/*********************************************************
Alexis C. Montenegro © October 2005                       
Use and/or modify this code freely. If you redistribute it
please include this and/or any other comment blocks and a 
description of any changes you make.                      
**********************************************************/

var fpArray = new Array();

function preMain(){
    setPriceStudy(false);
    setStudyTitle("Trend Continuation Factor");
    setCursorLabelName("TCF+", 0);
    setCursorLabelName("TCF-", 1);
    setDefaultBarFgColor(Color.blue, 0);
    setDefaultBarFgColor(Color.red, 1);
    setPlotType(PLOTTYPE_LINE,0);
    setPlotType(PLOTTYPE_LINE,1);
    setDefaultBarThickness(1,0);
    setDefaultBarThickness(1,1);
    var x=0;
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(2);		
        setDefault(20);
    }
	fpArray[x] = new FunctionParameter("Source", FunctionParameter.STRING);
	with(fpArray[x++]){
        addOption("open"); 
        addOption("high");
        addOption("low");
        addOption("close");
        addOption("hl2");
        addOption("hlc3");
        addOption("ohlc4"); 
        setDefault("close"); 
    }
    fpArray[x] = new FunctionParameter("Symbol", FunctionParameter.STRING);
    with(fpArray[x++]){
        setDefault();
	}
	fpArray[x] = new FunctionParameter("Interval", FunctionParameter.STRING);
	with(fpArray[x++]){
        setDefault();
    }
	fpArray[x] = new FunctionParameter("Params", FunctionParameter.BOOLEAN);
	with(fpArray[x++]){
        setName("Show Parameters");
        setDefault(false);
    }
}

var bInit = false;
var xTCF = null;
var xTCFPos = null;
var xTCFNeg = null;
function main(Length,Source,Symbol,Interval,Params){
    if(bInit == false){
        if(Symbol == null) Symbol = getSymbol();
        if(Interval == null) Interval = getInterval();
        var vSymbol = Symbol+","+Interval;
        xTCF = efsInternal("calcTCF",Length,eval(Source)(sym(vSymbol)));
        xTCFPos = getSeries(xTCF,0);
        xTCFNeg = getSeries(xTCF,1);
        addBand( 0, PS_SOLID, 1, Color.black,"0");
        setShowTitleParameters(eval(Params));
        bInit = true;
    }

    return new Array (xTCFPos,xTCFNeg);
}

var myLib = addLibrary("easyArray.efsLib");//comment out this line if not using the ezArray() function
var pVar = 0;
var nVar = 0;
var pCF = 0;
var nCF = 0;

/* add a / at the beginning of this line if using conventional logic             
var apVar = null;
var anVar = null;
var apCF = null;
var anCF = null;
//*/

function calcTCF(length,source){
  
        /*    ARRAY CREATED AND MAINTAINED USING CONVENTIONAL LOGIC     */
/* add a / at the beginning of this line if using conventional logic             
    if(apVar==null) apVar = new Array (length);
    if(anVar==null) anVar = new Array (length);
    if(apCF==null) apCF = new Array (length);
    if(anCF==null) anCF = new Array (length);

    if(getBarState()==BARSTATE_NEWBAR){
        apVar.pop();
        anVar.pop();
        apCF.pop();
        anCF.pop();
        apVar.unshift(pVar);
        anVar.unshift(nVar);
        apCF.unshift(pCF);
        anCF.unshift(nCF);
    }
    if(apVar[length-1]==null || anVar[length-1]==null || apCF[length-1]==null || anCF[length-1]==null) return;
        //                END CONVENTIONAL ARRAY LOGIC                  */

        /*    ARRAY CREATED AND MAINTAINED USING ezArray() FUNCTION     */
//*  remove a / at the beginning of this line if using conventional logic         
    var apVar = myLib.ezArray(pVar,length,"PosVar");
    var anVar = myLib.ezArray(nVar,length,"NegVar");
    var apCF  = myLib.ezArray(pCF,length,"PosCF");
    var anCF  = myLib.ezArray(nCF,length,"NegCF");
    if(apVar[length-1]==null || anVar[length-1]==null || apCF[length-1]==null || anCF[length-1]==null) return;
        //                    END ezArray() LOGIC                       */

    var Source_0 = source.getValue(0);
    var Source_1 = source.getValue(-1);
    if(Source_0==null || Source_1==null) return;
    
    if(Source_0>Source_1){
        pVar = Source_0-Source_1;
        nVar = 0;
    }else{
        pVar = 0;
        nVar = Source_1-Source_0;
    }
    
    if(pVar == 0){
        pCF = 0;
        nCF = nVar+anCF[1];
    }else{
        pCF = pVar+apCF[1];
        nCF = 0;
    }

// the following lines update the most recent element of the array
// and are required by both the conventional and ezArray() logic  
    apVar[0] = pVar;
    anVar[0] = nVar;
    apCF[0] = pCF;
    anCF[0] = nCF;
// end array update                                               
    
    var sumpVar = 0
    var sumnVar = 0;
    var sumpCF = 0;
    var sumnCF = 0
    
    for (var i=0; i<length; i++){
        sumpVar += apVar[i];
        sumnVar += anVar[i];
        sumpCF += apCF[i];
        sumnCF += anCF[i];
    }
    
    var pTCF = sumpVar-sumnCF;
    var nTCF = sumnVar-sumpCF;

    return new Array (pTCF, nTCF);
}