Support $__range_series variable

pkg/datasource/functions.go

@@ -8,6 +8,8 @@ import (
 	"github.com/alexanderzobnin/grafana-zabbix/pkg/timeseries"
 )
 
+const RANGE_VARIABLE_VALUE = "range_series"
+
 var errFunctionNotSupported = func(name string) error {
 	return fmt.Errorf("function not supported: %s", name)
 }
@@ -75,12 +77,18 @@ func applyFunctions(series []*timeseries.TimeSeriesData, functions []QueryFuncti
 func applyGroupBy(series timeseries.TimeSeries, params ...string) (timeseries.TimeSeries, error) {
 	pInterval := params[0]
 	pAgg := params[1]
+	aggFunc := getAggFunc(pAgg)
+
+	if pInterval == RANGE_VARIABLE_VALUE {
+		s := series.GroupByRange(aggFunc)
+		return s, nil
+	}
+
 	interval, err := gtime.ParseInterval(pInterval)
 	if err != nil {
 		return nil, errParsingFunctionParam(err)
 	}
 
-	aggFunc := getAggFunc(pAgg)
 	s := series.GroupBy(interval, aggFunc)
 	return s, nil
 }

pkg/timeseries/timeseries.go

@@ -75,6 +75,18 @@ func (ts TimeSeries) GroupBy(interval time.Duration, aggFunc AggFunc) TimeSeries
 	return groupedSeries
 }
 
+func (ts TimeSeries) GroupByRange(aggFunc AggFunc) TimeSeries {
+	if ts.Len() == 0 {
+		return ts
+	}
+
+	value := aggFunc(ts)
+	return []TimePoint{
+		{Time: ts[0].Time, Value: value},
+		{Time: ts[ts.Len()-1].Time, Value: value},
+	}
+}
+
 func (ts TimeSeries) Transform(transformFunc TransformFunc) TimeSeries {
 	for i, p := range ts {
 		ts[i] = transformFunc(p)