GODT-1332 moving cache does not work on Windows.

internal/users/users.go

@@ -20,6 +20,8 @@ package users
 
 import (
 	"context"
+	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -451,8 +453,169 @@ func (u *Users) DisableCache() error {
 	return nil
 }
 
-func (u *Users) MigrateCache(from, to string) error {
-	// NOTE(GODT-1158): Is it enough to just close the store? Do we need to force-close the cacher too?
+// isFolderEmpty checks whether a folder is empty.
+// path must point to an existing folder.
+func isFolderEmpty(path string) (bool, error) {
+	files, err := ioutil.ReadDir(path)
+	if err != nil {
+		return true, err
+	}
+	return len(files) == 0, nil
+}
+
+// checkFolderIsSuitableDestinationForCache determine if a folder is a suitable destination as a cache
+// if it is suitable (non existing, or empty and deletable) the folder is deleted.
+func checkFolderIsSuitableDestinationForCache(path string) error {
+	// Ensure the parent directory exists.
+	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
+		return err
+	}
+
+	// if the folder does not exists, its suitable
+	fileInfo, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	if !fileInfo.IsDir() {
+		return errors.New("the destination folder for message cache exists and is a file")
+	}
+
+	empty, err := isFolderEmpty(path)
+	if err != nil {
+		return err
+	}
+
+	if !empty {
+		return errors.New("the destination folder is not empty")
+	}
+	return os.Remove(path)
+}
+
+// copyFolder recursively copy folder at srcPath to dstPath.
+// srcPath must be an existing folder.
+// dstPath must point to a non-existing folder.
+func copyFolder(srcPath, dstPath string) error {
+	fiFrom, err := os.Stat(srcPath)
+	if err != nil {
+		return err
+	}
+
+	_, err = os.Stat(dstPath)
+	if !os.IsNotExist(err) {
+		return errors.New("the destination folder already exists")
+	}
+
+	if !fiFrom.IsDir() {
+		return errors.New("source is not an existing folder")
+	}
+
+	if err = os.MkdirAll(dstPath, 0700); err != nil {
+		return err
+	}
+	files, err := ioutil.ReadDir(srcPath)
+	if err != nil {
+		return err
+	}
+	// copy only regular files and folders
+	for _, fileInfo := range files {
+		mode := fileInfo.Mode()
+		if mode&os.ModeSymlink != 0 {
+			continue // we skip symbolic links to avoid potential endless recursion
+		}
+		srcSubPath := srcPath + "/" + fileInfo.Name()
+		dstSubPath := dstPath + "/" + fileInfo.Name()
+
+		if mode.IsDir() {
+			if err = copyFolder(srcSubPath, dstSubPath); err != nil {
+				return err
+			}
+			continue
+		}
+
+		if mode.IsRegular() {
+			if err = copyFile(srcSubPath, dstSubPath); err != nil {
+				return err
+			}
+			continue // unnecessary but safer if we had code below
+		}
+	}
+	return nil
+}
+
+// isSubfolderOf check whether path is subfolder of refPath or is the same.
+// RefPath must exist otherwise the function returns false.
+func isSubfolderOf(path, refPath string) bool {
+	refInfo, err := os.Stat(refPath)
+	if (err != nil) || (!refInfo.IsDir()) {
+		return false // refpath does not exist. Not acceptable as we use os.SameFile for testing identity
+	}
+
+	// we check path and all its parent folder to verify if it is refPath.
+	prevPath := ""
+	for path != prevPath {
+		pathInfo, err := os.Stat(path) // path may not exist, and it's acceptable, so wo keep going event if err != nil
+		if err == nil && os.SameFile(pathInfo, refInfo) {
+			return true
+		}
+		prevPath = path
+		path = filepath.Dir(path)
+	}
+	return false
+}
+
+// copyFile copies file srcPath to dstPath. both path are files names. srcPath must exist, dstPath will be overwritten
+// if it exists and is a file.
+func copyFile(srcPath, dstPath string) error {
+	srcInfo, err := os.Stat(srcPath)
+	if err != nil {
+		return errors.New("could not open source file")
+	}
+	if !srcInfo.Mode().IsRegular() {
+		return errors.New("source file is not a regular file")
+	}
+
+	dstInfo, err := os.Stat(dstPath)
+	if err == nil && !dstInfo.Mode().IsRegular() {
+		return errors.New("destination exists and is not a regular file")
+	}
+
+	src, err := os.Open(filepath.Clean(srcPath))
+	if err != nil {
+		return err
+	}
+	defer func() {
+		err = src.Close()
+	}()
+
+	dst, err := os.OpenFile(filepath.Clean(dstPath), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		err = dst.Close()
+	}()
+	_, err = io.Copy(dst, src)
+	return err
+}
+
+// MigrateCache moves the message cache folder from folder srcPath to folder dstPath.
+// srcPath must point to an existing folder. dstPath must be an empty folder or not exist.
+func (u *Users) MigrateCache(srcPath, dstPath string) error {
+	// NOTE(GODT-1158): Is it enough dstPath just close the store? Do we need dstPath force-close the cacher too?
+
+	fiSrc, err := os.Stat(srcPath)
+	if os.IsNotExist(err) {
+		logrus.WithError(err).Error("unknown source for cache migration")
+		return err
+	}
+	if !fiSrc.IsDir() {
+		logrus.WithError(err).Error("cache migration cannot be perform srcPath a file")
+		return err
+	}
 
 	for _, user := range u.users {
 		if err := user.closeStore(); err != nil {
@@ -460,12 +623,29 @@ func (u *Users) MigrateCache(from, to string) error {
 		}
 	}
 
-	// Ensure the parent directory exists.
-	if err := os.MkdirAll(filepath.Dir(to), 0700); err != nil {
+	if isSubfolderOf(dstPath, srcPath) {
+		return errors.New("the destination folder is a subfolder of the source folder")
+	}
+
+	if err = checkFolderIsSuitableDestinationForCache(dstPath); err != nil {
+		logrus.WithError(err).Error("destination folder is not suitable for cache migration")
 		return err
 	}
 
-	return os.Rename(from, to)
+	err = os.Rename(srcPath, dstPath)
+	if err == nil {
+		return nil
+	}
+
+	// Rename failed let's try an actual copy/delete
+	if err = copyFolder(srcPath, dstPath); err != nil {
+		return err
+	}
+
+	if err = os.RemoveAll(srcPath); err != nil { // we don't care much about error there.
+		logrus.Info("Original cache folder could not be entirely removed")
+	}
+	return nil
 }
 
 // hasUser returns whether the struct currently has a user with ID `id`.