// backend\frontend.go

package main

import (
	"embed"
	"fmt"
	"io/fs"
	"net/http"
	"path"
	"strings"
)

// Vite-Build einbetten.
// Beim Go-Build muss backend/web/dist bereits existieren.
//
//go:embed web/dist web/dist/*
var embeddedFrontend embed.FS

func makeFrontendHandler() (http.Handler, bool) {
	distFS, err := fs.Sub(embeddedFrontend, "web/dist")
	if err != nil {
		fmt.Println("⚠️  Frontend dist nicht im Binary gefunden – API läuft trotzdem:", err)
		return nil, false
	}

	// Prüfen, ob index.html vorhanden ist
	if _, err := fs.Stat(distFS, "index.html"); err != nil {
		fmt.Println("⚠️  Frontend index.html nicht im Binary gefunden – API läuft trotzdem:", err)
		return nil, false
	}

	fmt.Println("🖼️  Frontend dist: embedded web/dist")

	fileServer := http.FileServer(http.FS(distFS))

	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// /api bleibt API
		if strings.HasPrefix(r.URL.Path, "/api/") {
			http.NotFound(w, r)
			return
		}

		reqPath := r.URL.Path
		if reqPath == "" || reqPath == "/" {
			w.Header().Set("Cache-Control", "no-store")
			indexBytes, err := fs.ReadFile(distFS, "index.html")
			if err != nil {
				http.Error(w, "index.html nicht gefunden", http.StatusInternalServerError)
				return
			}
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			_, _ = w.Write(indexBytes)
			return
		}

		// URL-Pfad bereinigen
		clean := path.Clean("/" + reqPath)
		rel := strings.TrimPrefix(clean, "/")

		// Wenn echte Datei im embedded FS existiert -> ausliefern
		if fi, err := fs.Stat(distFS, rel); err == nil && !fi.IsDir() {
			ext := strings.ToLower(path.Ext(rel))
			if ext != "" && ext != ".html" {
				w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
			} else {
				w.Header().Set("Cache-Control", "no-store")
			}
			fileServer.ServeHTTP(w, r)
			return
		}

		// SPA-Fallback
		w.Header().Set("Cache-Control", "no-store")
		indexBytes, err := fs.ReadFile(distFS, "index.html")
		if err != nil {
			http.Error(w, "index.html nicht gefunden", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_, _ = w.Write(indexBytes)
	})

	return h, true
}

func registerFrontend(mux *http.ServeMux) {
	h, ok := makeFrontendHandler()
	if !ok {
		return
	}
	mux.Handle("/", h)
}