package main

import (
	"net/http"
	"os"
)

type fallbackFileSystem struct {
	http.FileSystem
	fallback string
}

func (fs *fallbackFileSystem) Open(name string) (http.File, error) {
	f, err := fs.FileSystem.Open(name)
	if os.IsNotExist(err) {
		return fs.FileSystem.Open(fs.fallback)
	}
	return f, err
}

func assetsHandler() http.Handler {
	assetsFileSystem := assetsFS()

	return http.FileServer(
		&fallbackFileSystem{
			FileSystem: http.FS(assetsFileSystem),
			fallback:   "index.html",
		})
}