feat: add KeyByOperator and wordCounter for stateful processing

1 files changed, 53 insertions, 0 deletions

diff --git a/core/operator/map.go b/core/operator/map.go
new file mode 100644
index 0000000..ef6912e
--- /dev/null
+++ b/core/operator/map.go
@@ -0,0 +1,53 @@
+package operator
+
+import (
+	"context"
+	"fmt"
+	"goflink/core"
+)
+
+// MapFunc is business logic for user implement
+type MapFunc[IN, OUT any] func(in IN) (OUT, error)
+
+type MapOperator[IN, OUT any] struct {
+	userFunc MapFunc[IN, OUT]
+}
+
+func NewMapOperator[IN, OUT any](fn MapFunc[IN, OUT]) *MapOperator[IN, OUT] {
+	return &MapOperator[IN, OUT]{
+		userFunc: fn,
+	}
+}
+
+func (fo *MapOperator[IN, OUT]) Open(ctx context.Context) error {
+	return nil
+}
+
+func (fo *MapOperator[IN, OUT]) Process(ctx context.Context, record core.StreamRecord[IN], out Emitter[OUT]) error {
+	if record.Type != core.RecordData {
+		//	 watermark and barrier
+		return out.Emit(ctx, core.StreamRecord[OUT]{
+			Type:      record.Type,
+			Key:       record.Key,
+			Timestamp: record.Timestamp,
+			BarrierID: record.BarrierID,
+		})
+	}
+
+	outValue, err := fo.userFunc(record.Value)
+
+	if err != nil {
+		return fmt.Errorf("cannot process value %v: %w", record.Value, err)
+	}
+
+	return out.Emit(ctx, core.StreamRecord[OUT]{
+		Type:      core.RecordData,
+		Key:       record.Key,
+		Timestamp: record.Timestamp,
+		Value:     outValue,
+	})
+}
+
+func (fo *MapOperator[IN, OUT]) Close(ctx context.Context) error {
+	return nil
+}