main.js

/**
 *    Copyright 2022, Optimizely and contributors
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

import { logger } from 'log';
import { Cookies, SetCookie } from 'cookies';
import {
  createInstance,
  enums as OptimizelyEnums,
} from '@optimizely/optimizely-sdk/dist/optimizely.lite.es';

import { getDatafile, dispatchEvent } from './optimizely_helper';

// Important: crypto and TextEncoder are not available globally in Akamai EdgeWorkers.
// We need to import them and set them as globalThis to make them available in the worker to get the SDK working.
import { crypto } from 'crypto'
import { TextEncoder} from 'encoding'

globalThis.crypto = crypto
globalThis.TextEncoder = TextEncoder

const AKAMAI_CLIENT_ENGINE = "javascript-sdk/akamai-edgeworker";
const COOKIE_NAME_OPTIMIZELY_VISITOR_ID = 'optimizely_visitor_id';
const VARIABLE_NAME_USER_ID = "PMUSER_OPTIMIZELY_USER_ID";
const VARIABLE_NAME_DECISION_EVENT = "PMUSER_OPTIMIZELY_DECISION_EVENT"; 

const SHOULD_DISPATCH_EVENT = false;

let logStash = [];

/** 
 * Generates a unique 16 digit user id for demo purpose. For production use, please use user Ids from your system
 * or autogenerate a uuid using a standard library such as https://www.npmjs.com/package/uuid.
 * 
 * Attribution:
 * This unique id generation function was taken from a Stack Overflow question and modified to fit our use case.
 * https://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid
 * This is the answer that was used
 * https://stackoverflow.com/a/21963136
 * Question by Jason Cohen:
 * https://stackoverflow.com/users/4926/jason-cohen
 * Answer by Jeff Ward:
 * https://stackoverflow.com/users/1026023/jeff-ward
 */
 var lut = []; for (var i=0; i<256; i++) { lut[i] = (i<16?'0':'')+(i).toString(16); }
 export function generateRandomUserId() {
   var d0 = Math.random()*0xffffffff|0;
   var d1 = Math.random()*0xffffffff|0;
   return lut[d0&0xff]+lut[d0>>8&0xff]+'-'+lut[d0>>16&0xff]+lut[d0>>24&0xff]+'-'+
   lut[d1&0xff]+lut[d1>>8&0xff]+'-'+lut[d1>>16&0x0f|0x40]+lut[d1>>24&0xff];
 }

// Helper function to log to the debug logger and print to the response body.
function logAndPrint(message) {
  logStash.push(message);
  logger.log(message);
};

/**
 * 1. Fetch the optimizely datafile based on the given sdk key.
 * 2. Read the user id from the cookie if available to enable sticky bucketing or generate a new one to be saved to the cookie.
 * 3. Create an optimizely instance.
 * 4. Access optimizelyConfig object and print datafile revision number.
 * 5. Get a decision for a specific flag and dispatch logx event.
 * 6. Get decisions for all the available flags.
 */
export async function onClientRequest (request) {
  logStash = [];
  let cookies = new Cookies(request.getHeader('Cookie'));

  // Fetch user Id from the cookie if available to make sure that a returning user from same browser session always sees the same variation.
  const userId = cookies.get(COOKIE_NAME_OPTIMIZELY_VISITOR_ID) || generateRandomUserId();
  
  // onClientRequest handler does not allow setting the cookie. Saving the user id in a variable
  // to be retrieved and set when onClientResponse handler is executed later on. 
  request.setVariable(VARIABLE_NAME_USER_ID, userId);

  // Add your SDK here.
  const datafile = await getDatafile("YOUR_SDK_KEY_HERE");

  if (datafile === '') {
    logAndPrint(`[optimizely] Failed to fetch the datafile, please check the optimizely sdk key`);
    sendGenericReponse(request, logStash);
    return;    
  }

  // Creating an optimizely SDK instance.
  const optimizelyClient = createInstance({
    datafile,

    // keep the LOG_LEVEL to ERROR in production. Setting LOG_LEVEL to INFO or DEBUG can adversely impact performance.
    logLevel: OptimizelyEnums.LOG_LEVEL.ERROR,

    clientEngine: AKAMAI_CLIENT_ENGINE,

    /* Add other Optimizely SDK initialization options here if needed */
  });
 
  const optimizelyUserContext = optimizelyClient.createUserContext(
    userId,
    {
      /* YOUR_OPTIONAL_ATTRIBUTES_HERE */
    }
  );

  if (SHOULD_DISPATCH_EVENT) {
    logAndPrint('[optimizely] Adding a Notification Listener to Capture Event Payload');
    
    // The default event dispatching mechanism of optimizely SDK does not work with Akamai edgeworker because it does not support
    // sending out more than one http sub request in onClientRequest handler. Optimizely SDK lets you add a notification listener
    // that can notify when an event is logged. This peice of code is capturing the event payload and storing it in to akamai variable
    // which will be later used in onClientResponse handler to dispatch the event to optimizely logx backend.
    optimizelyClient.notificationCenter.addNotificationListener(OptimizelyEnums.NOTIFICATION_TYPES.LOG_EVENT, ({ params }) => {
      // Set event payload in Akamai variable.
      request.setVariable(VARIABLE_NAME_DECISION_EVENT, JSON.stringify(params));
    });
  }

  // --- Using Optimizely Config
  const optimizelyConfig = optimizelyClient.getOptimizelyConfig();
  logAndPrint(`[optimizely] Datafile Revision: ${optimizelyConfig.revision}`);

  // --- For a single flag --- //
  const decision = optimizelyUserContext.decide("YOUR_FLAG_HERE");
  if (decision.enabled) {
    logAndPrint(
      `[optimizely] The Flag ${
        decision.flagKey
      } was Enabled for the user ${decision.userContext.getUserId()}`
    );
  } else {
    logAndPrint(
      `[optimizely] The Flag ${
        decision.flagKey
      } was Not Enabled for the user ${decision.userContext.getUserId()}`
    );
  }

  // Clearing notification listener so that it does not call the hanlder above for all other decisions.
  optimizelyClient.notificationCenter.clearNotificationListeners(OptimizelyEnums.NOTIFICATION_TYPES.LOG_EVENT);

  // --- For all flags --- //
  const allDecisions = optimizelyUserContext.decideAll();
  Object.entries(allDecisions).forEach(([flagKey, decision]) => {
    if (decision.enabled) {
      logAndPrint(
        `[optimizely] The Flag ${
          decision.flagKey
        } was Enabled for the user ${decision.userContext.getUserId()}`
      );
    } else {
      logAndPrint(
        `[optimizely] The Flag ${
          decision.flagKey
        } was Not Enabled for the user ${decision.userContext.getUserId()}`
      );
    }
  });

  sendGenericReponse(request, logStash);
}

/** 
 * 1. onClientRequest handler does not allow setting the cookie. We are saving the cookie in a variable and then settig it here.
 * 2. onClientRequest handler does not allow more than one http subrequests. We are dispatching the optimizely logx event from here.
 */
export async function onClientResponse (request, response) {
  const userId = request.getVariable(VARIABLE_NAME_USER_ID);
  if (SHOULD_DISPATCH_EVENT) {
    const eventPayload = request.getVariable(VARIABLE_NAME_DECISION_EVENT);
    if (eventPayload) {
      const eventResponseStatus = await dispatchEvent(eventPayload);
      logger.log(`[optimizely] Optimizely Logx Event dispatched. Response status code: ${eventResponseStatus}`);
    }
  }
  const cookie = new SetCookie({
    name: COOKIE_NAME_OPTIMIZELY_VISITOR_ID,
    value: userId,
  });
  response.setHeader('Set-Cookie', cookie.toHeader());
}

function sendGenericReponse(request, logStash) {
  request.respondWith(
    200,
    {"Content-Type": "text/plain"},
    'Welcome to the Optimizely Starter Kit for Akamai Edge Workers. Check log messages in response headers for decision results.\n\n'
    + 'Log Messages:\n' + logStash.join('\n'),
  );
}