feature: add psar

pkg/indicator/psar.go

@@ -0,0 +1,109 @@
+package indicator
+
+import (
+	"time"
+
+	"github.com/c9s/bbgo/pkg/types"
+)
+
+// Parabolic SAR(Stop and Reverse)
+// Refer: https://www.investopedia.com/terms/p/parabolicindicator.asp
+// The parabolic SAR indicator, developed by J. Wells Wilder, is used by traders to determine
+// trend direction and potential reversals in price. The indicator uses a trailing stop and
+// reverse method called "SAR," or stop and reverse, to identify suitable exit and entry points.
+// Traders also refer to the indicator as to the parabolic stop and reverse, parabolic SAR, or PSAR.
+//
+// The parabolic SAR indicator appears on a chart as a series of dots, either above or below an asset's
+// price, depending on the direction the price is moving. A dot is placed below the price when it is
+// trending upward, and above the price when it is trending downward.
+
+//go:generate callbackgen -type PSAR
+type PSAR struct {
+	types.SeriesBase
+	types.IntervalWindow
+	Input *types.Queue
+	Value *types.Queue // Stop and Reverse
+	AF    float64      // Acceleration Factor
+
+	EndTime         time.Time
+	UpdateCallbacks []func(value float64)
+}
+
+func (inc *PSAR) Last() float64 {
+	if inc.Value == nil {
+		return 0
+	}
+	return inc.Value.Last()
+}
+
+func (inc *PSAR) Length() int {
+	if inc.Value == nil {
+		return 0
+	}
+	return inc.Value.Length()
+}
+
+func (inc *PSAR) Update(value float64) {
+	if inc.Input == nil {
+		inc.SeriesBase.Series = inc
+		inc.Input = types.NewQueue(inc.Window)
+		inc.Value = types.NewQueue(inc.Window)
+		inc.AF = 0.02
+	}
+	inc.Input.Update(value)
+	if inc.Input.Length() == inc.Window {
+		pprev := inc.Value.Index(1)
+		ppsar := inc.Value.Last()
+		if value > ppsar { // rising formula
+			high := inc.Input.Highest(inc.Window)
+			inc.Value.Update(ppsar + inc.AF*(high-ppsar))
+			if high == value {
+				inc.AF += 0.02
+				if inc.AF > 0.2 {
+					inc.AF = 0.2
+				}
+			}
+			if pprev > ppsar { // reverse
+				inc.AF = 0.02
+			}
+		} else { // falling formula
+			low := inc.Input.Lowest(inc.Window)
+			inc.Value.Update(ppsar - inc.AF*(ppsar-low))
+			if low == value {
+				inc.AF += 0.02
+				if inc.AF > 0.2 {
+					inc.AF = 0.2
+				}
+			}
+			if pprev < ppsar { // reverse
+				inc.AF = 0.02
+			}
+		}
+	}
+}
+
+var _ types.SeriesExtend = &PSAR{}
+
+func (inc *PSAR) CalculateAndUpdate(kLines []types.KLine) {
+	for _, k := range kLines {
+		if inc.EndTime != zeroTime && !k.EndTime.After(inc.EndTime) {
+			continue
+		}
+		inc.Update(k.Close.Float64())
+	}
+
+	inc.EmitUpdate(inc.Last())
+	inc.EndTime = kLines[len(kLines)-1].EndTime.Time()
+}
+
+func (inc *PSAR) handleKLineWindowUpdate(interval types.Interval, window types.KLineWindow) {
+	if inc.Interval != interval {
+		return
+	}
+
+	inc.CalculateAndUpdate(window)
+}
+
+func (inc *PSAR) Bind(updater KLineWindowUpdater) {
+	updater.OnKLineWindowUpdate(inc.handleKLineWindowUpdate)
+}

pkg/indicator/psar_callbacks.go

@@ -0,0 +1,15 @@
+// Code generated by "callbackgen -type PSAR"; DO NOT EDIT.
+
+package indicator
+
+import ()
+
+func (inc *PSAR) OnUpdate(cb func(value float64)) {
+	inc.UpdateCallbacks = append(inc.UpdateCallbacks, cb)
+}
+
+func (inc *PSAR) EmitUpdate(value float64) {
+	for _, cb := range inc.UpdateCallbacks {
+		cb(value)
+	}
+}