discourse/plugins/chat/lib/post_notification_handler.rb

# frozen_string_literal: true

##
# Handles :post_alerter_after_save_post events from
# core. Used for notifying users that their chat message
# has been quoted in a post.
class Chat::PostNotificationHandler
  attr_reader :post

  def initialize(post, notified_users)
    @post = post
    @notified_users = notified_users
  end

  def handle
    return false if post.post_type == Post.types[:whisper]
    return false if post.topic.blank?
    return false if post.topic.private_message?

    quoted_users = extract_quoted_users(post)
    if @notified_users.present?
      quoted_users = quoted_users.where("users.id NOT IN (?)", @notified_users)
    end

    opts = { user_id: post.user.id, display_username: post.user.username }
    quoted_users.each do |user|
      # PostAlerter.create_notification handles many edge cases, such as
      # muting, ignoring, double notifications etc.
      PostAlerter.new.create_notification(user, Notification.types[:chat_quoted], post, opts)
    end
  end

  private

  def extract_quoted_users(post)
    usernames =
      post.raw.scan(/\[chat quote=\"([^;]+);.+\"\]/).uniq.map { |q| q.first.strip.downcase }
    User.where.not(id: post.user_id).where(username_lower: usernames)
  end
end