refactor: improve booking error handling and responses

Refactor booking retrieval to return errors instead of nil values,
enabling more robust error handling throughout the booking, payment,
and PDF endpoints. Add custom HTTP error page rendering for not found
and internal server errors. Update interfaces and tests to match new
method signatures. This improves user feedback and code maintainability.

internal/repository/booking/pg_store.go

@@ -81,10 +81,13 @@ func (ps *PgStore) CardTotal(from, to time.Time) (float64, error) {
 	return total, nil
 }
 
-func (ps *PgStore) Get(id int) *booking.Booking {
+func (ps *PgStore) Get(id int) (*booking.Booking, error) {
 	var b booking.Booking
-	ps.db.Preload("Items").Preload("Payments").First(&b, id)
-	return &b
+	res := ps.db.Preload("Items").Preload("Payments").First(&b, id)
+	if err := res.Error; err != nil {
+		return nil, err
+	}
+	return &b, nil
 }
 
 func (ps *PgStore) Create(b *booking.Booking) error {

internal/server/handle_bookings.go

@@ -16,6 +16,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	u "github.com/rjNemo/underscore"
 
+	"github.com/rjNemo/rentease/assets"
 	"github.com/rjNemo/rentease/internal/config"
 	"github.com/rjNemo/rentease/internal/constant"
 	"github.com/rjNemo/rentease/internal/service/booking"
@@ -167,7 +168,11 @@ func handleBookingPage(bs *booking.Service, hc *config.Host) http.HandlerFunc {
 			return
 		}
 
-		b := bs.One(id)
+		b, err := bs.One(id)
+		if err != nil {
+			renderHTTPErrorPage(w, http.StatusNotFound)
+			return
+		}
 
 		var eid string
 		if b.ExternalID == nil {
@@ -380,7 +385,10 @@ func handleCreateItem(bs *booking.Service, hc *config.Host) http.HandlerFunc {
 			return
 		}
 
-		b := bs.One(bid)
+		b, err := bs.One(bid)
+		if bookingLookupFailed(w, err) {
+			return
+		}
 
 		itemName := r.FormValue("item")
 		itm, ok := hc.Items[itemName]
@@ -550,3 +558,32 @@ func handleBookingCancel(bs *booking.Service) http.HandlerFunc {
 		}
 	}
 }
+
+func bookingLookupFailed(w http.ResponseWriter, err error) bool {
+	if err == nil {
+		return false
+	}
+
+	if errors.Is(err, booking.ErrBookingNotFound) {
+		renderHTTPErrorPage(w, http.StatusNotFound)
+		return true
+	}
+
+	renderHTTPErrorPage(w, http.StatusInternalServerError)
+	return true
+}
+
+func renderHTTPErrorPage(w http.ResponseWriter, status int) {
+	pagePath := fmt.Sprintf("assets/html/HTTP%d.html", status)
+	page, err := assets.Static.ReadFile(pagePath)
+	if err != nil {
+		http.Error(w, http.StatusText(status), status)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.WriteHeader(status)
+	if _, err := w.Write(page); err != nil {
+		slog.Error("failed to write error page", slog.Any("path", pagePath), slog.Any("error", err))
+	}
+}

internal/server/handle_payments.go

@@ -34,14 +34,20 @@ func handleCreatePayment(bs *booking.Service, hc *config.Host) http.HandlerFunc
 			}
 		}
 
-		b := bs.One(id)
+		b, err := bs.One(id)
+		if bookingLookupFailed(w, err) {
+			return
+		}
 
 		if _, err := bs.CreatePayment(b.ID, amount, r.FormValue("paymentMethod")); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
 
-		nb := bs.One(id)
+		nb, err := bs.One(id)
+		if bookingLookupFailed(w, err) {
+			return
+		}
 
 		component := view.PaymentList(
 			u.Map(nb.Payments, func(p booking.Payment) *view.PaymentViewModel {

internal/server/handle_pdf.go

@@ -22,7 +22,10 @@ func handlePdfCreateInvoice(bs *booking.Service, hc *config.Host) http.HandlerFu
 			return
 		}
 
-		b := bs.One(id)
+		b, err := bs.One(id)
+		if bookingLookupFailed(w, err) {
+			return
+		}
 
 		filePath, err := bs.BuildInvoice(b, hc)
 		if err != nil {

internal/server/server.go

@@ -130,5 +130,27 @@ func NewRouter(filesystem embed.FS, debug bool, origins []string) (*chi.Mux, err
 	fileServer := http.StripPrefix("/static/", http.FileServer(http.FS(assetsFS)))
 	r.Handle("/static/*", fileServer)
 
+	notFoundHandler, err := newHTTPErrorHandler(filesystem, http.StatusNotFound)
+	if err != nil {
+		return nil, fmt.Errorf("failed to setup not found handler: %w", err)
+	}
+	r.NotFound(notFoundHandler)
+
 	return r, nil
 }
+
+func newHTTPErrorHandler(filesystem embed.FS, statusCode int) (http.HandlerFunc, error) {
+	filePath := fmt.Sprintf("assets/html/HTTP%d.html", statusCode)
+	page, err := fs.ReadFile(filesystem, filePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read error page %s: %w", filePath, err)
+	}
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.WriteHeader(statusCode)
+		if _, err := w.Write(page); err != nil {
+			slog.Error("failed to write error page", slog.Any("error", err))
+		}
+	}, nil
+}

internal/service/booking/service.go

@@ -2,9 +2,12 @@ package booking
 
 import (
 	"context"
+	"errors"
 	"log/slog"
 	"time"
 
+	"gorm.io/gorm"
+
 	"github.com/rjNemo/rentease/internal/config"
 	stripeclient "github.com/rjNemo/rentease/internal/driver/stripe"
 )
@@ -14,7 +17,7 @@ type Store interface {
 	Search(value string) []*Line
 	List(from, to time.Time) ([]*Line, error)
 	CardTotal(from, to time.Time) (float64, error)
-	Get(id int) *Booking
+	Get(id int) (*Booking, error)
 	Create(b *Booking) error
 	Update(b *Booking) error
 	Cancel(id int) error
@@ -95,8 +98,15 @@ func (bs Service) Create(From time.Time, To time.Time, Name, PhoneNumber, Email,
 	return b
 }
 
-func (bs Service) One(id int) *Booking {
-	return bs.store.Get(id)
+func (bs Service) One(id int) (*Booking, error) {
+	b, err := bs.store.Get(id)
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return nil, ErrBookingNotFound
+		}
+		return nil, err
+	}
+	return b, nil
 }
 
 // Update updates an existing booking with new data

internal/service/booking/stripe_payment_link.go

@@ -22,7 +22,7 @@ func (bs Service) CreateStripePaymentLink(ctx context.Context, bookingID int) (s
 		return "", ErrStripeClientNotConfigured
 	}
 
-	b := bs.store.Get(bookingID)
+	b, _ := bs.store.Get(bookingID)
 	if b == nil || b.ID == 0 {
 		return "", ErrBookingNotFound
 	}

internal/service/booking/stripe_sync_test.go

@@ -52,7 +52,7 @@ func (m *mockStore) All() []*Line                                    { return ni
 func (m *mockStore) Search(string) []*Line                           { return nil }
 func (m *mockStore) List(time.Time, time.Time) ([]*Line, error)      { return nil, nil }
 func (m *mockStore) CardTotal(time.Time, time.Time) (float64, error) { return 0, nil }
-func (m *mockStore) Get(int) *Booking                                { return nil }
+func (m *mockStore) Get(int) (*Booking, error)                       { return nil, nil }
 func (m *mockStore) Create(*Booking) error                           { return nil }
 func (m *mockStore) Update(*Booking) error                           { return nil }
 func (m *mockStore) Cancel(int) error                                { return nil }