make webfinger server stuff more readable

(Johann150 yells at cloud)

packages/backend/src/server/well-known.ts

@@ -80,33 +80,50 @@ router.get('/.well-known/oauth-authorization-server', oauth);
 router.get('/.well-known/openid-configuration', oauth);
 
 router.get(webFingerPath, async ctx => {
-	const fromId = (id: User['id']): FindOptionsWhere<User> => ({
-		id,
-		host: IsNull(),
-		isSuspended: false,
-	});
+	const fromAcct = (acct_str: string): FindOptionsWhere<User> | number => {
+		const acct = Acct.parse(acct_str);
+		if (!acct.host || acct.host === config.host.toLowerCase()) {
+			return {
+				usernameLower: acct.username,
+				host: IsNull(),
+				isSuspended: false,
+			};
+		} else {
+			return 422;
+		}
+	};
 
-	const generateQuery = (resource: string): FindOptionsWhere<User> | number =>
-		resource.startsWith(`${config.url.toLowerCase()}/users/`) ?
-			fromId(resource.split('/').pop()!) :
-			fromAcct(Acct.parse(
-				resource.startsWith(`${config.url.toLowerCase()}/@`) ? resource.split('/').pop()! :
-				resource.startsWith('acct:') ? resource.slice('acct:'.length) :
-				resource));
+	const generateQuery = (resource: string): FindOptionsWhere<User> | number => {
+		if (resource.startsWith(`${config.url.toLowerCase()}/users/`)) {
+			return {
+				id: resource.split('/').pop()!,
+				host: IsNull(),
+				isSuspended: false,
+			};
+		} else if (resource.startsWith(`${config.url.toLowerCase()}/@`)) {
+			return fromAcct(resource.split('/').pop()!);
+		} else if (resource.startsWith("acct:")) {
+			return fromAcct(resource.slice('acct:'.length));
+		}
+		return fromAcct(resource);
+	};
 
-	const fromAcct = (acct: Acct.Acct): FindOptionsWhere<User> | number =>
-		!acct.host || acct.host === config.host.toLowerCase() ? {
-			usernameLower: acct.username,
-			host: IsNull(),
-			isSuspended: false,
-		} : 422;
+	let resource = ctx.query.resource;
 
-	if (typeof ctx.query.resource !== 'string') {
+	if (typeof resource !== 'string') {
 		ctx.status = 400;
 		return;
 	}
 
-	const query = generateQuery(ctx.query.resource.toLowerCase());
+	resource = resource.toLowerCase();
+
+	// Mastodon sometimes only checks for the domain name,
+	// which should be rewritten to the instance actor.
+	if (`https://${config.host}`.toLowerCase() === resource) {
+		resource = `acct:instance.actor@${config.host}`;
+	}
+
+	const query = generateQuery(resource);
 
 	if (typeof query === 'number') {
 		ctx.status = query;