Implement support for HEAD requests.

src/handlers/head.js

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2024 Adobe. All rights reserved.
+ * This file is licensed to you under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under
+ * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
+ * OF ANY KIND, either express or implied. See the License for the specific language
+ * governing permissions and limitations under the License.
+ */
+import { getSource } from '../routes/source.js';
+import getList from '../routes/list.js';
+import { getProperties } from '../routes/properties.js';
+
+function get404() {
+  return { status: 404, contentLength: 0 };
+}
+
+function getRobots() {
+  const body = 'User-agent: *\nDisallow: /';
+  return { contentLength: body.length, status: 200 };
+}
+
+export default async function headHandler({ env, daCtx, head }) {
+  const { path } = daCtx;
+
+  if (path.startsWith('/favicon.ico')) return get404();
+  if (path.startsWith('/robots.txt')) return getRobots();
+
+  if (path.startsWith('/source')) return getSource({ env, daCtx, head });
+  if (path.startsWith('/list')) {
+    const { body, contentType, status } = await getList({ env, daCtx });
+    return {
+      contentLength: body.length,
+      contentType,
+      status,
+    };
+  }
+  if (path.startsWith('/properties')) {
+    const { body, status, contentType } = getProperties();
+    return { status, contentType, contentLength: body.length };
+  }
+
+  return undefined;
+}

src/index.js

@@ -12,6 +12,7 @@
 import getDaCtx from './utils/daCtx.js';
 import daResp from './utils/daResp.js';
 
+import headHandler from './handlers/head.js';
 import getHandler from './handlers/get.js';
 import postHandler from './handlers/post.js';
 import deleteHandler from './handlers/delete.js';
@@ -26,6 +27,9 @@ export default {
 
     let respObj;
     switch (req.method) {
+      case 'HEAD':
+        respObj = await headHandler({ env, daCtx });
+        break;
       case 'GET':
         respObj = await getHandler({ env, daCtx });
         break;

src/storage/object/get.js

@@ -12,6 +12,7 @@
 import {
   S3Client,
   GetObjectCommand,
+  HeadObjectCommand,
 } from '@aws-sdk/client-s3';
 
 import getS3Config from '../utils/config.js';
@@ -21,21 +22,22 @@ function buildInput({ org, key }) {
   return { Bucket, Key: key };
 }
 
-export default async function getObject(env, { org, key }) {
+export default async function getObject(env, { org, key, head }) {
   const config = getS3Config(env);
   const client = new S3Client(config);
 
   const input = buildInput({ org, key });
-  const command = new GetObjectCommand(input);
+  const command = head ? new HeadObjectCommand(input) : new GetObjectCommand(input);
 
   try {
     const resp = await client.send(command);
     return {
       body: resp.Body,
       status: resp.$metadata.httpStatusCode,
       contentType: resp.ContentType,
+      contentLength: resp.ContentLength,
     };
   } catch (e) {
-    return { body: '', status: 404 };
+    return { body: '', status: 404, contentLength: 0 };
   }
 }

src/utils/daResp.js

@@ -9,12 +9,20 @@
  * OF ANY KIND, either express or implied. See the License for the specific language
  * governing permissions and limitations under the License.
  */
-export default function daResp({ status, body = '', contentType = 'application/json' }) {
+export default function daResp({
+  status,
+  body = '',
+  contentType = 'application/json',
+  contentLength,
+}) {
   const headers = new Headers();
   headers.append('Access-Control-Allow-Origin', '*');
-  headers.append('Access-Control-Allow-Methods', 'GET, PUT, POST, DELETE');
+  headers.append('Access-Control-Allow-Methods', 'HEAD, GET, PUT, POST, DELETE');
   headers.append('Access-Control-Allow-Headers', '*');
   headers.append('Content-Type', contentType);
+  if (contentLength) {
+    headers.append('Content-Length', contentLength);
+  }
 
   return new Response(body, { status, headers });
 }