feat: mail service

mail/internal/adapters/redisstate/stream_offset_store.go

@@ -0,0 +1,79 @@
+package redisstate
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// StreamOffsetStore provides the Redis-backed storage used for persisted
+// plain-XREAD consumer progress.
+type StreamOffsetStore struct {
+	client *redis.Client
+	keys   Keyspace
+}
+
+// NewStreamOffsetStore constructs one Redis-backed stream-offset store.
+func NewStreamOffsetStore(client *redis.Client) (*StreamOffsetStore, error) {
+	if client == nil {
+		return nil, errors.New("new stream offset store: nil redis client")
+	}
+
+	return &StreamOffsetStore{
+		client: client,
+		keys:   Keyspace{},
+	}, nil
+}
+
+// Load returns the last processed entry id for stream when one is stored.
+func (store *StreamOffsetStore) Load(ctx context.Context, stream string) (string, bool, error) {
+	if store == nil || store.client == nil {
+		return "", false, errors.New("load stream offset: nil store")
+	}
+	if ctx == nil {
+		return "", false, errors.New("load stream offset: nil context")
+	}
+
+	payload, err := store.client.Get(ctx, store.keys.StreamOffset(stream)).Bytes()
+	switch {
+	case errors.Is(err, redis.Nil):
+		return "", false, nil
+	case err != nil:
+		return "", false, fmt.Errorf("load stream offset: %w", err)
+	}
+
+	offset, err := UnmarshalStreamOffset(payload)
+	if err != nil {
+		return "", false, fmt.Errorf("load stream offset: %w", err)
+	}
+
+	return offset.LastProcessedEntryID, true, nil
+}
+
+// Save stores the last processed entry id for stream.
+func (store *StreamOffsetStore) Save(ctx context.Context, stream string, entryID string) error {
+	if store == nil || store.client == nil {
+		return errors.New("save stream offset: nil store")
+	}
+	if ctx == nil {
+		return errors.New("save stream offset: nil context")
+	}
+
+	offset := StreamOffset{
+		Stream:               stream,
+		LastProcessedEntryID: entryID,
+		UpdatedAt:            time.Now().UTC().Truncate(time.Millisecond),
+	}
+	payload, err := MarshalStreamOffset(offset)
+	if err != nil {
+		return fmt.Errorf("save stream offset: %w", err)
+	}
+	if err := store.client.Set(ctx, store.keys.StreamOffset(stream), payload, 0).Err(); err != nil {
+		return fmt.Errorf("save stream offset: %w", err)
+	}
+
+	return nil
+}