package src

import (
	"crypto/sha256"
	"encoding/hex"
	"io/fs"
	"os"
	"path"
	"strings"
	"sync"

	webui "xteve/html"
)

// webFS serves the web interface. It is the embedded copy by default and the
// local html/ directory when xTeVe runs with -dev.
var webFS fs.FS = webui.FS

var webETags sync.Map // path -> ETag, only used when not in dev mode

// initWebFS : selects embedded or on-disk web files.
func initWebFS(dev bool) {
	if dev {
		webFS = os.DirFS("html")
		return
	}
	webFS = webui.FS
}

// readWebFile : reads a file from the web interface, name relative to html/.
func readWebFile(name string) ([]byte, error) {
	name = strings.TrimPrefix(path.Clean("/"+name), "/")
	if name == "" || name == "." {
		return nil, fs.ErrNotExist
	}
	return fs.ReadFile(webFS, name)
}

// webFileETag : content hash used for HTTP caching of static web assets.
func webFileETag(name string, content []byte) string {
	if !System.Dev {
		if v, ok := webETags.Load(name); ok {
			return v.(string)
		}
	}
	sum := sha256.Sum256(content)
	etag := `"` + hex.EncodeToString(sum[:16]) + `"`
	if !System.Dev {
		webETags.Store(name, etag)
	}
	return etag
}