package utils

import (
	"bytes"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"syscall"

	"github.com/containers/libpod/pkg/lookup"
	"github.com/docker/docker/pkg/symlink"
	"github.com/opencontainers/runc/libcontainer/user"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"

	systemdDbus "github.com/coreos/go-systemd/dbus"
	"github.com/godbus/dbus"
)

// ExecCmd executes a command with args and returns its output as a string along
// with an error, if any
func ExecCmd(name string, args ...string) (string, error) {
	cmd := exec.Command(name, args...)
	var stdout bytes.Buffer
	var stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	err := cmd.Run()
	if err != nil {
		return "", fmt.Errorf("`%v %v` failed: %v %v (%v)", name, strings.Join(args, " "), stderr.String(), stdout.String(), err)
	}

	return stdout.String(), nil
}

// ExecCmdWithStdStreams execute a command with the specified standard streams.
func ExecCmdWithStdStreams(stdin io.Reader, stdout, stderr io.Writer, name string, args ...string) error {
	cmd := exec.Command(name, args...)
	cmd.Stdin = stdin
	cmd.Stdout = stdout
	cmd.Stderr = stderr

	err := cmd.Run()
	if err != nil {
		return fmt.Errorf("`%v %v` failed: %v", name, strings.Join(args, " "), err)
	}

	return nil
}

// StatusToExitCode converts wait status code to an exit code
func StatusToExitCode(status int) int {
	return ((status) & 0xff00) >> 8
}

// RunUnderSystemdScope adds the specified pid to a systemd scope
func RunUnderSystemdScope(pid int, slice string, unitName string) error {
	var properties []systemdDbus.Property
	conn, err := systemdDbus.New()
	if err != nil {
		return err
	}
	properties = append(properties, systemdDbus.PropSlice(slice))
	properties = append(properties, newProp("PIDs", []uint32{uint32(pid)}))
	properties = append(properties, newProp("Delegate", true))
	properties = append(properties, newProp("DefaultDependencies", false))
	ch := make(chan string)
	_, err = conn.StartTransientUnit(unitName, "replace", properties, ch)
	if err != nil {
		return err
	}
	defer conn.Close()

	// Block until job is started
	<-ch

	return nil
}

func newProp(name string, units interface{}) systemdDbus.Property {
	return systemdDbus.Property{
		Name:  name,
		Value: dbus.MakeVariant(units),
	}
}

// DetachError is special error which returned in case of container detach.
type DetachError struct{}

func (DetachError) Error() string {
	return "detached from container"
}

// CopyDetachable is similar to io.Copy but support a detach key sequence to break out.
func CopyDetachable(dst io.Writer, src io.Reader, keys []byte) (written int64, err error) {
	// Sanity check interfaces
	if dst == nil || src == nil {
		return 0, fmt.Errorf("src/dst reader/writer nil")
	}
	if len(keys) == 0 {
		// Default keys : ctrl-p ctrl-q
		keys = []byte{16, 17}
	}

	buf := make([]byte, 32*1024)
	for {
		nr, er := src.Read(buf)
		if nr > 0 {
			preservBuf := []byte{}
			for i, key := range keys {
				preservBuf = append(preservBuf, buf[0:nr]...)
				if nr != 1 || buf[0] != key {
					break
				}
				if i == len(keys)-1 {
					// src.Close()
					return 0, DetachError{}
				}
				nr, er = src.Read(buf)
			}
			nw, ew := dst.Write(preservBuf)
			nr = len(preservBuf)
			if nw > 0 {
				written += int64(nw)
			}
			if ew != nil {
				err = ew
				break
			}
			if nr != nw {
				err = io.ErrShortWrite
				break
			}
		}
		if er != nil {
			if er != io.EOF {
				err = er
			}
			break
		}
	}
	return written, err
}

// WriteGoroutineStacks writes out the goroutine stacks
// of the caller. Up to 32 MB is allocated to print the
// stack.
func WriteGoroutineStacks(w io.Writer) error {
	if w == nil {
		return fmt.Errorf("writer nil")
	}
	buf := make([]byte, 1<<20)
	for i := 0; ; i++ {
		n := runtime.Stack(buf, true)
		if n < len(buf) {
			buf = buf[:n]
			break
		}
		if len(buf) >= 32<<20 {
			break
		}
		buf = make([]byte, 2*len(buf))
	}
	_, err := w.Write(buf)
	return err
}

// WriteGoroutineStacksToFile write goroutine stacks
// to the specified file.
func WriteGoroutineStacksToFile(path string) error {
	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, 0666)
	if err != nil {
		return err
	}
	defer f.Close()
	defer f.Sync()

	return WriteGoroutineStacks(f)
}

// GenerateID generates a random unique id.
func GenerateID() string {
	b := make([]byte, 32)
	rand.Read(b)
	return hex.EncodeToString(b)
}

// openContainerFile opens a file inside a container rootfs safely
func openContainerFile(rootfs string, path string) (io.ReadCloser, error) {
	fp, err := symlink.FollowSymlinkInScope(filepath.Join(rootfs, path), rootfs)
	if err != nil {
		return nil, err
	}
	return os.Open(fp)
}

// GetUserInfo returns UID, GID and additional groups for specified user
// by looking them up in /etc/passwd and /etc/group
func GetUserInfo(rootfs string, userName string) (uint32, uint32, []uint32, error) {
	// We don't care if we can't open the file because
	// not all images will have these files
	passwdFile, err := openContainerFile(rootfs, "/etc/passwd")
	if err != nil {
		logrus.Warnf("Failed to open /etc/passwd: %v", err)
	} else {
		defer passwdFile.Close()
	}

	groupFile, err := openContainerFile(rootfs, "/etc/group")
	if err != nil {
		logrus.Warnf("Failed to open /etc/group: %v", err)
	} else {
		defer groupFile.Close()
	}

	execUser, err := user.GetExecUser(userName, nil, passwdFile, groupFile)
	if err != nil {
		return 0, 0, nil, err
	}

	uid := uint32(execUser.Uid)
	gid := uint32(execUser.Gid)
	additionalGids := make([]uint32, 0, len(execUser.Sgids))
	for _, g := range execUser.Sgids {
		additionalGids = append(additionalGids, uint32(g))
	}

	return uid, gid, additionalGids, nil
}

// GeneratePasswd generates a container specific passwd file,
// iff uid is not defined in the containers /etc/passwd
func GeneratePasswd(username string, uid, gid uint32, homedir, rootfs, rundir string) (string, error) {
	// if UID exists inside of container rootfs /etc/passwd then
	// don't generate passwd
	if _, err := lookup.GetUser(rootfs, strconv.Itoa(int(uid))); err == nil {
		return "", nil
	}
	passwdFile := filepath.Join(rundir, "passwd")
	originPasswdFile, err := symlink.FollowSymlinkInScope(filepath.Join(rootfs, "/etc/passwd"), rootfs)
	if err != nil {
		return "", errors.Wrapf(err, "unable to follow symlinks to passwd file")
	}
	info, err := os.Stat(originPasswdFile)
	if err != nil {
		if os.IsNotExist(err) {
			return "", nil
		}
		return "", errors.Wrapf(err, "unable to stat passwd file %s", originPasswdFile)
	}
	// Check if passwd file is world writable
	if info.Mode().Perm()&(0022) != 0 {
		return "", nil
	}
	passwdUID := info.Sys().(*syscall.Stat_t).Uid
	passwdGID := info.Sys().(*syscall.Stat_t).Gid

	if uid == passwdUID && info.Mode().Perm()&(0200) != 0 {
		return "", nil
	}

	orig, err := ioutil.ReadFile(originPasswdFile)
	if err != nil {
		// If no /etc/passwd in container ignore and return
		if os.IsNotExist(err) {
			return "", nil
		}
		return "", errors.Wrapf(err, "unable to read passwd file %s", originPasswdFile)
	}
	if username == "" {
		username = "default"
	}
	if homedir == "" {
		homedir = "/tmp"
	}
	pwd := fmt.Sprintf("%s%s:x:%d:%d:%s user:%s:/sbin/nologin\n", orig, username, uid, gid, username, homedir)
	if err := ioutil.WriteFile(passwdFile, []byte(pwd), info.Mode()); err != nil {
		return "", errors.Wrapf(err, "failed to create temporary passwd file")
	}
	if err := os.Chown(passwdFile, int(passwdUID), int(passwdGID)); err != nil {
		return "", errors.Wrapf(err, "failed to chown temporary passwd file")
	}

	return passwdFile, nil
}
