code-workshop-kit/src/middleware/change-participant-url-middleware.ts

The future of remote code workshops & training

import { Context, Next } from 'koa';
import { cwkState } from '../utils/CwkStateSingleton';
import { verifyJWT } from '../utils/verifyJWT';

export const changeParticipantUrlMiddleware =
  (dir: string) =>
  async (ctx: Context, next: Next): Promise<void> => {
    const fromIFrame = ctx.header['sec-fetch-dest'] === 'iframe';

    await next();

    if (ctx.status === 200 && ctx.response.is('html') && !fromIFrame) {
      const { state } = cwkState;
      const authToken = ctx.cookies.get('cwk_auth_token');

      if (authToken) {
        const authed = verifyJWT(dir, authToken, ctx);
        const followModeConnections = state.wsConnections && state.wsConnections['follow-mode'];

        if (
          authed &&
          typeof authed !== 'string' &&
          authed.username === cwkState.state.followModeInitiatedBy
        ) {
          if (
            state.adminConfig &&
            state.adminConfig.followMode &&
            state.wss &&
            state.wsConnections &&
            followModeConnections
          ) {
            // Send URL update message to all connections, which excludes follow mode initiator that changes the url
            // The websocket message is sent before the follow mode intiator has loaded the new page and established a new WS connection
            for (const entry of followModeConnections) {
              const [, connection] = entry;
              connection.send(
                JSON.stringify({
                  type: 'update-url',
                  data: ctx.url,
                  byAdmin: cwkState.state.followModeInitiatedBy,
                }),
              );
            }
          }
        }
      }
      state.previousAdminUrl = ctx.url;
      cwkState.state = state;
    }
  };