Starting steps for caching data to prevent constant db querying

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

backend/internal/storage/cache/cache.go

@@ -0,0 +1,26 @@
+package cache
+
+import (
+	"context"
+
+	"git.ewellenr.ca/receipt_indexer/backend/internal/storage"
+	auth_storage "git.ewellenr.ca/receipt_indexer/backend/internal/storage/auth"
+)
+
+type Storage struct {
+	Users interface {
+		Get(ctx context.Context, id int64) (*auth_storage.User, error)
+		Set(ctx context.Context, user *auth_storage.User) error
+		Delete(ctx context.Context, userID int64)
+	}
+	Receipts interface {
+		Get(ctx context.Context, id int64) (*storage.Receipt, error)
+		Set(ctx context.Context, receipt *storage.Receipt) error
+		Delete(ctx context.Context, id int64)
+	}
+	ReceiptImage interface {
+		Get(ctx context.Context, id int64) (*storage.Image, error)
+		Set(ctx context.Context, image *storage.Image) error
+		Delete(ctx context.Context, id int64)
+	}
+}

backend/internal/storage/cache/redis_user.go

@@ -0,0 +1,54 @@
+package cache
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	auth_storage "git.ewellenr.ca/receipt_indexer/backend/internal/storage/auth"
+	"github.com/redis/go-redis/v9"
+)
+
+type UserStore struct {
+	rdb *redis.Client
+}
+
+const UserExpTime = time.Minute
+
+func (s *UserStore) Get(ctx context.Context, userID int64) (*auth_storage.User, 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 user auth_storage.User
+	if data != "" {
+		err := json.Unmarshal([]byte(data), &user)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return &user, nil
+}
+
+func (s *UserStore) Set(ctx context.Context, user *auth_storage.User) error {
+	cacheKey := fmt.Sprintf("user-%d", user.ID)
+
+	json, err := json.Marshal(user)
+	if err != nil {
+		return err
+	}
+
+	return s.rdb.Set(ctx, cacheKey, json, UserExpTime).Err()
+}
+
+func (s *UserStore) Delete(ctx context.Context, userID int64) {
+	cacheKey := fmt.Sprintf("user-%d", userID)
+	s.rdb.Del(ctx, cacheKey)
+}