fix(docs): revert #5760 (#5800)

Author: coltondotio

packages/commons/docs-server/src/analytics/rewritePosthog.ts

@@ -3,52 +3,6 @@ import { type NextRequest, NextResponse } from "next/server";
 const POSTHOG_INGEST_HOST = "us.i.posthog.com";
 const POSTHOG_ASSETS_HOST = "us-assets.i.posthog.com";
 
-const HEADERS_TO_STRIP = [
-    // CloudFront headers
-    "cloudfront-forwarded-proto",
-    "cloudfront-is-android-viewer",
-    "cloudfront-is-desktop-viewer",
-    "cloudfront-is-ios-viewer",
-    "cloudfront-is-mobile-viewer",
-    "cloudfront-is-smarttv-viewer",
-    "cloudfront-is-tablet-viewer",
-    "cloudfront-viewer-address",
-    "cloudfront-viewer-asn",
-    "cloudfront-viewer-city",
-    "cloudfront-viewer-country",
-    "cloudfront-viewer-country-name",
-    "cloudfront-viewer-country-region",
-    "cloudfront-viewer-country-region-name",
-    "cloudfront-viewer-http-version",
-    "cloudfront-viewer-latitude",
-    "cloudfront-viewer-longitude",
-    "cloudfront-viewer-metro-code",
-    "cloudfront-viewer-postal-code",
-    "cloudfront-viewer-time-zone",
-    "cloudfront-viewer-tls",
-    // Vercel headers
-    "x-vercel-id",
-    "x-vercel-ip-as-number",
-    "x-vercel-ip-city",
-    "x-vercel-ip-continent",
-    "x-vercel-ip-country",
-    "x-vercel-ip-country-region",
-    "x-vercel-ip-latitude",
-    "x-vercel-ip-longitude",
-    "x-vercel-ip-postal-code",
-    "x-vercel-ip-timezone",
-    "x-vercel-ja3-digest",
-    "x-vercel-ja4-digest",
-    "x-vercel-proxied-for"
-];
-
-function stripHeaders(headers: Headers): Headers {
-    for (const header of HEADERS_TO_STRIP) {
-        headers.delete(header);
-    }
-    return headers;
-}
-
 /**
  * adapted from https://posthog.com/docs/advanced/proxy/nextjs-middleware
  *
@@ -70,8 +24,10 @@ function filterAsciiCookies(cookieHeader: string | null): string | undefined {
     );
 }
 
-export async function rewritePosthog(request: NextRequest): Promise<NextResponse> {
+export function rewritePosthog(request: NextRequest): NextResponse {
     try {
+        const url = request.nextUrl.clone();
+
         // More robust pathname extraction
         const pathnameParts = request.nextUrl.pathname.split("/api/fern-docs/analytics/posthog");
         const intendedPathname = pathnameParts[1] || "/";
@@ -80,9 +36,6 @@ export async function rewritePosthog(request: NextRequest): Promise<NextResponse
 
         const requestHeaders = new Headers(request.headers);
 
-        // Strip CloudFront and Vercel infrastructure headers
-        stripHeaders(requestHeaders);
-
         // Remove any non-ASCII cookies from the request headers
         if (requestHeaders.has("cookie")) {
             const filteredCookie = filterAsciiCookies(requestHeaders.get("cookie"));
@@ -95,29 +48,23 @@ export async function rewritePosthog(request: NextRequest): Promise<NextResponse
 
         requestHeaders.set("host", hostname);
 
-        // Construct the PostHog URL
-        const posthogUrl = `https://${hostname}${intendedPathname}`;
-
-        // Fetch from PostHog directly instead of rewriting
-        const posthogResponse = await fetch(posthogUrl, {
-            method: request.method,
-            headers: requestHeaders,
-            body: request.method !== "GET" && request.method !== "HEAD" ? await request.text() : undefined
-        });
+        // Ensure URL is properly constructed
+        url.pathname = intendedPathname;
+        url.protocol = "https";
+        url.hostname = hostname;
+        url.port = "443";
+        url.search = ""; // Clear search params to avoid issues
 
-        // Create response with PostHog's body and status
-        const responseHeaders = new Headers(posthogResponse.headers);
-
-        // Strip infrastructure headers from the response
-        stripHeaders(responseHeaders);
+        // Validate URL before rewrite
+        if (!url.hostname || !url.protocol) {
+            throw new Error("Invalid URL constructed");
+        }
 
-        return new NextResponse(posthogResponse.body, {
-            status: posthogResponse.status,
-            statusText: posthogResponse.statusText,
-            headers: responseHeaders
+        return NextResponse.rewrite(url, {
+            headers: requestHeaders
         });
     } catch (error) {
-        console.error("Error proxying to PostHog:", error);
+        console.error("Error rewriting PostHog URL:", error);
         // Always return 200 even if there's an error
         return new NextResponse(JSON.stringify({ success: true }), {
             status: 200,