Added support for AMP linker

README.md

@@ -234,13 +234,14 @@ For the above URL, the below SDK calls will be triggered:
 rudderanalytics.identify("12345", {name: "Firstname Lastname"});
 rudderanalytics.track("test event", {testProp: "prop1"});
 rudderanalytics.setAnonymousId("abcde");
+rudderanalytics.setAnonymousId(null, "<version>*<checkSum>*<idName1>*<idValue1>*<idName2>*<idValue2>...");
 ```
 
 You may use the below parameters as querystring parameter and trigger the corresponding call.
 
 `ajs_uid` 		: Makes a `rudderanalytics.identify()` call with `userId` having the value of the parameter value.
 
-`ajs_aid` 		: Makes a `rudderanalytics.setAnonymousId()` call with `anonymousId` having the value of the parameter value.
+`ajs_aid` 		: Makes a `rudderanalytics.setAnonymousId()` call with `anonymousId` having the value of the parameter value or call with `rudderAmpLinkerParm` having the value of `rudderstack` from the query param.
 
 `ajs_event`		: Makes a `rudderanalytics.track()` call with `event` name as parameter value.
 

analytics.js

@@ -37,6 +37,7 @@ import { EventRepository } from "./utils/EventRepository";
 import logger from "./utils/logUtil";
 import { addDomEventHandlers } from "./utils/autotrack.js";
 import ScriptLoader from "./integrations/ScriptLoader";
+import parseLinker from "./utils/linker";
 
 const queryDefaults = {
   trait: "ajs_trait_",
@@ -827,9 +828,20 @@ class Analytics {
     return this.anonymousId;
   }
 
-  setAnonymousId(anonymousId) {
+  /**
+   * Sets anonymous id in the followin precedence:
+   * 1. anonymousId: Id directly provided to the function.
+   * 2. rudderAmpLinkerParm: value generated from linker query parm (rudderstack)
+   *    using praseLinker util.
+   * 3. generateUUID: A new uniquie id is generated and assigned.
+   * 
+   * @param {string} anonymousId 
+   * @param {string} rudderAmpLinkerParm 
+   */
+  setAnonymousId(anonymousId, rudderAmpLinkerParm) {
     // if (!this.loaded) return;
-    this.anonymousId = anonymousId || generateUUID();
+    const parsedAnonymousId = rudderAmpLinkerParm ? parseLinker(rudderAmpLinkerParm) : null;
+    this.anonymousId = anonymousId || parsedAnonymousId || generateUUID();
     this.storage.setAnonymousId(this.anonymousId);
   }
 

utils/linker/base64decoder.js

@@ -0,0 +1,26 @@
+/**
+ * @description This is utility function for decoding from base 64 to utf8
+ * @version v1.0.0 
+ */
+
+ /**
+  * @param {string} str base64
+  * @returns {string} utf8 
+  */
+function b64DecodeUnicode(str) {
+  // Going backwards: from bytestream, to percent-encoding, to original string.
+  return decodeURIComponent(atob(str).split('').map(function (c) {
+    return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
+  }).join(''));
+}
+
+/**
+ * @param {string} value
+ * @return {string}
+ */
+function decode(data = "") {
+  data = data.endsWith("..") ? data.substr(0, data.length - 2) : data;
+  return b64DecodeUnicode(data);
+}
+
+export default decode

utils/linker/crc32.js

@@ -0,0 +1,42 @@
+/**
+ * @description This is utility function for crc32 algorithm
+ * @version v1.0.0 
+ */
+
+/**
+ * @description generate crc table
+ * @params none
+ * @returns arrray of CRC table
+ */
+
+const makeCRCTable = function () {
+  const crcTable = []
+  let c
+  for (var n = 0; n < 256; n++) {
+    c = n
+    for (var k = 0; k < 8; k++) {
+      c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1
+    }
+    crcTable[n] = c
+  }
+  return crcTable
+}
+
+
+/**
+ * 
+ * @param {string} str
+ * @returns {Bystream} crc32
+ */
+const crc32 = function (str) {
+  const crcTable = makeCRCTable()
+  let crc = 0 ^ -1
+
+  for (let i = 0; i < str.length; i++) {
+    crc = (crc >>> 8) ^ crcTable[(crc ^ str.charCodeAt(i)) & 0xff]
+  }
+
+  return (crc ^ -1) >>> 0
+}
+
+export default crc32

utils/linker/index.js

@@ -4,9 +4,9 @@
  * @author Parth Mahajan, Ayush Mehra
  */
 
-import crc32 from "./utils/crc32";
-import USER_INTERFACE from "./utils/userLib";
-import decode from "./utils/base64decoder";
+import crc32 from "./crc32";
+import USER_INTERFACE from "./userLib";
+import decode from "./base64decoder";
 
 const KEY_VALIDATOR = /^[a-zA-Z0-9\-_.]+$/;
 const CHECKSUM_OFFSET_MAX_MIN = 1;

utils/linker/userLib.js

@@ -0,0 +1,20 @@
+/**
+ * @description An interface to fetch user device details.
+ * @version v1.0.0
+ */
+
+const USER_INTERFACE = {
+  /**
+   * @param {*} req
+   * @returns {string} user language
+   */
+  getUserLanguage: () => navigator && navigator.language,
+
+  /** 
+   * @param {*} req 
+   * @returns {string} userAgent
+   */
+  getUserAgent:  () => navigator && navigator.userAgent
+}
+
+export default USER_INTERFACE;