a correct implementation of filer

go/filer/directory.go

@@ -0,0 +1,18 @@
+package filer
+
+import ()
+
+type DirectoryId int32
+
+type DirectoryEntry struct {
+	Name string //dir name without path
+	Id   DirectoryId
+}
+
+type DirectoryManager interface {
+	FindDirectory(dirPath string) (DirectoryId, error)
+	ListDirectories(dirPath string) (dirNames []DirectoryEntry, err error)
+	MakeDirectory(currentDirPath string, dirName string) (DirectoryId, error)
+	MoveUnderDirectory(oldDirPath string, newParentDirPath string) error
+	DeleteDirectory(dirPath string) error
+}