package main

import (
	"fmt"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
)

// Frontend (Vite build) als SPA ausliefern: Dateien aus dist, sonst index.html
func registerFrontend(mux *http.ServeMux) {
	// Kandidaten: zuerst ENV, dann typische Ordner
	candidates := []string{
		strings.TrimSpace(os.Getenv("FRONTEND_DIST")),
		"web/dist",
		"dist",
	}

	var distAbs string
	for _, c := range candidates {
		if c == "" {
			continue
		}
		abs, err := resolvePathRelativeToApp(c)
		if err != nil {
			continue
		}
		if fi, err := os.Stat(filepath.Join(abs, "index.html")); err == nil && !fi.IsDir() {
			distAbs = abs
			break
		}
	}

	if distAbs == "" {
		fmt.Println("⚠️  Frontend dist nicht gefunden (tried: FRONTEND_DIST, frontend/dist, dist) – API läuft trotzdem.")
		return
	}

	fmt.Println("🖼️  Frontend dist:", distAbs)

	fileServer := http.FileServer(http.Dir(distAbs))

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		// /api bleibt bei deinen API-Routen (längeres Pattern gewinnt),
		// aber falls mal was durchrutscht:
		if strings.HasPrefix(r.URL.Path, "/api/") {
			http.NotFound(w, r)
			return
		}

		// 1) Wenn echte Datei existiert -> ausliefern
		reqPath := r.URL.Path
		if reqPath == "" || reqPath == "/" {
			// index.html
			w.Header().Set("Cache-Control", "no-store")
			http.ServeFile(w, r, filepath.Join(distAbs, "index.html"))
			return
		}

		// URL-Pfad in Dateisystem-Pfad umwandeln (ohne Traversal)
		clean := path.Clean("/" + reqPath) // path.Clean (für URL-Slashes)
		rel := strings.TrimPrefix(clean, "/")
		onDisk := filepath.Join(distAbs, filepath.FromSlash(rel))

		if fi, err := os.Stat(onDisk); err == nil && !fi.IsDir() {
			// Statische Assets ruhig cachen (Vite hashed assets)
			ext := strings.ToLower(filepath.Ext(onDisk))
			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
		}

		// 2) SPA-Fallback: alle "Routen" ohne Datei -> index.html
		w.Header().Set("Cache-Control", "no-store")
		http.ServeFile(w, r, filepath.Join(distAbs, "index.html"))
	})
}

func makeFrontendHandler() (http.Handler, bool) {
	// Kandidaten: zuerst ENV, dann typische Ordner
	candidates := []string{
		strings.TrimSpace(os.Getenv("FRONTEND_DIST")),
		"web/dist",
		"dist",
	}

	var distAbs string
	for _, c := range candidates {
		if c == "" {
			continue
		}
		abs, err := resolvePathRelativeToApp(c)
		if err != nil {
			continue
		}
		if fi, err := os.Stat(filepath.Join(abs, "index.html")); err == nil && !fi.IsDir() {
			distAbs = abs
			break
		}
	}

	if distAbs == "" {
		fmt.Println("⚠️  Frontend dist nicht gefunden (tried: FRONTEND_DIST, web/dist, dist) – API läuft trotzdem.")
		return nil, false
	}

	fmt.Println("🖼️  Frontend dist:", distAbs)

	fileServer := http.FileServer(http.Dir(distAbs))

	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")
			http.ServeFile(w, r, filepath.Join(distAbs, "index.html"))
			return
		}

		// URL-Pfad in Dateisystem-Pfad umwandeln (ohne Traversal)
		clean := path.Clean("/" + reqPath)
		rel := strings.TrimPrefix(clean, "/")
		onDisk := filepath.Join(distAbs, filepath.FromSlash(rel))

		if fi, err := os.Stat(onDisk); err == nil && !fi.IsDir() {
			ext := strings.ToLower(filepath.Ext(onDisk))
			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")
		http.ServeFile(w, r, filepath.Join(distAbs, "index.html"))
	})

	return h, true
}