fix: address code review findings

cmd/api/handlers.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"crypto/hmac"
+	"crypto/subtle"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -435,7 +435,7 @@ func adminAuth(hc *HandlerContext, w http.ResponseWriter, r *http.Request) bool
 		return false
 	}
 	providedAPIKey := r.Header.Get("X-Admin-Api-Key")
-	if !hmac.Equal([]byte(providedAPIKey), []byte(expectedAPIKey)) {
+	if subtle.ConstantTimeCompare([]byte(providedAPIKey), []byte(expectedAPIKey)) != 1 {
 		http.Error(w, "unauthorized", http.StatusUnauthorized)
 		return false
 	}

cmd/api/main.go

@@ -39,6 +39,35 @@ func main() {
 	http.HandleFunc("/internal/admin/stations/", makeHandler(AdminStationStatus, handlerCtx))
 	http.HandleFunc("/metrics", makeHandler(MetricsHandler, handlerCtx))
 
+	// User preferences routes
+	http.HandleFunc("/v1/preferences/saved-cities", func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			GetSavedCities(handlerCtx, w, r)
+		case http.MethodPost:
+			AddSavedCity(handlerCtx, w, r)
+		default:
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+	http.HandleFunc("/v1/preferences/saved-cities/", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodDelete {
+			RemoveSavedCity(handlerCtx, w, r)
+		} else {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+	http.HandleFunc("/v1/preferences/search-history", func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			GetSearchHistory(handlerCtx, w, r)
+		case http.MethodPost:
+			AddSearchHistory(handlerCtx, w, r)
+		default:
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+
 	log.Println("Trip Planner API starting on :8080")
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }

internal/cache/preferences.go

@@ -6,13 +6,6 @@ import (
 	"time"
 )
 
-// PreferenceKey defines the structure for preference cache keys.
-type PreferenceKey struct {
-	UserID   string // user identifier
-	Kind     string // "saved_city" or "search_history"
-	CityCode string // city code for saved_city
-}
-
 // PreferenceSavedCity represents a user's saved city preference.
 type PreferenceSavedCity struct {
 	CityCode string `json:"city_code"`

internal/routing/graph.go

@@ -1038,8 +1038,6 @@ func SelectHubStations(stations []StationInfo, minOutgoingFlights int) []*Node {
 	return hubs
 }
 
-// getStationNeighbors returns neighboring stations for a given station ID in the same city.
-
 // RouteStatus represents the current status of a route leg.
 type RouteStatus int32