import * as express from "express";
import { createDecoder, createVerifier } from "fast-jwt";

import HttpError from "../interfaces/http-error";
import HttpStatusCode from "../interfaces/http-status";

if (!process.env.PUBLIC_KEY && !process.env.REALM_URL) {
  throw new Error("Requires PUBLIC_KEY or REALM_URL");
}
if (process.env.PUBLIC_KEY && process.env.REALM_URL && !process.env.PREFERRED_AUTH) {
  throw new Error(
    "PREFERRED_AUTH must be specified when both REALM_URL and PUBLIC_KEY are provided.",
  );
}

const jwtVerify = createVerifier({
  key: async () => {
    return `-----BEGIN PUBLIC KEY-----\n${process.env.PUBLIC_KEY}\n-----END PUBLIC KEY-----`;
  },
});

const jwtDecode = createDecoder();

export async function expressAuthentication(
  request: express.Request,
  securityName: string,
  scopes?: string[],
) {
  if (process.env.AUTH_BYPASS) return { preferred_username: "bypassed" };

  if (securityName !== "bearerAuth") throw new Error("Unknown authentication method.");

  const token = request.headers["authorization"]?.includes("Bearer ")
    ? request.headers["authorization"].split(" ")[1]
    : request.headers["authorization"];

  if (!token) throw new HttpError(HttpStatusCode.UNAUTHORIZED, "กรุณาเข้าสู่ระบบก่อนใช้งาน!");

  let payload: Record<string, any> = {};

  switch (process.env.PREFERRED_AUTH) {
    case "online":
      payload = await verifyOnline(token);
      break;
    case "offline":
      payload = await verifyOffline(token);
      break;
    default:
      if (process.env.REALM_URL) payload = await verifyOnline(token);
      if (process.env.PUBLIC_KEY) payload = await verifyOffline(token);
      break;
  }

  if (scopes && scopes.length > 0 && scopes.every((v) => !payload.role.includes(v))) {
    throw new HttpError(HttpStatusCode.FORBIDDEN, "You are not allowed to perform this action.");
  }

  return payload;
}

async function verifyOffline(token: string) {
  const payload = await jwtVerify(token).catch((_) => null);
  if (!payload) throw new HttpError(HttpStatusCode.UNAUTHORIZED, "Invalid token provided.");
  return payload;
}

async function verifyOnline(token: string) {
  const res = await fetch(`${process.env.REALM_URL}/protocol/openid-connect/userinfo`, {
    headers: { authorization: `Bearer ${token}` },
  }).catch((e) => console.error(e));

  if (!res) throw new Error("Cannot connect to auth service.");
  if (!res.ok) throw new HttpError(HttpStatusCode.UNAUTHORIZED, "Invalid token provided.");

  return await jwtDecode(token);
}