import { enc, HmacSHA256, SHA256 } from 'crypto-js';
import dayjs from "dayjs";
import utc from "dayjs/plugin/utc";
import { Client, Message, MQTTError } from 'paho-mqtt';

dayjs.extend(utc);

// Helper functions to perform sigv4 operations
function SigV4Utils() { }
SigV4Utils.sign = function (key: CryptoJS.lib.WordArray, msg: string) {
  const hash = HmacSHA256(msg, key);
  return hash.toString(enc.Hex);
};
SigV4Utils.sha256 = function (msg: string) {
  const hash = SHA256(msg);
  return hash.toString(enc.Hex);
};
SigV4Utils.getSignatureKey = function (key: string, dateStamp: string, regionName: string, serviceName: string) {
  const kDate = HmacSHA256(dateStamp, 'AWS4' + key);
  const kRegion = HmacSHA256(regionName, kDate);
  const kService = HmacSHA256(serviceName, kRegion);
  const kSigning = HmacSHA256('aws4_request', kService);
  return kSigning;
};

export const startSession = ({
  endpoint,
  region,
  accessKeyId,
  secretAccessKey,
  sessionToken,
  clientId,
}: {
  endpoint: string;
  region: string;
  accessKeyId: string;
  secretAccessKey: string;
  sessionToken: string;
  clientId: string;
},
  {
    onConnect,
    onFailure,
    onMessageArrived,
    onConnectionLost,
  }: {
    onConnect: () => void;
    onFailure: (e: MQTTError) => void;
    onMessageArrived: (m: Message) => void;
    onConnectionLost: (e: MQTTError) => void;
  }) => {
  // Get timestamp and format data
  const time = dayjs().utc();
  const dateStamp = time.format('YYYYMMDD');
  const amzdate = dateStamp + 'T' + time.format('HHmmss') + 'Z';
  // Define constants used to create the message to be signed
  const service = 'iotdevicegateway';
  const secretKey = secretAccessKey
  const accessKey = accessKeyId
  const algorithm = 'AWS4-HMAC-SHA256';
  const method = 'GET';
  const canonicalUri = '/mqtt';
  const host = endpoint;

  // Set credential scope to today for a specific service in a specific region
  const credentialScope = dateStamp + '/' + region + '/' + service + '/' + 'aws4_request';
  // Start populating the query string
  let canonicalQuerystring = 'X-Amz-Algorithm=AWS4-HMAC-SHA256';
  // Add credential information
  canonicalQuerystring += '&X-Amz-Credential=' + encodeURIComponent(accessKey + '/' + credentialScope);
  // Add current date
  canonicalQuerystring += '&X-Amz-Date=' + amzdate;
  // Add expiry date
  // canonicalQuerystring += '&X-Amz-Expires=86400';
  // Add headers, only using one = host
  canonicalQuerystring += '&X-Amz-SignedHeaders=host';
  const canonicalHeaders = 'host:' + host + '\n';
  // No payload, empty
  const payloadHash = 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'; // empty string -> echo -n "" | xxd  | shasum -a 256
  // Build canonical request
  const canonicalRequest = method + '\n' + canonicalUri + '\n' + canonicalQuerystring + '\n' + canonicalHeaders + '\nhost\n' + payloadHash;
  // console.log('canonicalRequest: \n' + canonicalRequest);
  // Hash the canonical request and create the message to be signed
  const stringToSign = algorithm + '\n' + amzdate + '\n' + credentialScope + '\n' + SigV4Utils.sha256(canonicalRequest);
  // Derive the key to be used for the signature based on the scoped down request
  const signingKey = SigV4Utils.getSignatureKey(secretKey, dateStamp, region, service);
  // console.log('stringToSign: \n'); console.log(stringToSign);
  // console.log('signingKey: \n'); console.log(signingKey);
  // Calculate signature
  const signature = SigV4Utils.sign(signingKey, stringToSign);
  // Append signature to message
  canonicalQuerystring += '&X-Amz-Signature=' + signature;
  // Append existing security token to the request (since we are using STS credetials) or do nothing if using IAM credentials
  if (sessionToken !== "") {
    canonicalQuerystring += '&X-Amz-Security-Token=' + encodeURIComponent(sessionToken);
  }
  const requestUrl = 'wss://' + host + canonicalUri + '?' + canonicalQuerystring;
  // console.log(requestUrl);

  const mqtt_client = new Client(requestUrl, clientId);
  mqtt_client.onMessageArrived = onMessageArrived;
  mqtt_client.onConnectionLost = onConnectionLost;
  mqtt_client.connect({
    onSuccess: onConnect,
    onFailure: onFailure,
    useSSL: true,
    timeout: 5,
  });

  return mqtt_client;
}