var assert = require('assert');

var topic = {"ChannelName":"t_amb","DeviceAddress":"c4:93:00:0a:8a:0d:01:99","DeviceType":"prostarsolar","GatewayAddress":"C493000A8A0D","TechName":"prostarsolar_[c4:93:00:0a:8a:0d:01:99]","TenantID":194};
var payload = {"Timestamp":1515422927,"Value":"0"};
var now = 1515422927;


var lambda = function(topic, payload, now){
  var inpValue = parseInt(payload.Value);
  var outValue;
  var binaryInput = Array(16).join("0") + inpValue.toString(2);
  var binRep = binaryInput.substring(binaryInput.length - 16);
  var sign = 1;
  var fraction;
  if (parseInt(binRep[0]) === 1){
    sign = -1;
  }
  var exponent = parseInt(binRep.substring(1, 6), 2);
  if (exponent === 30.0){
    fraction = parseInt("1".concat(binRep.substring(7, 17)), 2);
  } else {
    fraction = parseInt(binRep.substring(7, 17), 2);
  }
  if (exponent === 0){
    outValue = sign * Math.pow(2,-14) * fraction / Math.pow(2.0, 10.0);
  } else if (exponent === 0b11111){
    if (fraction == 0){
      outValue = sign * Infinity;
    } else {
      outValue = NaN;
    }
  } else {
    var frac_part = 1.0 + fraction / Math.pow(2.0, 10.0);
    outValue = sign * Math.pow(2 , exponent - 15) * frac_part;
  }


  return outValue;
}

var intToFloat16 = function(intToConvert){
  var binRep = pad(intToConvert.toString(2), 16, "0");
  var sign = 1;
  var fraction;
  if (parseInt(binRep[0]) === 1){
    sign = -1;
  }
  var exponent = parseInt(binRep.substring(1, 6), 2);
  if (exponent === 30.0){
    fraction = parseInt("1".concat(binRep.substring(7, 17)), 2);
  } else {
    fraction = parseInt(binRep.substring(7, 17), 2);
  }

  // console.log("Sign: " + sign);
  // console.log("exponent: " + exponent + " -- " + binRep.substring(1, 6));
  // console.log("fraction: " + fraction);

  if (exponent === 0){
    return sign * (2 ** -14) * fraction / (2.0 ** 10.0);
  } else if (exponent === 0b11111){
    if (fraction == 0){
      return sign * Infinity;
    } else {
      return NaN;
    }
  } else {
    var frac_part = 1.0 + fraction / (2.0 ** 10.0);
    return sign * (2 ** (exponent - 15)) * frac_part;
  }
}

var pad = function(start, numChars, padWith){
  var fullString = Array(numChars).join(padWith) + start;
  return fullString.substring(fullString.length - 16);
}

var test_values = [
    [0b0000000000000000, 0.],
    [0b1000000000000000, -0.],
    [0b0011110000000000, 1],
    [0b0011110000000001, 1.0009765625],
    [0b1011110000000001, -1.0009765625],
    [0b1100000000000000, -2],
    [0b0100000000000000, 2],
    [0b0111101111111111, 65504.],
    [0b1111101111111111, -65504.],
    [0b0000010000000000, 6.10352e-5],
    [0b0000001111111111, 6.09756e-5],
    [0b0000000000000001, 5.96046e-8],
    [0b0111110000000000, Infinity],
    [0b1111110000000000, -Infinity],
    [0b0011010101010101, 0.333251953125]
]


describe('intToFloat16', function(){
  for (var i = 0; i < test_values.length; i++){
    var testInput = test_values[i][0];
    var expectedVal = test_values[i][1];


    payload.Value = testInput;
    // var testVal = intToFloat16(testInput);
    var testVal = lambda(topic, payload, now);

    it("should return " + test_values[i][1] + " for " + test_values[i][0].toString(2) + " : " + testVal, function(){
      assert.equal(testVal, expectedVal);
    })
  }
})