Added @tryghost/domain-events package

refs https://github.com/TryGhost/Team/issues/1054

This package will be used as a singleton for listenig and sending events
throughout the members application.

ghost/domain-events/.eslintrc.js

@@ -0,0 +1,10 @@
+module.exports = {
+    parser: '@babel/eslint-parser',
+    parserOptions: {
+        requireConfigFile: false
+    },
+    plugins: ['ghost'],
+    extends: [
+        'plugin:ghost/node'
+    ]
+};

ghost/domain-events/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2013-2021 Ghost Foundation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

ghost/domain-events/README.md

@@ -0,0 +1,55 @@
+# Domain Events
+
+## Install
+
+`npm install @tryghost/domain-events --save`
+
+or
+
+`yarn add @tryghost/domain-events`
+
+
+## Usage
+
+```js
+const DomainEvents = require('@tryghost/domain-events');
+
+class MyEvent {
+    constructor(message) {
+        this.timestamp = new Date();
+        this.data = {
+            message
+        };
+    }
+}
+
+DomainEvents.subscribe(MyEvent, function handler(event) {
+    console.log(event.data.message);
+});
+
+const event = new MyEvent('hello world');
+
+DomainEvents.dispatch(event);
+```
+
+
+## Develop
+
+This is a mono repository, managed with [lerna](https://lernajs.io/).
+
+Follow the instructions for the top-level repo.
+1. `git clone` this repo & `cd` into it as usual
+2. Run `yarn` to install top-level dependencies.
+
+
+## Run
+
+- `yarn dev`
+
+
+## Test
+
+- `yarn lint` run just eslint
+- `yarn test` run lint and tests
+
+

ghost/domain-events/index.js

@@ -0,0 +1 @@
+module.exports = require('./lib/DomainEvents');

ghost/domain-events/jsconfig.json

@@ -0,0 +1,14 @@
+{
+  "include": [
+    "index.js",
+    "lib/**/*.js"
+  ],
+  "compilerOptions": {
+     "checkJs": true,
+     "module": "commonjs",
+     "target": "es2018",
+     "moduleResolution": "node",
+     "strictFunctionTypes": true,
+     "noImplicitAny": true
+  }
+}

ghost/domain-events/lib/DomainEvents.js

@@ -0,0 +1,44 @@
+const EventEmitter = require('events').EventEmitter;
+
+/**
+ * @template T
+ * @typedef {import('./').ConstructorOf<T>} ConstructorOf<T>
+ */
+
+/**
+ * @template Data
+ * @typedef {object} IEvent
+ * @prop {Date} timestamp
+ * @prop {Data} data
+ */
+
+class DomainEvents {
+    /**
+     * @private
+     * @type EventEmitter
+     */
+    static ee = new EventEmitter;
+
+    /**
+     * @template Data
+     * @template {IEvent<Data>} EventClass
+     * @param {ConstructorOf<EventClass>} Event
+     * @param {(event: EventClass) => void} handler
+     *
+     * @returns {void}
+     */
+    static subscribe(Event, handler) {
+        DomainEvents.ee.on(Event.name, handler);
+    }
+
+    /**
+     * @template Data
+     * @param {IEvent<Data>} event
+     * @returns {void}
+     */
+    static dispatch(event) {
+        DomainEvents.ee.emit(event.constructor.name, event);
+    }
+}
+
+module.exports = DomainEvents;

ghost/domain-events/lib/index.d.ts

@@ -0,0 +1 @@
+export declare type ConstructorOf<T> = new (...args: any[]) => T

ghost/domain-events/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "@tryghost/domain-events",
+  "version": "0.0.0",
+  "repository": "https://github.com/TryGhost/Members/tree/main/packages/domain-events",
+  "author": "Ghost Foundation",
+  "license": "MIT",
+  "main": "index.js",
+  "types": "types",
+  "scripts": {
+    "dev": "echo \"Implement me!\"",
+    "test": "NODE_ENV=testing c8 --check-coverage mocha './test/**/*.test.js'",
+    "lint": "eslint . --ext .js --cache",
+    "posttest": "yarn lint"
+  },
+  "files": [
+    "index.js",
+    "lib"
+  ],
+  "publishConfig": {
+    "access": "public"
+  },
+  "devDependencies": {
+    "@babel/eslint-parser": "^7.15.4",
+    "c8": "7.9.0",
+    "mocha": "9.1.1",
+    "should": "13.2.3",
+    "sinon": "11.1.2"
+  },
+  "dependencies": {}
+}

ghost/domain-events/test/.eslintrc.js

@@ -0,0 +1,6 @@
+module.exports = {
+    plugins: ['ghost'],
+    extends: [
+        'plugin:ghost/test'
+    ]
+};

ghost/domain-events/test/DomainEvents.test.js

@@ -0,0 +1,49 @@
+const should = require('should');
+const DomainEvents = require('../');
+
+class TestEvent {
+    /**
+     * @param {string} message
+     */
+    constructor(message) {
+        this.timestamp = new Date();
+        this.data = {
+            message
+        };
+    }
+}
+
+describe('DomainEvents', function () {
+    it('Will call multiple subscribers with the event when it is dispatched', function (done) {
+        const event = new TestEvent('Hello, world!');
+
+        let called = 0;
+
+        /**
+         * @param {TestEvent} receivedEvent
+         */
+        function handler1(receivedEvent) {
+            should.equal(receivedEvent, event);
+            called += 1;
+            if (called === 2) {
+                done();
+            }
+        }
+
+        /**
+         * @param {TestEvent} receivedEvent
+         */
+        function handler2(receivedEvent) {
+            should.equal(receivedEvent, event);
+            called += 1;
+            if (called === 2) {
+                done();
+            }
+        }
+
+        DomainEvents.subscribe(TestEvent, handler1);
+        DomainEvents.subscribe(TestEvent, handler2);
+
+        DomainEvents.dispatch(event);
+    });
+});