Implementing usergroups caching

Signed-off-by: Ethan Wellenreiter <ewellenreiter@gmail.com>

backend/internal/storage/cache/cache.go

@@ -34,8 +34,8 @@ type Storage struct {
 		Delete(ctx context.Context, name string)
 	}
 	UserGroups interface {
-		Get(ctx context.Context, userid int64) (*[]int64, error)
-		Set(ctx context.Context, groups *[]int64) error
+		Get(ctx context.Context, userid int64) (*storage.UserGroups, error)
+		Set(ctx context.Context, groups *storage.UserGroups) error
 		Delete(ctx context.Context, userid int64)
 	}
 	Receipts interface {

backend/internal/storage/cache/redis_usergroups.go

@@ -0,0 +1,51 @@
+package cache
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"git.ewellenr.ca/receipt_indexer/backend/internal/storage"
+	"github.com/redis/go-redis/v9"
+)
+
+type UserGroupsStore struct {
+	rdb *redis.Client
+}
+
+func (s *UserGroupsStore) Get(ctx context.Context, userid int64) (*storage.UserGroups, error) {
+	cacheKey := fmt.Sprintf("user-%d", userid)
+
+	data, err := s.rdb.Get(ctx, cacheKey).Result()
+	if err == redis.Nil {
+		return nil, nil
+	} else if err != nil {
+		return nil, err
+	}
+
+	var usergroups storage.UserGroups
+	if data != "" {
+		err := json.Unmarshal([]byte(data), &usergroups)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return &usergroups, nil
+}
+
+func (s *UserGroupsStore) Set(ctx context.Context, groups *storage.UserGroups) error {
+	cacheKey := fmt.Sprintf("user-%d", groups.UserID)
+
+	json, err := json.Marshal(groups)
+	if err != nil {
+		return err
+	}
+
+	return s.rdb.Set(ctx, cacheKey, json, RolesExpTime).Err()
+}
+
+func (s *UserGroupsStore) Delete(ctx context.Context, userid int64) {
+	cacheKey := fmt.Sprintf("user-%d", userid)
+	s.rdb.Del(ctx, cacheKey)
+}