#81 Add utility function to get a string-formatted list of users

src/activity/activity.service.test.ts

@@ -0,0 +1,35 @@
+import { UnhandledError } from '../util/common.errors';
+import { ActivityService } from './activity.service';
+
+const sut = new ActivityService();
+describe('activity', () => {
+  describe('activity.service', () => {
+    describe('userListToString', () => {
+      it('must throw an error if the user list is empty', () => {
+        expect(() => sut.userListToString([])).toThrow(UnhandledError);
+      });
+      it('must just return the name or email of a single user', () => {
+        expect(sut.userListToString([{ name: 'John', email: '[email protected]' }])).toEqual('John');
+        expect(sut.userListToString([{ email: '[email protected]' }])).toEqual('[email protected]');
+      });
+      it('must return names separated by & for two users', () => {
+        expect(
+          sut.userListToString([
+            { name: 'Jack', email: '[email protected]' },
+            { name: 'Jill', email: '[email protected]' },
+          ]),
+        ).toEqual('Jack & Jill');
+      });
+      it('must return names separated by commas and & for three or more users', () => {
+        expect(
+          sut.userListToString([
+            { name: 'Jack', email: '[email protected]' },
+            { name: 'Jill', email: '[email protected]' },
+            { name: 'Bob', email: '[email protected]' },
+            { email: '[email protected]' },
+          ]),
+        ).toEqual('Jack, Jill, Bob & [email protected]');
+      });
+    });
+  });
+});

src/activity/activity.service.ts

@@ -0,0 +1,32 @@
+import { UnhandledError } from '../util/common.errors';
+
+export interface RecentActivityItem {
+  text: string;
+  action?: {
+    name: string;
+    link: string;
+  };
+}
+
+export class ActivityService {
+  /**
+   * Get a formatted string list of users.
+   * @param users List of userlike objects (contain and email and optionally a name)
+   * @returns A formatted string list of users.
+   */
+  userListToString(
+    users: {
+      name?: string;
+      email: string;
+    }[],
+  ) {
+    if (users.length === 0) {
+      throw new UnhandledError('Cannot format an empty user list');
+    }
+    const names = users.map((user) => user.name ?? user.email);
+    if (names.length === 1) {
+      return names[0];
+    }
+    return `${names.slice(0, -1).join(', ')} & ${names[names.length - 1]}`;
+  }
+}

src/util/common.errors.ts

@@ -0,0 +1 @@
+export class UnhandledError extends Error {}