added custom filter options

filesystem.go

@@ -16,12 +16,13 @@ const writeFlag = os.O_RDWR | os.O_CREATE | os.O_TRUNC
 
 // WriteOnlyOnceFileSystem is a file write only wrapper for a webdav.FileSystem
 type WriteOnlyOnceFileSystem struct {
-	fs webdav.FileSystem
+	Filters []Filter
+	fs      webdav.FileSystem
 }
 
 // NewWriteOnlyOnceFileSystem returns a new WriteOnlyOnceFileSystem wrapping a webdav.FileSystem
 func NewWriteOnlyOnceFileSystem(fs webdav.FileSystem) *WriteOnlyOnceFileSystem {
-	return &WriteOnlyOnceFileSystem{fs}
+	return &WriteOnlyOnceFileSystem{fs: fs}
 }
 
 // Mkdir is not permitted
@@ -38,6 +39,12 @@ func (fs *WriteOnlyOnceFileSystem) OpenFile(ctx context.Context, name string, fl
 			return nil, ErrWonly
 		}
 	}
+	for _, filter := range fs.Filters {
+		err = filter.Filter(name)
+		if err != nil {
+			return nil, err
+		}
+	}
 	f, err := fs.fs.OpenFile(ctx, name, flag, perm)
 	if err != nil {
 		return nil, err
@@ -45,8 +52,15 @@ func (fs *WriteOnlyOnceFileSystem) OpenFile(ctx context.Context, name string, fl
 	return &File{f}, nil
 }
 
-// RemoveAll is not permitted
+// RemoveAll only permits deleting empty files
 func (fs *WriteOnlyOnceFileSystem) RemoveAll(ctx context.Context, name string) error {
+	fi, err := fs.fs.Stat(ctx, name)
+	if err != nil {
+		return err
+	}
+	if fi.Mode().IsRegular() && fi.Size() == 0 {
+		return fs.fs.RemoveAll(ctx, name)
+	}
 	return ErrWonly
 }