Initialize middleware

fresh.gen.ts

@@ -4,6 +4,7 @@
 
 import * as $_404 from "./routes/_404.tsx";
 import * as $_app from "./routes/_app.tsx";
+import * as $_middleware from "./routes/_middleware.tsx";
 import * as $connectivity_test from "./routes/connectivity-test.tsx";
 import * as $file_id_analyzer from "./routes/file-id-analyzer.tsx";
 import * as $filter_query_browser from "./routes/filter-query-browser.tsx";
@@ -32,6 +33,7 @@ const manifest = {
   routes: {
     "./routes/_404.tsx": $_404,
     "./routes/_app.tsx": $_app,
+    "./routes/_middleware.tsx": $_middleware,
     "./routes/connectivity-test.tsx": $connectivity_test,
     "./routes/file-id-analyzer.tsx": $file_id_analyzer,
     "./routes/filter-query-browser.tsx": $filter_query_browser,

routes/_middleware.tsx

@@ -0,0 +1,47 @@
+import { FreshContext } from "$fresh/server.ts";
+
+const HEADER = new TextEncoder().encode("<!--- See something wrong? Let us know in our chat: https://t.me/grammyjs --->");
+
+export async function handler(req: Request, ctx: FreshContext) {
+  try {
+    const res = await ctx.next();
+    if (
+      res.body != null &&
+      res.status == 200 &&
+      res.headers.get("content-type")?.includes("text/html")
+    ) {
+      const reader = res.body.getReader();
+      let headerSent = false;
+      const rs = new ReadableStream({
+        async pull(controller) {
+          const result = await reader.read();
+          if (result?.done) {
+            controller.close();
+          } else if (result?.value) {
+            if (!headerSent) {
+              headerSent = true;
+              controller.enqueue(HEADER);
+              return;
+            }
+            controller.enqueue(result.value);
+          } else if (!result) {
+            controller.error();
+          }
+        },
+        async cancel(reason) {
+          try {
+            await res.body?.cancel(reason);
+          } catch {
+            //
+          }
+        },
+      });
+      return new Response(rs, { headers: res.headers, status: res.status });
+    } else {
+      return res;
+    }
+  } catch (err) {
+    console.trace(err);
+  }
+  return Response.redirect(new URL("/", req.url));
+}