Allow caching directory listings (kotx#22)

Adds a simple `DIRECTORY_CACHE_CONTROL` option to control the
otherwise hardcoded Cache-Control header on directory listing responses.
Also place the directory listing into Cloudflare cache
if configured to do so.

The new option defaults to `no-store` and will be treated as `no-store`
if not present. This is backwards compatible with previous versions.

src/index.ts

@@ -9,6 +9,7 @@ interface Env {
   NOTFOUND_FILE?: string
   DIRECTORY_LISTING?: boolean
   HIDE_HIDDEN_FILES?: boolean
+  DIRECTORY_CACHE_CONTROL?: string
 }
 
 type ParsedRange = { offset: number, length: number } | { suffix: number };
@@ -121,7 +122,7 @@ ${htmlList.join("\n")}
       "access-control-allow-origin": env.ALLOWED_ORIGINS || "",
       "last-modified": lastModified === null ? "" : lastModified.toUTCString(),
       "content-type": "text/html",
-      "cache-control": "no-store"
+      "cache-control": env.DIRECTORY_CACHE_CONTROL || "no-store"
     }
   });
 }
@@ -163,7 +164,12 @@ export default {
           // return the dir listing
           let listResponse = await makeListingResponse(path, env, request);
 
-          if (listResponse !== null) return listResponse;
+          if (listResponse !== null) {
+            if (listResponse.headers.get("cache-control") !== "no-store") {
+              ctx.waitUntil(cache.put(request, listResponse.clone()));
+            }
+            return listResponse;
+          }
         }
       }
 
@@ -254,7 +260,12 @@ export default {
           // return the dir listing
           let listResponse = await makeListingResponse(path, env, request);
 
-          if (listResponse !== null) return listResponse;
+          if (listResponse !== null) {
+            if (listResponse.headers.get("cache-control") !== "no-store") {
+              ctx.waitUntil(cache.put(request, listResponse.clone()));
+            }
+            return listResponse;
+          }
         }
 
         if (env.NOTFOUND_FILE && env.NOTFOUND_FILE != "") {

wrangler.toml

@@ -37,6 +37,9 @@ DIRECTORY_LISTING = false
 # Enable to hide files or directories beginning with . from directory listings.
 HIDE_HIDDEN_FILES = false
 
+# Set a cache header here, e.g. "max-age=86400", if you want to cache directory listings.
+DIRECTORY_CACHE_CONTROL = "no-store"
+
 [[r2_buckets]]
 binding = "R2_BUCKET"
 bucket_name = "kot"         # Set this to your R2 bucket name. Required