/*
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"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	otiai10Cpy "github.com/otiai10/copy"

	"github.com/GoogleContainerTools/kaniko/pkg/constants"
	"github.com/docker/docker/builder/dockerignore"
	"github.com/docker/docker/pkg/fileutils"
	v1 "github.com/google/go-containerregistry/pkg/v1"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

type WhitelistEntry struct {
	Path            string
	PrefixMatchOnly bool
}

var initialWhitelist = []WhitelistEntry{
	{
		Path:            "/kaniko",
		PrefixMatchOnly: false,
	},
	{
		// /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,
	},
	{
		// similarly, we whitelist /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,
	},
}

var whitelist = initialWhitelist

var volumes = []string{}

var excluded []string

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

// 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 extract == nil {
		return nil, errors.New("must supply an extract function")
	}
	if img == nil {
		return nil, errors.New("image cannot be nil")
	}
	if err := DetectFilesystemWhitelist(constants.WhitelistPath); err != nil {
		return nil, err
	}
	logrus.Debugf("Mounted directories: %v", whitelist)
	layers, err := img.Layers()
	if err != nil {
		return nil, err
	}
	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)
				}
				continue
			}
			if err := extract(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(constants.RootDir, func(path string, info os.FileInfo, _ error) error {
		if CheckWhitelist(path) {
			if !isExist(path) {
				logrus.Debugf("Path %s whitelisted, but not exists", path)
				return nil
			}
			if info.IsDir() {
				return filepath.SkipDir
			}
			logrus.Debugf("Not deleting %s, as it's whitelisted", path)
			return nil
		}
		if childDirInWhitelist(path) {
			logrus.Debugf("Not deleting %s, as it contains a whitelisted path", path)
			return nil
		}
		if path == constants.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
}

// ChildDirInWhitelist returns true if there is a child file or directory of the path in the whitelist
func childDirInWhitelist(path string) bool {
	for _, d := range whitelist {
		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 CheckWhitelist(abs) && !checkWhitelistRoot(dest) {
		logrus.Debugf("Not adding %s because it is whitelisted", 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
		}

		// 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, hdr.AccessTime, hdr.ModTime); err != nil {
			return err
		}

		currFile.Close()
	case tar.TypeDir:
		logrus.Tracef("creating dir %s", path)
		if err := mkdirAllWithPermissions(path, mode, uid, 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 CheckWhitelist(abs) {
			logrus.Tracef("skipping symlink from %s to %s because %s is whitelisted", 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 IsInWhitelist(path string) bool {
	for _, wl := range whitelist {
		if !wl.PrefixMatchOnly && path == wl.Path {
			return true
		}
	}
	return false
}

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

	return false
}

func checkWhitelistRoot(root string) bool {
	if root == constants.RootDir {
		return false
	}
	return CheckWhitelist(root)
}

// Get whitelist 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 DetectFilesystemWhitelist(path string) error {
	whitelist = initialWhitelist
	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] != constants.RootDir {
			logrus.Tracef("Appending %s from line: %s", lineArr[4], line)
			whitelist = append(whitelist, WhitelistEntry{
				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", fullPath)
	err := filepath.Walk(fullPath, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if CheckWhitelist(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 {
	path = filepath.Clean(path)
	dirs := strings.Split(path, "/")
	dirPath := constants.RootDir
	paths := []string{constants.RootDir}
	for index, dir := range dirs {
		if dir == "" || index == (len(dirs)-1) {
			continue
		}
		dirPath = filepath.Join(dirPath, dir)
		paths = append(paths, dirPath)
	}
	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{constants.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 err
	}
	dest, err := os.Create(path)
	if err != nil {
		return err
	}
	defer dest.Close()
	if _, err := io.Copy(dest, reader); err != nil {
		return err
	}
	return setFilePermissions(path, perm, int(uid), int(gid))
}

// AddVolumePath adds the given path to the volume whitelist.
func AddVolumePathToWhitelist(path string) {
	logrus.Infof("adding volume %s to whitelist", path)
	whitelist = append(whitelist, WhitelistEntry{
		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) error {
	resp, err := http.Get(rawurl)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	// TODO: set uid and gid according to current user
	if err := CreateFile(dest, resp.Body, 0600, 0, 0); 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)
}

// CopyDir copies the file or directory at src to dest
// It returns a list of files it copied over
func CopyDir(src, dest, buildcontext string) ([]string, error) {
	files, err := RelativeFiles("", src)
	if err != nil {
		return nil, err
	}
	var copiedFiles []string
	for _, file := range files {
		fullPath := filepath.Join(src, file)
		fi, err := os.Lstat(fullPath)
		if err != nil {
			return nil, err
		}
		if excludeFile(fullPath, buildcontext) {
			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 := int(fi.Sys().(*syscall.Stat_t).Uid)
			gid := int(fi.Sys().(*syscall.Stat_t).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, buildcontext); err != nil {
				return nil, err
			}
		} else {
			// ... Else, we want to copy over a file
			if _, err := CopyFile(fullPath, destPath, buildcontext); err != nil {
				return nil, err
			}
		}
		copiedFiles = append(copiedFiles, destPath)
	}
	return copiedFiles, nil
}

// CopySymlink copies the symlink at src to dest
func CopySymlink(src, dest, buildcontext string) (bool, error) {
	if excludeFile(src, buildcontext) {
		logrus.Debugf("%s found in .dockerignore, ignoring", src)
		return true, nil
	}
	link, err := filepath.EvalSymlinks(src)
	if err != nil {
		return false, err
	}
	if FilepathExists(dest) {
		if err := os.RemoveAll(dest); err != nil {
			return false, err
		}
	}
	if err := createParentDirectory(dest); err != nil {
		return false, err
	}
	return false, os.Symlink(link, dest)
}

// CopyFile copies the file at src to dest
func CopyFile(src, dest, buildcontext string) (bool, error) {
	if excludeFile(src, buildcontext) {
		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 := fi.Sys().(*syscall.Stat_t).Uid
	gid := fi.Sys().(*syscall.Stat_t).Gid
	return false, CreateFile(dest, srcFile, fi.Mode(), uid, gid)
}

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

// excludeFile returns true if the .dockerignore specified this file should be ignored
func excludeFile(path, buildcontext string) bool {
	if HasFilepathPrefix(path, buildcontext, false) {
		var err error
		path, err = filepath.Rel(buildcontext, 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, excluded)
	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 {
		if prefixArray[index] == pathArray[index] {
			continue
		}
		return false
	}
	return true
}

func Volumes() []string {
	return volumes
}

func mkdirAllWithPermissions(path string, mode os.FileMode, uid, gid int) error {
	if err := os.MkdirAll(path, mode); err != nil {
		return err
	}

	if err := os.Chown(path, uid, 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)
}

// 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 NotSymLink = fmt.Errorf("not a symlink")

func CanonicalizeLink(path string) (string, error) {
	fi, err := os.Lstat(path)
	if err != nil {
		return "", err
	}
	if !IsSymlink(fi) {
		return "", NotSymLink
	}
	return filepath.EvalSymlinks(path)
}

// otiai10Cpy.Copy in case the src file is a symlink, will copy the target
// file at destination instead of creating a symlink. See #915 for more details.
func CopyFileOrSymlink(src string, destDir string) error {
	destFile := filepath.Join(destDir, src)
	if fi, _ := os.Lstat(src); IsSymlink(fi) {
		if link, err := os.Readlink(src); err != nil {
			return err
		} else {
			return os.Symlink(link, destFile)
		}
	} else {
		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
}