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: / var / canvas / lib / lti / messages /
Filename : resource_link_request.rb
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# frozen_string_literal: true

#
# Copyright (C) 2018 - present 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/>.

module Lti::Messages
  # A "factory" class that builds an ID Token (JWT) to be used in LTI Advantage
  # LTI Resource Link Requests (a.k.a standard LTI 1.3 tool launches).
  #
  # This class relies on a another class (LtiAdvantage::Messages::ResourceLinkRequest)
  # to model the data in the JWT body and produce a signature.
  #
  # For details on the data included in the ID token please refer
  # to http://www.imsglobal.org/spec/lti/v1p3/.
  #
  # For implementation details on LTI Advantage launches in
  # Canvas, please see the inline documentation of
  # app/models/lti/lti_advantage_adapter.rb.
  class ResourceLinkRequest < JwtMessage
    def initialize(tool:, context:, user:, expander:, return_url:, opts: {})
      super
      @message = LtiAdvantage::Messages::ResourceLinkRequest.new
    end

    def generate_post_payload_message(validate_launch: true)
      add_resource_link_request_claims! if include_claims?(:rlid)
      add_line_item_url_to_ags_claim! if include_assignment_and_grade_service_claims?
      super
    end

    def generate_post_payload_for_assignment(assignment, _outcome_service_url, _legacy_outcome_service_url, _lti_turnitin_outcomes_placement_url)
      @assignment = assignment
      to_cached_hash
    end

    def generate_post_payload_for_homework_submission(assignment)
      @assignment = assignment
      to_cached_hash
    end

    private

    def tag_from_resource_link
      ContentTag.find_by(associated_asset: resource_link) if resource_link
    end

    def add_resource_link_request_claims!
      @message.resource_link.id = launch_resource_link_id
      @message.resource_link.description = @assignment&.description
      @message.resource_link.title = @assignment&.title.presence || resource_link&.title.presence || tag_from_resource_link&.title.presence || @context.name
    end

    def add_lti1p1_claims!
      @message.lti1p1.resource_link_id = resource_link&.lti_1_1_id if include_lti1p1_resource_link_id_migration?
      super
    end

    def include_lti1p1_claims?
      super || include_lti1p1_resource_link_id_migration?
    end

    # @see https://www.imsglobal.org/spec/lti/v1p3/migr#remapping-parameters for more info on LTI 1.1 -> 1.3 migration
    # parameters
    def include_lti1p1_resource_link_id_migration?
      launch_resource_link_id != resource_link&.lti_1_1_id && resource_link&.lti_1_1_id.present?
    end

    # whenever possible, use the correct resource link id whether that comes from
    # the associated assignment or from the request parameters. fall back to the
    # context rlid only if needed
    def launch_resource_link_id
      resource_link&.resource_link_uuid || Lti::Asset.opaque_identifier_for(@context)
    end

    def unexpanded_custom_parameters
      # Add in link-specific custom params (e.g. created by deep linking)
      super.merge!(resource_link&.custom || {})
    end

    def resource_link
      assignment_resource_link || @opts[:resource_link]
    end

    def assignment_resource_link
      return if @assignment.nil?

      unless defined?(@assignment_resource_link)
        launch_error = Lti::IMS::AdvantageErrors::InvalidLaunchError
        unless @assignment.external_tool?
          raise launch_error.new(nil, api_message: "Assignment not configured for external tool launches")
        end
        unless ContextExternalTool.from_assignment(@assignment) == @tool
          raise launch_error.new(nil, api_message: "Assignment not configured for launches with specified tool")
        end

        @assignment_resource_link = line_item_for_assignment&.resource_link
      end

      @assignment_resource_link
    end

    def line_item_for_assignment
      @line_item_for_assignment ||= @assignment&.line_items&.find(&:assignment_line_item?)
    end

    # follows the spec at https://www.imsglobal.org/spec/lti-ags/v2p0/#assignment-and-grade-service-claim
    # and only adds the 'lineitem' property "when the LTI message is launching a resource associated
    # to one and only one line item"
    def add_line_item_url_to_ags_claim!
      return if line_item_for_assignment.blank?

      @message.assignment_and_grade_service.lineitem =
        @expander.controller.lti_line_item_show_url(
          host: @context.root_account.environment_specific_domain,
          course_id: course_id_for_ags_url,
          id: line_item_for_assignment.id
        )
    end
  end
end