import * as oauth from "oauth4webapi";
import type { OIDCProvider } from "../types";
import { getCallbackURL } from "../utils/callback";

export async function OIDCAuthorization(
  request: Request,
  provider: OIDCProvider,
): Promise<Response> {
  const callback_url = getCallbackURL(request);
  const code_verifier = oauth.generateRandomCodeVerifier();
  const code_challenge = await oauth.calculatePKCECodeChallenge(code_verifier);
  const code_challenge_method = "S256";
  const { client_id, client_secret, issuer, scope, params } = provider;

  const client: oauth.Client = {
    client_id,
    client_secret,
    token_endpoint_auth_method: "client_secret_basic",
  };

  const as = await oauth
    .discoveryRequest(issuer, { algorithm: "oidc" })
    .then((response) => oauth.processDiscoveryResponse(issuer, response));

  const cookies: string[] = [];
  const cookieMaxage = new Date(Date.now() + 300 * 1000);

  const authorizationURL = new URL(as.authorization_endpoint!);
  authorizationURL.searchParams.set("client_id", client.client_id);
  authorizationURL.searchParams.set("redirect_uri", callback_url.toString());
  authorizationURL.searchParams.set("response_type", "code");
  authorizationURL.searchParams.set("scope", scope);
  authorizationURL.searchParams.set("code_challenge", code_challenge);
  authorizationURL.searchParams.set(
    "code_challenge_method",
    code_challenge_method,
  );

  if (params) {
    Object.entries(params).map(([key, value]) => {
      authorizationURL.searchParams.set(key, value);
    });
  }

  if (as.code_challenge_methods_supported?.includes("S256") !== true) {
    const nonce = oauth.generateRandomNonce();
    authorizationURL.searchParams.set("nonce", nonce);
    cookies.push(
      `__session-nonce=${nonce};Path=/;HttpOnly;SameSite=lax;MaxAge=25000`,
    );
  }

  cookies.push(
    `__session-code-verifier=${code_verifier};Path=/;HttpOnly;SameSite=lax;MaxAge=25000`,
  );

  const res = new Response(null, {
    status: 302,
    headers: {
      Location: authorizationURL.href,
    },
  });

  cookies.forEach((cookie) => {
    res.headers.append("Set-Cookie", cookie);
  });

  return res;
}