package docker

 
 import (
 	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
 )
 
 type ChangeType int
 
 const (
 	ChangeModify = iota
 	ChangeAdd
 	ChangeDelete
 )
 
 type Change struct {
 	Path string
 	Kind ChangeType
 }
 
 func (change *Change) String() string {
 	var kind string
 	switch change.Kind {
 	case ChangeModify:
 		kind = "C"
 	case ChangeAdd:
 		kind = "A"
 	case ChangeDelete:
 		kind = "D"
 	}
 	return fmt.Sprintf("%s %s", kind, change.Path)
 }
 
 func Changes(layers []string, rw string) ([]Change, error) {
 	var changes []Change
 	err := filepath.Walk(rw, func(path string, f os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
 
 		// Rebase path
 		path, err = filepath.Rel(rw, path)
 		if err != nil {
 			return err
 		}
 		path = filepath.Join("/", path)
 
 		// Skip root
 		if path == "/" {
 			return nil
 		}
 
 		// Skip AUFS metadata
 		if matched, err := filepath.Match("/.wh..wh.*", path); err != nil || matched {
 			return err
 		}
 
 		change := Change{
 			Path: path,
 		}
 
 		// Find out what kind of modification happened
 		file := filepath.Base(path)
 		// If there is a whiteout, then the file was removed
 		if strings.HasPrefix(file, ".wh.") {

 			originalFile := file[len(".wh."):]

 			change.Path = filepath.Join(filepath.Dir(path), originalFile)
 			change.Kind = ChangeDelete
 		} else {
 			// Otherwise, the file was added
 			change.Kind = ChangeAdd
 
 			// ...Unless it already existed in a top layer, in which case, it's a modification
 			for _, layer := range layers {
 				stat, err := os.Stat(filepath.Join(layer, path))
 				if err != nil && !os.IsNotExist(err) {
 					return err
 				}
 				if err == nil {
 					// The file existed in the top layer, so that's a modification
 
 					// However, if it's a directory, maybe it wasn't actually modified.
 					// If you modify /foo/bar/baz, then /foo will be part of the changed files only because it's the parent of bar
 					if stat.IsDir() && f.IsDir() {
 						if f.Size() == stat.Size() && f.Mode() == stat.Mode() && f.ModTime() == stat.ModTime() {
 							// Both directories are the same, don't record the change
 							return nil
 						}
 					}
 					change.Kind = ChangeModify
 					break
 				}
 			}
 		}
 
 		// Record change
 		changes = append(changes, change)
 		return nil
 	})
 	if err != nil {
 		return nil, err
 	}
 	return changes, nil
 }