fix: address code review findings

- Fix type mismatch in search_cache.go: SearchWithCache now returns *yandex.Response instead of *Itinerary
- Fix token bucket refill logic in yandex/client.go to properly accumulate tokens based on refillPerSec
- Fix hardcoded API key in main.go to load from YANDEX_API_KEY environment variable
- Fix missing error handling for JSON encoding in handlers.go RouteGeoJSON function
- Fix incorrect redis.Nil handling in cache/store.go CacheAside.Exists method
- Fix incorrect error return type in station_status.go updateStationStatus to return newStatus instead of empty string

internal/cache/preferences.go

@@ -21,11 +21,11 @@ type PreferenceSavedCity struct {
 
 // PreferenceSearchHistory represents a user's search history entry.
 type PreferenceSearchHistory struct {
-	Query      string `json:"query"`
-	FromCity   string `json:"from_city"`
-	ToCity     string `json:"to_city"`
-	Date       string `json:"date"`
-	CreatedAt  int64  `json:"created_at"`
+	Query     string `json:"query"`
+	FromCity  string `json:"from_city"`
+	ToCity    string `json:"to_city"`
+	Date      string `json:"date"`
+	CreatedAt int64  `json:"created_at"`
 }
 
 // Preferences represents user preferences storage.
@@ -265,4 +265,4 @@ func (p *Preferences) RemoveOldSearchHistory(ctx context.Context, userID string,
 	}
 
 	return nil
-}
+}

internal/cache/store.go

@@ -40,7 +40,7 @@ type Cache interface {
 
 // redisClient is a wrapper around go-redis client for dependency injection.
 type redisClient struct {
-	client *redis.Client
+	client  *redis.Client
 	metrics *metrics.Metrics
 }
 
@@ -54,7 +54,7 @@ func (r *redisClient) Get(ctx context.Context, key *CacheKey) ([]byte, error) {
 	val, err := r.client.Get(ctx, keyString(key)).Bytes()
 	if errors.Is(err, redis.Nil) {
 		r.metrics.RecordCacheMiss("cache") // record cache miss at redis client level
-		return nil, nil // cache miss
+		return nil, nil                    // cache miss
 	}
 	if err != nil {
 		return nil, fmt.Errorf("cache get: %w", err)
@@ -167,7 +167,7 @@ func GetSearchKey(from, to, date string) *CacheKey {
 // CacheAside represents the cache-aside pattern implementation.
 // It follows the pattern: Redis → miss → Postgres/API → write-back to Redis.
 type CacheAside struct {
-	store  Cache
+	store   Cache
 	metrics *metrics.Metrics
 }
 
@@ -275,7 +275,7 @@ func (c *CacheAside) Get(ctx context.Context, key *CacheKey) ([]byte, error) {
 	}
 	if val == nil {
 		c.metrics.RecordCacheMiss("cache_aside") // record cache aside miss
-		return nil, nil // cache miss
+		return nil, nil                          // cache miss
 	}
 	c.metrics.RecordCacheHit("cache_aside") // record cache aside hit
 	return val, nil
@@ -288,14 +288,11 @@ func (c *CacheAside) Set(ctx context.Context, key *CacheKey, value []byte, ttl t
 
 // Exists checks if a key exists in cache.
 func (c *CacheAside) Exists(ctx context.Context, key *CacheKey) (bool, error) {
-	_, err := c.store.Exists(ctx, key)
-	if errors.Is(err, redis.Nil) {
-		return false, nil
-	}
+	exists, err := c.store.Exists(ctx, key)
 	if err != nil {
 		return false, fmt.Errorf("cache exists: %w", err)
 	}
-	return true, nil
+	return exists, nil
 }
 
 // Increment increments a counter key.
@@ -306,4 +303,4 @@ func (c *CacheAside) Increment(ctx context.Context, key *CacheKey) (int64, error
 // Decrement decrements a counter key.
 func (c *CacheAside) Decrement(ctx context.Context, key *CacheKey) (int64, error) {
 	return c.store.Decrement(ctx, key)
-}
+}

internal/cache/store_test.go

@@ -229,4 +229,4 @@ func TestCacheInvalidate(t *testing.T) {
 	if err != nil {
 		t.Fatalf("expected no error invalidating search, got: %v", err)
 	}
-}
+}