Revert "Fix"

This reverts commit 8afdb5ae.

src/server/activitypub/post.ts

 import * as express from 'express';
 import context from '../../remote/activitypub/renderer/context';
 import render from '../../remote/activitypub/renderer/note';
+import parseAcct from '../../acct/parse';
 import Post from '../../models/post';
 import User from '../../models/user';
 
 const app = express();
 app.disable('x-powered-by');
 
-app.get('/posts/:post', async (req, res, next) => {
+app.get('/@:user/:post', async (req, res, next) => {
 	const accepted = req.accepts(['html', 'application/activity+json', 'application/ld+json']);
 	if (!(['application/activity+json', 'application/ld+json'] as any[]).includes(accepted)) {
 		return next();
 	}
 
-	const post = await Post.findOne({
-		_id: req.params.post
-	});
-	if (post === null) {
-		return res.sendStatus(404);
+	const { username, host } = parseAcct(req.params.user);
+	if (host !== null) {
+		return res.sendStatus(422);
 	}
 
 	const user = await User.findOne({
-		_id: post.userId
+		usernameLower: username.toLowerCase(),
+		host: null
 	});
 	if (user === null) {
 		return res.sendStatus(404);
 	}
 
+	const post = await Post.findOne({
+		_id: req.params.post,
+		userId: user._id
+	});
+	if (post === null) {
+		return res.sendStatus(404);
+	}
+
 	const rendered = await render(user, post);
 	rendered['@context'] = context;