Version 3 starter

backend/internal/api/handler/not_found.go

@@ -0,0 +1,65 @@
+package handler
+
+import (
+	"embed"
+	"errors"
+	"io"
+	"io/fs"
+	"mime"
+	"net/http"
+	"path/filepath"
+	"strings"
+
+	h "npm/internal/api/http"
+)
+
+//go:embed assets
+var assets embed.FS
+var assetsSub fs.FS
+
+var errIsDir = errors.New("path is dir")
+
+// NotFound is a json error handler for 404's and method not allowed.
+// It also serves the react frontend as embedded files in the golang binary.
+func NotFound() func(http.ResponseWriter, *http.Request) {
+	assetsSub, _ = fs.Sub(assets, "assets")
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		path := strings.TrimLeft(r.URL.Path, "/")
+		if path == "" {
+			path = "index.html"
+		}
+
+		err := tryRead(assetsSub, path, w)
+		if err == errIsDir {
+			err = tryRead(assetsSub, "index.html", w)
+			if err != nil {
+				h.ResultErrorJSON(w, r, http.StatusNotFound, "Not found", nil)
+			}
+		} else if err == nil {
+			return
+		}
+
+		h.ResultErrorJSON(w, r, http.StatusNotFound, "Not found", nil)
+	}
+}
+
+func tryRead(folder fs.FS, requestedPath string, w http.ResponseWriter) error {
+	f, err := folder.Open(requestedPath)
+	if err != nil {
+		return err
+	}
+
+	// nolint: errcheck
+	defer f.Close()
+
+	stat, _ := f.Stat()
+	if stat.IsDir() {
+		return errIsDir
+	}
+
+	contentType := mime.TypeByExtension(filepath.Ext(requestedPath))
+	w.Header().Set("Content-Type", contentType)
+	_, err = io.Copy(w, f)
+	return err
+}