var volts=null;
    var amps=null;
    var ohms=null;
    var watts=null;
    var calcVolts=false;
    var calcAmps=false;
    var calcOhms=true;
    var calcWatts=true;

    function readVolts(inedit)
    {
        val = $('#iVoltage').val();

        if (val=="" || val==null)
        {
            volts=null;
        }
        else if ($.isNumeric(val))
        {
            volts=Number(val);
        }
        else if (!inedit)
        {
            $('#iVoltage').val(volts);
        }

       updateForm();
    }

    function readAmps(inedit)
    {
        var val=$('#iCurrent').val();
        var scale=$('#sCurrentUnit').val();
        if (val=="" || val==null)
        {
            amps=null;
        }
        else if ($.isNumeric(val))
        {
            amps=Number(val)*Number(scale);
        }
        else if (!inedit)
        {
            $('#iCurrent').val(amps/scale);
        }

       updateForm();
    }

    function readOhms(inedit)
    {
        var val=$('#iResistance').val();
        var scale=$('#sResistanceUnit').val();
        if (val=="" || val==null)
        {
            ohms=null;
        }
        else if ($.isNumeric(val))
        {
            ohms=Number(val)*Number(scale);
        }
        else if (!inedit)
        {
            $('#iResistance').val(ohms/scale);
        }

       updateForm();
    }

    function readWatts(inedit)
    {
        val = $('#iPower').val();

        if (val=="" || val==null)
        {
            watts=null;
        }
        else if ($.isNumeric(val))
        {
            watts=Number(val);
        }
        else if (!inedit)
        {
            $('#iPower').val(watts);
        }

       updateForm();
    }

    function updateForm()
    {
        numFields=0;

        if (volts>0)
            numFields++;
        if (amps>0)
            numFields++;
        if (ohms>0)
            numFields++;
        if (watts>0)
            numFields++;

        if (numFields>=2)
        {
            $('#btnCalc').removeAttr('disabled');
        }
        else
        {
            $('#btnCalc').attr('disabled','disabled');
        }

        if (numFields==2 || numFields==3)
        {
            if (volts>0)
            {
                calcVolts=false;
                $('#iVoltage').removeClass('to-calc');
            }
            else
            {
                calcVolts=true;
                $('#iVoltage').addClass('to-calc');
            }
            if (amps>0)
            {
                calcAmps=false;
                $('#iCurrent').removeClass('to-calc');
            }
            else
            {
                calcAmps=true;
                $('#iCurrent').addClass('to-calc');
            }
            if (ohms>0)
            {
                calcOhms=false;
                $('#iResistance').removeClass('to-calc');
            }
            else
            {
                calcOhms=true;
                $('#iResistance').addClass('to-calc');
            }
            if (watts>0)
            {
                calcWatts=false;
                $('#iPower').removeClass('to-calc');
            }
            else
            {
                calcWatts=true;
                $('#iPower').addClass('to-calc');
            }
        }
    }

    function calc()
    {
        updateForm();

        $('#iVoltage').parent().parent().removeClass('has-error');
        $('#iCurrent').parent().parent().removeClass('has-error');
        $('#iResistance').parent().parent().removeClass('has-error');
        $('#iPower').parent().parent().removeClass('has-error');
        $('#iVoltage').attr('title','');
        $('#iCurrent').attr('title','');
        $('#iResistance').attr('title','');
        $('#iPower').attr('title','');

        if (calcVolts && calcAmps)
        {
            amps  = Math.sqrt((watts/ohms),2);
            volts = amps*ohms;
        }
        else if (calcVolts && calcOhms)
        {
            volts = watts/amps;
            ohms  = volts/amps;
        }
        else if (calcVolts && calcWatts)
        {
            volts = amps*ohms;
            watts = amps*amps*ohms;
        }
        else if (calcAmps && calcOhms)
        {
            amps  = watts/volts;
            ohms  = volts/amps;
        }
        else if (calcAmps && calcWatts)
        {
            amps  = volts/ohms;
            watts = volts*amps;
        }
        else if (calcOhms && calcWatts)
        {
            ohms  = volts/amps;
            watts = volts*amps;
        }
        else if (calcVolts)
        {
            volts = amps*ohms;
            testWatts = volts*amps;
            if (Math.abs((testWatts-watts)/testWatts)>0.0001)
            {
                $("#iPower").parent().parent().addClass("has-error");
                $("#iPower").attr('data-original-title','Expected '+testWatts);
            }
        }
        else if (calcAmps)
        {
            amps  = volts/ohms;
            testWatts = volts*amps;
            if (Math.abs((testWatts-watts)/testWatts)>0.0001)
            {
                $("#iPower").parent().parent().addClass("has-error");
                $("#iPower").attr('data-original-title','Expected '+testWatts);
            }
        }
        else if (calcOhms)
        {
            ohms  = volts/amps;
            testWatts = volts*amps;
            if (Math.abs((testWatts-watts)/testWatts)>0.0001)
            {
                $("#iPower").parent().parent().addClass("has-error");
                $("#iPower").attr('data-original-title','Expected '+testWatts);
            }
        }
        else if (calcWatts)
        {
            watts = volts*amps;
            testOhms = volts/amps;
            if (Math.abs((testOhms-ohms)/testOhms)>0.0001)
            {
                $("#iResistance").parent().parent().addClass("has-error");
                $("#iResistance").attr('data-original-title','Expected '+testOhms);
            }
        }

        volts = Math.round (volts*100000);
        volts = volts/100000;
        amps = Math.round(amps*100000);
        amps = amps/100000;
        ohms = Math.round(ohms*100000);
        ohms = ohms/100000;
        watts = Math.round(watts*100000);
        watts = watts/100000;

        $('#iVoltage').val(volts);
        $('#iCurrent').val(amps/$('#sCurrentUnit').val());
        $('#iResistance').val(ohms/$('#sResistanceUnit').val());
        $('#iPower').val(watts);
    }

    $(document).ready(function() {
        $('#iVoltage').change(function () {
            readVolts(false);});
        $('#iVoltage').keyup(function () {
            readVolts(true);});
            $('#iCurrent').change(readAmps);

        $('#iCurrent').change(function () {
            readAmps(false);});
        $('#iCurrent').keyup(function () {
            readAmps(true);});

        $('#sCurrentUnit').change(function () {
            readAmps(false);});

        $('#iResistance').change(function () {
            readOhms(false);});
        $('#iResistance').keyup(function () {
            readOhms(true);});

        $('#sResistanceUnit').change(function () {
            readOhms(false);});

        $('#iPower').change(function () {
            readWatts(false);});
        $('#iPower').keyup(function () {
            readWatts(true);});

        $('input').not('#search input').keyup(function(e) {
            var focusables = $("input:focusable").not('#search input');
            if (e.keyCode == 40) {
                // down key
                var current = focusables.index(this);
                next = focusables.eq(current+1).length ? focusables.eq(current+1) : focusables.eq(0);
                next.focus();
            } else if (e.keyCode == 38) {
                // up key
                var current = focusables.index(this),
                prev = focusables.eq(current-1).length ? focusables.eq(current-1) : focusables.eq(focusables.length-1);
                prev.focus();
            }
        });

        $('#btnCalc').click(calc);
        $('input').keypress(function (e) {
            if (e.which == 13 && $('#btnCalc').attr('disabled')==undefined) {
                console.log("calrc");
                calc();
            }
        });

        $('[data-toggle="tooltip"]').tooltip({ container: 'body'});
    });