/*********************************************************
Alexis C. Montenegro © June 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(true);
    setStudyTitle("MAChannel");
    setCursorLabelName("Upper", 0);
    setCursorLabelName("MA", 1);
    setCursorLabelName("Lower", 2);
    setDefaultBarFgColor(Color.blue, 0);    
    setDefaultBarFgColor(Color.red, 1);
    setDefaultBarFgColor(Color.blue, 2);
    setPlotType(PLOTTYPE_LINE,0);
    setPlotType(PLOTTYPE_LINE,1);
    setPlotType(PLOTTYPE_LINE,2);
    setDefaultBarThickness(1,0);
    setDefaultBarThickness(1,1);
    setDefaultBarThickness(1,2);
    var x=0;
    fpArray[x] = new FunctionParameter("Type", FunctionParameter.STRING);
    with(fpArray[x++]){
        addOption("sma");
        addOption("ema");
        addOption("wma");
        addOption("vwma");
        setDefault("sma");
    }
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.NUMBER);
    with(fpArray[x++]){
        setLowerLimit(1);		
        setDefault(10);
    }
	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("Bands", FunctionParameter.STRING);
	with(fpArray[x++]){
        setName("Bands based on");
        addOption("Points");
        addOption("Percent");
        addOption("Std Deviation");
        addOption("ATR");
        setDefault("Points");
    }
	fpArray[x] = new FunctionParameter("Value", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setName("Value/Multiple");
        setLowerLimit(0);
        setDefault(0);
    }
    fpArray[x] = new FunctionParameter("Offset", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(0);
        setDefault(0);
    }
	fpArray[x] = new FunctionParameter("LineColor1", FunctionParameter.COLOR);
	with(fpArray[x++]){
        setName("Channel Color");
        setDefault(Color.blue);
    }
	fpArray[x] = new FunctionParameter("LineColor2", FunctionParameter.COLOR);
	with(fpArray[x++]){
        setName("Basis Color");
        setDefault(Color.red);
    }
    fpArray[x] = new FunctionParameter("Params", FunctionParameter.BOOLEAN);
	with(fpArray[x++]){
        setName("Show Parameters");
        setDefault(false);
    }
}

var bInit = false;
var xMA = null;
var xBands = null;
var xBandsUpper = 0;
var xBandsBasis = 0;
var xBandsLower = 0;

function main(Type,Length,Source,Symbol,Interval,Bands,Value,Offset,LineColor1,LineColor2,Params) {
    if(bInit == false){
        if(Symbol == null) Symbol = getSymbol();
        if(Interval == null) Interval = getInterval();
        var vSymbol = Symbol+","+Interval;
        xBands = efsInternal("calcBands",Type,Length,Source,Bands,Value,Offset,sym(vSymbol));
        xBandsUpper = getSeries(xBands,0);
        xBandsBasis = getSeries(xBands,1);
        xBandsLower = getSeries(xBands,2);
        setDefaultBarFgColor(LineColor1,0);
        setDefaultBarFgColor(LineColor2,1);
        setDefaultBarFgColor(LineColor1,2);    
        setShowTitleParameters(eval(Params));
        bInit = true;
    }
    return new Array (xBandsUpper,xBandsBasis,xBandsLower);
}

var xInit = false;
var xValue = null;
var xMA = null
var xATR = null;

function calcBands(type,length,source,bands,value,offset,series){
    var nATR = null;
    var nUpper = null;
    var nLower = null;
    var ySum = 0;
    var vStdDev = 0;
    if(xInit==false){
        xValue = offsetSeries(eval(source)(),offset);
        xMA = offsetSeries(eval(type)(length,eval(source)()),offset);
        xATR = offsetSeries(atr(length),offset);
        xInit=true;
    }
    if(bands == "Points"){
        var nMA = xMA.getValue(0)
        if(nMA == null) return;
        nUpper = nMA+value;
        nLower = nMA-value;
    }
    else if(bands == "Percent"){
        var nMA = xMA.getValue(0)
        if(nMA == null) return;
        nUpper = nMA*(1+(value/100));
        nLower = nMA*(1-(value/100));
    }
    else if(bands == "ATR"){
        var nMA = xMA.getValue(0)
        var nATR = xATR.getValue(0);
        if(nMA == null || nATR == null) return;
        nUpper = nMA+(nATR*value);
        nLower = nMA-(nATR*value);
    }
    else if(bands == "Std Deviation"){
        var nMA = xMA.getValue(0)
        if(nMA == null) return;
        
        for(var i=0; i<length; i++){
            ySum += (xValue.getValue(-i)-nMA)*(xValue.getValue(-i)-nMA);
        }
        vStdDev=Math.sqrt(ySum/(length)); 
        nUpper = nMA+(value*vStdDev);
        nLower = nMA-(value*vStdDev);
    }   
    return new Array (nUpper,nMA,nLower);
}