initial pipeline for functions processing

pkg/datasource/datasource.go

@@ -122,8 +122,6 @@ func (ds *ZabbixDatasource) QueryData(ctx context.Context, req *backend.QueryDat
 		ds.logger.Debug("DS query", "query", q)
 		if err != nil {
 			res.Error = err
-		} else if len(query.Functions) > 0 {
-			res.Error = ErrFunctionsNotSupported
 		} else if query.Mode != 0 {
 			res.Error = ErrNonMetricQueryNotSupported
 		} else {

pkg/datasource/functions.go

@@ -0,0 +1,40 @@
+package datasource
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/alexanderzobnin/grafana-zabbix/pkg/timeseries"
+)
+
+var errFunctionNotSupported = func(name string) error {
+	return fmt.Errorf("function not supported: %s", name)
+}
+
+type DataProcessingFunc = func(series timeseries.TimeSeries, params ...string) timeseries.TimeSeries
+
+var funcMap map[string]DataProcessingFunc
+
+func init() {
+	funcMap = make(map[string]DataProcessingFunc)
+	funcMap["groupBy"] = applyGroupBy
+}
+
+func applyFunctions(series []*timeseries.TimeSeriesData, functions []QueryFunction) ([]*timeseries.TimeSeriesData, error) {
+	for _, f := range functions {
+		if applyFunc, ok := funcMap[f.Def.Name]; ok {
+			for _, s := range series {
+				s.TS = applyFunc(s.TS, f.Params...)
+			}
+		} else {
+			err := errFunctionNotSupported(f.Def.Name)
+			return series, err
+		}
+	}
+	return series, nil
+}
+
+func applyGroupBy(series timeseries.TimeSeries, params ...string) timeseries.TimeSeries {
+	s := series.GroupBy(time.Minute, "avg")
+	return s
+}

pkg/datasource/zabbix.go

@@ -75,6 +75,10 @@ func (ds *ZabbixDatasourceInstance) queryNumericDataForItems(ctx context.Context
 
 	series := convertHistoryToTimeSeries(history, items)
 	// TODO: handle time series functions
+	series, err = applyFunctions(series, query.Functions)
+	if err != nil {
+		return nil, err
+	}
 
 	frame := convertTimeSeriesToDataFrame(series)
 

pkg/timeseries/timeseries.go

@@ -30,6 +30,10 @@ func (tsd *TimeSeriesData) Add(point TimePoint) *TimeSeriesData {
 	return tsd
 }
 
+func (ts TimeSeries) GroupBy(interval time.Duration, agg string) TimeSeries {
+	return ts
+}
+
 // Aligns point's time stamps according to provided interval.
 func (ts TimeSeries) Align(interval time.Duration) TimeSeries {
 	if interval <= 0 || ts.Len() < 2 {