// arduino_serial.js
// kll node + serial 
// start with:  node arduino_serial.js 
//         or:  node arduino_serial.js /dev/ttyACM0
// see http://www.dyn-web.com/tutorials/php-js/json/parse.php
// see http://www.w3schools.com/json/json_eval.asp


'use strict';

const serialport = require('serialport');// include the library
const SerialPort = serialport.SerialPort; // make a local instance of it

   // get port name from the command line / or use default
var portName = "/dev/ttyACM0";
var portNameCLI = process.argv[2];
   console.log("port from command line:" + portNameCLI);
   if ( portNameCLI > "") { portName = portNameCLI; console.log(" used "); } else { console.log(" use default "); }

/*
// list serial port info:
serialport.list(function (err, ports) {
  ports.forEach(function(port) {
    if ( port.comName == portName ) {
    console.log("port: " + port.comName + " manuf: " + port.manufacturer + " lets try that one");
				     }  });  });
*/


var myPort = new SerialPort(portName, 
	 { baudRate: 9600, parser: serialport.parsers.readline("\n") }
		);   // look for return and newline at the end of each data packet

// these are the definitions for the serial events:
myPort.on('open', showPortOpen);
myPort.on('data', saveLatestData);
myPort.on('close', showPortClose);
myPort.on('error', showError);

// the functions called when the serial events occur:
function showPortOpen() {
  console.log('port open:' + portName +' Data rate: ' + myPort.options.baudRate);
  myPort.flush();
}

function saveLatestData(data) {
  var channel = 0;
  if (isValidJSON(data)) {
     let serialData = JSON.parse(data); // convert to JSON 
     console.log("string:" + data);     // show full string for better understanding
     console.log("channels: " + serialData.CHANNELS);
     console.log("time: " + serialData.TIME); 

     for ( channel = 0; channel < serialData.CHANNELS; channel++ ) {
       console.log(serialData.DESC[channel] + " : " + serialData.AIN[channel]); 
                                                           }
     								// console.log(serialData.A0 + " mul 2.5  " +serialData.A0 * 2.5);
				} else {  console.log(data);  } // show all
}

function showPortClose() {
  console.log('port closed.');
}

function showError(error) {
  console.log('Serial port error: ' + error);
}


function isValidJSON(jsonOBJ) {
        try {
            JSON.parse(jsonOBJ);
            return true;
        } catch (e) {
            return false;
        }
}