fix: normalize accept-encoding header

.gitignore

@@ -131,3 +131,6 @@ dist
 
 #vim
 .vim
+
+# custom
+src/list.ts

src/create-main-handler.ts

@@ -4,7 +4,6 @@ import {
     cloneHeaders,
     cloneRequest,
     denyHeaders,
-    filterUpstreamHeaders,
     getBuildTarget,
     isForbidden,
     isJsResponse,
@@ -82,9 +81,7 @@ export function createMainHandler(
     return async function requestHandler(
         request: Request,
     ): Promise<Response> {
-        // Step: tracing
         const rootSpan = otel.trace.getActiveSpan();
-        rootSpan?.addEvent(Deno.env.get('DENO_REGION') ?? '');
         const originalUserAgent = request.headers.get('user-agent') ?? '';
         const [buildTarget, upstreamUserAgent] = getBuildTarget(
             originalUserAgent,
@@ -165,7 +162,6 @@ export function createMainHandler(
             headers: cloneHeaders(
                 request.headers,
                 denyHeaders,
-                filterUpstreamHeaders,
                 (
                     pair: [string, string] | null,
                 ) => (pair && pair[0] === 'user-agent'

src/main.ts

@@ -26,6 +26,22 @@ if (config.CACHE) {
         if (headerName === 'origin') {
             return '*';
         }
+        if (headerName === 'accept-encoding') {
+            // Weighted ("Accept-Encoding: deflate, gzip;q=1.0, *;q=0.5"): leave it as-is
+            if (headerValue?.includes('=')) {
+                return headerValue;
+            }
+            if (headerValue?.includes('br')) {
+                return 'br';
+            }
+            if (headerValue?.includes('gzip')) {
+                return 'gzip';
+            }
+            if (headerValue?.includes('deflate')) {
+                return 'deflate';
+            }
+            return '';
+        }
         return headerValue ?? '';
     };
     let persistenceFactory: CachePersistenceFactory | undefined;

src/utils.ts

@@ -67,16 +67,20 @@ export const cloneHeaders = (
 
 const denyHeadersList = [
     'access-control-expose-headers',
+    'accept-encoding',
+    'accept-ranges',
     'age',
-    'date',
     'alt-svc',
     'cf-cache-status',
     'cf-ray',
     'content-length',
+    'date',
     'host',
+    'last-modified',
     'nel',
     'report-to',
     'server',
+    'server-timing',
     'via',
     'x-amz-cf-id',
     'x-amz-cf-pop',
@@ -93,16 +97,6 @@ export const denyHeaders = (
     pair: [string, string] | null,
 ) => (pair !== null && denyHeadersList.includes(pair[0]) ? null : pair);
 
-export const filterUpstreamHeaders = (
-    pair: [string, string] | null,
-) => (pair !== null && ['accept-encoding'].includes(pair[0])
-    ? [
-        pair[0],
-        pair[1].split(',').map((i) => i.trim()).filter((i) => i !== 'zstd')
-            .join(','),
-    ] as [string, string]
-    : pair);
-
 export const isJsResponse = (response: Response): boolean => {
     return !!(response.headers.get('content-type')?.startsWith(
         'application/javascript',