implemented os file interface acstraction

pkg/provider/parse/parse.go

@@ -0,0 +1,34 @@
+// Copyright (C) 2022 Marius Schellenberger
+
+package parse
+
+import (
+	"cachefs/pkg/provider"
+	"cachefs/pkg/provider/mount"
+	"errors"
+	"fmt"
+	neturl "net/url"
+	"path/filepath"
+)
+
+var (
+	ErrPathNotAbsolute   = errors.New("path is not absolute")
+	ErrUnsupportedScheme = errors.New("unsupported scheme")
+)
+
+func FS(url string) (provider.FS, error) {
+	u, err := neturl.Parse(url)
+	if err != nil {
+		return nil, err
+	}
+	if !filepath.IsAbs(u.Path) {
+		return nil, ErrPathNotAbsolute
+	}
+	switch u.Scheme {
+	case "file":
+		return mount.NewFS(u.Path), nil
+		//case "sftp":
+		//	return sftp.FS(u.Path), nil
+	}
+	return nil, fmt.Errorf("%w: %s", ErrUnsupportedScheme, u.Scheme)
+}