notification_message_creator.rb

#
# Copyright (C) 2013 Instructure, Inc.
#
# This file is part of Canvas.
#
# Canvas is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, version 3 of the License.
#
# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#

class NotificationMessageCreator
  include LocaleSelection

  attr_accessor :notification, :asset, :asset_context, :to_users, :to_channels, :message_data

  # Options can include:
  #  :to_list - A list of Users, User IDs, and CommunicationChannels to send to
  #  :data, :asset_context - Options merged with Message options
  def initialize(notification, asset, options={})
    @notification = notification
    @asset = asset
    @to_users = []
    @to_channels = []
    if options[:to_list]
      @to_users = users_from_to_list(options[:to_list])
      @to_channels = communication_channels_from_to_list(options[:to_list])
    end
    @message_data = options.delete(:data)
    @asset_context = options.delete(:asset_context)
  end

  # Public: create (and dispatch, and queue delayed) a message
  # for this notication, associated with the given asset, sent to the given recipients
  #
  # asset - what the message applies to. An assignment, a discussion, etc.
  # to_list - a list of who to send the message to. the list can contain Users, User ids, or CommunicationChannels
  # options - a hash of extra options to merge with the options used to build the Message
  #
  # Returns a list of the messages dispatched immediately
  def create_message
    @user_counts = {}

    to_user_channels = Hash.new([])
    @to_users.each do |user|
      to_user_channels[user] += [user.email_channel]
    end
    @to_channels.each do |channel|
      to_user_channels[channel.user] += [channel]
    end
    to_user_channels.each_value{ |channels| channels.uniq! }

    dashboard_messages = []
    immediate_messages = []
    delayed_messages = []

    # Looping on users and channels might be a bad thing. If you had a User and their CommunicationChannel in
    # the to_list (which currently never happens, I think), duplicate messages could be sent.
    to_user_channels.each do |user, channels|
      next unless asset_filtered_by_user(user)
      user_locale = infer_locale(:user => user,
                                 :context => user_asset_context(asset_filtered_by_user(user)))
      I18n.with_locale(user_locale) do
        channels.each do |default_channel|
          if @notification.registration?
            registration_channels = if default_channel then
                                      [default_channel]
                                    else
                                      immediate_channels_for(user)
                                    end
            immediate_messages += build_immediate_messages_for(user, registration_channels)
          else
            if @notification.summarizable?
              delayed_messages += build_summaries_for(user, default_channel)
            end
          end
        end

        unless @notification.registration?
          if @notification.summarizable? && too_many_messages_for?(user) && no_daily_messages_in(delayed_messages)
            fallback = build_fallback_for(user)
            delayed_messages << fallback if fallback
          end

          unless user.pre_registered?
            immediate_messages += build_immediate_messages_for(user)
            dashboard_messages << build_dashboard_message_for(user) if @notification.dashboard? && @notification.show_in_feed?
          end
        end
      end
    end

    delayed_messages.each{ |message| message.save! }
    dispatch_dashboard_messages(dashboard_messages)
    dispatch_immediate_messages(immediate_messages)

    @user_counts.each{|user_id, cnt| recent_messages_for_user(user_id, cnt) }

    return immediate_messages + dashboard_messages
  end

  private

  def no_daily_messages_in(delayed_messages)
    !delayed_messages.any?{ |message| message.frequency == 'daily' }
  end

  def build_fallback_for(user)
    fallback_channel = immediate_channels_for(user).find{ |cc| cc.path_type == 'email'}
    return unless fallback_channel
    fallback_policy = nil
    NotificationPolicy.unique_constraint_retry do
      fallback_policy = fallback_channel.notification_policies.by('daily').where(:notification_id => nil).first
      fallback_policy ||= fallback_channel.notification_policies.create!(frequency: 'daily')
    end

    build_summary_for(user, fallback_policy)
  end

  def build_summaries_for(user, channel=user.email_channel)
    delayed_policies_for(user, channel).map{ |policy| build_summary_for(user, policy) }
  end

  def build_summary_for(user, policy)
    user.shard.activate do
      message = user.messages.build(message_options_for(user))
      message.parse!('summary')
      delayed_message = policy.delayed_messages.build(:notification => @notification,
                                    :frequency => policy.frequency,
                                    :communication_channel_id => policy.communication_channel_id,
                                    :root_account_id => message.context_root_account.try(:id),
                                    :linked_name => 'work on this link!!!',
                                    :name_of_topic => message.subject,
                                    :link => message.url,
                                    :summary => message.body)
      delayed_message.context = @asset
      delayed_message.save! if Rails.env.test?
      delayed_message
    end
  end

  def build_immediate_messages_for(user, channels=immediate_channels_for(user).reject(&:unconfirmed?))
    return [] unless asset_filtered_by_user(user)
    messages = []
    message_options = message_options_for(user)
    channels.reject!{ |channel| ['email', 'sms'].include?(channel.path_type) } if too_many_messages_for?(user) && @notification.summarizable?
    channels.reject!(&:bouncing?)
    channels.each do |channel|
      messages << user.messages.build(message_options.merge(:communication_channel => channel,
                                                            :to => channel.path))
      increment_user_counts(user) if ['email', 'sms'].include?(channel.path_type)
    end
    messages.each(&:parse!)
    messages
  end

  def dispatch_immediate_messages(messages)
    Message.transaction do
      # Cancel any that haven't been sent out for the same purpose
      cancel_pending_duplicate_messages
      messages.each do |message|
        message.stage_without_dispatch!
        message.save!
      end
    end
    MessageDispatcher.batch_dispatch(messages)

    messages
  end

  def build_dashboard_message_for(user)
    message = user.messages.build(message_options_for(user).merge(:to => 'dashboard'))
    message.parse!
    message
  end

  def dispatch_dashboard_messages(messages)
    messages.each do |message|
      message.set_asset_context_code
      message.infer_defaults
      message.create_stream_items
    end
    messages
  end

  def unretired_policies_for(user)
    user.notification_policies.where("communication_channels.workflow_state<>'retired'")
  end

  def delayed_policies_for(user, channel=user.email_channel)
    # This condition is weird. Why would not throttling stop sending notifications?
    # Why could an inactive email channel stop us here? We handle that later! And could still send
    # notifications without it!
    return [] if !too_many_messages_for?(user) && channel && !channel.active?

    # If any channel has a policy, even policy-less channels don't get the notification based on the
    # notification default frequency. Is that right?
    policies= []
    user_has_policy = unretired_policies_for(user).for(@notification).exists?
    if user_has_policy
      policies += unretired_policies_for(user).for(@notification).by(['daily', 'weekly']).where("communication_channels.path_type='email'")
    elsif channel &&
          channel.active? &&
          channel.path_type == 'email' &&
        ['daily', 'weekly'].include?(@notification.default_frequency)
      policies << channel.notification_policies.create!(:notification => @notification,
                                            :frequency => @notification.default_frequency)
    end
    policies
  end

  def users_from_to_list(to_list)
    to_list = [to_list] unless to_list.is_a? Enumerable

    to_users = []
    to_users += User.find(to_list.select{ |to| to.is_a? Numeric }.uniq)
    to_users += to_list.select{ |to| to.is_a? User }
    to_users.uniq!

    to_users
  end

  def communication_channels_from_to_list(to_list)
    to_list = [to_list] unless to_list.is_a? Enumerable
    to_list.select{ |to| to.is_a? CommunicationChannel }.uniq
  end

  def asset_filtered_by_user(user)
    if asset.respond_to?(:filter_asset_by_recipient) # Does this ever happen?
      asset.filter_asset_by_recipient(@notification, user)
    else
      asset
    end
  end

  def message_options_for(user)
    user_asset = asset_filtered_by_user(user)

    user_asset_context = %w{ContentMigration Submission WikiPage}.include?(user_asset.class.name) ? user_asset.context(user) : user_asset

    message_options = {
      :subject => @notification.subject,
      :notification => @notification,
      :notification_name => @notification.name,
      :user => user,
      :context => user_asset,
      :asset_context => user_asset_context
    }
    # can't just merge these because nil values need to be overwritten in a later merge
    message_options[:delay_for] = @notification.delay_for if @notification.delay_for
    message_options[:data] = @message_data if @message_data
    message_options[:asset_context] = @asset_context if @asset_context
    message_options
  end

  def increment_user_counts(user_id, count=1)
    @user_counts[user_id] ||= 0
    @user_counts[user_id] += count
  end

  def user_asset_context(user_asset)
    if user_asset.is_a?(Context)
      user_asset
    elsif user_asset.respond_to?(:context)
      user_asset.context
    end
  end

  # Finds channels for a user that should get this notification immediately
  #
  # If the user doesn't have a policy for this notification on a non-push
  # channel and the default frequency is immediate, the user should get the
  # notification by email.
  # Unregistered users don't get notifications. (registration notifications
  # are a special case handled elsewhere)
  def immediate_channels_for(user)
    return [] unless user.registered?

    active_channel_scope = user.communication_channels.active.for(@notification)
    immediate_channel_scope = user.communication_channels.active.for_notification_frequency(@notification, 'immediately')

    user_has_a_policy = active_channel_scope.where.not(path_type: 'push').exists?
    if !user_has_a_policy && @notification.default_frequency == 'immediately'
      return [user.email_channel, *immediate_channel_scope.where(path_type: 'push')].compact
    end
    immediate_channel_scope
  end

  def cancel_pending_duplicate_messages
    # doesn't include dashboard messages. should it?
    Message.where(:notification_id => @notification).
      for(@asset).
      by_name(@notification.name).
      for_user(@to_users + @to_channels).
      cancellable.
      update_all(:workflow_state => 'cancelled')
  end

  def too_many_messages_for?(user)
    all_messages = recent_messages_for_user(user.id) || 0
    @user_counts[user.id] = all_messages
    all_messages >= user.max_messages_per_day
  end

  # Cache the count for number of messages sent to a user/user-with-category,
  # it can also be manually re-set to reflect new rows added... this cache
  # data can get out of sync if messages are cancelled for being repeats...
  # not sure if we care about that...
  def recent_messages_for_user(id, messages=nil)
    if !id
      nil
    elsif messages
      Rails.cache.write(['recent_messages_for', id].cache_key, messages, :expires_in => 1.hour)
    else
      user_id = id
      messages = Rails.cache.fetch(['recent_messages_for', id].cache_key, :expires_in => 1.hour) do
        Message.where("dispatch_at>? AND user_id=? AND to_email=?", 24.hours.ago, user_id, true).count
      end
    end
  end
end