let last_known_version = "1.2.2";
const api_root = "https://XXX.workers.dev/version/";

const x86_64_apple_darwin = api_root + "x86_64-apple-darwin";
const x86_64_unknown_linux_gnu = api_root + "x86_64-unknown-linux-gnu";
const x86_64_pc_windows_msvc = api_root + "x86_64-pc-windows-msvc";

const re_x86_64_apple_darwin = /href="\/denoland\/deno\/releases\/download\/v(.*?)\/deno-x86_64-apple-darwin.zip"/;
const re_x86_64_unknown_linux_gnu = /href="\/denoland\/deno\/releases\/download\/v(.*?)\/deno-x86_64-unknown-linux-gnu.zip"/;
const re_x86_64_pc_windows_msvc = /href="\/denoland\/deno\/releases\/download\/v(.*?)\/deno-x86_64-pc-windows-msvc.zip"/;

addEventListener("fetch", event => {
  event.respondWith(handle_request(event.request));
});

async function handle_request(req) {
  let regex;
  switch (req.url) {
    case x86_64_apple_darwin: regex = re_x86_64_apple_darwin; break;
    case x86_64_unknown_linux_gnu: regex = re_x86_64_unknown_linux_gnu; break;
    case x86_64_pc_windows_msvc: regex = re_x86_64_pc_windows_msvc; break;
    default:
      return new Response("", { status: 404 });
  }

  const res = await fetch("https://github.com/denoland/deno/releases/");
  if (!res.ok) {
    return new Reponse(last_known_version, { status: 200 });
  }

  const text = await res.text();
  const match = text.match(regex);
  if (match === null) {
    return new Reponse(last_known_version, { status: 200 });
  }

  last_known_version = match[1];
  return new Response(last_known_version, { status: 200 });
}