at-container-registry/pkg/appview/handlers/errors.go

package handlers

import (
	"encoding/json"
	"log/slog"
	"net/http"
)

// NotFoundHandler handles 404 errors
type NotFoundHandler struct {
	BaseUIHandler
}

func (h *NotFoundHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	RenderNotFound(w, r, &h.BaseUIHandler)
}

// RenderNotFound renders the 404 page template.
// Use this from other handlers when a resource is not found.
func RenderNotFound(w http.ResponseWriter, r *http.Request, h *BaseUIHandler) {
	w.WriteHeader(http.StatusNotFound)

	meta := NewPageMeta(
		"404 - Lost at Sea | "+h.ClientShortName,
		"Page not found - the requested resource doesn't exist on "+h.ClientShortName,
	).WithRobots("noindex").
		WithSiteName(h.ClientShortName)

	data := struct {
		PageData
		Meta *PageMeta
	}{
		PageData: NewPageData(r, h),
		Meta:     meta,
	}

	if err := h.Templates.ExecuteTemplate(w, "404", data); err != nil {
		http.Error(w, "Page not found", http.StatusNotFound)
	}
}

// RenderHTMXError sends an error response suitable for htmx. For htmx requests
// it sets an HX-Trigger header so the client fires a toast event; the JS
// fallback in app.js will show a generic toast even without the header.
// For non-htmx requests it falls back to http.Error. serverErr is logged but
// never exposed to the user — pass userMsg for anything screen-readable.
func RenderHTMXError(w http.ResponseWriter, r *http.Request, status int, userMsg string, serverErr error) {
	if serverErr != nil {
		slog.Error("htmx handler error",
			"path", r.URL.Path,
			"status", status,
			"err", serverErr,
		)
	}
	if userMsg == "" {
		userMsg = http.StatusText(status)
	}
	if r.Header.Get("HX-Request") == "true" {
		trigger := map[string]map[string]string{
			"toast": {"message": userMsg, "type": "error"},
		}
		if b, err := json.Marshal(trigger); err == nil {
			w.Header().Set("HX-Trigger", string(b))
		}
		w.Header().Set("HX-Reswap", "none")
		w.WriteHeader(status)
		return
	}
	http.Error(w, userMsg, status)
}