package archive

import (
	"bufio"
	"bytes"
	"compress/bzip2"
	"compress/gzip"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"strings"
	"syscall"

	"github.com/dotcloud/docker/pkg/system"
	"github.com/dotcloud/docker/utils"
	"github.com/dotcloud/docker/vendor/src/code.google.com/p/go/src/pkg/archive/tar"
)

type (
	Archive       io.ReadCloser
	ArchiveReader io.Reader
	Compression   int
	TarOptions    struct {
		Includes    []string
		Excludes    []string
		Compression Compression
		NoLchown    bool
	}
)

var (
	ErrNotImplemented = errors.New("Function not implemented")
)

const (
	Uncompressed Compression = iota
	Bzip2
	Gzip
	Xz
)

func IsArchive(header []byte) bool {
	compression := DetectCompression(header)
	if compression != Uncompressed {
		return true
	}
	r := tar.NewReader(bytes.NewBuffer(header))
	_, err := r.Next()
	return err == nil
}

func DetectCompression(source []byte) Compression {
	for compression, m := range map[Compression][]byte{
		Bzip2: {0x42, 0x5A, 0x68},
		Gzip:  {0x1F, 0x8B, 0x08},
		Xz:    {0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00},
	} {
		if len(source) < len(m) {
			utils.Debugf("Len too short")
			continue
		}
		if bytes.Compare(m, source[:len(m)]) == 0 {
			return compression
		}
	}
	return Uncompressed
}

func xzDecompress(archive io.Reader) (io.ReadCloser, error) {
	args := []string{"xz", "-d", "-c", "-q"}

	return CmdStream(exec.Command(args[0], args[1:]...), archive)
}

func DecompressStream(archive io.Reader) (io.ReadCloser, error) {
	buf := bufio.NewReader(archive)
	bs, err := buf.Peek(10)
	if err != nil {
		return nil, err
	}
	utils.Debugf("[tar autodetect] n: %v", bs)

	compression := DetectCompression(bs)

	switch compression {
	case Uncompressed:
		return ioutil.NopCloser(buf), nil
	case Gzip:
		return gzip.NewReader(buf)
	case Bzip2:
		return ioutil.NopCloser(bzip2.NewReader(buf)), nil
	case Xz:
		return xzDecompress(buf)
	default:
		return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
	}
}

func CompressStream(dest io.WriteCloser, compression Compression) (io.WriteCloser, error) {

	switch compression {
	case Uncompressed:
		return utils.NopWriteCloser(dest), nil
	case Gzip:
		return gzip.NewWriter(dest), nil
	case Bzip2, Xz:
		// archive/bzip2 does not support writing, and there is no xz support at all
		// However, this is not a problem as docker only currently generates gzipped tars
		return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
	default:
		return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
	}
}

func (compression *Compression) Extension() string {
	switch *compression {
	case Uncompressed:
		return "tar"
	case Bzip2:
		return "tar.bz2"
	case Gzip:
		return "tar.gz"
	case Xz:
		return "tar.xz"
	}
	return ""
}

func addTarFile(path, name string, tw *tar.Writer) error {
	fi, err := os.Lstat(path)
	if err != nil {
		return err
	}

	link := ""
	if fi.Mode()&os.ModeSymlink != 0 {
		if link, err = os.Readlink(path); err != nil {
			return err
		}
	}

	hdr, err := tar.FileInfoHeader(fi, link)
	if err != nil {
		return err
	}

	if fi.IsDir() && !strings.HasSuffix(name, "/") {
		name = name + "/"
	}

	hdr.Name = name

	stat, ok := fi.Sys().(*syscall.Stat_t)
	if ok {
		// Currently go does not fill in the major/minors
		if stat.Mode&syscall.S_IFBLK == syscall.S_IFBLK ||
			stat.Mode&syscall.S_IFCHR == syscall.S_IFCHR {
			hdr.Devmajor = int64(major(uint64(stat.Rdev)))
			hdr.Devminor = int64(minor(uint64(stat.Rdev)))
		}

	}

	capability, _ := system.Lgetxattr(path, "security.capability")
	if capability != nil {
		hdr.Xattrs = make(map[string]string)
		hdr.Xattrs["security.capability"] = string(capability)
	}

	if err := tw.WriteHeader(hdr); err != nil {
		return err
	}

	if hdr.Typeflag == tar.TypeReg {
		if file, err := os.Open(path); err != nil {
			return err
		} else {
			_, err := io.Copy(tw, file)
			if err != nil {
				return err
			}
			file.Close()
		}
	}

	return nil
}

func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, Lchown bool) error {
	// hdr.Mode is in linux format, which we can use for sycalls,
	// but for os.Foo() calls we need the mode converted to os.FileMode,
	// so use hdrInfo.Mode() (they differ for e.g. setuid bits)
	hdrInfo := hdr.FileInfo()

	switch hdr.Typeflag {
	case tar.TypeDir:
		// Create directory unless it exists as a directory already.
		// In that case we just want to merge the two
		if fi, err := os.Lstat(path); !(err == nil && fi.IsDir()) {
			if err := os.Mkdir(path, hdrInfo.Mode()); err != nil {
				return err
			}
		}

	case tar.TypeReg, tar.TypeRegA:
		// Source is regular file
		file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, hdrInfo.Mode())
		if err != nil {
			return err
		}
		if _, err := io.Copy(file, reader); err != nil {
			file.Close()
			return err
		}
		file.Close()

	case tar.TypeBlock, tar.TypeChar, tar.TypeFifo:
		mode := uint32(hdr.Mode & 07777)
		switch hdr.Typeflag {
		case tar.TypeBlock:
			mode |= syscall.S_IFBLK
		case tar.TypeChar:
			mode |= syscall.S_IFCHR
		case tar.TypeFifo:
			mode |= syscall.S_IFIFO
		}

		if err := syscall.Mknod(path, mode, int(mkdev(hdr.Devmajor, hdr.Devminor))); err != nil {
			return err
		}

	case tar.TypeLink:
		if err := os.Link(filepath.Join(extractDir, hdr.Linkname), path); err != nil {
			return err
		}

	case tar.TypeSymlink:
		if err := os.Symlink(hdr.Linkname, path); err != nil {
			return err
		}

	case tar.TypeXGlobalHeader:
		utils.Debugf("PAX Global Extended Headers found and ignored")
		return nil

	default:
		return fmt.Errorf("Unhandled tar header type %d\n", hdr.Typeflag)
	}

	if err := os.Lchown(path, hdr.Uid, hdr.Gid); err != nil && Lchown {
		return err
	}

	for key, value := range hdr.Xattrs {
		if err := system.Lsetxattr(path, key, []byte(value), 0); err != nil {
			return err
		}
	}

	// There is no LChmod, so ignore mode for symlink. Also, this
	// must happen after chown, as that can modify the file mode
	if hdr.Typeflag != tar.TypeSymlink {
		if err := os.Chmod(path, hdrInfo.Mode()); err != nil {
			return err
		}
	}

	ts := []syscall.Timespec{timeToTimespec(hdr.AccessTime), timeToTimespec(hdr.ModTime)}
	// syscall.UtimesNano doesn't support a NOFOLLOW flag atm, and
	if hdr.Typeflag != tar.TypeSymlink {
		if err := system.UtimesNano(path, ts); err != nil && err != system.ErrNotSupportedPlatform {
			return err
		}
	} else {
		if err := system.LUtimesNano(path, ts); err != nil && err != system.ErrNotSupportedPlatform {
			return err
		}
	}
	return nil
}

// Tar creates an archive from the directory at `path`, and returns it as a
// stream of bytes.
func Tar(path string, compression Compression) (io.ReadCloser, error) {
	return TarWithOptions(path, &TarOptions{Compression: compression})
}

func escapeName(name string) string {
	escaped := make([]byte, 0)
	for i, c := range []byte(name) {
		if i == 0 && c == '/' {
			continue
		}
		// all printable chars except "-" which is 0x2d
		if (0x20 <= c && c <= 0x7E) && c != 0x2d {
			escaped = append(escaped, c)
		} else {
			escaped = append(escaped, fmt.Sprintf("\\%03o", c)...)
		}
	}
	return string(escaped)
}

// TarWithOptions creates an archive from the directory at `path`, only including files whose relative
// paths are included in `options.Includes` (if non-nil) or not in `options.Excludes`.
func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error) {
	pipeReader, pipeWriter := io.Pipe()

	compressWriter, err := CompressStream(pipeWriter, options.Compression)
	if err != nil {
		return nil, err
	}

	tw := tar.NewWriter(compressWriter)

	go func() {
		// In general we log errors here but ignore them because
		// during e.g. a diff operation the container can continue
		// mutating the filesystem and we can see transient errors
		// from this

		if options.Includes == nil {
			options.Includes = []string{"."}
		}

		for _, include := range options.Includes {
			filepath.Walk(filepath.Join(srcPath, include), func(filePath string, f os.FileInfo, err error) error {
				if err != nil {
					utils.Debugf("Tar: Can't stat file %s to tar: %s\n", srcPath, err)
					return nil
				}

				relFilePath, err := filepath.Rel(srcPath, filePath)
				if err != nil {
					return nil
				}

				for _, exclude := range options.Excludes {
					matched, err := filepath.Match(exclude, relFilePath)
					if err != nil {
						utils.Errorf("Error matching: %s (pattern: %s)", relFilePath, exclude)
						return err
					}
					if matched {
						utils.Debugf("Skipping excluded path: %s", relFilePath)
						if f.IsDir() {
							return filepath.SkipDir
						}
						return nil
					}
				}

				if err := addTarFile(filePath, relFilePath, tw); err != nil {
					utils.Debugf("Can't add file %s to tar: %s\n", srcPath, err)
				}
				return nil
			})
		}

		// Make sure to check the error on Close.
		if err := tw.Close(); err != nil {
			utils.Debugf("Can't close tar writer: %s\n", err)
		}
		if err := compressWriter.Close(); err != nil {
			utils.Debugf("Can't close compress writer: %s\n", err)
		}
		if err := pipeWriter.Close(); err != nil {
			utils.Debugf("Can't close pipe writer: %s\n", err)
		}
	}()

	return pipeReader, nil
}

// Untar reads a stream of bytes from `archive`, parses it as a tar archive,
// and unpacks it into the directory at `path`.
// The archive may be compressed with one of the following algorithms:
//  identity (uncompressed), gzip, bzip2, xz.
// FIXME: specify behavior when target path exists vs. doesn't exist.
func Untar(archive io.Reader, dest string, options *TarOptions) error {
	if archive == nil {
		return fmt.Errorf("Empty archive")
	}

	decompressedArchive, err := DecompressStream(archive)
	if err != nil {
		return err
	}
	defer decompressedArchive.Close()

	tr := tar.NewReader(decompressedArchive)

	var dirs []*tar.Header

	// Iterate through the files in the archive.
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			// end of tar archive
			break
		}
		if err != nil {
			return err
		}

		// Normalize name, for safety and for a simple is-root check
		hdr.Name = filepath.Clean(hdr.Name)

		if !strings.HasSuffix(hdr.Name, "/") {
			// Not the root directory, ensure that the parent directory exists
			parent := filepath.Dir(hdr.Name)
			parentPath := filepath.Join(dest, parent)
			if _, err := os.Lstat(parentPath); err != nil && os.IsNotExist(err) {
				err = os.MkdirAll(parentPath, 0777)
				if err != nil {
					return err
				}
			}
		}

		path := filepath.Join(dest, hdr.Name)

		// If path exits we almost always just want to remove and replace it
		// The only exception is when it is a directory *and* the file from
		// the layer is also a directory. Then we want to merge them (i.e.
		// just apply the metadata from the layer).
		if fi, err := os.Lstat(path); err == nil {
			if fi.IsDir() && hdr.Name == "." {
				continue
			}
			if !(fi.IsDir() && hdr.Typeflag == tar.TypeDir) {
				if err := os.RemoveAll(path); err != nil {
					return err
				}
			}
		}
		if err := createTarFile(path, dest, hdr, tr, options == nil || !options.NoLchown); err != nil {
			return err
		}

		// Directory mtimes must be handled at the end to avoid further
		// file creation in them to modify the directory mtime
		if hdr.Typeflag == tar.TypeDir {
			dirs = append(dirs, hdr)
		}
	}

	for _, hdr := range dirs {
		path := filepath.Join(dest, hdr.Name)
		ts := []syscall.Timespec{timeToTimespec(hdr.AccessTime), timeToTimespec(hdr.ModTime)}
		if err := syscall.UtimesNano(path, ts); err != nil {
			return err
		}
	}

	return nil
}

// TarUntar is a convenience function which calls Tar and Untar, with
// the output of one piped into the other. If either Tar or Untar fails,
// TarUntar aborts and returns the error.
func TarUntar(src string, dst string) error {
	utils.Debugf("TarUntar(%s %s)", src, dst)
	archive, err := TarWithOptions(src, &TarOptions{Compression: Uncompressed})
	if err != nil {
		return err
	}
	defer archive.Close()
	return Untar(archive, dst, nil)
}

// UntarPath is a convenience function which looks for an archive
// at filesystem path `src`, and unpacks it at `dst`.
func UntarPath(src, dst string) error {
	archive, err := os.Open(src)
	if err != nil {
		return err
	}
	defer archive.Close()
	if err := Untar(archive, dst, nil); err != nil {
		return err
	}
	return nil
}

// CopyWithTar creates a tar archive of filesystem path `src`, and
// unpacks it at filesystem path `dst`.
// The archive is streamed directly with fixed buffering and no
// intermediary disk IO.
//
func CopyWithTar(src, dst string) error {
	srcSt, err := os.Stat(src)
	if err != nil {
		return err
	}
	if !srcSt.IsDir() {
		return CopyFileWithTar(src, dst)
	}
	// Create dst, copy src's content into it
	utils.Debugf("Creating dest directory: %s", dst)
	if err := os.MkdirAll(dst, 0755); err != nil && !os.IsExist(err) {
		return err
	}
	utils.Debugf("Calling TarUntar(%s, %s)", src, dst)
	return TarUntar(src, dst)
}

// CopyFileWithTar emulates the behavior of the 'cp' command-line
// for a single file. It copies a regular file from path `src` to
// path `dst`, and preserves all its metadata.
//
// If `dst` ends with a trailing slash '/', the final destination path
// will be `dst/base(src)`.
func CopyFileWithTar(src, dst string) (err error) {
	utils.Debugf("CopyFileWithTar(%s, %s)", src, dst)
	srcSt, err := os.Stat(src)
	if err != nil {
		return err
	}
	if srcSt.IsDir() {
		return fmt.Errorf("Can't copy a directory")
	}
	// Clean up the trailing /
	if dst[len(dst)-1] == '/' {
		dst = path.Join(dst, filepath.Base(src))
	}
	// Create the holding directory if necessary
	if err := os.MkdirAll(filepath.Dir(dst), 0700); err != nil && !os.IsExist(err) {
		return err
	}

	r, w := io.Pipe()
	errC := utils.Go(func() error {
		defer w.Close()

		srcF, err := os.Open(src)
		if err != nil {
			return err
		}
		defer srcF.Close()

		tw := tar.NewWriter(w)
		hdr, err := tar.FileInfoHeader(srcSt, "")
		if err != nil {
			return err
		}
		hdr.Name = filepath.Base(dst)
		if err := tw.WriteHeader(hdr); err != nil {
			return err
		}
		if _, err := io.Copy(tw, srcF); err != nil {
			return err
		}
		tw.Close()
		return nil
	})
	defer func() {
		if er := <-errC; err != nil {
			err = er
		}
	}()
	return Untar(r, filepath.Dir(dst), nil)
}

// CmdStream executes a command, and returns its stdout as a stream.
// If the command fails to run or doesn't complete successfully, an error
// will be returned, including anything written on stderr.
func CmdStream(cmd *exec.Cmd, input io.Reader) (io.ReadCloser, error) {
	if input != nil {
		stdin, err := cmd.StdinPipe()
		if err != nil {
			return nil, err
		}
		// Write stdin if any
		go func() {
			io.Copy(stdin, input)
			stdin.Close()
		}()
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	stderr, err := cmd.StderrPipe()
	if err != nil {
		return nil, err
	}
	pipeR, pipeW := io.Pipe()
	errChan := make(chan []byte)
	// Collect stderr, we will use it in case of an error
	go func() {
		errText, e := ioutil.ReadAll(stderr)
		if e != nil {
			errText = []byte("(...couldn't fetch stderr: " + e.Error() + ")")
		}
		errChan <- errText
	}()
	// Copy stdout to the returned pipe
	go func() {
		_, err := io.Copy(pipeW, stdout)
		if err != nil {
			pipeW.CloseWithError(err)
		}
		errText := <-errChan
		if err := cmd.Wait(); err != nil {
			pipeW.CloseWithError(fmt.Errorf("%s: %s", err, errText))
		} else {
			pipeW.Close()
		}
	}()
	// Run the command and return the pipe
	if err := cmd.Start(); err != nil {
		return nil, err
	}
	return pipeR, nil
}

// NewTempArchive reads the content of src into a temporary file, and returns the contents
// of that file as an archive. The archive can only be read once - as soon as reading completes,
// the file will be deleted.
func NewTempArchive(src Archive, dir string) (*TempArchive, error) {
	f, err := ioutil.TempFile(dir, "")
	if err != nil {
		return nil, err
	}
	if _, err := io.Copy(f, src); err != nil {
		return nil, err
	}
	if err = f.Sync(); err != nil {
		return nil, err
	}
	if _, err := f.Seek(0, 0); err != nil {
		return nil, err
	}
	st, err := f.Stat()
	if err != nil {
		return nil, err
	}
	size := st.Size()
	return &TempArchive{f, size}, nil
}

type TempArchive struct {
	*os.File
	Size int64 // Pre-computed from Stat().Size() as a convenience
}

func (archive *TempArchive) Read(data []byte) (int, error) {
	n, err := archive.File.Read(data)
	if err != nil {
		os.Remove(archive.File.Name())
	}
	return n, err
}
