Poloniex private API for Google Apps Script (Google Sheet)

poloniex_private_api.gs

// work in progress

// you need a poloniex API key and secret with trading option enabled
// you can test it with:
// = polo("returnBalances","BTC")
// or
// = polo("returnBalances","all")
// or buy and sell:
// polo("BUY","BTC_LTC", 0.0251, 1) or polo("SELL","BTC_LTC", 0.0251, 1)


function polo(command,currencyPair,rate,amount){

// fillOrKill, immediateOrCancel, postOnly set to true are missing
  poloniex_auth_(command,[{key: "currencyPair",value: currencyPair},{key: "rate",value: rate},{key: "amount",value: amount}], function(result){
    Logger.log(result)
    return JSON.stringify(result)
  })

}

function poloniex_auth_(command,params,callback) {
      
  // I assume that all the keys are in the "keys" spreadsheet. The key is in cell B4 and the secret in cell C4.
    
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("keys");
  
  var key = sheet.getRange("B4").getValue();
    
  var secret = sheet.getRange("C4").getValue();
  
  var nonce = 1495932972127042 + new Date().getTime();
     
  var payload = {
    "nonce": nonce,
    "command": command
  }
  
  params.forEach( function(param){
    payload[param.key] = param.value;
  })
  
  var payloadEncoded = Object.keys(payload).map(function(param) {
    return encodeURIComponent(param) + '=' + encodeURIComponent(payload[param]);
  }).join('&');
    
  var uri = "https://poloniex.com/tradingApi";

  var signature = Utilities.computeHmacSignature(Utilities.MacAlgorithm.HMAC_SHA_512, payloadEncoded, secret);
    
  var stringSignature = signature.map(function(byte) {
    return ('0' + (byte & 0xFF).toString(16)).slice(-2);
  }).join('')
    
  var headers = {
    "key": key,
    "sign": stringSignature
  }
  
  var params = {
    "method": "post",
    "headers": headers,
    "payload": payloadEncoded
  }
  
  var response = UrlFetchApp.fetch(uri, params);
  
  var dataAll = JSON.parse(response.getContentText());
  
  callback(dataAll)

}

So I've gotten the trading bit to work just fine, but I can't seem to get a simple query on my balances to work. I'm trying:
polo("returnBalances","BTC")
But I get the following error message:

Request failed for https://poloniex.com/tradingApi returned code 422. Truncated server response: {"error":"Invalid currencyPair parameter."} (use muteHttpExceptions option to examine full response) (line 66).

Thoughts?

I have the same issue as citadella