refactor(media-apis): Implement a decorator to convert header to Note instance

Just find the related note in an Interceptor (in both public and private routes)

Related issue: https://github.com/hedgedoc/hedgedoc/issues/1594

Signed-off-by: Lautaro Alvarez <lautarolalvarez@gmail.com>
Signed-off-by: David Mehren <git@herrmehren.de>

src/api/utils/note-header.interceptor.ts

@@ -0,0 +1,37 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import {
+  CallHandler,
+  ExecutionContext,
+  Injectable,
+  NestInterceptor,
+} from '@nestjs/common';
+import { Request } from 'express';
+import { Observable } from 'rxjs';
+
+import { Note } from '../../notes/note.entity';
+import { NotesService } from '../../notes/notes.service';
+
+/**
+ * Saves the note identified by the `HedgeDoc-Note` header
+ * under the `note` property of the request object.
+ */
+@Injectable()
+export class NoteHeaderInterceptor implements NestInterceptor {
+  constructor(private noteService: NotesService) {}
+
+  async intercept<T>(
+    context: ExecutionContext,
+    next: CallHandler,
+  ): Promise<Observable<T>> {
+    const request: Request & {
+      note: Note;
+    } = context.switchToHttp().getRequest();
+    const noteId: string = request.headers['hedgedoc-note'] as string;
+    request.note = await this.noteService.getNoteByIdOrAlias(noteId);
+    return next.handle();
+  }
+}