package main

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

// spaHandler serves the built frontend from dir, falling back to index.html
// for any path that isn't an actual file so client-side routes (e.g. a list's
// /lion-fancy-sharpness URL) resolve correctly on a hard refresh.
func spaHandler(dir string) http.Handler {
	fs := http.FileServer(http.Dir(dir))
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		cleanPath := filepath.Clean(r.URL.Path)

		if strings.HasPrefix(cleanPath, "/assets/") {
			w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
		} else {
			w.Header().Set("Cache-Control", "no-cache")
		}

		if info, err := os.Stat(filepath.Join(dir, cleanPath)); err == nil && !info.IsDir() {
			fs.ServeHTTP(w, r)
			return
		}
		http.ServeFile(w, r, filepath.Join(dir, "index.html"))
	})
}