discourse/app/models/user_action_observer.rb

class UserActionObserver < ActiveRecord::Observer
  observe :post_action, :topic, :post, :notification, :topic_user


  def after_save(model)
    case 
    when (model.is_a?(PostAction) and (model.is_bookmark? or model.is_like?)) 
      log_post_action(model)
    when (model.is_a?(Topic))
      log_topic(model)
    when (model.is_a?(Post))
      log_post(model)
    when (model.is_a?(Notification))
      log_notification(model)
    when (model.is_a?(TopicUser))
      log_topic_user(model)
    end
  end

  protected 

  def log_topic_user(model)
    action = UserAction::STAR

    row = { 
        action_type: action, 
        user_id: model.user_id, 
        acting_user_id: model.user_id, 
        target_topic_id: model.topic_id, 
        target_post_id: -1,
        created_at: model.starred_at
    }

    if model.starred 
      UserAction.log_action!(row)
    else 
      UserAction.remove_action!(row)    
    end
  end
  
  def log_notification(model)
    
    action =
      case model.notification_type
        when Notification.Types[:quoted]
          UserAction::QUOTE
        when Notification.Types[:replied]
          UserAction::RESPONSE
        when Notification.Types[:mentioned]
          UserAction::MENTION
        when Notification.Types[:edited]
          UserAction::EDIT
      end

    # like is skipped
    return unless action

    post = Post.where(post_number: model.post_number, topic_id: model.topic_id).first

    # stray data
    return unless post

    row = { 
        action_type: action, 
        user_id: model.user_id, 
        acting_user_id: (action == UserAction::EDIT) ? post.last_editor_id : post.user_id, 
        target_topic_id: model.topic_id, 
        target_post_id: post.id,
        created_at: model.created_at
    }

    if post.deleted_at.nil? 
      UserAction.log_action!(row)
    else 
      UserAction.remove_action!(row)    
    end
  end

  def log_post(model)
    
    # first post gets nada
    return if model.post_number == 1


    row = { 
        action_type: UserAction::POST, 
        user_id: model.user_id, 
        acting_user_id: model.user_id, 
        target_post_id: model.id,
        target_topic_id: model.topic_id,
        created_at: model.created_at
    }
   
    rows = [row]

    if model.topic.private_message? 
      rows = []
      model.topic.topic_allowed_users.each do |ta|
        row = row.dup
        row[:user_id] = ta.user_id 
        row[:action_type] = ta.user_id == model.user_id ? UserAction::NEW_PRIVATE_MESSAGE : UserAction::GOT_PRIVATE_MESSAGE
        rows << row
      end
    end

    rows.each do |row|
      if model.deleted_at.nil? 
        UserAction.log_action!(row)
      else 
        UserAction.remove_action!(row)    
      end
    end

    return if model.topic.private_message?

    # a bit odd but we may have stray records
    if model.topic and model.topic.user_id != model.user_id 
      row[:action_type] = UserAction::TOPIC_RESPONSE 
      row[:user_id] = model.topic.user_id 

      if model.deleted_at.nil? 
        UserAction.log_action!(row)
      else 
        UserAction.remove_action!(row)    
      end
    end

  end

  def log_topic(model)
    row = { 
        action_type: model.archetype == Archetype.private_message ? UserAction::NEW_PRIVATE_MESSAGE : UserAction::NEW_TOPIC, 
        user_id: model.user_id, 
        acting_user_id: model.user_id, 
        target_topic_id: model.id,
        target_post_id: -1, 
        created_at: model.created_at
    }

    rows = [row]

    if model.private_message?
      model.topic_allowed_users.reject{|a| a.user_id == model.user_id}.each do |ta|
        row = row.dup
        row[:user_id] = ta.user_id 
        row[:action_type] = UserAction::GOT_PRIVATE_MESSAGE
        rows << row
      end
    end

    rows.each do |row|
      if model.deleted_at.nil? 
        UserAction.log_action!(row)
      else 
        UserAction.remove_action!(row)    
      end
    end
  end

  def log_post_action(model)
    action = UserAction::BOOKMARK if model.is_bookmark?
    action = UserAction::LIKE if model.is_like?

    row = {
      action_type: action, 
      user_id: model.user_id, 
      acting_user_id: model.user_id, 
      target_post_id: model.post_id,
      target_topic_id: model.post.topic_id,
      created_at: model.created_at
    }

    if model.deleted_at.nil?
      UserAction.log_action!(row)
    else
      UserAction.remove_action!(row)
    end

    if model.is_like? 
      row[:action_type] = UserAction::WAS_LIKED
      row[:user_id] = model.post.user_id
      if model.deleted_at.nil?
        UserAction.log_action!(row)
      else
        UserAction.remove_action!(row)
      end
    end
  end
end