mastodon/app/services/resolve_url_service.rb

# frozen_string_literal: true

class ResolveURLService < BaseService
  include JsonLdHelper
  include Authorization

  USERNAME_STATUS_RE = %r{/@(?<username>#{Account::USERNAME_RE})/(?<status_id>[0-9]+)\Z}

  def call(url, on_behalf_of: nil)
    @url          = url
    @on_behalf_of = on_behalf_of

    if local_url?
      process_local_url
    elsif !fetched_resource.nil?
      process_url
    else
      process_url_from_db
    end
  end

  private

  def process_url
    if equals_or_includes_any?(type, ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES)
      ActivityPub::FetchRemoteActorService.new.call(resource_url, prefetched_body: body)
    elsif equals_or_includes_any?(type, ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
      status = FetchRemoteStatusService.new.call(resource_url, prefetched_body: body)
      authorize_with @on_behalf_of, status, :show? unless status.nil?
      status
    end
  end

  def process_url_from_db
    if [500, 502, 503, 504, nil].include?(fetch_resource_service.response_code)
      account = Account.find_by(uri: @url)
      return account unless account.nil?
    end

    return unless @on_behalf_of.present? && [401, 403, 404].include?(fetch_resource_service.response_code)

    # It may happen that the resource is a private toot, and thus not fetchable,
    # but we can return the toot if we already know about it.
    scope = Status.where(uri: @url)

    # We don't have an index on `url`, so try guessing the `uri` from `url`
    parsed_url = Addressable::URI.parse(@url)
    parsed_url.path.match(USERNAME_STATUS_RE) do |matched|
      parsed_url.path = "/users/#{matched[:username]}/statuses/#{matched[:status_id]}"
      scope = scope.or(Status.where(uri: parsed_url.to_s, url: @url))
    end

    status = scope.first

    authorize_with @on_behalf_of, status, :show? unless status.nil?
    status
  rescue Mastodon::NotPermittedError
    nil
  end

  def fetched_resource
    @fetched_resource ||= fetch_resource_service.call(@url)
  end

  def fetch_resource_service
    @_fetch_resource_service ||= FetchResourceService.new
  end

  def resource_url
    fetched_resource.first
  end

  def body
    fetched_resource.second[:prefetched_body]
  end

  def type
    json_data['type']
  end

  def json_data
    @json_data ||= body_to_json(body)
  end

  def local_url?
    TagManager.instance.local_url?(@url)
  end

  def process_local_url
    recognized_params = Rails.application.routes.recognize_path(@url)

    case recognized_params[:controller]
    when 'statuses'
      return unless recognized_params[:action] == 'show'

      status = Status.find_by(id: recognized_params[:id])
      check_local_status(status)
    when 'accounts'
      return unless recognized_params[:action] == 'show'

      Account.find_local(recognized_params[:username])
    when 'home'
      return unless recognized_params[:action] == 'index' && recognized_params[:username_with_domain].present?

      if recognized_params[:any]&.match?(/\A[0-9]+\Z/)
        status = Status.find_by(id: recognized_params[:any])
        check_local_status(status)
      elsif recognized_params[:any].blank?
        username, domain = recognized_params[:username_with_domain].gsub(/\A@/, '').split('@')
        return unless username.present? && domain.present?

        Account.find_remote(username, domain)
      end
    end
  end

  def check_local_status(status)
    return if status.nil?

    authorize_with @on_behalf_of, status, :show?
    status
  rescue Mastodon::NotPermittedError
    nil
  end
end