# Parabolic SAR (SDK Trading)

registerIndicator("sar", "Parabolic SAR(v1.0)", function (context) {
    var dataInputHigh = getDataInput(context, 0)
    var dataInputLow = getDataInput(context, 1)

    var dataOutput = getDataOutput(context, "sar")

    var acceleration = getIndiParameter(context, "acceleration")
    var af = acceleration
    var afMax = getIndiParameter(context, "afMax")

    var calculatedLength = getCalculatedLength(context)
    var i = calculatedLength

    if (i > 0) {
        i--
    } else {
        dataOutput[i] = 0
        i = 1
    }

    var prevH = dataInputHigh[i - 1]
    var prevL = dataInputLow[i - 1]
    var currH = null
    var currL = null

    var isLong = true
    var ep = prevH
    var sar = prevL

    while (i < dataInputHigh.length) {
        currH = dataInputHigh[i]
        currL = dataInputLow[i]

        if (isLong) {
            if (currL <= sar) {
                isLong = false
                sar = Math.max(ep, currH, prevH)

                dataOutput[i] = sar

                af = acceleration
                ep = currL
                sar = sar + af * (ep - sar)
                sar = Math.max(sar, currH, prevH)
            } else {
                dataOutput[i] = sar

                if (currH > ep) {
                    ep = currH
                    af += acceleration
                    if (af > afMax) {
                        af = afMax
                    }
                }
                sar = sar + af * (ep - sar)
                sar = Math.min(sar, currL, prevL)
            }
        } else {
            if (currH >= sar) {
                isLong = true
                sar = Math.min(ep, currL, prevL)

                dataOutput[i] = sar

                af = acceleration
                ep = currH
                sar = sar + af * (ep - sar)
                sar = Math.min(sar, currL, prevL)
            }else{
                dataOutput[i] = sar

                if (currL < ep) {
                    ep = currL
                    af += acceleration
                    if (af > afMax) {
                        af = afMax
                    }
                }
                sar = sar + af * (ep - sar)
                sar = Math.max(sar, currH, prevH)
            }
        }
        i++

        prevH = currH
        prevL = currL
    }
},[{
    name: "acceleration",
    value: 0.02,
    required: true,
    type: PARAMETER_TYPE.NUMBER,
    range: [0.01, 0.1]
},{
    name: "afMax",
    value: 0.2,
    required: true,
    type: PARAMETER_TYPE.NUMBER,
    range: [0.1, 1]
}],
[{
    name: DATA_NAME.HIGH,
    index: 0
},{
    name: DATA_NAME.LOW,
    index: 1
}],
[{
    name: "sar",
    visible: true,
    renderType: RENDER_TYPE.ROUND,
    color: "steelblue"
}],
WHERE_TO_RENDER.CHART_WINDOW)