Standard Notes CloudFlare Proxy

standard-notes-proxy.js

export default {
	/**
	 * @param {Request} request
	 */
	async fetch(request) {
		const corsHeaders = {
			"Access-Control-Allow-Origin": "*",
			"Access-Control-Allow-Methods": "GET,HEAD,POST,OPTIONS",
			"Access-Control-Max-Age": "86400",
		};

		/**
		 * @param {Request} request
		 */
		async function handleRequest(request) {
			// Rewrite request to point to API URL. This also makes the request mutable so you can add the correct Origin header to make the API server think that this request is not cross-site.
			const newUrl = new URL(request.url)
			newUrl.hostname = 'api.standardnotes.com/'
			const newRequest = new Request(newUrl.toString(), request);
			newRequest.headers.set('Origin', 'https://app.standardnotes.com');
			let response = await fetch(newRequest);
			// Recreate the response so you can modify the headers

			response = new Response(response.body, response);
			// Set CORS headers
			response.headers.set("Access-Control-Allow-Origin", request.headers.get("Origin"));

			// Append to/Add Vary header so browser will cache response correctly
			response.headers.append("Vary", "Origin");

			return response;
		}

		/**
		 * @param {Request} request
		 */
		async function handleOptions(request) {
			if (
				request.headers.get("Origin") !== null &&
				request.headers.get("Access-Control-Request-Method") !== null &&
				request.headers.get("Access-Control-Request-Headers") !== null
			) {
				// Handle CORS preflight requests.
				return new Response(null, {
					headers: {
						...corsHeaders,
						"Access-Control-Allow-Headers": request.headers.get(
							"Access-Control-Request-Headers"
						),
					},
				});
			} else {
				// Handle standard OPTIONS request.
				return new Response(null, {
					headers: {
						Allow: "GET, HEAD, POST, OPTIONS",
					},
				});
			}
		}

		if (request.method === "OPTIONS") {
			// Handle CORS preflight requests
			return handleOptions(request);
		} else if (
			request.method === "GET" ||
			request.method === "HEAD" ||
			request.method === "POST"
		) {
			// Handle requests to the API server
			return handleRequest(request);
		} else {
			return new Response(null, {
				status: 405,
				statusText: "Method Not Allowed",
			});
		}
	},
};