last annotation helper

last_value_annotation_series.go

@@ -0,0 +1,37 @@
+package chart
+
+import "fmt"
+
+// LastValueAnnotation returns an annotation series of just the last value of a value provider.
+func LastValueAnnotation(innerSeries ValueProvider, vfs ...ValueFormatter) AnnotationSeries {
+	var vf ValueFormatter
+	if len(vfs) > 0 {
+		vf = vfs[0]
+	} else if typed, isTyped := innerSeries.(ValueFormatterProvider); isTyped {
+		_, vf = typed.GetValueFormatters()
+	} else {
+		vf = FloatValueFormatter
+	}
+
+	var lastValue Value2
+	if typed, isTyped := innerSeries.(LastValueProvider); isTyped {
+		lastValue.XValue, lastValue.YValue = typed.GetLastValue()
+		lastValue.Label = vf(lastValue.YValue)
+	} else {
+		lastValue.XValue, lastValue.YValue = innerSeries.GetValue(innerSeries.Len() - 1)
+		lastValue.Label = vf(lastValue.YValue)
+	}
+
+	var seriesName string
+	var seriesStyle Style
+	if typed, isTyped := innerSeries.(Series); isTyped {
+		seriesName = fmt.Sprintf("%s - Last Value", typed.GetName())
+		seriesStyle = typed.GetStyle()
+	}
+
+	return AnnotationSeries{
+		Name:        seriesName,
+		Style:       seriesStyle,
+		Annotations: []Value2{lastValue},
+	}
+}