Change how a site in proxy mode is resolved (#2890)

Author: taranvohra

.changeset/lucky-pens-brush.md

@@ -0,0 +1,5 @@
+---
+'gitbook': patch
+---
+
+Change how a site in proxy mode is resolved

packages/gitbook/src/lib/links.ts

@@ -45,6 +45,11 @@ export async function getBasePath(): Promise<string> {
 export async function getHost(): Promise<string> {
     assertIsNotV2();
     const headersList = await headers();
+    const mode = headersList.get('x-gitbook-mode');
+    if (mode === 'proxy') {
+        return headersList.get('x-forwarded-host') ?? '';
+    }
+
     return headersList.get('x-gitbook-host') ?? headersList.get('host') ?? '';
 }
 

packages/gitbook/src/middleware.ts

@@ -1,4 +1,9 @@
-import { type ContentAPITokenPayload, CustomizationThemeMode, GitBookAPI } from '@gitbook/api';
+import {
+    type ContentAPITokenPayload,
+    CustomizationThemeMode,
+    GitBookAPI,
+    type PublishedSiteContent,
+} from '@gitbook/api';
 import { setContext, setTag } from '@sentry/nextjs';
 import { getURLLookupAlternatives, normalizeURL } from '@v2/lib/data';
 import assertNever from 'assert-never';
@@ -181,7 +186,9 @@ export async function middleware(request: NextRequest) {
     headers.set('x-gitbook-origin-basepath', originBasePath);
     headers.set(
         'x-gitbook-basepath',
-        mode === 'proxy' ? originBasePath : joinPath(originBasePath, resolved.basePath)
+        mode === 'proxy'
+            ? getProxyModeBasePath(inputURL, resolved)
+            : joinPath(originBasePath, resolved.basePath)
     );
     headers.set('x-gitbook-content-space', resolved.space);
     if ('site' in resolved) {
@@ -335,7 +342,10 @@ function getInputURL(request: NextRequest): {
     // to determine the site to serve.
     const xGitbookSite = request.headers.get('x-gitbook-site-url');
     if (xGitbookSite) {
-        mode = 'proxy';
+        return {
+            mode: 'proxy',
+            url: new URL(xGitbookSite),
+        };
     }
 
     return { url, mode };
@@ -400,16 +410,8 @@ async function lookupSiteInSingleMode(url: URL): Promise<LookupResult> {
  * GITBOOK_MODE=proxy
  * When proxying a site on a different base URL.
  */
-async function lookupSiteInProxy(request: NextRequest, _url: URL): Promise<LookupResult> {
-    const rawSiteUrl = request.headers.get('x-gitbook-site-url');
-    if (!rawSiteUrl) {
-        throw new Error(
-            'Missing x-gitbook-site-url header. It should be passed when using GITBOOK_MODE=proxy.'
-        );
-    }
-
-    const siteUrl = new URL(rawSiteUrl);
-    return await lookupSiteInMultiMode(request, siteUrl);
+async function lookupSiteInProxy(request: NextRequest, url: URL): Promise<LookupResult> {
+    return await lookupSiteInMultiMode(request, url);
 }
 
 /**
@@ -916,3 +918,21 @@ function writeCookies<R extends NextResponse>(
 
     return response;
 }
+
+/**
+ * Compute the final base path for a site served in proxy mode.
+ * For e.g. if the input URL is `https://example.com/docs/v2/foo/bar` on which
+ * the site is served at `https://example.com/docs` and the resolved base path is `/v2`
+ * then the proxy site path would be `/docs/v2/`.
+ */
+function getProxyModeBasePath(
+    input: URL,
+    resolved: Pick<PublishedSiteContent, 'basePath' | 'pathname'>
+): string {
+    const inputPathname = stripURLSearch(input).pathname;
+    const proxySitePath = inputPathname
+        .replace(resolved.pathname, '')
+        .replace(resolved.basePath, '');
+
+    return joinPath(normalizePathname(proxySitePath), resolved.basePath);
+}