Fix lint warnings and code cleanup

- Remove duplicate calc structs, use model.CalcXxx
- Replace log.Printf with logger in recommend handler
- Remove dead code (unused var, dummy imports)
- Clean up response helpers
- Add api/ package with route registration

Co-Authored-By: Claude <noreply@anthropic.com>

internal/api/router.go

@@ -0,0 +1,87 @@
+package api
+
+import (
+	"database/sql"
+	"encoding/json"
+	"net/http"
+
+	"floorvisualizer/internal/handler"
+	"floorvisualizer/internal/middleware"
+	"floorvisualizer/internal/model"
+	"floorvisualizer/internal/openrouter"
+	"floorvisualizer/internal/service"
+)
+
+// RegisterRoutes sets up all HTTP routes with injected dependencies.
+func RegisterRoutes(mux *http.ServeMux, client *openrouter.Client, db *sql.DB, authSvc *service.AuthService) {
+	auth := middleware.RequireAuth(authSvc)
+
+	// Pre-build handlers — dependencies injected once
+	var (
+		register         = handler.Register(authSvc, db)
+		login            = handler.Login(authSvc, db)
+		me               = auth(handler.Me(db))
+		uploadAvatar     = auth(handler.UploadAvatar(db))
+		favorites        = auth(handler.Favorites(db))
+		favoritesSub     = auth(handler.Favorites(db))
+		projects         = auth(handler.Projects(db))
+		projectsSub      = auth(handler.Projects(db))
+		frequentBrands   = auth(handler.FrequentBrands(db))
+		products         = handler.Products(db)
+		productsSub      = handler.Products(db)
+		productOpts      = handler.ProductOptions(db)
+		filterOpts       = handler.FilterOptions(db)
+		recommend        = handler.Recommend(db)
+		floorGenerate    = handler.FloorGenerate(client, db)
+		floorOptions     = handler.FloorOptions(db)
+		articleRecommend = handler.ArticleRecommend(db)
+		articles         = handler.Articles(db)
+		articlesSub      = handler.Articles(db)
+	)
+
+	// Route mapping
+	mux.HandleFunc("/auth/register", register)
+	mux.HandleFunc("/auth/login", login)
+	mux.HandleFunc("/user/me", me)
+	mux.HandleFunc("/user/avatar", uploadAvatar)
+	mux.HandleFunc("/user/favorites", favorites)
+	mux.HandleFunc("/user/favorites/", favoritesSub)
+	mux.HandleFunc("/user/projects", projects)
+	mux.HandleFunc("/user/projects/", projectsSub)
+	mux.HandleFunc("/user/frequent-brands", frequentBrands)
+	mux.HandleFunc("/healthz", handler.Healthz)
+	mux.HandleFunc("/upload", handler.Upload)
+	mux.HandleFunc("/products", products)
+	mux.HandleFunc("/products/", productsSub)
+	mux.HandleFunc("/product-options", productOpts)
+	mux.HandleFunc("/filter-options", filterOpts)
+	mux.HandleFunc("/recommend/api", recommend)
+	mux.HandleFunc("/calculator/calc", handler.Calc)
+	mux.HandleFunc("/floor/generate", floorGenerate)
+	mux.HandleFunc("/floor/status", handler.FloorStatus)
+	mux.HandleFunc("/floor/options", floorOptions)
+	mux.HandleFunc("/articles/recommend", articleRecommend)
+	mux.HandleFunc("/articles", articles)
+	mux.HandleFunc("/articles/", articlesSub)
+
+	// Static files
+	mux.Handle("/outputs/", http.StripPrefix("/outputs/", http.FileServer(http.Dir("./outputs"))))
+	mux.Handle("/uploads/", http.StripPrefix("/uploads/", http.FileServer(http.Dir("./uploads"))))
+	mux.Handle("/knowledge_images/", http.StripPrefix("/knowledge_images/", http.FileServer(http.Dir("./knowledge_images"))))
+	mux.Handle("/images/knowledge/", http.StripPrefix("/images/knowledge/", http.FileServer(http.Dir("./knowledge_images"))))
+}
+
+// ── Response helpers ──────────────────────────────────────
+
+// JSON writes a success response with the API envelope.
+func JSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(model.ApiResponse{Code: status, Data: v})
+}
+
+func Error(w http.ResponseWriter, status int, msg string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(model.ApiError{Code: status, Error: msg})
+}

internal/handler/api.go

@@ -0,0 +1,15 @@
+package handler
+
+import (
+	"database/sql"
+
+	"floorvisualizer/internal/openrouter"
+	"floorvisualizer/internal/service"
+)
+
+// API holds all handler dependencies, injected once at startup.
+type API struct {
+	DB      *sql.DB
+	Client  *openrouter.Client
+	AuthSvc *service.AuthService
+}

internal/handler/article_handler.go

@@ -9,7 +9,7 @@ import (
 	"floorvisualizer/internal/repository"
 )
 
-func handleArticles(db *sql.DB) http.HandlerFunc {
+func Articles(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		// /articles/{id} — detail
 		idStr := strings.TrimPrefix(r.URL.Path, "/articles/")
@@ -56,7 +56,7 @@ func handleArticles(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleArticleRecommend(db *sql.DB) http.HandlerFunc {
+func ArticleRecommend(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		count := 6
 		if c, err := strconv.Atoi(r.URL.Query().Get("count")); err == nil && c > 0 && c <= 20 {

internal/handler/auth_handler.go

@@ -8,7 +8,7 @@ import (
 	"floorvisualizer/internal/service"
 )
 
-func handleRegister(authSvc *service.AuthService, db *sql.DB) http.HandlerFunc {
+func Register(authSvc *service.AuthService, db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			writeErr(w, 405, "Method not allowed")
@@ -28,7 +28,7 @@ func handleRegister(authSvc *service.AuthService, db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleLogin(authSvc *service.AuthService, db *sql.DB) http.HandlerFunc {
+func Login(authSvc *service.AuthService, db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			writeErr(w, 405, "Method not allowed")

internal/handler/calc_handler.go

@@ -4,68 +4,10 @@ import (
 	"encoding/json"
 	"math"
 	"net/http"
+
+	"floorvisualizer/internal/model"
 )
 
-// ── Calculator models ───────────────────────────────────────
-
-type CalcRoomInput struct {
-	Name       string          `json:"name"`
-	Length     float64         `json:"length"`
-	Width      float64         `json:"width"`
-	Deductions []CalcDeduction `json:"deductions"`
-}
-
-type CalcDeduction struct {
-	Name   string  `json:"name"`
-	Shape  string  `json:"shape"`  // rectangle, circle, custom
-	Length float64 `json:"length"`
-	Width  float64 `json:"width"`
-	Radius float64 `json:"radius"`
-	Area   float64 `json:"area"` // custom area override
-}
-
-type CalcInput struct {
-	FloorType    string         `json:"floor_type"` // wood, tile
-	Rooms        []CalcRoomInput `json:"rooms"`
-	PatternIndex int            `json:"pattern_index"`
-	PieceLength  float64        `json:"piece_length"`
-	PieceWidth   float64        `json:"piece_width"`
-	PiecesPerBox int            `json:"pieces_per_box"`
-	PricePerSqm  float64        `json:"price_per_sqm"`
-	JointWidth   float64        `json:"joint_width"`
-}
-
-type CalcRoomResult struct {
-	Name           string          `json:"name"`
-	Length         float64         `json:"length"`
-	Width          float64         `json:"width"`
-	Area           float64         `json:"area"`
-	Deductions     []CalcDeduction `json:"deductions"`
-	DeductionTotal float64         `json:"deduction_total"`
-	NetArea        float64         `json:"net_area"`
-}
-
-type CalcResult struct {
-	FloorType     string          `json:"floor_type"`
-	Rooms         []CalcRoomResult `json:"rooms"`
-	TotalRoomArea float64         `json:"total_room_area"`
-	TotalDeduct   float64         `json:"total_deduct"`
-	TotalNetArea  float64         `json:"total_net_area"`
-	WasteRate     float64         `json:"waste_rate"`
-	WasteArea     float64         `json:"waste_area"`
-	TotalArea     float64         `json:"total_area"`
-	PiecesNeeded  int             `json:"pieces_needed"`
-	BoxesNeeded   *float64        `json:"boxes_needed,omitempty"`
-	JointWidth    float64         `json:"joint_width"`
-	GroutKg       *float64        `json:"grout_kg,omitempty"`
-	GroutBags     *int            `json:"grout_bags,omitempty"`
-	PricePerSqm   float64         `json:"price_per_sqm"`
-	TotalPrice    *float64        `json:"total_price,omitempty"`
-	PatternName   string          `json:"pattern_name"`
-	PieceLength   float64         `json:"piece_length"`
-	PieceWidth    float64         `json:"piece_width"`
-}
-
 var woodPatternsCalc = []struct {
 	Name  string
 	Waste float64
@@ -90,13 +32,13 @@ var tilePatternsCalc = []struct {
 
 // ── Handler ─────────────────────────────────────────────────
 
-func handleCalc(w http.ResponseWriter, r *http.Request) {
+func Calc(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		writeErr(w, 405, "Method not allowed")
 		return
 	}
 
-	var input CalcInput
+	var input model.CalcInput
 	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
 		writeJSON(w, 400, map[string]string{"error": "invalid JSON: " + err.Error()})
 		return
@@ -117,7 +59,7 @@ func handleCalc(w http.ResponseWriter, r *http.Request) {
 
 // ── Calculation ─────────────────────────────────────────────
 
-func calculate(input CalcInput) CalcResult {
+func calculate(input model.CalcInput) model.CalcResult {
 	patterns := woodPatternsCalc
 	if input.FloorType == "tile" {
 		patterns = tilePatternsCalc
@@ -127,14 +69,14 @@ func calculate(input CalcInput) CalcResult {
 	}
 	wasteRate := patterns[input.PatternIndex].Waste
 
-	var roomResults []CalcRoomResult
+	var roomResults []model.CalcRoomResult
 	totalRoomArea := 0.0
 	totalDeduct := 0.0
 
 	for _, room := range input.Rooms {
 		area := room.Length * room.Width
 		deductTotal := 0.0
-		var dedResults []CalcDeduction
+		var dedResults []model.CalcDeduction
 
 		for _, d := range room.Deductions {
 			dedArea := deductionArea(d)
@@ -144,9 +86,11 @@ func calculate(input CalcInput) CalcResult {
 		}
 
 		netArea := area - deductTotal
-		if netArea < 0 { netArea = 0 }
+		if netArea < 0 {
+			netArea = 0
+		}
 
-		roomResults = append(roomResults, CalcRoomResult{
+		roomResults = append(roomResults, model.CalcRoomResult{
 			Name: room.Name, Length: room.Length, Width: room.Width,
 			Area: round2(area), Deductions: dedResults,
 			DeductionTotal: round2(deductTotal), NetArea: round2(netArea),
@@ -156,7 +100,9 @@ func calculate(input CalcInput) CalcResult {
 	}
 
 	totalNetArea := totalRoomArea - totalDeduct
-	if totalNetArea < 0 { totalNetArea = 0 }
+	if totalNetArea < 0 {
+		totalNetArea = 0
+	}
 
 	// Adjust piece for joint
 	effLength := input.PieceLength
@@ -167,14 +113,16 @@ func calculate(input CalcInput) CalcResult {
 	}
 
 	pieceArea := effLength * effWidth
-	if pieceArea <= 0 { pieceArea = 1 }
+	if pieceArea <= 0 {
+		pieceArea = 1
+	}
 
 	totalPieces := totalNetArea / pieceArea
 	wasteArea := totalNetArea * wasteRate
 	totalArea := totalNetArea + wasteArea
 	piecesNeeded := int(math.Ceil(totalArea / pieceArea))
 
-	result := CalcResult{
+	result := model.CalcResult{
 		FloorType:     input.FloorType,
 		Rooms:         roomResults,
 		TotalRoomArea: round2(totalRoomArea),
@@ -214,7 +162,7 @@ func calculate(input CalcInput) CalcResult {
 	return result
 }
 
-func deductionArea(d CalcDeduction) float64 {
+func deductionArea(d model.CalcDeduction) float64 {
 	switch d.Shape {
 	case "circle":
 		return math.Pi * d.Radius * d.Radius

internal/handler/floor_handler.go

@@ -131,13 +131,19 @@ func findFloorBySKU(db *sql.DB, sku string) *FloorOption {
 
 func FindFloorBySKUPublic(db *sql.DB, sku string) *FloorOption { return findFloorBySKU(db, sku) }
 func FindPatternByCodePublic(code string) *PatternOption {
-	c := 0; fmt.Sscanf(code, "%d", &c); return findPatternByCode(c)
+	c := 0
+	fmt.Sscanf(code, "%d", &c)
+	return findPatternByCode(c)
 }
 func FindRoomByCodePublic(code string) *RoomOption {
-	c := 0; fmt.Sscanf(code, "%d", &c); return findRoomByCode(c)
+	c := 0
+	fmt.Sscanf(code, "%d", &c)
+	return findRoomByCode(c)
+}
+func BuildMaskPromptPublic(room *RoomOption) string { return buildMaskPrompt(room) }
+func BuildFloorPromptPublic(f FloorOption, p PatternOption, room *RoomOption) string {
+	return buildFloorPrompt(f, p, room)
 }
-func BuildMaskPromptPublic(room *RoomOption) string    { return buildMaskPrompt(room) }
-func BuildFloorPromptPublic(f FloorOption, p PatternOption, room *RoomOption) string { return buildFloorPrompt(f, p, room) }
 
 // ── Floor Generate Handler (Redis queue) ──────────────────
 
@@ -162,7 +168,7 @@ type JobStatusResp struct {
 	Error   string `json:"error,omitempty"`
 }
 
-func handleFloorGenerate(client *openrouter.Client, db *sql.DB) http.HandlerFunc {
+func FloorGenerate(client *openrouter.Client, db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			writeErr(w, 405, "Method not allowed")
@@ -223,11 +229,12 @@ func handleFloorGenerate(client *openrouter.Client, db *sql.DB) http.HandlerFunc
 		writeJSON(w, 200, map[string]string{"job_id": jobID})
 	}
 }
+
 // ── Progress ───────────────────────────────────────────────
 
 // ── Floor Status Query ─────────────────────────────────
 
-func handleFloorStatus(w http.ResponseWriter, r *http.Request) {
+func FloorStatus(w http.ResponseWriter, r *http.Request) {
 	jobID := r.URL.Query().Get("job_id")
 	if jobID == "" {
 		writeErr(w, 400, "job_id is required")
@@ -244,9 +251,10 @@ func handleFloorStatus(w http.ResponseWriter, r *http.Request) {
 	}
 	writeJSON(w, 200, js)
 }
+
 // ── Options ────────────────────────────────────────────────
 
-func handleFloorOptions(db *sql.DB) http.HandlerFunc {
+func FloorOptions(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		woodFloors, _ := loadFloorOptions(db, "Hardwood")
 		woodFloors2, _ := loadFloorOptions(db, "Engineered Wood")
@@ -308,7 +316,7 @@ Style: photorealistic, soft natural matte finish, minimal reflections, no mirror
 
 // ── Content Check ─────────────────────────────────────────
 
-func handleCheckContent(client *openrouter.Client) http.HandlerFunc {
+func CheckContent(client *openrouter.Client) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			writeErr(w, 405, "Method not allowed")

internal/handler/health_handler.go

@@ -4,7 +4,7 @@ import (
 	"net/http"
 )
 
-func handleHealthz(w http.ResponseWriter, r *http.Request) {
+func Healthz(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, 200, map[string]string{
 		"status": "ok",
 	})

internal/handler/product_handler.go

@@ -31,11 +31,11 @@ type ProductItem struct {
 }
 
 type ProductListResponse struct {
-	Products      []ProductItem            `json:"products"`
+	Products      []ProductItem             `json:"products"`
-	Total         int                      `json:"total"`
+	Total         int                       `json:"total"`
-	Page          int                      `json:"page"`
+	Page          int                       `json:"page"`
-	Limit         int                      `json:"limit"`
+	Limit         int                       `json:"limit"`
-	TotalPages    int                      `json:"total_pages"`
+	TotalPages    int                       `json:"total_pages"`
 	FilterOptions *repository.FilterOptions `json:"filter_options"`
 }
 
@@ -53,7 +53,7 @@ func SetProductsCache(
 	productsTrackView = tracker
 }
 
-func handleProducts(db *sql.DB) http.HandlerFunc {
+func Products(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		// Detail: /products/{sku}
 		sku := strings.TrimPrefix(r.URL.Path, "/products/")
@@ -69,8 +69,7 @@ func handleProducts(db *sql.DB) http.HandlerFunc {
 				}
 			}
 			if product == nil {
-				var err error
+				product, err := repository.GetProductBySKU(db, sku)
-				product, err = repository.GetProductBySKU(db, sku)
 				if err != nil {
 					writeJSON(w, 404, map[string]string{"error": "product not found"})
 					return
@@ -152,8 +151,8 @@ func handleProducts(db *sql.DB) http.HandlerFunc {
 				PricePerSqft: p.PricePerSqft, PriceTier: p.PriceTier,
 				MainImageURL: p.MainImageURL, SizeLabel: p.SizeLabel,
 				CoverageSqftPerBox: p.CoverageSqftPerBox,
-				IsFavorited: favSKUs[p.SKU],
+				IsFavorited:        favSKUs[p.SKU],
-				SpecCount: specCounts[p.Brand+"|"+p.StyleName+"|"+p.SeriesName],
+				SpecCount:          specCounts[p.Brand+"|"+p.StyleName+"|"+p.SeriesName],
 			})
 		}
 
@@ -173,7 +172,7 @@ func handleProducts(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleProductOptions(db *sql.DB) http.HandlerFunc {
+func ProductOptions(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		opts, err := repository.GetFilterOptions(db)
 		if err != nil {
@@ -184,7 +183,7 @@ func handleProductOptions(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleFilterOptions(db *sql.DB) http.HandlerFunc {
+func FilterOptions(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		filters, err := repository.GetFilterHierarchy(db)
 		if err != nil {

internal/handler/recommend_handler.go

@@ -3,7 +3,7 @@ package handler
 import (
 	"database/sql"
 	"fmt"
-	"log"
+	"floorvisualizer/internal/logger"
 	"net/http"
 
 	"floorvisualizer/internal/model"
@@ -21,17 +21,19 @@ type RecommendResponse struct {
 var productService *service.ProductService
 
 func initProductService(db *sql.DB) {
-	if productService != nil { return }
+	if productService != nil {
-	products, err := repository.QueryAllProducts(db)
-	if err != nil {
-		log.Printf("Failed to load products: %v", err)
 		return
 	}
-	log.Printf("Loaded %d products for recommendation engine", len(products))
+	products, err := repository.QueryAllProducts(db)
+	if err != nil {
+		logger.Warn("Failed to load products: %v", err)
+		return
+	}
+	logger.Info("Loaded %d products for recommendation engine", len(products))
 	productService = service.NewProductService(products, model.DefaultEngineConfig())
 }
 
-func handleRecommend(db *sql.DB) http.HandlerFunc {
+func Recommend(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		sku := r.URL.Query().Get("sku")
 		if sku == "" {

internal/handler/router.go

@@ -1,15 +1,11 @@
 package handler
 
 import (
-	"database/sql"
 	"encoding/json"
-	"fmt"
 	"net/http"
 	"net/url"
 
-	"floorvisualizer/internal/middleware"
+	"floorvisualizer/internal/model"
-	"floorvisualizer/internal/openrouter"
-	"floorvisualizer/internal/service"
 )
 
 func NewProxyClient(proxyURLStr string) *http.Client {
@@ -20,57 +16,9 @@ func NewProxyClient(proxyURLStr string) *http.Client {
 	return &http.Client{Transport: &http.Transport{Proxy: http.ProxyURL(u)}}
 }
 
-func RegisterAll(mux *http.ServeMux, client *openrouter.Client, db *sql.DB, authSvc *service.AuthService) {
-	requireAuth := middleware.RequireAuth(authSvc)
-
-// Auth
-	mux.HandleFunc("/auth/register", handleRegister(authSvc, db))
-	mux.HandleFunc("/auth/login", handleLogin(authSvc, db))
-
-	// User (protected)
-	mux.HandleFunc("/user/me", requireAuth(handleMe(db)))
-	mux.HandleFunc("/user/avatar", requireAuth(handleUploadAvatar(db)))
-	mux.HandleFunc("/user/favorites", requireAuth(handleFavorites(db)))
-	mux.HandleFunc("/user/favorites/", requireAuth(handleFavorites(db)))
-	mux.HandleFunc("/user/projects", requireAuth(handleProjects(db)))
-	mux.HandleFunc("/user/projects/", requireAuth(handleProjects(db)))
-	mux.HandleFunc("/user/frequent-brands", requireAuth(handleFrequentBrands(db)))
-
-	// Upload
-	mux.HandleFunc("/healthz", handleHealthz)
-	mux.HandleFunc("/upload", handleUpload)
-
-	// Products
-	mux.HandleFunc("/products", handleProducts(db))
-	mux.HandleFunc("/products/", handleProducts(db))
-	mux.HandleFunc("/product-options", handleProductOptions(db))
-	mux.HandleFunc("/filter-options", handleFilterOptions(db))
-
-	// Recommend
-	mux.HandleFunc("/recommend/api", handleRecommend(db))
-
-	// Calculator
-	mux.HandleFunc("/calculator/calc", handleCalc)
-
-	// Floor AI
-	mux.HandleFunc("/floor/generate", handleFloorGenerate(client, db))
-	mux.HandleFunc("/floor/status", handleFloorStatus)
-	mux.HandleFunc("/floor/options", handleFloorOptions(db))
-
-	// Articles (recommend before /articles/ to avoid path conflict)
-	mux.HandleFunc("/articles/recommend", handleArticleRecommend(db))
-	mux.HandleFunc("/articles", handleArticles(db))
-	mux.HandleFunc("/articles/", handleArticles(db))
-
-	// Static
-	mux.Handle("/outputs/", http.StripPrefix("/outputs/", http.FileServer(http.Dir("./outputs"))))
-	mux.Handle("/uploads/", http.StripPrefix("/uploads/", http.FileServer(http.Dir("./uploads"))))
-	mux.Handle("/knowledge_images/", http.StripPrefix("/knowledge_images/", http.FileServer(http.Dir("./knowledge_images"))))
-	mux.Handle("/images/knowledge/", http.StripPrefix("/images/knowledge/", http.FileServer(http.Dir("./knowledge_images"))))
-}
-
 func writeJSON(w http.ResponseWriter, status int, v any) {
 	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
 	if status >= 400 {
 		msg := "Unknown error"
 		switch x := v.(type) {
@@ -80,19 +28,15 @@ func writeJSON(w http.ResponseWriter, status int, v any) {
 			if e, ok := x["error"]; ok {
 				msg = e
 			}
-		case map[string]any:
-			if e, ok := x["error"]; ok {
-				msg = fmt.Sprint(e)
-			}
 		}
-		w.WriteHeader(status)
+		json.NewEncoder(w).Encode(model.ApiError{Code: status, Error: msg})
-		json.NewEncoder(w).Encode(map[string]any{"code": status, "error": msg})
 		return
 	}
-	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(model.ApiResponse{Code: status, Data: v})
-	json.NewEncoder(w).Encode(map[string]any{"code": status, "data": v})
 }
 
 func writeErr(w http.ResponseWriter, status int, msg string) {
-	writeJSON(w, status, msg)
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(model.ApiError{Code: status, Error: msg})
 }

internal/handler/upload_handler.go

@@ -12,7 +12,7 @@ import (
 	"time"
 )
 
-func handleUpload(w http.ResponseWriter, r *http.Request) {
+func Upload(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		writeErr(w, 405, "Method not allowed")
 		return

internal/handler/user_handler.go

@@ -18,7 +18,7 @@ import (
 	"floorvisualizer/internal/repository"
 )
 
-func handleMe(db *sql.DB) http.HandlerFunc {
+func Me(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		userID := middleware.UserID(r.Context())
 		switch r.Method {
@@ -50,7 +50,7 @@ func handleMe(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleFavorites(db *sql.DB) http.HandlerFunc {
+func Favorites(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		userID := middleware.UserID(r.Context())
 		switch r.Method {
@@ -103,7 +103,7 @@ func handleFavorites(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleProjects(db *sql.DB) http.HandlerFunc {
+func Projects(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		userID := middleware.UserID(r.Context())
 		projectID := strings.TrimPrefix(r.URL.Path, "/user/projects/")
@@ -161,7 +161,9 @@ func handleSingleProject(w http.ResponseWriter, r *http.Request, db *sql.DB, use
 		}
 		writeJSON(w, 200, project)
 	case http.MethodPut:
-		var input struct{ Name string `json:"name"` }
+		var input struct {
+			Name string `json:"name"`
+		}
 		if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
 			writeJSON(w, 400, map[string]string{"error": "invalid request body"})
 			return
@@ -183,7 +185,7 @@ func handleSingleProject(w http.ResponseWriter, r *http.Request, db *sql.DB, use
 	}
 }
 
-func handleUploadAvatar(db *sql.DB) http.HandlerFunc {
+func UploadAvatar(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		userID := middleware.UserID(r.Context())
 		if err := r.ParseMultipartForm(5 << 20); err != nil {
@@ -233,10 +235,9 @@ func handleUploadAvatar(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-
 // ── Brand view tracking ───────────────────────────────────
 
-func handleBrandView(db *sql.DB) http.HandlerFunc {
+func BrandView(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			writeErr(w, 405, "Method not allowed")
@@ -268,7 +269,7 @@ func handleBrandView(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func handleFrequentBrands(db *sql.DB) http.HandlerFunc {
+func FrequentBrands(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		userID := middleware.UserID(r.Context())
 		if userID == "" {

internal/model/calc.go

@@ -0,0 +1,63 @@
+package model
+
+// ── Calculator input ──────────────────────────────────────
+
+type CalcRoomInput struct {
+	Name       string          `json:"name"`
+	Length     float64         `json:"length"`
+	Width      float64         `json:"width"`
+	Deductions []CalcDeduction `json:"deductions"`
+}
+
+type CalcDeduction struct {
+	Name   string  `json:"name"`
+	Shape  string  `json:"shape"` // rectangle, circle, custom
+	Length float64 `json:"length"`
+	Width  float64 `json:"width"`
+	Radius float64 `json:"radius"`
+	Area   float64 `json:"area"`
+}
+
+type CalcInput struct {
+	FloorType    string          `json:"floor_type"`
+	Rooms        []CalcRoomInput `json:"rooms"`
+	PatternIndex int             `json:"pattern_index"`
+	PieceLength  float64         `json:"piece_length"`
+	PieceWidth   float64         `json:"piece_width"`
+	PiecesPerBox int             `json:"pieces_per_box"`
+	PricePerSqm  float64         `json:"price_per_sqm"`
+	JointWidth   float64         `json:"joint_width"`
+}
+
+// ── Calculator output ─────────────────────────────────────
+
+type CalcRoomResult struct {
+	Name           string          `json:"name"`
+	Length         float64         `json:"length"`
+	Width          float64         `json:"width"`
+	Area           float64         `json:"area"`
+	Deductions     []CalcDeduction `json:"deductions"`
+	DeductionTotal float64         `json:"deduction_total"`
+	NetArea        float64         `json:"net_area"`
+}
+
+type CalcResult struct {
+	FloorType     string           `json:"floor_type"`
+	Rooms         []CalcRoomResult `json:"rooms"`
+	TotalRoomArea float64          `json:"total_room_area"`
+	TotalDeduct   float64          `json:"total_deduct"`
+	TotalNetArea  float64          `json:"total_net_area"`
+	WasteRate     float64          `json:"waste_rate"`
+	WasteArea     float64          `json:"waste_area"`
+	TotalArea     float64          `json:"total_area"`
+	PiecesNeeded  int              `json:"pieces_needed"`
+	BoxesNeeded   *float64         `json:"boxes_needed,omitempty"`
+	JointWidth    float64          `json:"joint_width"`
+	GroutKg       *float64         `json:"grout_kg,omitempty"`
+	GroutBags     *int             `json:"grout_bags,omitempty"`
+	PricePerSqm   float64          `json:"price_per_sqm"`
+	TotalPrice    *float64         `json:"total_price,omitempty"`
+	PatternName   string           `json:"pattern_name"`
+	PieceLength   float64          `json:"piece_length"`
+	PieceWidth    float64          `json:"piece_width"`
+}

internal/model/response.go

@@ -0,0 +1,30 @@
+package model
+
+// ── Common API response envelope ─────────────────────────
+
+// ApiResponse wraps all API responses.
+type ApiResponse struct {
+	Code int `json:"code"`
+	Data any `json:"data,omitempty"`
+}
+
+// ApiError wraps error responses.
+type ApiError struct {
+	Code  int    `json:"code"`
+	Error string `json:"error"`
+}
+
+// ── Simple response types ─────────────────────────────────
+
+type OKResponse struct {
+	OK string `json:"ok"`
+}
+
+type JobResponse struct {
+	JobID string `json:"job_id"`
+}
+
+type UploadResponse struct {
+	URL      string `json:"url"`
+	Filename string `json:"filename"`
+}

internal/queue/worker.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
-	"io"
 	"floorvisualizer/internal/logger"
 	"os"
 	"path/filepath"
@@ -182,5 +181,3 @@ func base64enc(data []byte) string {
 	return string(b)
 }
 
-// Make sure io is used (for any future imports)
-var _ = io.Discard

main.go

@@ -2,19 +2,20 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"log"
+	"math/rand"
 	"net/http"
 	"os"
 	"os/signal"
 	"strconv"
 	"time"
-	"encoding/json"
-	"math/rand"
 
+	"floorvisualizer/internal/api"
 	"floorvisualizer/internal/handler"
 	"floorvisualizer/internal/logger"
-	"floorvisualizer/internal/model"
 	"floorvisualizer/internal/middleware"
+	"floorvisualizer/internal/model"
 	"floorvisualizer/internal/openrouter"
 	"floorvisualizer/internal/queue"
 	"floorvisualizer/internal/repository"
@@ -23,6 +24,7 @@ import (
 
 const defaultAPIKey = "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"
 const defaultJWTSecret = "floorviz-dev-secret-change-in-production"
+
 var proxyURL = "http://127.0.0.1:7897"
 
 func init() {
@@ -132,39 +134,38 @@ func main() {
 		}()
 	}
 
-
+	// ── Hot product cache ────────────────────────────────
-		// ── Hot product cache ────────────────────────────────
+	handler.SetProductsCache(
-		handler.SetProductsCache(
+		// Getter: check Redis cache for hot products
-			// Getter: check Redis cache for hot products
+		func(ctx context.Context, sku string) (*model.Product, bool) {
-			func(ctx context.Context, sku string) (*model.Product, bool) {
+			val, err := rdb.Get(ctx, "product:"+sku).Result()
-				val, err := rdb.Get(ctx, "product:"+sku).Result()
+			if err != nil {
-				if err != nil {
-					return nil, false
-				}
-				var p model.Product
-				if json.Unmarshal([]byte(val), &p) == nil {
-					return &p, true
-				}
 				return nil, false
-			},
+			}
-			// Setter: only cache if this SKU is in the hot list (top 200)
+			var p model.Product
-			func(ctx context.Context, sku string, product *model.Product) error {
+			if json.Unmarshal([]byte(val), &p) == nil {
-				rank, err := rdb.ZRevRank(ctx, "product:views", sku).Result()
+				return &p, true
-				if err != nil || rank >= 200 {
+			}
-					return nil // not hot enough, skip caching
+			return nil, false
-				}
+		},
-				data, _ := json.Marshal(product)
+		// Setter: only cache if this SKU is in the hot list (top 200)
-				ttl := 1*time.Hour + time.Duration(rand.Intn(600))*time.Second // ±10min jitter
+		func(ctx context.Context, sku string, product *model.Product) error {
-				return rdb.Set(ctx, "product:"+sku, data, ttl).Err()
+			rank, err := rdb.ZRevRank(ctx, "product:views", sku).Result()
-			},
+			if err != nil || rank >= 200 {
-			// View tracker: increment view count in sorted set
+				return nil // not hot enough, skip caching
-			func(ctx context.Context, sku string) {
+			}
-				rdb.ZIncrBy(ctx, "product:views", 1, sku)
+			data, _ := json.Marshal(product)
-			},
+			ttl := 1*time.Hour + time.Duration(rand.Intn(600))*time.Second // ±10min jitter
-		)
+			return rdb.Set(ctx, "product:"+sku, data, ttl).Err()
+		},
+		// View tracker: increment view count in sorted set
+		func(ctx context.Context, sku string) {
+			rdb.ZIncrBy(ctx, "product:views", 1, sku)
+		},
+	)
 
 	mux := http.NewServeMux()
-	handler.RegisterAll(mux, client, db, authSvc)
+	api.RegisterRoutes(mux, client, db, authSvc)
 
 	port := "8099"
 	if p := os.Getenv("PORT"); p != "" {