vkpay params example

let stringify = require('json-stable-stringify');  //  canonical json implementation
let md5 = require('md5');
let base64 = require('base-64');
let sha1 = require('sha1');

let amount = 1;
let merch_data = {
  amount: amount,
  order_id: ++last_order_id,
  currency: "RUB",
  ts: (Date.now() / 1000 | 0), // так можно отбросить дробную часть)
  cashback: {pay_time: (Date.now() / 1000 | 0 + 200), amount_percent: 30}
};

let merch_data_base64 = base64.encode(JSON.stringify(merch_data))
let data = {
  cashback: merch_data.cashback,
  order_id: merch_data.order_id,
  ts: merch_data.ts,
  currency: "RUB",
  merchant_data: merch_data_base64,
  merchant_sign: sha1(merch_data_base64 + MERCH_PRIVATE_KEY),
  event_name: "not required!!", // you can put here any data you want
  your_custom_params_here: 123,
};

let pay_window_params = {
  amount: amount,
  data: data,
  description: "Оплата заказа",
  action: "pay-to-service",
  merchant_id: MERCH_ID,
  version: 2
}

let params = ""
Object.keys(pay_window_params).sort((a, b) => a > b).forEach(
        function (key) { if (key != "action") params += key + "=" + ( key == "data"? stringify( pay_window_params[key] ) : pay_window_params[key]  ) }
)
pay_window_params.sign = md5(params + APP_SECRET_KET)
console.log("sign_params_str: ", params)
console.log("result: " + JSON.stringify(pay_window_params));