3 files changed, 195 insertions, 0 deletions
diff --git a/packages/integrations/vercel/src/index.ts b/packages/integrations/vercel/src/index.ts
new file mode 100644
index 000000000..49a924b2d
--- /dev/null
+++ b/packages/integrations/vercel/src/index.ts
@@ -0,0 +1,66 @@
+import type { AstroAdapter, AstroConfig, AstroIntegration } from 'astro';
+import type { PathLike } from 'fs';
+import fs from 'fs/promises';
+import esbuild from 'esbuild';
+import { fileURLToPath } from 'url';
+
+const writeJson = (path: PathLike, data: any) =>
+	fs.writeFile(path, JSON.stringify(data), { encoding: 'utf-8' });
+
+const ENTRYFILE = '__astro_entry';
+
+export function getAdapter(): AstroAdapter {
+	return {
+		name: '@astrojs/vercel',
+		serverEntrypoint: '@astrojs/vercel/server-entrypoint',
+		exports: ['_default'],
+	};
+}
+
+export default function vercel(): AstroIntegration {
+	let _config: AstroConfig;
+	return {
+		name: '@astrojs/vercel',
+		hooks: {
+			'astro:config:setup': ({ config }) => {
+				config.outDir = new URL('./.output/', config.outDir);
+				config.build.format = 'directory';
+			},
+			'astro:config:done': ({ setAdapter, config }) => {
+				setAdapter(getAdapter());
+				_config = config;
+			},
+			'astro:build:start': async ({ buildConfig }) => {
+				buildConfig.serverEntry = `${ENTRYFILE}.mjs`;
+				buildConfig.client = new URL('./static/', _config.outDir);
+				buildConfig.server = new URL('./server/pages/', _config.outDir);
+			},
+			'astro:build:done': async ({ dir, routes }) => {
+				const pagesDir = new URL('./server/pages/', dir);
+
+				// Convert server entry to CommonJS
+				await esbuild.build({
+					entryPoints: [fileURLToPath(new URL(`./${ENTRYFILE}.mjs`, pagesDir))],
+					outfile: fileURLToPath(new URL(`./${ENTRYFILE}.js`, pagesDir)),
+					bundle: true,
+					format: 'cjs',
+					platform: 'node',
+					target: 'node14',
+				});
+				await fs.rm(new URL(`./${ENTRYFILE}.mjs`, pagesDir));
+
+				// Routes Manifest
+				// https://vercel.com/docs/file-system-api#configuration/routes
+				await writeJson(new URL(`./routes-manifest.json`, dir), {
+					version: 3,
+					basePath: '/',
+					pages404: false,
+					rewrites: routes.map((route) => ({
+						source: route.pathname,
+						destination: `/${ENTRYFILE}`,
+					})),
+				});
+			},
+		},
+	};
+}
diff --git a/packages/integrations/vercel/src/request-transform.ts b/packages/integrations/vercel/src/request-transform.ts
new file mode 100644
index 000000000..0a87ca642
--- /dev/null
+++ b/packages/integrations/vercel/src/request-transform.ts
@@ -0,0 +1,95 @@
+import { Readable } from 'stream';
+import type { IncomingMessage, ServerResponse } from 'http';
+
+/*
+  Credits to the SvelteKit team
+	https://github.com/sveltejs/kit/blob/69913e9fda054fa6a62a80e2bb4ee7dca1005796/packages/kit/src/node.js
+*/
+
+function get_raw_body(req: IncomingMessage) {
+	return new Promise<Uint8Array | null>((fulfil, reject) => {
+		const h = req.headers;
+
+		if (!h['content-type']) {
+			return fulfil(null);
+		}
+
+		req.on('error', reject);
+
+		const length = Number(h['content-length']);
+
+		// https://github.com/jshttp/type-is/blob/c1f4388c71c8a01f79934e68f630ca4a15fffcd6/index.js#L81-L95
+		if (isNaN(length) && h['transfer-encoding'] == null) {
+			return fulfil(null);
+		}
+
+		let data = new Uint8Array(length || 0);
+
+		if (length > 0) {
+			let offset = 0;
+			req.on('data', (chunk) => {
+				const new_len = offset + Buffer.byteLength(chunk);
+
+				if (new_len > length) {
+					return reject({
+						status: 413,
+						reason: 'Exceeded "Content-Length" limit',
+					});
+				}
+
+				data.set(chunk, offset);
+				offset = new_len;
+			});
+		} else {
+			req.on('data', (chunk) => {
+				const new_data = new Uint8Array(data.length + chunk.length);
+				new_data.set(data, 0);
+				new_data.set(chunk, data.length);
+				data = new_data;
+			});
+		}
+
+		req.on('end', () => {
+			fulfil(data);
+		});
+	});
+}
+
+export async function getRequest(base: string, req: IncomingMessage): Promise<Request> {
+	let headers = req.headers as Record<string, string>;
+	if (req.httpVersionMajor === 2) {
+		// we need to strip out the HTTP/2 pseudo-headers because node-fetch's
+		// Request implementation doesn't like them
+		headers = Object.assign({}, headers);
+		delete headers[':method'];
+		delete headers[':path'];
+		delete headers[':authority'];
+		delete headers[':scheme'];
+	}
+	return new Request(base + req.url, {
+		method: req.method,
+		headers,
+		body: await get_raw_body(req), // TODO stream rather than buffer
+	});
+}
+
+export async function setResponse(res: ServerResponse, response: Response): Promise<void> {
+	const headers = Object.fromEntries(response.headers);
+
+	if (response.headers.has('set-cookie')) {
+		// @ts-expect-error (headers.raw() is non-standard)
+		headers['set-cookie'] = response.headers.raw()['set-cookie'];
+	}
+
+	res.writeHead(response.status, headers);
+
+	if (response.body instanceof Readable) {
+		response.body.pipe(res);
+	} else {
+		if (response.body) {
+			res.write(await response.arrayBuffer());
+		}
+
+		res.end();
+	}
+}
diff --git a/packages/integrations/vercel/src/server-entrypoint.ts b/packages/integrations/vercel/src/server-entrypoint.ts
new file mode 100644
index 000000000..df01fe32a
--- /dev/null
+++ b/packages/integrations/vercel/src/server-entrypoint.ts
@@ -0,0 +1,34 @@
+import type { SSRManifest } from 'astro';
+import { App } from 'astro/app';
+import { polyfill } from '@astrojs/webapi';
+import type { IncomingMessage, ServerResponse } from 'http';
+
+import { getRequest, setResponse } from './request-transform.js';
+
+polyfill(globalThis, {
+	exclude: 'window document',
+});
+
+export const createExports = (manifest: SSRManifest) => {
+	const app = new App(manifest);
+
+	const _default = async (req: IncomingMessage, res: ServerResponse) => {
+		let request: Request;
+
+		try {
+			request = await getRequest(`https://${req.headers.host}`, req);
+		} catch (err: any) {
+			res.statusCode = err.status || 400;
+			return res.end(err.reason || 'Invalid request body');
+		}
+
+		if (!app.match(request)) {
+			res.statusCode = 404;
+			return res.end('Not found');
+		}
+
+		await setResponse(res, await app.render(request));
+	};
+
+	return { _default };
+};