Fix redirect to flutter not works

fresh.gen.ts

@@ -30,6 +30,7 @@ import * as $api_user from "./routes/api/user.ts";
 import * as $file_id_ from "./routes/file/[id].ts";
 import * as $file_verify_id_ from "./routes/file/[verify]/[id].ts";
 import * as $file_middleware from "./routes/file/_middleware.ts";
+import * as $index from "./routes/index.ts";
 import * as $thumbnail_id_ from "./routes/thumbnail/[id].ts";
 import * as $thumbnail_middleware from "./routes/thumbnail/_middleware.ts";
 import * as $upload from "./routes/upload.tsx";
@@ -67,6 +68,7 @@ const manifest = {
         "./routes/file/[id].ts": $file_id_,
         "./routes/file/[verify]/[id].ts": $file_verify_id_,
         "./routes/file/_middleware.ts": $file_middleware,
+        "./routes/index.ts": $index,
         "./routes/thumbnail/[id].ts": $thumbnail_id_,
         "./routes/thumbnail/_middleware.ts": $thumbnail_middleware,
         "./routes/upload.tsx": $upload,

routes/index.ts

@@ -0,0 +1,26 @@
+import { Handlers } from "$fresh/server.ts";
+import { get_task_manager } from "../server.ts";
+import { get_host } from "../server/utils.ts";
+import { exists } from "std/fs/exists.ts";
+
+export const handler: Handlers = {
+    async GET(req, _ctx) {
+        const m = get_task_manager();
+        if (m.cfg.redirect_to_flutter) {
+            let flutter_base = import.meta.resolve("../static/flutter").slice(
+                7,
+            );
+            if (Deno.build.os === "windows") {
+                flutter_base = flutter_base.slice(1);
+            }
+            if (m.cfg.flutter_frontend) {
+                flutter_base = m.cfg.flutter_frontend;
+            }
+            if (!await exists(flutter_base)) {
+                return new Response("404 Not Found", {status: 404});
+            }
+            return Response.redirect(`${get_host(req)}/flutter/`);
+        }
+        return new Response("404 Not Found", {status: 404});
+    }
+};