feat: use postgres

mail/internal/adapters/redisstate/offset_codec.go

@@ -0,0 +1,40 @@
+package redisstate
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+// StreamOffset stores the persisted progress of one plain-XREAD consumer.
+type StreamOffset struct {
+	// Stream stores the Redis Stream key the offset belongs to.
+	Stream string `json:"stream"`
+
+	// LastProcessedEntryID stores the most recently processed Stream entry id.
+	LastProcessedEntryID string `json:"last_processed_entry_id"`
+
+	// UpdatedAt stores when the offset was last persisted.
+	UpdatedAt time.Time `json:"updated_at"`
+}
+
+// MarshalStreamOffset returns the JSON encoding of the persisted offset.
+func MarshalStreamOffset(offset StreamOffset) ([]byte, error) {
+	payload, err := json.Marshal(offset)
+	if err != nil {
+		return nil, fmt.Errorf("marshal stream offset: %w", err)
+	}
+	return payload, nil
+}
+
+// UnmarshalStreamOffset parses one persisted offset payload.
+func UnmarshalStreamOffset(payload []byte) (StreamOffset, error) {
+	var offset StreamOffset
+	if err := json.Unmarshal(payload, &offset); err != nil {
+		return StreamOffset{}, fmt.Errorf("unmarshal stream offset: %w", err)
+	}
+	if offset.UpdatedAt.IsZero() {
+		return StreamOffset{}, fmt.Errorf("unmarshal stream offset: updated_at must not be zero")
+	}
+	return offset, nil
+}