Complete refactor to new grpc control plane and only http proxy for carts (#4)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

pkg/actor/state.go

@@ -0,0 +1,98 @@
+package actor
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"io"
+	"time"
+
+	"github.com/gogo/protobuf/proto"
+)
+
+type StateStorage struct {
+	registry MutationRegistry
+}
+
+type StorageEvent struct {
+	Type      string        `json:"type"`
+	TimeStamp time.Time     `json:"timestamp"`
+	Mutation  proto.Message `json:"mutation"`
+}
+
+type rawEvent struct {
+	Type      string          `json:"type"`
+	TimeStamp time.Time       `json:"timestamp"`
+	Mutation  json.RawMessage `json:"mutation"`
+}
+
+func NewState(registry MutationRegistry) *StateStorage {
+	return &StateStorage{
+		registry: registry,
+	}
+}
+
+var ErrUnknownType = errors.New("unknown type")
+
+func (s *StateStorage) Load(r io.Reader, onMessage func(msg proto.Message)) error {
+	var err error
+	var evt *StorageEvent
+	scanner := bufio.NewScanner(r)
+	for err == nil {
+		evt, err = s.Read(scanner)
+		if err == nil {
+			onMessage(evt.Mutation)
+		}
+	}
+	if err == io.EOF {
+		return nil
+	}
+	return err
+}
+
+func (s *StateStorage) Append(io io.Writer, mutation proto.Message, timeStamp time.Time) error {
+	typeName, ok := s.registry.GetTypeName(mutation)
+	if !ok {
+		return ErrUnknownType
+	}
+	event := &StorageEvent{
+		Type:      typeName,
+		TimeStamp: timeStamp,
+		Mutation:  mutation,
+	}
+	jsonBytes, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+	if _, err := io.Write(jsonBytes); err != nil {
+		return err
+	}
+	io.Write([]byte("\n"))
+	return nil
+}
+
+func (s *StateStorage) Read(r *bufio.Scanner) (*StorageEvent, error) {
+	var event rawEvent
+
+	if r.Scan() {
+		b := r.Bytes()
+		err := json.Unmarshal(b, &event)
+		if err != nil {
+			return nil, err
+		}
+		typeName := event.Type
+		mutation, ok := s.registry.Create(typeName)
+		if !ok {
+			return nil, ErrUnknownType
+		}
+		if err := json.Unmarshal(event.Mutation, mutation); err != nil {
+			return nil, err
+		}
+		return &StorageEvent{
+			Type:      typeName,
+			TimeStamp: event.TimeStamp,
+			Mutation:  mutation,
+		}, r.Err()
+	}
+	return nil, io.EOF
+}