refactor: reorganize files in commons package

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

commons/src/parse-url/parse-url.ts

@@ -0,0 +1,35 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { MissingTrailingSlashError, WrongProtocolError } from './errors.js'
+import { Optional } from '@mrdrogdrog/optional'
+
+/**
+ * Parses the given string as URL
+ *
+ * @param {String | undefined} url the raw url
+ * @return An {@link Optional} that contains the parsed URL or is empty if the raw value isn't a valid URL
+ * @throws WrongProtocolError if the protocol of the URL isn't either http nor https
+ * @throws MissingTrailingSlashError if the URL has a path that doesn't end with a trailing slash
+ */
+export function parseUrl(url: string | undefined): Optional<URL> {
+  return createOptionalUrl(url)
+    .guard(
+      (value) => value.protocol === 'https:' || value.protocol === 'http:',
+      () => new WrongProtocolError()
+    )
+    .guard(
+      (value) => value.pathname.endsWith('/'),
+      () => new MissingTrailingSlashError()
+    )
+}
+
+function createOptionalUrl(url: string | undefined): Optional<URL> {
+  try {
+    return Optional.ofNullable(url).map((value) => new URL(value))
+  } catch (error) {
+    return Optional.empty()
+  }
+}