Adds support base64 encoding in Netlify Functions (#3592)

* Adding support for base64 encoded responses in Netlify Functions

* chore: add changeset

* removing the regex check for a more simple header-based check

* nit: cleaning up the readme a bit

6 files changed, 164 insertions, 7 deletions

diff --git a/packages/integrations/netlify/README.md b/packages/integrations/netlify/README.md
index b0daeadef..dba81568e 100644
--- a/packages/integrations/netlify/README.md
+++ b/packages/integrations/netlify/README.md
@@ -58,3 +58,27 @@ And then point to the dist in your `netlify.toml`:
 [functions]
   directory = "dist/functions"
 ```
+
+### binaryMediaTypes
+
+> This option is only needed for the Functions adapter and is not needed for Edge Functions.
+
+Netlify Functions sending binary data in the `body` need to be base64 encoded. The `@astrojs/netlify/functions` adapter handles this automatically based on the `Content-Type` header.
+
+We check for common mime types for audio, image, and video files. To include specific mime types that should be treated as binary data, include the `binaryMediaTypes` option with a list of binary mime types.
+
+```js
+import fs from 'node:fs';
+
+export function get() {
+	const buffer = fs.readFileSync('../image.jpg');
+
+  // Return the buffer directly, @astrojs/netlify will base64 encode the body
+  return new Response(buffer, {
+    status: 200,
+		headers: {
+			'content-type': 'image/jpeg'
+		}
+  });
+}
+```
diff --git a/packages/integrations/netlify/src/integration-functions.ts b/packages/integrations/netlify/src/integration-functions.ts
index 8f9b291fa..4242a7b00 100644
--- a/packages/integrations/netlify/src/integration-functions.ts
+++ b/packages/integrations/netlify/src/integration-functions.ts
@@ -1,20 +1,22 @@
 import type { AstroAdapter, AstroConfig, AstroIntegration } from 'astro';
 import { createRedirects } from './shared.js';
+import type { Args } from './netlify-functions.js';
 
-export function getAdapter(): AstroAdapter {
+export function getAdapter(args: Args = {}): AstroAdapter {
 	return {
 		name: '@astrojs/netlify/functions',
 		serverEntrypoint: '@astrojs/netlify/netlify-functions.js',
 		exports: ['handler'],
-		args: {},
+		args,
 	};
 }
 
 interface NetlifyFunctionsOptions {
 	dist?: URL;
+	binaryMediaTypes?: string[];
 }
 
-function netlifyFunctions({ dist }: NetlifyFunctionsOptions = {}): AstroIntegration {
+function netlifyFunctions({ dist, binaryMediaTypes }: NetlifyFunctionsOptions = {}): AstroIntegration {
 	let _config: AstroConfig;
 	let entryFile: string;
 	return {
@@ -28,7 +30,7 @@ function netlifyFunctions({ dist }: NetlifyFunctionsOptions = {}): AstroIntegrat
 				}
 			},
 			'astro:config:done': ({ config, setAdapter }) => {
-				setAdapter(getAdapter());
+				setAdapter(getAdapter({ binaryMediaTypes }));
 				_config = config;
 			},
 			'astro:build:start': async ({ buildConfig }) => {
diff --git a/packages/integrations/netlify/src/netlify-functions.ts b/packages/integrations/netlify/src/netlify-functions.ts
index 66e5271f5..f8b3ab21b 100644
--- a/packages/integrations/netlify/src/netlify-functions.ts
+++ b/packages/integrations/netlify/src/netlify-functions.ts
@@ -7,11 +7,49 @@ polyfill(globalThis, {
 	exclude: 'window document',
 });
 
-interface Args {}
+export interface Args {
+	binaryMediaTypes?: string[];
+}
+
+function parseContentType(header?: string) {
+	return header?.split(';')[0] ?? '';
+}
 
 export const createExports = (manifest: SSRManifest, args: Args) => {
 	const app = new App(manifest);
 
+	const binaryMediaTypes = args.binaryMediaTypes ?? [];
+	const knownBinaryMediaTypes = new Set([
+		'audio/3gpp',
+		'audio/3gpp2',
+		'audio/aac',
+		'audio/midi',
+		'audio/mpeg',
+		'audio/ogg',
+		'audio/opus',
+		'audio/wav',
+		'audio/webm',
+		'audio/x-midi',
+		'image/avif',
+		'image/bmp',
+		'image/gif',
+		'image/vnd.microsoft.icon',
+		'image/jpeg',
+		'image/png',
+		'image/svg+xml',
+		'image/tiff',
+		'image/webp',
+		'video/3gpp',
+		'video/3gpp2',
+		'video/mp2t',
+		'video/mp4',
+		'video/mpeg',
+		'video/ogg',
+		'video/x-msvideo',
+		'video/webm',
+		...binaryMediaTypes,
+	]);
+
 	const handler: Handler = async (event) => {
 		const { httpMethod, headers, rawUrl, body: requestBody, isBase64Encoded } = event;
 		const init: RequestInit = {
@@ -34,13 +72,20 @@ export const createExports = (manifest: SSRManifest, args: Args) => {
 		}
 
 		const response: Response = await app.render(request);
-		const responseBody = await response.text();
-
 		const responseHeaders = Object.fromEntries(response.headers.entries());
+		
+		const responseContentType = parseContentType(responseHeaders['content-type']);
+		const responseIsBase64Encoded = knownBinaryMediaTypes.has(responseContentType);
+
+		const responseBody = responseIsBase64Encoded
+			? Buffer.from(await response.text(), 'binary').toString('base64')
+			: await response.text();
+		
 		const fnResponse: any = {
 			statusCode: response.status,
 			headers: responseHeaders,
 			body: responseBody,
+			isBase64Encoded: responseIsBase64Encoded,
 		};
 
 		// Special-case set-cookie which has to be set an different way :/
diff --git a/packages/integrations/netlify/test/functions/base64-response.test.js b/packages/integrations/netlify/test/functions/base64-response.test.js
new file mode 100644
index 000000000..10d43b046
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/base64-response.test.js
@@ -0,0 +1,64 @@
+import { expect } from 'chai';
+import { loadFixture, testIntegration } from './test-utils.js';
+import netlifyAdapter from '../../dist/index.js';
+
+describe('Base64 Responses', () => {
+	/** @type {import('../../../astro/test/test-utils').Fixture} */
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/base64-response/', import.meta.url).toString(),
+			experimental: {
+				ssr: true,
+			},
+			adapter: netlifyAdapter({
+				dist: new URL('./fixtures/base64-response/dist/', import.meta.url),
+				binaryMediaTypes: ['font/otf']
+			}),
+			site: `http://example.com`,
+			integrations: [testIntegration()],
+		});
+		await fixture.build();
+	});
+
+	it('Can return base64 encoded strings', async () => {
+		const entryURL = new URL(
+			'./fixtures/base64-response/.netlify/functions-internal/entry.mjs',
+			import.meta.url
+		);
+		const { handler } = await import(entryURL);
+		const resp = await handler({
+			httpMethod: 'GET',
+			headers: {},
+			rawUrl: 'http://example.com/image',
+			body: '{}',
+			isBase64Encoded: false,
+		});
+		expect(resp.statusCode, 'successful response').to.equal(200);
+		expect(resp.isBase64Encoded, 'includes isBase64Encoded flag').to.be.true;
+
+		const buffer = Buffer.from(resp.body, 'base64');
+		expect(buffer.toString(), 'decoded base64 string matches').to.equal('base64 test string');
+	});
+
+	it('Can define custom binaryMediaTypes', async () => {
+		const entryURL = new URL(
+			'./fixtures/base64-response/.netlify/functions-internal/entry.mjs',
+			import.meta.url
+		);
+		const { handler } = await import(entryURL);
+		const resp = await handler({
+			httpMethod: 'GET',
+			headers: {},
+			rawUrl: 'http://example.com/font',
+			body: '{}',
+			isBase64Encoded: false,
+		});
+		expect(resp.statusCode, 'successful response').to.equal(200);
+		expect(resp.isBase64Encoded, 'includes isBase64Encoded flag').to.be.true;
+
+		const buffer = Buffer.from(resp.body, 'base64');
+		expect(buffer.toString(), 'decoded base64 string matches').to.equal('base64 test font');
+	});
+});
diff --git a/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js
new file mode 100644
index 000000000..3ec4c8364
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js
@@ -0,0 +1,11 @@
+
+export function get() {
+	const buffer = Buffer.from('base64 test font', 'utf-8')
+
+  return new Response(buffer, {
+    status: 200,
+		headers: {
+			'Content-Type': 'font/otf'
+		}
+  });
+}
diff --git a/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js
new file mode 100644
index 000000000..ca3b4d9d3
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js
@@ -0,0 +1,11 @@
+
+export function get() {
+	const buffer = Buffer.from('base64 test string', 'utf-8')
+
+  return new Response(buffer, {
+    status: 200,
+		headers: {
+			'content-type': 'image/jpeg;foo=foo'
+		}
+  });
+}