/*
   Copyright The containerd 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 client

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"syscall"

	"github.com/Microsoft/hcsshim"
	"golang.org/x/sys/windows"
)

// forceRemoveAll is the same as os.RemoveAll, but is aware of io.containerd.snapshotter.v1.windows
// and uses hcsshim to unmount and delete container layers contained therein, in the correct order,
// when passed a containerd root data directory (i.e. the `--root` directory for containerd).
func forceRemoveAll(path string) error {
	// snapshots/windows/windows.go init()
	const snapshotPlugin = "io.containerd.snapshotter.v1" + "." + "windows"
	// snapshots/windows/windows.go NewSnapshotter()
	snapshotDir := filepath.Join(path, snapshotPlugin, "snapshots")
	if stat, err := os.Stat(snapshotDir); err == nil && stat.IsDir() {
		if err := cleanupWCOWLayers(snapshotDir); err != nil {
			return fmt.Errorf("failed to cleanup WCOW layers in %s: %w", snapshotDir, err)
		}
	}

	return os.RemoveAll(path)
}

func cleanupWCOWLayers(root string) error {
	// See snapshots/windows/windows.go getSnapshotDir()
	var layerNums []int
	var rmLayerNums []int
	if err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if path != root && info.IsDir() {
			name := filepath.Base(path)
			if strings.HasPrefix(name, "rm-") {
				layerNum, err := strconv.Atoi(strings.TrimPrefix(name, "rm-"))
				if err != nil {
					return err
				}
				rmLayerNums = append(rmLayerNums, layerNum)
			} else {
				layerNum, err := strconv.Atoi(name)
				if err != nil {
					return err
				}
				layerNums = append(layerNums, layerNum)
			}
			return filepath.SkipDir
		}

		return nil
	}); err != nil {
		return err
	}

	sort.Sort(sort.Reverse(sort.IntSlice(rmLayerNums)))
	for _, rmLayerNum := range rmLayerNums {
		if err := cleanupWCOWLayer(filepath.Join(root, "rm-"+strconv.Itoa(rmLayerNum))); err != nil {
			return err
		}
	}

	sort.Sort(sort.Reverse(sort.IntSlice(layerNums)))
	for _, layerNum := range layerNums {
		if err := cleanupWCOWLayer(filepath.Join(root, strconv.Itoa(layerNum))); err != nil {
			return err
		}
	}

	return nil
}

func cleanupWCOWLayer(layerPath string) error {
	info := hcsshim.DriverInfo{
		HomeDir: filepath.Dir(layerPath),
	}

	// ERROR_DEV_NOT_EXIST is returned if the layer is not currently prepared or activated.
	// ERROR_FLT_INSTANCE_NOT_FOUND is returned if the layer is currently activated but not prepared.
	if err := hcsshim.UnprepareLayer(info, filepath.Base(layerPath)); err != nil {
		if hcserror, ok := err.(*hcsshim.HcsError); !ok || (hcserror.Err != windows.ERROR_DEV_NOT_EXIST && hcserror.Err != syscall.Errno(windows.ERROR_FLT_INSTANCE_NOT_FOUND)) {
			return fmt.Errorf("failed to unprepare %s: %w", layerPath, err)
		}
	}

	if err := hcsshim.DeactivateLayer(info, filepath.Base(layerPath)); err != nil {
		return fmt.Errorf("failed to deactivate %s: %w", layerPath, err)
	}

	if err := hcsshim.DestroyLayer(info, filepath.Base(layerPath)); err != nil {
		return fmt.Errorf("failed to destroy %s: %w", layerPath, err)
	}

	return nil
}