/*
Copyright 2018 Google LLC

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 util

import (
	"archive/tar"
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"math"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"github.com/GoogleContainerTools/kaniko/pkg/config"
	"github.com/GoogleContainerTools/kaniko/pkg/timing"
	"github.com/docker/docker/builder/dockerignore"
	"github.com/docker/docker/pkg/fileutils"
	v1 "github.com/google/go-containerregistry/pkg/v1"
	"github.com/karrick/godirwalk"
	otiai10Cpy "github.com/otiai10/copy"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

const DoNotChangeUID = -1
const DoNotChangeGID = -1

const (
	snapshotTimeout = "SNAPSHOT_TIMEOUT_DURATION"
	defaultTimeout  = "90m"
)

type IgnoreListEntry struct {
	Path            string
	PrefixMatchOnly bool
}

var initialIgnoreList = []IgnoreListEntry{
	{
		Path:            config.KanikoDir,
		PrefixMatchOnly: false,
	},
	{
		// similarly, we ignore /etc/mtab, since there is no way to know if the file was mounted or came
		// from the base image
		Path:            "/etc/mtab",
		PrefixMatchOnly: false,
	},
	{
		// we ingore /tmp/apt-key-gpghome, since the apt keys are added temporarily in this directory.
		// from the base image
		Path:            "/tmp/apt-key-gpghome",
		PrefixMatchOnly: true,
	},
}

var ignorelist = initialIgnoreList

var volumes = []string{}

type FileContext struct {
	Root          string
	ExcludedFiles []string
}

type ExtractFunction func(string, *tar.Header, io.Reader) error

type FSConfig struct {
	includeWhiteout bool
	extractFunc     ExtractFunction
}

type FSOpt func(*FSConfig)

func IgnoreList() []IgnoreListEntry {
	return ignorelist
}

func AddToIgnoreList(entry IgnoreListEntry) {
	ignorelist = append(ignorelist, entry)
}

func IncludeWhiteout() FSOpt {
	return func(opts *FSConfig) {
		opts.includeWhiteout = true
	}
}

func ExtractFunc(extractFunc ExtractFunction) FSOpt {
	return func(opts *FSConfig) {
		opts.extractFunc = extractFunc
	}
}

// GetFSFromImage extracts the layers of img to root
// It returns a list of all files extracted
func GetFSFromImage(root string, img v1.Image, extract ExtractFunction) ([]string, error) {
	if img == nil {
		return nil, errors.New("image cannot be nil")
	}

	layers, err := img.Layers()
	if err != nil {
		return nil, err
	}

	return GetFSFromLayers(root, layers, ExtractFunc(extract))
}

func GetFSFromLayers(root string, layers []v1.Layer, opts ...FSOpt) ([]string, error) {
	cfg := new(FSConfig)

	for _, opt := range opts {
		opt(cfg)
	}

	if cfg.extractFunc == nil {
		return nil, errors.New("must supply an extract function")
	}

	if err := DetectFilesystemIgnoreList(config.IgnoreListPath); err != nil {
		return nil, err
	}

	logrus.Debugf("Mounted directories: %v", ignorelist)

	extractedFiles := []string{}
	for i, l := range layers {
		if mediaType, err := l.MediaType(); err == nil {
			logrus.Tracef("Extracting layer %d of media type %s", i, mediaType)
		} else {
			logrus.Tracef("Extracting layer %d", i)
		}

		r, err := l.Uncompressed()
		if err != nil {
			return nil, err
		}
		defer r.Close()

		tr := tar.NewReader(r)
		for {
			hdr, err := tr.Next()
			if err == io.EOF {
				break
			}

			if err != nil {
				return nil, errors.Wrap(err, fmt.Sprintf("error reading tar %d", i))
			}

			path := filepath.Join(root, filepath.Clean(hdr.Name))
			base := filepath.Base(path)
			dir := filepath.Dir(path)

			if strings.HasPrefix(base, ".wh.") {
				logrus.Debugf("Whiting out %s", path)

				name := strings.TrimPrefix(base, ".wh.")
				if err := os.RemoveAll(filepath.Join(dir, name)); err != nil {
					return nil, errors.Wrapf(err, "removing whiteout %s", hdr.Name)
				}

				if !cfg.includeWhiteout {
					logrus.Debug("not including whiteout files")
					continue
				}

			}

			if err := cfg.extractFunc(root, hdr, tr); err != nil {
				return nil, err
			}

			extractedFiles = append(extractedFiles, filepath.Join(root, filepath.Clean(hdr.Name)))
		}
	}
	return extractedFiles, nil
}

// DeleteFilesystem deletes the extracted image file system
func DeleteFilesystem() error {
	logrus.Info("Deleting filesystem...")
	return filepath.Walk(config.RootDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			// ignore errors when deleting.
			return nil
		}

		if CheckIgnoreList(path) {
			if !isExist(path) {
				logrus.Debugf("Path %s ignored, but not exists", path)
				return nil
			}
			if info.IsDir() {
				return filepath.SkipDir
			}
			logrus.Debugf("Not deleting %s, as it's ignored", path)
			return nil
		}
		if childDirInIgnoreList(path) {
			logrus.Debugf("Not deleting %s, as it contains a ignored path", path)
			return nil
		}
		if path == config.RootDir {
			return nil
		}
		return os.RemoveAll(path)
	})
}

// isExists returns true if path exists
func isExist(path string) bool {
	if _, err := os.Stat(path); err == nil {
		return true
	}
	return false
}

// childDirInIgnoreList returns true if there is a child file or directory of the path in the ignorelist
func childDirInIgnoreList(path string) bool {
	for _, d := range ignorelist {
		if HasFilepathPrefix(d.Path, path, d.PrefixMatchOnly) {
			return true
		}
	}
	return false
}

// unTar returns a list of files that have been extracted from the tar archive at r to the path at dest
func unTar(r io.Reader, dest string) ([]string, error) {
	var extractedFiles []string
	tr := tar.NewReader(r)
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, err
		}
		if err := ExtractFile(dest, hdr, tr); err != nil {
			return nil, err
		}
		extractedFiles = append(extractedFiles, filepath.Join(dest, filepath.Clean(hdr.Name)))
	}
	return extractedFiles, nil
}

func ExtractFile(dest string, hdr *tar.Header, tr io.Reader) error {
	path := filepath.Join(dest, filepath.Clean(hdr.Name))
	base := filepath.Base(path)
	dir := filepath.Dir(path)
	mode := hdr.FileInfo().Mode()
	uid := hdr.Uid
	gid := hdr.Gid

	abs, err := filepath.Abs(path)
	if err != nil {
		return err
	}

	if CheckIgnoreList(abs) && !checkIgnoreListRoot(dest) {
		logrus.Debugf("Not adding %s because it is ignored", path)
		return nil
	}
	switch hdr.Typeflag {
	case tar.TypeReg:
		logrus.Tracef("creating file %s", path)

		// It's possible a file is in the tar before its directory,
		// or a file was copied over a directory prior to now
		fi, err := os.Stat(dir)
		if os.IsNotExist(err) || !fi.IsDir() {
			logrus.Debugf("base %s for file %s does not exist. Creating.", base, path)

			if err := os.MkdirAll(dir, 0755); err != nil {
				return err
			}
		}

		// Check if something already exists at path (symlinks etc.)
		// If so, delete it
		if FilepathExists(path) {
			if err := os.RemoveAll(path); err != nil {
				return errors.Wrapf(err, "error removing %s to make way for new file.", path)
			}
		}

		currFile, err := os.Create(path)
		if err != nil {
			return err
		}

		if _, err = io.Copy(currFile, tr); err != nil {
			return err
		}

		if err = setFilePermissions(path, mode, uid, gid); err != nil {
			return err
		}

		if err = setFileTimes(path, hdr.AccessTime, hdr.ModTime); err != nil {
			return err
		}

		currFile.Close()
	case tar.TypeDir:
		logrus.Tracef("creating dir %s", path)
		if err := mkdirAllWithPermissions(path, mode, int64(uid), int64(gid)); err != nil {
			return err
		}

	case tar.TypeLink:
		logrus.Tracef("link from %s to %s", hdr.Linkname, path)
		abs, err := filepath.Abs(hdr.Linkname)
		if err != nil {
			return err
		}
		if CheckIgnoreList(abs) {
			logrus.Tracef("skipping symlink from %s to %s because %s is ignored", hdr.Linkname, path, hdr.Linkname)
			return nil
		}
		// The base directory for a link may not exist before it is created.
		if err := os.MkdirAll(dir, 0755); err != nil {
			return err
		}
		// Check if something already exists at path
		// If so, delete it
		if FilepathExists(path) {
			if err := os.RemoveAll(path); err != nil {
				return errors.Wrapf(err, "error removing %s to make way for new link", hdr.Name)
			}
		}
		link := filepath.Clean(filepath.Join(dest, hdr.Linkname))
		if err := os.Link(link, path); err != nil {
			return err
		}

	case tar.TypeSymlink:
		logrus.Tracef("symlink from %s to %s", hdr.Linkname, path)
		// The base directory for a symlink may not exist before it is created.
		if err := os.MkdirAll(dir, 0755); err != nil {
			return err
		}
		// Check if something already exists at path
		// If so, delete it
		if FilepathExists(path) {
			if err := os.RemoveAll(path); err != nil {
				return errors.Wrapf(err, "error removing %s to make way for new symlink", hdr.Name)
			}
		}
		if err := os.Symlink(hdr.Linkname, path); err != nil {
			return err
		}
	}
	return nil
}

func IsInIgnoreList(path string) bool {
	return IsInProvidedIgnoreList(path, ignorelist)
}

func IsInProvidedIgnoreList(path string, wl []IgnoreListEntry) bool {
	for _, entry := range wl {
		if !entry.PrefixMatchOnly && path == entry.Path {
			return true
		}
	}
	return false
}

func CheckIgnoreList(path string) bool {
	for _, wl := range ignorelist {
		if HasFilepathPrefix(path, wl.Path, wl.PrefixMatchOnly) {
			return true
		}
	}

	return false
}

func checkIgnoreListRoot(root string) bool {
	if root == config.RootDir {
		return false
	}
	return CheckIgnoreList(root)
}

// Get ignorelist from roots of mounted files
// Each line of /proc/self/mountinfo is in the form:
// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
// (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
// Where (5) is the mount point relative to the process's root
// From: https://www.kernel.org/doc/Documentation/filesystems/proc.txt
func DetectFilesystemIgnoreList(path string) error {
	ignorelist = initialIgnoreList
	volumes = []string{}
	f, err := os.Open(path)
	if err != nil {
		return err
	}
	defer f.Close()
	reader := bufio.NewReader(f)
	for {
		line, err := reader.ReadString('\n')
		logrus.Tracef("Read the following line from %s: %s", path, line)
		if err != nil && err != io.EOF {
			return err
		}
		lineArr := strings.Split(line, " ")
		if len(lineArr) < 5 {
			if err == io.EOF {
				logrus.Tracef("Reached end of file %s", path)
				break
			}
			continue
		}
		if lineArr[4] != config.RootDir {
			logrus.Tracef("Appending %s from line: %s", lineArr[4], line)
			ignorelist = append(ignorelist, IgnoreListEntry{
				Path:            lineArr[4],
				PrefixMatchOnly: false,
			})
		}
		if err == io.EOF {
			logrus.Tracef("Reached end of file %s", path)
			break
		}
	}
	return nil
}

// RelativeFiles returns a list of all files at the filepath relative to root
func RelativeFiles(fp string, root string) ([]string, error) {
	var files []string
	fullPath := filepath.Join(root, fp)
	logrus.Debugf("Getting files and contents at root %s for %s", root, fullPath)
	err := filepath.Walk(fullPath, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if CheckIgnoreList(path) && !HasFilepathPrefix(path, root, false) {
			return nil
		}
		relPath, err := filepath.Rel(root, path)
		if err != nil {
			return err
		}
		files = append(files, relPath)
		return nil
	})
	return files, err
}

// ParentDirectories returns a list of paths to all parent directories
// Ex. /some/temp/dir -> [/, /some, /some/temp, /some/temp/dir]
func ParentDirectories(path string) []string {
	dir := filepath.Clean(path)
	var paths []string
	for {
		if dir == filepath.Clean(config.RootDir) || dir == "" || dir == "." {
			break
		}
		dir, _ = filepath.Split(dir)
		dir = filepath.Clean(dir)
		paths = append([]string{dir}, paths...)
	}
	if len(paths) == 0 {
		paths = []string{config.RootDir}
	}
	return paths
}

// ParentDirectoriesWithoutLeadingSlash returns a list of paths to all parent directories
// all subdirectories do not contain a leading /
// Ex. /some/temp/dir -> [/, some, some/temp, some/temp/dir]
func ParentDirectoriesWithoutLeadingSlash(path string) []string {
	path = filepath.Clean(path)
	dirs := strings.Split(path, "/")
	dirPath := ""
	paths := []string{config.RootDir}
	for index, dir := range dirs {
		if dir == "" || index == (len(dirs)-1) {
			continue
		}
		dirPath = filepath.Join(dirPath, dir)
		paths = append(paths, dirPath)
	}
	return paths
}

// FilepathExists returns true if the path exists
func FilepathExists(path string) bool {
	_, err := os.Lstat(path)
	return !os.IsNotExist(err)
}

// CreateFile creates a file at path and copies over contents from the reader
func CreateFile(path string, reader io.Reader, perm os.FileMode, uid uint32, gid uint32) error {
	// Create directory path if it doesn't exist
	if err := createParentDirectory(path); err != nil {
		return errors.Wrap(err, "creating parent dir")
	}

	dest, err := os.Create(path)
	if err != nil {
		return errors.Wrap(err, "creating file")
	}
	defer dest.Close()
	if _, err := io.Copy(dest, reader); err != nil {
		return errors.Wrap(err, "copying file")
	}
	return setFilePermissions(path, perm, int(uid), int(gid))
}

// AddVolumePath adds the given path to the volume ignorelist.
func AddVolumePathToIgnoreList(path string) {
	logrus.Infof("adding volume %s to ignorelist", path)
	ignorelist = append(ignorelist, IgnoreListEntry{
		Path:            path,
		PrefixMatchOnly: true,
	})
	volumes = append(volumes, path)
}

// DownloadFileToDest downloads the file at rawurl to the given dest for the ADD command
// From add command docs:
// 	1. If <src> is a remote file URL:
// 		- destination will have permissions of 0600
// 		- If remote file has HTTP Last-Modified header, we set the mtime of the file to that timestamp
func DownloadFileToDest(rawurl, dest string, uid, gid int64) error {
	resp, err := http.Get(rawurl)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		return fmt.Errorf("invalid response status %d", resp.StatusCode)
	}

	if err := CreateFile(dest, resp.Body, 0600, uint32(uid), uint32(gid)); err != nil {
		return err
	}
	mTime := time.Time{}
	lastMod := resp.Header.Get("Last-Modified")
	if lastMod != "" {
		if parsedMTime, err := http.ParseTime(lastMod); err == nil {
			mTime = parsedMTime
		}
	}
	return os.Chtimes(dest, mTime, mTime)
}

// DetermineTargetFileOwnership returns the user provided uid/gid combination.
// If they are set to -1, the uid/gid from the original file is used.
func DetermineTargetFileOwnership(fi os.FileInfo, uid, gid int64) (int64, int64) {
	if uid <= DoNotChangeUID {
		uid = int64(fi.Sys().(*syscall.Stat_t).Uid)
	}
	if gid <= DoNotChangeGID {
		gid = int64(fi.Sys().(*syscall.Stat_t).Gid)
	}
	return uid, gid
}

// CopyDir copies the file or directory at src to dest
// It returns a list of files it copied over
func CopyDir(src, dest string, context FileContext, uid, gid int64) ([]string, error) {
	files, err := RelativeFiles("", src)
	if err != nil {
		return nil, errors.Wrap(err, "copying dir")
	}
	var copiedFiles []string
	for _, file := range files {
		fullPath := filepath.Join(src, file)
		fi, err := os.Lstat(fullPath)
		if err != nil {
			return nil, errors.Wrap(err, "copying dir")
		}
		if context.ExcludesFile(fullPath) {
			logrus.Debugf("%s found in .dockerignore, ignoring", src)
			continue
		}
		destPath := filepath.Join(dest, file)
		if fi.IsDir() {
			logrus.Tracef("Creating directory %s", destPath)

			mode := fi.Mode()
			uid, gid = DetermineTargetFileOwnership(fi, uid, gid)
			if err := mkdirAllWithPermissions(destPath, mode, uid, gid); err != nil {
				return nil, err
			}
		} else if IsSymlink(fi) {
			// If file is a symlink, we want to create the same relative symlink
			if _, err := CopySymlink(fullPath, destPath, context); err != nil {
				return nil, err
			}
		} else {
			// ... Else, we want to copy over a file
			if _, err := CopyFile(fullPath, destPath, context, uid, gid); err != nil {
				return nil, err
			}
		}
		copiedFiles = append(copiedFiles, destPath)
	}
	return copiedFiles, nil
}

// CopySymlink copies the symlink at src to dest.
func CopySymlink(src, dest string, context FileContext) (bool, error) {
	if context.ExcludesFile(src) {
		logrus.Debugf("%s found in .dockerignore, ignoring", src)
		return true, nil
	}
	if FilepathExists(dest) {
		if err := os.RemoveAll(dest); err != nil {
			return false, err
		}
	}
	if err := createParentDirectory(dest); err != nil {
		return false, err
	}
	link, err := os.Readlink(src)
	if err != nil {
		logrus.Debugf("could not read link for %s", src)
	}
	return false, os.Symlink(link, dest)
}

// CopyFile copies the file at src to dest
func CopyFile(src, dest string, context FileContext, uid, gid int64) (bool, error) {
	if context.ExcludesFile(src) {
		logrus.Debugf("%s found in .dockerignore, ignoring", src)
		return true, nil
	}
	if src == dest {
		// This is a no-op. Move on, but don't list it as ignored.
		// We have to make sure we do this so we don't overwrite our own file.
		// See iusse #904 for an example.
		return false, nil
	}
	fi, err := os.Stat(src)
	if err != nil {
		return false, err
	}
	logrus.Debugf("Copying file %s to %s", src, dest)
	srcFile, err := os.Open(src)
	if err != nil {
		return false, err
	}
	defer srcFile.Close()
	uid, gid = DetermineTargetFileOwnership(fi, uid, gid)
	return false, CreateFile(dest, srcFile, fi.Mode(), uint32(uid), uint32(gid))
}

func NewFileContextFromDockerfile(dockerfilePath, buildcontext string) (FileContext, error) {
	fileContext := FileContext{Root: buildcontext}
	excludedFiles, err := getExcludedFiles(dockerfilePath, buildcontext)
	if err != nil {
		return fileContext, err
	}
	fileContext.ExcludedFiles = excludedFiles
	return fileContext, nil
}

// getExcludedFiles returns a list of files to exclude from the .dockerignore
func getExcludedFiles(dockerfilePath, buildcontext string) ([]string, error) {
	path := dockerfilePath + ".dockerignore"
	if !FilepathExists(path) {
		path = filepath.Join(buildcontext, ".dockerignore")
	}
	if !FilepathExists(path) {
		return nil, nil
	}
	logrus.Infof("Using dockerignore file: %v", path)
	contents, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, errors.Wrap(err, "parsing .dockerignore")
	}
	reader := bytes.NewBuffer(contents)
	return dockerignore.ReadAll(reader)
}

// ExcludesFile returns true if the file context specified this file should be ignored.
// Usually this is specified via .dockerignore
func (c FileContext) ExcludesFile(path string) bool {
	if HasFilepathPrefix(path, c.Root, false) {
		var err error
		path, err = filepath.Rel(c.Root, path)
		if err != nil {
			logrus.Errorf("unable to get relative path, including %s in build: %v", path, err)
			return false
		}
	}
	match, err := fileutils.Matches(path, c.ExcludedFiles)
	if err != nil {
		logrus.Errorf("error matching, including %s in build: %v", path, err)
		return false
	}
	return match
}

// HasFilepathPrefix checks if the given file path begins with prefix
func HasFilepathPrefix(path, prefix string, prefixMatchOnly bool) bool {
	prefix = filepath.Clean(prefix)
	prefixArray := strings.Split(prefix, "/")
	path = filepath.Clean(path)
	pathArray := strings.SplitN(path, "/", len(prefixArray)+1)

	if len(pathArray) < len(prefixArray) {
		return false
	}
	if prefixMatchOnly && len(pathArray) == len(prefixArray) {
		return false
	}

	for index := range prefixArray {
		m, err := filepath.Match(prefixArray[index], pathArray[index])
		if err != nil {
			return false
		}
		if !m {
			return false
		}
	}
	return true
}

func Volumes() []string {
	return volumes
}

func mkdirAllWithPermissions(path string, mode os.FileMode, uid, gid int64) error {
	// Check if a file already exists on the path, if yes then delete it
	info, err := os.Stat(path)
	if !os.IsNotExist(err) && !info.IsDir() {
		logrus.Tracef("removing file because it needs to be a directory %s", path)
		if err := os.Remove(path); err != nil {
			return errors.Wrapf(err, "error removing %s to make way for new directory.", path)
		}
	}

	if err := os.MkdirAll(path, mode); err != nil {
		return err
	}
	if uid > math.MaxUint32 || gid > math.MaxUint32 {
		// due to https://github.com/golang/go/issues/8537
		return errors.New(fmt.Sprintf("Numeric User-ID or Group-ID greater than %v are not properly supported.", uint64(math.MaxUint32)))
	}
	if err := os.Chown(path, int(uid), int(gid)); err != nil {
		return err
	}
	// In some cases, MkdirAll doesn't change the permissions, so run Chmod
	// Must chmod after chown because chown resets the file mode.
	return os.Chmod(path, mode)
}

func setFilePermissions(path string, mode os.FileMode, uid, gid int) error {
	if err := os.Chown(path, uid, gid); err != nil {
		return err
	}
	// manually set permissions on file, since the default umask (022) will interfere
	// Must chmod after chown because chown resets the file mode.
	return os.Chmod(path, mode)
}

func setFileTimes(path string, aTime, mTime time.Time) error {
	// The zero value of time.Time is not a valid argument to os.Chtimes as it cannot be
	// converted into a valid argument to the syscall that os.Chtimes uses. If mTime or
	// aTime are zero we convert them to the zero value for Unix Epoch.
	if mTime.IsZero() {
		logrus.Tracef("mod time for %s is zero, converting to zero for epoch", path)
		mTime = time.Unix(0, 0)
	}

	if aTime.IsZero() {
		logrus.Tracef("access time for %s is zero, converting to zero for epoch", path)
		aTime = time.Unix(0, 0)
	}

	// We set AccessTime because its a required arg but we only care about
	// ModTime. The file will get accessed again so AccessTime will change.
	if err := os.Chtimes(path, aTime, mTime); err != nil {
		return errors.Wrapf(
			err,
			"couldn't modify times: atime %v mtime %v",
			aTime,
			mTime,
		)
	}

	return nil
}

// CreateTargetTarfile creates target tar file for downloading the context file.
// Make directory if directory does not exist
func CreateTargetTarfile(tarpath string) (*os.File, error) {
	baseDir := filepath.Dir(tarpath)
	if _, err := os.Lstat(baseDir); os.IsNotExist(err) {
		logrus.Debugf("baseDir %s for file %s does not exist. Creating.", baseDir, tarpath)
		if err := os.MkdirAll(baseDir, 0755); err != nil {
			return nil, err
		}
	}
	return os.Create(tarpath)

}

// Returns true if a file is a symlink
func IsSymlink(fi os.FileInfo) bool {
	return fi.Mode()&os.ModeSymlink != 0
}

var ErrNotSymLink = fmt.Errorf("not a symlink")

func GetSymLink(path string) (string, error) {
	if err := getSymlink(path); err != nil {
		return "", err
	}
	return os.Readlink(path)
}

func EvalSymLink(path string) (string, error) {
	if err := getSymlink(path); err != nil {
		return "", err
	}
	return filepath.EvalSymlinks(path)
}

func getSymlink(path string) error {
	fi, err := os.Lstat(path)
	if err != nil {
		return err
	}
	if !IsSymlink(fi) {
		return ErrNotSymLink
	}
	return nil
}

// For cross stage dependencies kaniko must persist the referenced path so that it can be used in
// the dependent stage. For symlinks we copy the target path because copying the symlink would
// result in a dead link
func CopyFileOrSymlink(src string, destDir string, root string) error {
	destFile := filepath.Join(destDir, src)
	src = filepath.Join(root, src)
	if fi, _ := os.Lstat(src); IsSymlink(fi) {
		link, err := os.Readlink(src)
		if err != nil {
			return errors.Wrap(err, "copying file or symlink")
		}
		if err := createParentDirectory(destFile); err != nil {
			return err
		}
		return os.Symlink(link, destFile)
	}
	return otiai10Cpy.Copy(src, destFile)
}

func createParentDirectory(path string) error {
	baseDir := filepath.Dir(path)
	if info, err := os.Lstat(baseDir); os.IsNotExist(err) {
		logrus.Tracef("baseDir %s for file %s does not exist. Creating.", baseDir, path)
		if err := os.MkdirAll(baseDir, 0755); err != nil {
			return err
		}
	} else if IsSymlink(info) {
		logrus.Infof("destination cannot be a symlink %v", baseDir)
		return errors.New("destination cannot be a symlink")
	}
	return nil
}

// UpdateInitialIgnoreList will add /var/run to ignored paths if
func UpdateInitialIgnoreList(ignoreVarRun bool) {
	if !ignoreVarRun {
		return
	}
	logrus.Trace("Adding /var/run to initialIgnoreList ")
	initialIgnoreList = append(initialIgnoreList, IgnoreListEntry{
		// /var/run is a special case. It's common to mount in /var/run/docker.sock or something similar
		// which leads to a special mount on the /var/run/docker.sock file itself, but the directory to exist
		// in the image with no way to tell if it came from the base image or not.
		Path:            "/var/run",
		PrefixMatchOnly: false,
	})
}

type walkFSResult struct {
	filesAdded    []string
	existingPaths map[string]struct{}
}

// WalkFS given a directory and list of existing files,
// returns a list of changed filed determined by changeFunc and a list
// of deleted files.
// It timesout after 90 mins. Can be configured via setting an environment variable
// SNAPSHOT_TIMEOUT in the kaniko pod definition.
func WalkFS(dir string, existingPaths map[string]struct{}, changeFunc func(string) (bool, error)) ([]string, map[string]struct{}) {
	timeOutStr := os.Getenv(snapshotTimeout)
	if timeOutStr == "" {
		logrus.Tracef("%s environment not set. Using default snapshot timeout %s", snapshotTimeout, defaultTimeout)
		timeOutStr = defaultTimeout
	}
	timeOut, err := time.ParseDuration(timeOutStr)
	if err != nil {
		logrus.Fatalf("could not parse duration %s", timeOutStr)
	}
	timer := timing.Start("Walking filesystem with timeout")
	ch := make(chan walkFSResult, 1)

	go func() {
		ch <- gowalkDir(dir, existingPaths, changeFunc)
	}()

	// Listen on our channel AND a timeout channel - which ever happens first.
	select {
	case res := <-ch:
		timing.DefaultRun.Stop(timer)
		return res.filesAdded, res.existingPaths
	case <-time.After(timeOut):
		timing.DefaultRun.Stop(timer)
		logrus.Fatalf("timed out snapshotting FS in %s", timeOutStr)
		return nil, nil
	}
}

func gowalkDir(dir string, existingPaths map[string]struct{}, changeFunc func(string) (bool, error)) walkFSResult {
	foundPaths := make([]string, 0)
	godirwalk.Walk(dir, &godirwalk.Options{
		Callback: func(path string, ent *godirwalk.Dirent) error {
			logrus.Tracef("Analyzing path %s", path)
			if IsInIgnoreList(path) {
				if IsDestDir(path) {
					logrus.Tracef("Skipping paths under %s, as it is a ignored directory", path)
					return filepath.SkipDir
				}
				return nil
			}
			delete(existingPaths, path)
			if t, err := changeFunc(path); err != nil {
				return err
			} else if t {
				foundPaths = append(foundPaths, path)
			}
			return nil
		},
		Unsorted: true,
	},
	)
	return walkFSResult{foundPaths, existingPaths}
}

// GetFSInfoMap given a directory gets a map of FileInfo for all files
func GetFSInfoMap(dir string, existing map[string]os.FileInfo) (map[string]os.FileInfo, []string) {
	fileMap := map[string]os.FileInfo{}
	foundPaths := []string{}
	timer := timing.Start("Walking filesystem with Stat")
	godirwalk.Walk(dir, &godirwalk.Options{
		Callback: func(path string, ent *godirwalk.Dirent) error {
			if IsInIgnoreList(path) {
				if IsDestDir(path) {
					logrus.Tracef("Skipping paths under %s, as it is a ignored directory", path)
					return filepath.SkipDir
				}
				return nil
			}
			if fi, err := os.Lstat(path); err == nil {
				if fiPrevious, ok := existing[path]; ok {
					// check if file changed
					if !isSame(fiPrevious, fi) {
						fileMap[path] = fi
						foundPaths = append(foundPaths, path)
					}
				} else {
					// new path
					fileMap[path] = fi
					foundPaths = append(foundPaths, path)
				}

			}
			return nil
		},
		Unsorted: true,
	},
	)
	timing.DefaultRun.Stop(timer)
	return fileMap, foundPaths
}

func isSame(fi1, fi2 os.FileInfo) bool {
	return fi1.Mode() == fi2.Mode() &&
		// file modification time
		fi1.ModTime() == fi2.ModTime() &&
		// file size
		fi1.Size() == fi2.Size() &&
		// file user id
		uint64(fi1.Sys().(*syscall.Stat_t).Uid) == uint64(fi2.Sys().(*syscall.Stat_t).Uid) &&
		// file group id is
		uint64(fi1.Sys().(*syscall.Stat_t).Gid) == uint64(fi2.Sys().(*syscall.Stat_t).Gid)
}
