feat: Add StepHistory class

docs/account.md

@@ -3,7 +3,7 @@
 User account related utilities that also interact with stored config file. Several methods depend on `sdk` parameter, which should be provided as an instance of `ServerlessSDK` from `@serverless/platform-client` library.
 
 ```javascript
-const accountUtils = require('@serverless/utils/account);
+const accountUtils = require('@serverless/utils/account');
 ```
 
 Exposes following _async_ methods:

docs/telemetry.md

@@ -0,0 +1,11 @@
+## Utilities related to telemetry
+
+```javascript
+const telemetryUtils = require('@serverless/utils/telemetry');
+```
+
+Exposes following classes and methods:
+
+### `StepHistory`
+
+Helper class for recording step history for recording telemetry steps in Interactive CLI flow. It extends `Map` class by adding `timestamp` and wrapping value in an object with timestamp and offers `toJSON` method that formats map into JSON-serializable object, as well as `valuesMap` that returns `Map` object that maps original keys to provided `value`. It also offers `valuesMap` method, which just returns regular `Map` without `timestamp`.

telemetry.js

@@ -0,0 +1,23 @@
+'use strict';
+
+class StepHistory extends Map {
+  set(key, value) {
+    const valueWithTimestamp = {
+      value,
+      timestamp: Date.now(),
+    };
+    return super.set(key, valueWithTimestamp);
+  }
+
+  valuesMap() {
+    return new Map(Array.from(this.entries()).map(([key, obj]) => [key, obj.value]));
+  }
+
+  toJSON() {
+    return Array.from(this.entries()).map(([key, obj]) => ({ key, ...obj }));
+  }
+}
+
+module.exports = {
+  StepHistory,
+};

test/telemetry.js

@@ -0,0 +1,28 @@
+'use strict';
+const telemetry = require('../telemetry');
+const expect = require('chai').expect;
+
+describe('telemetry', () => {
+  describe('StepHistory', () => {
+    it('stores values within object with a timestamp', () => {
+      const history = new telemetry.StepHistory();
+      history.set('key', 'val');
+      expect(history.get('key').value).to.equal('val');
+      expect(history.get('key')).to.have.property('timestamp');
+    });
+
+    it('supports `toJSON` method', () => {
+      const history = new telemetry.StepHistory([['key', 'val']]);
+      const result = history.toJSON();
+      expect(result).to.have.lengthOf(1);
+      expect(result[0].key).to.equal('key');
+      expect(result[0].value).to.equal('val');
+      expect(result[0]).to.have.property('timestamp');
+    });
+
+    it('supports `valuesMap` method', () => {
+      const history = new telemetry.StepHistory([['key', 'val']]);
+      expect(history.valuesMap()).to.deep.equal(new Map([['key', 'val']]));
+    });
+  });
+});