Mail the author, without naming a provider

We mail the author without naming a provider. The handler asks for a mailer, and a class that extends it is enough to provide one.

fronds/blog/handlers/PostHandler.ts
1import { ErrorCode, FougereError, Repository } from '@fougere/core';
2import Post from '../entities/Post.js';
+import Mailer from '../services/Mailer.js';
4 
5export default class PostHandler extends Repository<Post> {
+  constructor(private mailer: Mailer) {
+    super();
+  }
+ 
10  async publish(id: Post['id']): Promise<Post> {
11    const post = await this.findById(id);
12    if (!post) throw new FougereError({ code: ErrorCode.NOT_FOUND, message: 'No such post' });
13    if (post.status === 'published') throw new FougereError({ code: ErrorCode.CONFLICT, message: 'Already published' });
14 
+    await this.mailer.send(`Published: ${post.title}`);
+ 
17    return this.update(id, { status: 'published' });
18  }
19}

point at a lettered line, or tap it, to see what grows from it

The handler names the capability; the config, if ever needed, names who answers.

Try it

$ curl -X POST localhost:4100/api/blog/posts/$ID/publish
mail: Published: Hi

Add FakeMailer extends Mailer and the app refuses to start, naming both classes and the line that settles it: ports: { Mailer: '…' }.

In the docsPort