package web

import (
	"embed"
	"io/fs"
	"net/http"
	"os"
	"path"
)

//go:embed dist
var assets embed.FS

//go:embed index.html
var Index embed.FS

//go:embed 404.html
var NotFound embed.FS

// fsFunc is short-hand for constructing a http.FileSystem
// implementation
type fsFunc func(name string) (fs.File, error)

func (f fsFunc) Open(name string) (fs.File, error) {
	return f(name)
}

// AssetsHandler returns an http.Handler that will serve files from
// the Assets embed.FS.  When locating a file, it will strip the given
// prefix from the request and prepend the root to the filesystem
// lookup: typical prefix might be /assets/, and root would be dist.
func AssetsHandler(prefix, root string) http.Handler {
	handler := fsFunc(func(name string) (fs.File, error) {
		assetPath := path.Join(root, name)

		// If we can't find the asset, return the default index.html
		// content
		f, err := assets.Open(assetPath)
		if os.IsNotExist(err) {
			return NotFound.Open("404.html")
		}

		// Otherwise assume this is a legitimate request routed
		// correctly
		return f, err
	})

	return http.StripPrefix(prefix, http.FileServer(http.FS(handler)))
}