import { User } from '../models/user';

export function parseUser(jwt: string): User {
  const token = decodeJWT(jwt);
  if (token === null) {
    throw new Error(`The JWT token provided was not valid:\n${jwt}`);
  }
  const user = JSON.parse(token.payload) as User;
  // store token:
  user.token = jwt;
  return user;
}

export function decodeJWT(str: string) {
  const parts = str.split('.');
  if (parts.length < 2) {
    return null;
  }
  return {
    header: decodeBase64Url(parts[0]),
    payload: decodeBase64Url(parts[1]),
    signature: parts[2]
  };
}

export function decodeBase64Url(base64Url: string) {
  // convert Base64Url to Base64: https://tools.ietf.org/html/rfc4648#section-5
  let output = base64Url.replace(/-/g, '+').replace(/_/g, '/');
  const padding = (4 - output.length % 4) % 4;
  if (padding === 3) {
    throw Error('Invalid base64 input');
  }
  output += new Array(1 + padding).join('=');
  const decoded = atob(output);
  try {
    return decodeURIComponent(decoded.split('')
      .map(c => '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2))
      .join(''));
  } catch {
    return decoded;
  }
}

// eslint-disable-next-line @typescript-eslint/no-empty-object-type
export function encodeBase64Url(input: {}) {
  const encodedToURI: string = encodeURI(JSON.stringify(input));
  let result = '';
  for (let i = 0; i < encodedToURI.length; i++) {
    const c = encodedToURI[i];
    if (c === '%') {
      result += String.fromCharCode(parseInt((encodedToURI[++i] + encodedToURI[++i]), 16));
    } else {
      result += c;
    }
  }
  return btoa(result);
}