spa_webapp.go

//go:build webapp
// +build webapp

package main

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

//go:embed ui/build/*
var staticFiles embed.FS

type spaHandler struct {
	staticFS   embed.FS
	staticPath string
	indexPath  string
}

func (h spaHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// get the absolute path to prevent directory traversal
	path, err := filepath.Abs(r.URL.Path)
	if err != nil {
		// if we failed to get the absolute path respond with a 400 bad request and stop
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	// prepend the path with the path to the static directory
	path = filepath.Join(h.staticPath, path)

	_, err = h.staticFS.Open(path)
	if os.IsNotExist(err) {
		// file does not exist, serve index.html
		index, err := h.staticFS.ReadFile(filepath.Join(h.staticPath, h.indexPath))
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.WriteHeader(http.StatusAccepted)
		w.Write(index)
		return
	} else if err != nil {
		// if we got an error (that wasn't that the file doesn't exist) stating the
		// file, return a 500 internal server error and stop
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// get the subdirectory of the static dir
	statics, err := fs.Sub(h.staticFS, h.staticPath)
	// otherwise, use http.FileServer to serve the static dir
	http.FileServer(http.FS(statics)).ServeHTTP(w, r)
}

func getSpaHandler() http.Handler {
	return spaHandler{staticFS: staticFiles, staticPath: "ui/build", indexPath: "index.html"}
}