Slightly messy reference for implementing client-side OAuth 2 flow in a CLI app

cli-oauth.ts

// quick and dirty reference for oauth flow in CLI apps
let server: http.Server;

const recievedCode = new Promise<string>((resolve, reject) => {
  server = http.createServer((req, res) => {
    const { pathname, searchParams } = new URL(
      req.url,
      "http://localhost:3000/"
    );

    if (pathname.includes("oauth")) {
      console.log({
        message: "got oauth callback",
        parameters: searchParams.toString(),
      });

      if (searchParams.has("code")) {
        resolve(searchParams.get("code"));
      } else {
        reject("bad oauth response");
      }

      res.writeHead(200, "OK");
      res.end();
    } else {
      res.writeHead(200, "OK");
      res.write(`signed in`);
      res.end();
    }
  });

  server.listen(3000);
});

open(
  `https://id.twitch.tv/oauth2/authorize?client_id=${clientId}&redirect_uri=${encodeURIComponent(
    "http://localhost:3000/oauth"
  )}&response_type=code&scope=${encodeURIComponent(
    ["channel:manage:broadcast", "analytics:read:extensions"].join(" ")
  )}&login_hint=${username}&hint=${username}`
);

const code = await recievedCode;
server.close();

console.log({
  message: "exchanging access code for token",
  code,
});

const response = await fetch(
  `https://id.twitch.tv/oauth2/token?client_id=${clientId}&client_secret=${clientSecret}&code=${code}&grant_type=authorization_code&redirect_uri=${encodeURIComponent(
    "http://localhost:3000/"
  )}`,
  {
    method: "POST",
  }
);

if (response.ok) {
  try {
    const body = await response.json();
    console.log({ message: "successfully got access token" });
    return body.access_token;
  } catch (err) {
    console.log({
      message: "failed to parse sign in response",
      error: err,
    });
  }
} else {
  try {
    console.log({
      message: "bad request to token endpoint",
      body: await response.json(),
    });
  } catch {}
}

npm install open