import { Application, Router } from "https://deno.land/x/[email protected]/mod.ts";
import { Session } from "https://deno.land/x/[email protected]/mod.ts";
import { OAuth2Client } from "https://deno.land/x/oauth2_client/mod.ts";

const oauth2Client = new OAuth2Client({
  clientId: Deno.env.get("CLIENT_ID")!,
  clientSecret: Deno.env.get("CLIENT_SECRET")!,
  authorizationEndpointUri: "https://github.com/login/oauth/authorize",
  tokenUri: "https://github.com/login/oauth/access_token",
  redirectUri: "http://localhost:8000/oauth2/callback",
  defaults: {
    scope: "read:user",
  },
});

type AppState = {
  session: Session;
};

const router = new Router<AppState>();
router.get("/login", async (ctx) => {
  // Construct the URL for the authorization redirect and get a PKCE codeVerifier
  const { uri, codeVerifier } = await oauth2Client.code.getAuthorizationUri();

  // Store both the state and codeVerifier in the user session
  ctx.state.session.flash("codeVerifier", codeVerifier);

  // Redirect the user to the authorization endpoint
  ctx.response.redirect(uri);
});
router.get("/oauth2/callback", async (ctx) => {
  // Make sure the codeVerifier is present for the user's session
  const codeVerifier = ctx.state.session.get("codeVerifier");
  if (typeof codeVerifier !== "string") {
    throw new Error("invalid codeVerifier");
  }

  // Exchange the authorization code for an access token
  const tokens = await oauth2Client.code.getToken(ctx.request.url, {
    codeVerifier,
  });

  // Use the access token to make an authenticated API request
  const userResponse = await fetch("https://api.github.com/user", {
    headers: {
      Authorization: `Bearer ${tokens.accessToken}`,
    },
  });
  const { login } = await userResponse.json();

  ctx.response.body = `Hello, ${login}!`;
});

const app = new Application<AppState>();
app.use(Session.initMiddleware());
app.use(router.allowedMethods(), router.routes());

await app.listen({ port: 8000 });