mastodon/app/lib/activitypub/activity.rb

# frozen_string_literal: true

class ActivityPub::Activity
  include JsonLdHelper
  include Redisable

  SUPPORTED_TYPES = %w(Note Question).freeze
  CONVERTED_TYPES = %w(Image Audio Video Article Page Event).freeze

  def initialize(json, account, **options)
    @json    = json
    @account = account
    @object  = @json['object']
    @options = options
  end

  def perform
    raise NotImplementedError
  end

  class << self
    def factory(json, account, **options)
      @json = json
      klass&.new(json, account, **options)
    end

    private

    def klass
      case @json['type']
      when 'Create'
        ActivityPub::Activity::Create
      when 'Announce'
        ActivityPub::Activity::Announce
      when 'Delete'
        ActivityPub::Activity::Delete
      when 'Follow'
        ActivityPub::Activity::Follow
      when 'Like'
        ActivityPub::Activity::Like
      when 'Block'
        ActivityPub::Activity::Block
      when 'Update'
        ActivityPub::Activity::Update
      when 'Undo'
        ActivityPub::Activity::Undo
      when 'Accept'
        ActivityPub::Activity::Accept
      when 'Reject'
        ActivityPub::Activity::Reject
      when 'Flag'
        ActivityPub::Activity::Flag
      when 'Add'
        ActivityPub::Activity::Add
      when 'Remove'
        ActivityPub::Activity::Remove
      when 'Move'
        ActivityPub::Activity::Move
      end
    end
  end

  protected

  def status_from_uri(uri)
    ActivityPub::TagManager.instance.uri_to_resource(uri, Status)
  end

  def account_from_uri(uri)
    ActivityPub::TagManager.instance.uri_to_resource(uri, Account)
  end

  def object_uri
    @object_uri ||= begin
      str = value_or_id(@object)

      if str&.start_with?('bear:')
        Addressable::URI.parse(str).query_values['u']
      else
        str
      end
    end
  end

  def unsupported_object_type?
    @object.is_a?(String) || !(supported_object_type? || converted_object_type?)
  end

  def supported_object_type?
    equals_or_includes_any?(@object['type'], SUPPORTED_TYPES)
  end

  def converted_object_type?
    equals_or_includes_any?(@object['type'], CONVERTED_TYPES)
  end

  def distribute(status)
    crawl_links(status)

    notify_about_reblog(status) if reblog_of_local_account?(status) && !reblog_by_following_group_account?(status)
    notify_about_mentions(status) unless spammy_mentions?(status)

    # Only continue if the status is supposed to have arrived in real-time.
    # Note that if @options[:override_timestamps] isn't set, the status
    # may have a lower snowflake id than other existing statuses, potentially
    # "hiding" it from paginated API calls
    return unless @options[:override_timestamps] || status.within_realtime_window?

    distribute_to_followers(status)
  end

  def reblog_of_local_account?(status)
    status.reblog? && status.reblog.account.local?
  end

  def reblog_by_following_group_account?(status)
    status.reblog? && status.account.group? && status.reblog.account.following?(status.account)
  end

  def spammy_mentions?(status)
    status.has_non_mention_links? &&
    @account.followers.local.count == 0
  end

  def notify_about_reblog(status)
    NotifyService.new.call(status.reblog.account, :reblog, status)
  end

  def notify_about_mentions(status)
    status.active_mentions.includes(:account).each do |mention|
      next unless mention.account.local? && audience_includes?(mention.account)
      NotifyService.new.call(mention.account, :mention, mention)
    end
  end

  def crawl_links(status)
    return if status.spoiler_text?

    # Spread out crawling randomly to avoid DDoSing the link
    LinkCrawlWorker.perform_in(rand(1..59).seconds, status.id)
  end

  def distribute_to_followers(status)
    ::DistributionWorker.perform_async(status.id)
  end

  def delete_arrived_first?(uri)
    redis.exists?("delete_upon_arrival:#{@account.id}:#{uri}")
  end

  def delete_later!(uri)
    redis.setex("delete_upon_arrival:#{@account.id}:#{uri}", 6.hours.seconds, true)
  end

  def status_from_object
    # If the status is already known, return it
    status = status_from_uri(object_uri)

    return status unless status.nil?

    # If the boosted toot is embedded and it is a self-boost, handle it like a Create
    unless unsupported_object_type?
      actor_id = value_or_id(first_of_value(@object['attributedTo']))

      if actor_id == @account.uri
        return ActivityPub::Activity.factory({ 'type' => 'Create', 'actor' => actor_id, 'object' => @object }, @account).perform
      end
    end

    fetch_remote_original_status
  end

  def dereference_object!
    return unless @object.is_a?(String)

    dereferencer = ActivityPub::Dereferencer.new(@object, permitted_origin: @account.uri, signature_account: signed_fetch_account)

    @object = dereferencer.object unless dereferencer.object.nil?
  end

  def signed_fetch_account
    return Account.find(@options[:delivered_to_account_id]) if @options[:delivered_to_account_id].present?

    first_mentioned_local_account || first_local_follower
  end

  def first_mentioned_local_account
    audience = (as_array(@json['to']) + as_array(@json['cc'])).map { |x| value_or_id(x) }.uniq
    local_usernames = audience.select { |uri| ActivityPub::TagManager.instance.local_uri?(uri) }
                              .map { |uri| ActivityPub::TagManager.instance.uri_to_local_id(uri, :username) }

    return if local_usernames.empty?

    Account.local.where(username: local_usernames).first
  end

  def first_local_follower
    @account.followers.local.first
  end

  def follow_request_from_object
    @follow_request ||= FollowRequest.find_by(target_account: @account, uri: object_uri) unless object_uri.nil?
  end

  def follow_from_object
    @follow ||= ::Follow.find_by(target_account: @account, uri: object_uri) unless object_uri.nil?
  end

  def fetch_remote_original_status
    if object_uri.start_with?('http')
      return if ActivityPub::TagManager.instance.local_uri?(object_uri)
      ActivityPub::FetchRemoteStatusService.new.call(object_uri, id: true, on_behalf_of: @account.followers.local.first)
    elsif @object['url'].present?
      ::FetchRemoteStatusService.new.call(@object['url'])
    end
  end

  def lock_or_return(key, expire_after = 2.hours.seconds)
    yield if redis.set(key, true, nx: true, ex: expire_after)
  ensure
    redis.del(key)
  end

  def lock_or_fail(key)
    RedisLock.acquire({ redis: Redis.current, key: key }) do |lock|
      if lock.acquired?
        yield
      else
        raise Mastodon::RaceConditionError
      end
    end
  end

  def fetch?
    !@options[:delivery]
  end

  def followed_by_local_accounts?
    @account.passive_relationships.exists? || @options[:relayed_through_account]&.passive_relationships&.exists?
  end

  def requested_through_relay?
    @options[:relayed_through_account] && Relay.find_by(inbox_url: @options[:relayed_through_account].inbox_url)&.enabled?
  end

  def reject_payload!
    Rails.logger.info("Rejected #{@json['type']} activity #{@json['id']} from #{@account.uri}#{@options[:relayed_through_account] && "via #{@options[:relayed_through_account].uri}"}")
    nil
  end
end