/*
Copyright 2018 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package mount

import (
	"fmt"
	"os"
	"syscall"

	"k8s.io/klog"
)

// CleanupMountPoint unmounts the given path and
// deletes the remaining directory if successful.
// if extensiveMountPointCheck is true
// IsNotMountPoint will be called instead of IsLikelyNotMountPoint.
// IsNotMountPoint is more expensive but properly handles bind mounts within the same fs.
func CleanupMountPoint(mountPath string, mounter Interface, extensiveMountPointCheck bool) error {
	// mounter.ExistsPath cannot be used because for containerized kubelet, we need to check
	// the path in the kubelet container, not on the host.
	pathExists, pathErr := PathExists(mountPath)
	if !pathExists {
		klog.Warningf("Warning: Unmount skipped because path does not exist: %v", mountPath)
		return nil
	}
	corruptedMnt := IsCorruptedMnt(pathErr)
	if pathErr != nil && !corruptedMnt {
		return fmt.Errorf("Error checking path: %v", pathErr)
	}
	return doCleanupMountPoint(mountPath, mounter, extensiveMountPointCheck, corruptedMnt)
}

// doCleanupMountPoint unmounts the given path and
// deletes the remaining directory if successful.
// if extensiveMountPointCheck is true
// IsNotMountPoint will be called instead of IsLikelyNotMountPoint.
// IsNotMountPoint is more expensive but properly handles bind mounts within the same fs.
// if corruptedMnt is true, it means that the mountPath is a corrupted mountpoint, and the mount point check
// will be skipped
func doCleanupMountPoint(mountPath string, mounter Interface, extensiveMountPointCheck bool, corruptedMnt bool) error {
	if !corruptedMnt {
		var notMnt bool
		var err error
		if extensiveMountPointCheck {
			notMnt, err = IsNotMountPoint(mounter, mountPath)
		} else {
			notMnt, err = mounter.IsLikelyNotMountPoint(mountPath)
		}

		if err != nil {
			return err
		}

		if notMnt {
			klog.Warningf("Warning: %q is not a mountpoint, deleting", mountPath)
			return os.Remove(mountPath)
		}
	}

	// Unmount the mount path
	klog.V(4).Infof("%q is a mountpoint, unmounting", mountPath)
	if err := mounter.Unmount(mountPath); err != nil {
		return err
	}

	notMnt, mntErr := mounter.IsLikelyNotMountPoint(mountPath)
	if mntErr != nil {
		return mntErr
	}
	if notMnt {
		klog.V(4).Infof("%q is unmounted, deleting the directory", mountPath)
		return os.Remove(mountPath)
	}
	return fmt.Errorf("Failed to unmount path %v", mountPath)
}

// TODO: clean this up to use pkg/util/file/FileExists
// PathExists returns true if the specified path exists.
func PathExists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	} else if os.IsNotExist(err) {
		return false, nil
	} else if IsCorruptedMnt(err) {
		return true, err
	} else {
		return false, err
	}
}

// IsCorruptedMnt return true if err is about corrupted mount point
func IsCorruptedMnt(err error) bool {
	if err == nil {
		return false
	}
	var underlyingError error
	switch pe := err.(type) {
	case nil:
		return false
	case *os.PathError:
		underlyingError = pe.Err
	case *os.LinkError:
		underlyingError = pe.Err
	case *os.SyscallError:
		underlyingError = pe.Err
	}

	return underlyingError == syscall.ENOTCONN || underlyingError == syscall.ESTALE || underlyingError == syscall.EIO
}