some refactor of experimental topic helpers

CHANGELOG.md

@@ -1,3 +1,5 @@
+* refactored experimental topic iterators in topicsugar package
+
 ## v3.80.9
 * Fixed bug in experimental api: `ydb.ParamsBuilder().Param().Optional()` receive pointer and really produce optional value.
 

examples/topic/topicreader/topicreader_simple_iterators.go

@@ -0,0 +1,55 @@
+//go:build go1.23
+
+package topicreaderexamples
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ydb-platform/ydb-go-sdk/v3/topic/topicreader"
+	"github.com/ydb-platform/ydb-go-sdk/v3/topic/topicsugar"
+	firestore "google.golang.org/genproto/firestore/bundle"
+)
+
+// IterateOverMessagesAsString is simple example for easy start read messages
+// it is not recommend way for heavy-load processing, batch processing usually will faster
+func IterateOverMessagesAsString(ctx context.Context, reader *topicreader.Reader) error {
+	for msg, err := range topicsugar.StringIterator(ctx, reader) {
+		if err != nil {
+			return err
+		}
+		fmt.Println(msg.Data)
+		_ = reader.Commit(msg.Context(), msg)
+	}
+
+	return nil
+}
+
+// IterateOverStructUnmarshalledFromJSON is example for effective way for unmarshal json message content to value
+func IterateOverStructUnmarshalledFromJSON(ctx context.Context, r *topicreader.Reader) error {
+	//nolint:tagliatelle
+	type S struct {
+		MyField int `json:"my_field"`
+	}
+
+	for msg, err := range topicsugar.JSONIterator[S](ctx, r) {
+		if err != nil {
+			return err
+		}
+		fmt.Println(msg.Data.MyField)
+	}
+
+	return nil
+}
+
+// IterateOverProtobufMessages is example for effective way for unmarshal protobuf message content to value
+func IterateOverProtobufMessages(ctx context.Context, r *topicreader.Reader) error {
+	for msg, err := range topicsugar.ProtobufIterator[*firestore.BundledDocumentMetadata](ctx, r) {
+		if err != nil {
+			return err
+		}
+		fmt.Println(msg.Data.GetName())
+	}
+
+	return nil
+}

tests/integration/topic_helpers_test.go

@@ -46,6 +46,29 @@ func TestMessageReaderIterator(t *testing.T) {
 	require.Equal(t, []string{"asd", "ddd", "ggg"}, results)
 }
 
+func TestStringReaderIterator(t *testing.T) {
+	scope := newScope(t)
+	ctx := scope.Ctx
+
+	err := scope.TopicWriter().Write(ctx,
+		topicwriter.Message{Data: strings.NewReader("asd")},
+		topicwriter.Message{Data: strings.NewReader("ddd")},
+		topicwriter.Message{Data: strings.NewReader("ggg")},
+	)
+	require.NoError(t, err)
+
+	var results []string
+	for mess, err := range topicsugar.StringIterator(ctx, scope.TopicReader()) {
+		require.NoError(t, err)
+
+		results = append(results, mess.Data)
+		if len(results) == 3 {
+			break
+		}
+	}
+	require.Equal(t, []string{"asd", "ddd", "ggg"}, results)
+}
+
 func TestMessageJsonUnmarshalIterator(t *testing.T) {
 	scope := newScope(t)
 	ctx := scope.Ctx
@@ -71,7 +94,7 @@ func TestMessageJsonUnmarshalIterator(t *testing.T) {
 	var results []testStruct
 	expectedSeqno := int64(1)
 	expectedOffset := int64(0)
-	for mess, err := range topicsugar.TopicUnmarshalJSONIterator[testStruct](ctx, scope.TopicReader()) {
+	for mess, err := range topicsugar.JSONIterator[testStruct](ctx, scope.TopicReader()) {
 		require.NoError(t, err)
 		require.Equal(t, expectedSeqno, mess.SeqNo)
 		require.Equal(t, expectedOffset, mess.Offset)

topic/topicsugar/cdc-reader.go

@@ -87,5 +87,5 @@ func UnmarshalCDCStream[T YDBCDCItem[K], K any](
 		return json.Unmarshal(data, dst)
 	}
 
-	return TopicUnmarshalJSONFunc[YDBCDCMessage[T, K]](ctx, reader, unmarshal)
+	return IteratorFunc[YDBCDCMessage[T, K]](ctx, reader, unmarshal)
 }

topic/topicsugar/iterators.go

@@ -1,21 +1,26 @@
+//go:build go1.23
+
 package topicsugar
 
 import (
 	"context"
 	"encoding/json"
+	"slices"
+
+	"google.golang.org/protobuf/proto"
 
 	"github.com/ydb-platform/ydb-go-sdk/v3/internal/xiter"
 	"github.com/ydb-platform/ydb-go-sdk/v3/topic/topicreader"
 )
 
-// MessageReader is interface for topicreader.Message
+// TopicMessageReader is interface for topicreader.Message
 //
 // Experimental: https://github.com/ydb-platform/ydb-go-sdk/blob/master/VERSIONING.md#experimental
 type TopicMessageReader interface {
 	ReadMessage(ctx context.Context) (*topicreader.Message, error)
 }
 
-// TopicMessagesIterator is typed representation of cdc event
+// TopicMessageIterator iterator wrapper over topic reader
 //
 // Experimental: https://github.com/ydb-platform/ydb-go-sdk/blob/master/VERSIONING.md#experimental
 func TopicMessageIterator(ctx context.Context, r TopicMessageReader) xiter.Seq2[*topicreader.Message, error] {
@@ -33,24 +38,67 @@ func TopicMessageIterator(ctx context.Context, r TopicMessageReader) xiter.Seq2[
 	}
 }
 
-// TopicUnmarshalJSONIterator is typed representation of cdc event
+// BytesIterator produce iterator over topic messages with Data as []byte, []byte is content of the message
+func BytesIterator(
+	ctx context.Context,
+	r TopicMessageReader,
+) xiter.Seq2[*TypedTopicMessage[[]byte], error] {
+	var unmarshalFunc TypedUnmarshalFunc[*[]byte] = func(data []byte, dst *[]byte) error {
+		*dst = slices.Clone(data)
+
+		return nil
+	}
+
+	return IteratorFunc[[]byte](ctx, r, unmarshalFunc)
+}
+
+// StringIterator produce iterator over topic messages with Data is string, created from message content
+func StringIterator(
+	ctx context.Context,
+	r TopicMessageReader,
+) xiter.Seq2[*TypedTopicMessage[string], error] {
+	var unmarshalFunc TypedUnmarshalFunc[*string] = func(data []byte, dst *string) error {
+		*dst = string(data)
+
+		return nil
+	}
+
+	return IteratorFunc[string](ctx, r, unmarshalFunc)
+}
+
+// JSONIterator produce iterator over topic messages with Data is T, created unmarshalled from message
 //
 // Experimental: https://github.com/ydb-platform/ydb-go-sdk/blob/master/VERSIONING.md#experimental
-func TopicUnmarshalJSONIterator[T any](
+func JSONIterator[T any](
 	ctx context.Context,
 	r TopicMessageReader,
 ) xiter.Seq2[*TypedTopicMessage[T], error] {
 	var unmarshalFunc TypedUnmarshalFunc[*T] = func(data []byte, dst *T) error {
 		return json.Unmarshal(data, dst)
 	}
 
-	return TopicUnmarshalJSONFunc[T](ctx, r, unmarshalFunc)
+	return IteratorFunc[T](ctx, r, unmarshalFunc)
+}
+
+// ProtobufIterator produce iterator over topic messages with Data is T, created unmarshalled from message
+//
+// Experimental: https://github.com/ydb-platform/ydb-go-sdk/blob/master/VERSIONING.md#experimental
+func ProtobufIterator[T proto.Message](
+	ctx context.Context,
+	r TopicMessageReader,
+) xiter.Seq2[*TypedTopicMessage[T], error] {
+	var unmarshalFunc TypedUnmarshalFunc[*T] = func(data []byte, dst *T) error {
+		return proto.Unmarshal(data, *dst)
+	}
+
+	return IteratorFunc[T](ctx, r, unmarshalFunc)
 }
 
-// TopicUnmarshalJSONIterator is typed representation of cdc event
+// IteratorFunc produce iterator over topic messages with Data is T,
+// created unmarshalled from message by custom function
 //
 // Experimental: https://github.com/ydb-platform/ydb-go-sdk/blob/master/VERSIONING.md#experimental
-func TopicUnmarshalJSONFunc[T any](
+func IteratorFunc[T any](
 	ctx context.Context,
 	r TopicMessageReader,
 	f TypedUnmarshalFunc[*T],