1 files changed, 81 insertions, 0 deletions
diff --git a/core/operator/keyed_process.go b/core/operator/keyed_process.go
new file mode 100644
index 0000000..b507d87
--- /dev/null
+++ b/core/operator/keyed_process.go
@@ -0,0 +1,81 @@
+package operator
+
+import (
+	"context"
+	"fmt"
+	"goflink/core"
+)
+
+type KeyedProcesser[IN, OUT any] interface {
+	Open(ctx context.Context) error
+	ProcessElement(ctx context.Context, record core.StreamRecord[IN], out Emitter[OUT]) error
+	Close(ctx context.Context) error
+	OnTimer(ctx context.Context, timestamp int64, out Emitter[OUT]) error
+}
+
+type KeyProcessOperator[IN, OUT any] struct {
+	userFunc    KeyedProcesser[IN, OUT]
+	timeService core.InternalTimerService 
+	backend     core.StateBackend
+}
+
+func NewKeyProcessOperator[IN, OUT any](userFunc KeyedProcesser[IN, OUT]) *KeyProcessOperator[IN, OUT] {
+	return &KeyProcessOperator[IN, OUT]{
+		userFunc:    userFunc,
+		timeService: core.NewTimerService(),
+	}
+}
+
+func (k *KeyProcessOperator[IN, OUT]) Open(ctx context.Context) error {
+	// init backend
+	be, ok := core.ExtractStateBackend(ctx)
+	if !ok {
+		return fmt.Errorf("state backend not found")
+	}
+
+	k.backend = be
+	// inject the timer to context for user use
+	ctx = core.InjectTimerService(ctx, k.timeService)
+	return k.userFunc.Open(ctx)
+
+}
+
+func (k *KeyProcessOperator[IN, OUT]) Process(ctx context.Context, record core.StreamRecord[IN], out Emitter[OUT]) error {
+
+	switch record.Type {
+	case core.RecordData:
+		if err := k.backend.SetCurrentKey(record.Key); err != nil {
+			return err
+		}
+
+		return k.userFunc.ProcessElement(ctx, record, out)
+	case core.RecordWatermark:
+		// advance the timer
+		triggerTimerQueue := k.timeService.AdvanceWatermark(record.Timestamp)
+
+		for _, t := range triggerTimerQueue {
+
+			if err := k.backend.SetCurrentKey(t.Key); err != nil {
+				return err
+			}
+			if err := k.userFunc.OnTimer(ctx, t.Timestamp, out); err != nil {
+				return err
+			}
+		}
+		return out.Emit(ctx, core.StreamRecord[OUT]{
+			Type:      core.RecordWatermark,
+			Timestamp: record.Timestamp,
+		})
+	default:
+		return out.Emit(ctx, core.StreamRecord[OUT]{
+			Timestamp: record.Timestamp,
+			BarrierID: record.BarrierID,
+			Key:       record.Key,
+		})
+	}
+
+}
+
+func (k *KeyProcessOperator[IN, OUT]) Close(ctx context.Context) error {
+	return k.userFunc.Close(ctx)
+}