#{@post.active_flags.last.post_action_type.name_key}",
            locale: SiteSetting.default_locale,
            base_path: Discourse.base_path
          )
        }
      )
    end

    PostAction.agree_flags!(@post, @user, delete_post: true)
  end

  def trash_user_actions
    UserAction.where(target_post_id: @post.id).each do |ua|
      row = {
        action_type: ua.action_type,
        user_id: ua.user_id,
        acting_user_id: ua.acting_user_id,
        target_topic_id: ua.target_topic_id,
        target_post_id: ua.target_post_id
      }
      UserAction.remove_action!(row)
    end
  end

  def recover_user_actions
    # TODO: Use a trash concept for `user_actions` to avoid churn and simplify this?
    UserActionCreator.log_post(@post)
  end

  def remove_associated_replies
    post_ids = PostReply.where(reply_id: @post.id).pluck(:post_id)

    if post_ids.present?
      PostReply.where(reply_id: @post.id).delete_all
      Post.where(id: post_ids).each { |p| p.update_column :reply_count, p.replies.count }
    end
  end

  def remove_associated_notifications
    Notification
      .where(topic_id: @post.topic_id, post_number: @post.post_number)
      .delete_all
  end

  def update_associated_category_latest_topic
    return unless @post.topic && @post.topic.category
    return unless @post.id == @post.topic.category.latest_post_id || (@post.is_first_post? && @post.topic_id == @post.topic.category.latest_topic_id)

    @post.topic.category.update_latest
  end

  def update_user_counts
    author = @post.user

    return unless author

    author.create_user_stat if author.user_stat.nil?

    if @post.created_at == author.user_stat.first_post_created_at
      author.user_stat.first_post_created_at = author.posts.order('created_at ASC').first.try(:created_at)
    end

    if @post.topic && !@post.topic.private_message?
      if @post.post_type == Post.types[:regular] && !@post.is_first_post? && !@topic.nil?
        author.user_stat.post_count -= 1
      end
      author.user_stat.topic_count -= 1 if @post.is_first_post?
    end

    # We don't count replies to your own topics in topic_reply_count
    if @topic && author.id != @topic.user_id
      author.user_stat.update_topic_reply_count
    end

    author.user_stat.save!

    if @post.created_at == author.last_posted_at
      author.last_posted_at = author.posts.order('created_at DESC').first.try(:created_at)
      author.save!
    end

    if @post.is_first_post? && @post.topic && !@post.topic.private_message?
      # Update stats of all people who replied
      counts = Post.where(post_type: Post.types[:regular], topic_id: @post.topic_id).where('post_number > 1').group(:user_id).count
      counts.each do |user_id, count|
        if user_stat = UserStat.where(user_id: user_id).first
          user_stat.update_attributes(post_count: user_stat.post_count - count)
        end
      end
    end
  end

end