Implement Redis caching for Reddit image fetching

redis/client.go

@@ -0,0 +1,118 @@
+package redis
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"github.com/redis/go-redis/v9"
+	"os"
+	"strconv"
+	"time"
+)
+
+type contextKey string
+
+const redisKey contextKey = "redisClient"
+
+const CacheKey = "top-wallpaper:latestImage"
+
+type Cache interface {
+	Get(key string) (string, error)
+	Set(key string, value string, expiration int64) error
+	Close() error
+}
+
+type Redis struct {
+	client *redis.Client
+}
+
+func NewRedis() (*Redis, error) {
+
+	redisUrl := os.Getenv("REDIS_URL")
+	if redisUrl == "" {
+		return nil, errors.New("REDIS_URL not set, cannot initialize Redis client")
+	}
+
+	redisPort := os.Getenv("REDIS_PORT")
+	if redisPort == "" {
+		redisPort = "6379"
+	}
+
+	redisDb := os.Getenv("REDIS_DB")
+	if redisDb == "" {
+		redisDb = "0"
+	}
+
+	redisDbInt, err := strconv.ParseInt(redisDb, 10, 64)
+	if err != nil {
+		return nil, errors.New("REDIS_DB is not a valid integer, cannot initialize Redis client")
+	}
+
+	rc := redis.NewClient(&redis.Options{
+		Addr:     fmt.Sprintf("%s:%s", redisUrl, redisPort),
+		Password: os.Getenv("REDIS_PASSWORD"),
+		DB:       int(redisDbInt),
+	})
+
+	cmd := rc.Ping(context.Background())
+
+	if cmd.Err() != nil {
+		return nil, fmt.Errorf("could not connect to Redis: %v", cmd.Err())
+	}
+	if cmd.Val() != "PONG" {
+		return nil, fmt.Errorf("unexpected response from Redis: %s", cmd.Val())
+	}
+
+	return &Redis{
+		client: rc,
+	}, nil
+}
+
+func (r *Redis) Get(key string) (string, error) {
+	cmd := r.client.Get(context.Background(), key)
+	if cmd.Err() != nil {
+		if errors.Is(cmd.Err(), redis.Nil) {
+			return "", nil // Key does not exist
+		}
+		return "", fmt.Errorf("could not get value for key %s: %v", key, cmd.Err())
+	}
+	return cmd.Val(), nil
+}
+
+func (r *Redis) Set(key string, value string, expiration time.Duration) error {
+	cmd := r.client.Set(context.Background(), key, value, expiration)
+	if cmd.Err() != nil {
+		return fmt.Errorf("could not set value for key %s: %v", key, cmd.Err())
+	}
+	if cmd.Val() != "OK" {
+		return fmt.Errorf("unexpected response from Redis when setting key %s: %s", key, cmd.Val())
+	}
+
+	return nil
+}
+
+func (r *Redis) Close() error {
+	if r.client == nil {
+		return nil
+	}
+	err := r.client.Close()
+	if err != nil {
+		return fmt.Errorf("could not close Redis client: %v", err)
+	}
+	return nil
+}
+
+func WithContext(ctx context.Context, r *Redis) context.Context {
+	return context.WithValue(ctx, redisKey, r)
+}
+
+func FromContext(ctx context.Context) (*Redis, error) {
+	r, ok := ctx.Value(redisKey).(*Redis)
+	if !ok {
+		return nil, errors.New("no Redis client found in context")
+	}
+	if r == nil {
+		return nil, errors.New("redis client is nil")
+	}
+	return r, nil
+}