feat: new middleware redirect_as2

middlewares/redirect_as2.ts

@@ -0,0 +1,68 @@
+import type { Middleware } from "../core/server.ts";
+
+export type Options = (url: URL) => Promise<URL> | URL | undefined | void;
+
+export interface CommonOptions {
+  /**
+   * User domain.
+   * @default
+   * ```ts
+   * new URL(req.url).host
+   * ```
+   * @example
+   * ```ts
+   * site.options.location.host
+   * ```
+   */
+  host?: URL["host"];
+}
+
+export interface HatsuOptions extends CommonOptions {
+  /**
+   * Hatsu instance.
+   * @default `hatsu.local`
+   */
+  instance: URL["host"];
+}
+
+export interface BridgyFedOptions extends CommonOptions {
+  /**
+   * BridgyFed instance.
+   * @default `fed.brid.gy`
+   */
+  instance?: URL["host"];
+}
+
+export const hatsu = (options: HatsuOptions): Options => (url: URL) => {
+  const { host, origin, pathname } = new URL(url);
+  if (pathname === "/") {
+    return new URL(`https://${options.instance}/users/${options.host ?? host}`);
+  } else {return new URL(
+      `${origin}${pathname}`,
+      `https://${options.instance}/posts/`,
+    );}
+};
+
+export const bridgyFed =
+  (options?: BridgyFedOptions): Options => (url: URL) => {
+    const { host, origin, pathname } = new URL(url);
+    const instance = options?.instance ?? "fed.brid.gy";
+    if (pathname === "/") return new URL(`https://${instance}/${host}`);
+    else return new URL(`${origin}${pathname}`, `https://${instance}/r/`);
+  };
+
+export default (rewriteUrl: Options): Middleware => async (req, next) => {
+  const accept = req.headers.get("accept");
+  if (
+    accept && [
+      "application/activity+json",
+      'application/ld+json;profile="http://www.w3.org/ns/activitystreams"',
+      'application/ld+json; profile="http://www.w3.org/ns/activitystreams"',
+    ].some((type) => (accept.includes(type)))
+  ) {
+    const dest = await rewriteUrl(new URL(req.url));
+    if (dest) return Response.redirect(dest);
+  }
+
+  return await next(req);
+};