// Package spa provides the HTTP handler that serves a single-page application.
package spa

import (
	"net/http"
	"path/filepath"

	"code.nochebuena.dev/einherjar/contracts/logging"
)

type handler struct {
	logger    logging.Logger
	staticDir string
	fs        http.Handler
}

// NewHandler returns an http.Handler that serves static files from staticDir.
// Requests for paths that exist on disk are served directly.
// Any other path receives index.html, delegating routing to the SPA.
func NewHandler(logger logging.Logger, staticDir string) http.Handler {
	return &handler{
		logger:    logger,
		staticDir: staticDir,
		fs:        http.FileServer(http.Dir(staticDir)),
	}
}

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// http.Dir.Open sanitises the path, preventing directory traversal.
	f, err := http.Dir(h.staticDir).Open(r.URL.Path)
	if err != nil {
		// Path does not exist — hand off to the SPA router.
		http.ServeFile(w, r, filepath.Join(h.staticDir, "index.html"))
		return
	}
	defer f.Close()

	stat, err := f.Stat()
	if err != nil || stat.IsDir() {
		// Directory listing is disabled; treat directories as SPA routes.
		http.ServeFile(w, r, filepath.Join(h.staticDir, "index.html"))
		return
	}

	h.fs.ServeHTTP(w, r)
}