Merge pull request #3183 from mozilla/add-experiments-support, r=@chenba

Connect with #3170

Unfortunately, I was not able to 100% move the base experiment in content-server over to our fxa-shared project. Please see the linked issue for the different things I tried.

To spare my sanity I opted to update the experiment file to typecript and pull over the same tests from content-server.

This should be enough for me to build out the experiment parts needed in the auth-server and finish #2595.

packages/fxa-shared/experiments/base.ts

@@ -0,0 +1,84 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import md5 = require('js-md5');
+
+class BaseGroupingRule {
+  public name: string = '';
+  public deprecated: boolean = false;
+
+  /**
+   * Return a 32 bit hash of `key`
+   *
+   * @param {String} key
+   * @returns {Number}
+   */
+  public hash(key: string): number {
+    // md5 returns 32 hex bytes, we want 32 bits. 32bits = 8 hex bytes.
+    const hash = md5(`${this.name}:${key}`).substr(0, 8);
+    return parseInt(hash, 16);
+  }
+
+  /**
+   * Return a number in the range [0,1], using `key` as a stable identifier.
+   * The same number is always returned for the same `key`.
+   *
+   * @param {String} key
+   * @returns {Number}
+   */
+  public luckyNumber(key: string): number {
+    // hash returns a 32 bit value, divide by 2^32 to
+    // ensure the number is between 0 and 1.
+    return this.hash(key) / 0xffffffff;
+  }
+
+  /**
+   * Decide membership in a trial using `key` as a stable identifier.
+   *
+   * @param {Number} percent in the range [0,1]
+   * @param {String} key
+   * @returns {Boolean}
+   */
+  public bernoulliTrial(percent: number, key: string): boolean {
+    return this.luckyNumber(key) <= percent;
+  }
+
+  /**
+   * Make a uniform choice amongst `choices` using `key` as a stable identifier.
+   *
+   * @param {String[]} choices
+   * @param {String} key
+   * @returns {String}
+   */
+  public uniformChoice(choices: string[], key: string): string {
+    return choices[this.hash(key) % choices.length];
+  }
+
+  /**
+   * Use `subject` data to make a choice.
+   *
+   * @param {Object} subject data used to decide
+   */
+  public choose(subject: object): string | boolean {
+    if (this.deprecated) {
+      throw new Error(`Experiment deprecated: ${this.name}`);
+    }
+    throw new Error('choose must be overridden');
+  }
+
+  /**
+   * Is this a test email?
+   *
+   * @param {String} email
+   * @returns {Boolean}
+   */
+  public isTestEmail(email: string): boolean {
+    return (
+      /.+@softvision\.(com|ro)$/.test(email) ||
+      /.+@mozilla\.(com|org)$/.test(email)
+    );
+  }
+}
+
+export default BaseGroupingRule;

packages/fxa-shared/package.json

@@ -46,16 +46,20 @@
     "tslint": "^5.18.0",
     "tslint-config-prettier": "^1.18.0",
     "tslint-plugin-prettier": "^2.0.1",
-    "typescript": "^3.5.3"
+    "typescript": "^3.5.3",
+    "underscore": "1.8.3",
+    "uuid": "^3.3.3"
   },
   "dependencies": {
+    "@types/js-md5": "^0.4.2",
     "accept-language": "^2.0.17",
     "ajv": "^6.10.2",
     "bluebird": "^3.5.5",
     "celebrate": "^10.0.1",
     "cors": "^2.8.5",
     "generic-pool": "^3.7.1",
     "joi": "^14.3.1",
+    "js-md5": "^0.7.3",
     "moment": "^2.24.0",
     "node-uap": "git://github.com/vladikoff/node-uap.git#9cdd16247",
     "redis": "^2.8.0"