@atomicjolt/lti-client/src/libs/capabilities.ts

Client Javascript libraries to handle LTI.

import i18next from "i18next";
import { Capability } from "../types";

export function getCapabilities(): Promise<Capability[]> {
  return new Promise((resolve, reject) => {
    let parent = window.parent || window.opener;

    const timeout = setTimeout(() => {
      console.log(i18next.t("capabilities request timeout"));
      reject(
        new Error(i18next.t("Timeout while waiting for capabilities response"))
      );
    }, 1000);

    const receiveMessage = (event: MessageEvent) => {
      if (
        typeof event.data === "object" &&
        event.data.subject === "lti.capabilities.response" &&
        event.data.message_id === "aj-lti-caps"
      ) {
        removeEventListener("message", receiveMessage);
        clearTimeout(timeout);

        if (event.data.error) {
          // handle errors
          console.error(event.data.error.code);
          console.error(event.data.error.message);
          reject(new Error(event.data.errormessage));
          return;
        }
        resolve(event.data.supported_messages);
      }
    };

    window.addEventListener("message", receiveMessage);
    parent.postMessage(
      {
        subject: "lti.capabilities",
        message_id: "aj-lti-caps",
      },
      "*"
    );
    // Platform will post a message back or we'll timeout
  });
}

export async function getCapability(
  subject: String
): Promise<Capability | null> {
  const caps = await getCapabilities();
  if (caps) {
    return caps.find((element) => element.subject == subject) || null;
  }
  return null;
}