Returning to platform...

import { SignJWT } from 'jose'; import type { BaseLogger } from 'pino'; import type { LTISession } from '../interfaces/ltiSession.js'; import type { DeepLinkingContentItem } from '../schemas/lti13/deepLinking/contentItem.schema.js'; import { escapeHtml } from '../utils/htmlEscaping.js'; /** * Deep Linking service for LTI 1.3. * Generates signed JWT responses containing selected content items to return to the platform. * * @see https://www.imsglobal.org/spec/lti-dl/v2p0 */ export class DeepLinkingService { /** * Creates a new DeepLinkingService instance. * * @param keyPair - RSA key pair for signing client assertion JWTs (must be RS256 compatible) * @param logger - Logger instance for debug and error logging * @param keyId - Key identifier for JWT header, should match JWKS key ID (defaults to 'main') */ constructor( private keyPair: CryptoKeyPair, private logger: BaseLogger, private keyId = 'main', ) {} /** * Creates a Deep Linking response with selected content items. * Generates a signed JWT and returns an HTML form that auto-submits to the platform. * * @param session - Active LTI session containing Deep Linking configuration * @param contentItems - Array of content items selected by the user * @returns Promise resolving to an HTML string containing auto-submit form * @throws {Error} When Deep Linking is not available for the session * * @example * ```typescript * const html = await deepLinkingService.createResponse(session, [ * { * type: 'ltiResourceLink', * title: 'Quiz 1', * url: 'https://tool.example.com/quiz/1' * } * ]); * // Returns HTML form that auto-submits to platform * ``` */ async createResponse( session: LTISession, contentItems: DeepLinkingContentItem[], ): Promise { if (!session.services?.deepLinking) { throw new Error('Deep Linking not available for this session'); } this.logger.debug( { contentItemCount: contentItems.length, returnUrl: session.services.deepLinking.returnUrl, }, 'Creating Deep Linking response', ); const jwt = await this.createDeepLinkingJWT(session, contentItems); return this.generateAutoSubmitForm(session.services.deepLinking.returnUrl, jwt); } /** * Creates a signed JWT containing the Deep Linking response payload. * * @param session - Active LTI session with Deep Linking configuration * @param contentItems - Array of selected content items * @returns Promise resolving to a signed JWT string */ private async createDeepLinkingJWT( session: LTISession, contentItems: DeepLinkingContentItem[], ): Promise { const deepLinking = session.services!.deepLinking!; const payload = { iss: session.platform.clientId, aud: session.platform.issuer, exp: Math.floor(Date.now() / 1000) + 600, iat: Math.floor(Date.now() / 1000), nonce: crypto.randomUUID(), 'https://purl.imsglobal.org/spec/lti/claim/message_type': 'LtiDeepLinkingResponse', 'https://purl.imsglobal.org/spec/lti/claim/version': '1.3.0', 'https://purl.imsglobal.org/spec/lti/claim/deployment_id': session.platform.deploymentId, 'https://purl.imsglobal.org/spec/lti-dl/claim/content_items': contentItems, 'https://purl.imsglobal.org/spec/lti-dl/claim/data': deepLinking.data, }; return await new SignJWT(payload) .setProtectedHeader({ alg: 'RS256', typ: 'JWT', kid: this.keyId, }) .sign(this.keyPair.privateKey); } /** * Generates an HTML form that auto-submits the Deep Linking response to the platform. * * @param returnUrl - Platform's Deep Linking return URL * @param jwt - Signed JWT containing the response * @returns HTML string with auto-submit form */ private generateAutoSubmitForm(returnUrl: string, jwt: string): string { return ` Returning to platform... `; } }