const baseRequest = {
  apiVersion: 2,
  apiVersionMinor: 0
};

const allowedCardNetworks = ["AMEX", "DISCOVER", "INTERAC", "JCB", "MASTERCARD", "VISA"];

const allowedCardAuthMethods = ["PAN_ONLY", "CRYPTOGRAM_3DS"];

const tokenizationSpecification = {
  type: 'PAYMENT_GATEWAY',
  parameters: {
    'gateway': 'example',
    'gatewayMerchantId': 'exampleGatewayMerchantId'
  }
};

const baseCardPaymentMethod = {
  type: 'CARD',
  parameters: {
    allowedAuthMethods: allowedCardAuthMethods,
    allowedCardNetworks: allowedCardNetworks
  }
};

const cardPaymentMethod = Object.assign(
  {},
  baseCardPaymentMethod,
  {
    tokenizationSpecification: tokenizationSpecification
  }
);

let paymentsClient = null;

function getGoogleIsReadyToPayRequest() {
  return Object.assign(
      {},
      baseRequest,
      {
        allowedPaymentMethods: [baseCardPaymentMethod]
      }
  );
}

function getGooglePaymentDataRequest() {
  const paymentDataRequest = Object.assign({}, baseRequest);
  paymentDataRequest.allowedPaymentMethods = [cardPaymentMethod];
  paymentDataRequest.transactionInfo = getGoogleTransactionInfo();
  paymentDataRequest.merchantInfo = {
  merchantName: 'Example Merchant'
  };

  paymentDataRequest.callbackIntents = ["PAYMENT_AUTHORIZATION"];

  return paymentDataRequest;
}

function getGooglePaymentsClient() {
  if ( paymentsClient === null ) {
    paymentsClient = new google.payments.api.PaymentsClient({
        environment: 'TEST',
      paymentDataCallbacks: {
        onPaymentAuthorized: onPaymentAuthorized
      }
    });
  }
  return paymentsClient;
}
function onPaymentAuthorized(paymentData) {
  return new Promise(function(resolve, reject){
    // handle the response
    processPayment(paymentData)
      .then(function() {
        resolve({transactionState: 'SUCCESS'});
      })
      .catch(function() {
        resolve({
          transactionState: 'ERROR',
          error: {
            intent: 'PAYMENT_AUTHORIZATION',
            message: 'Insufficient funds, try again. Next attempt should work.',
            reason: 'PAYMENT_DATA_INVALID'
          }
        });
	    });
  });
}
function onGooglePayLoaded() {
  const paymentsClient = getGooglePaymentsClient();
  paymentsClient.isReadyToPay(getGoogleIsReadyToPayRequest())
    .then(function(response) {
      if (response.result) {
        addGooglePayButton();
      }
    })
    .catch(function(err) {
      console.error(err);
    });
}

function addGooglePayButton() {
  const paymentsClient = getGooglePaymentsClient();
  const button =
      paymentsClient.createButton({onClick: onGooglePaymentButtonClicked});
  document.getElementById('container').appendChild(button);
}

function getGoogleTransactionInfo() {
  return {
        displayItems: [
        {
          label: "Subtotal",
          type: "SUBTOTAL",
          price: "11.00",
        },
      {
          label: "Tax",
          type: "TAX",
          price: "1.00",
        }
    ],
    countryCode: 'RO',
    currencyCode: "EUR",
    totalPriceStatus: "FINAL",
    totalPrice: "1.00",
    totalPriceLabel: "Total"
  };
}

function onGooglePaymentButtonClicked() {
  const paymentDataRequest = getGooglePaymentDataRequest();
  paymentDataRequest.transactionInfo = getGoogleTransactionInfo();

  const paymentsClient = getGooglePaymentsClient();
  paymentsClient.loadPaymentData(paymentDataRequest);
}

let attempts = 0;

function processPayment(paymentData) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      paymentToken = paymentData.paymentMethodData.tokenizationData.token;

			if (attempts++ % 2 == 0) {
	      reject(new Error('Every other attempt fails, next one should succeed'));      
      } else {
	      resolve({});      
      }
    }, 500);
  });
}