package container

import (
	"bufio"
	"fmt"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"

	"github.com/hpcng/warewulf/internal/pkg/util"
	"github.com/hpcng/warewulf/internal/pkg/wwlog"
	"github.com/pkg/errors"
)

type completeUserInfo struct {
	Name        string
	UidHost     int      `access:"r,w"`
	GidHost     int      `access:"r,w"`
	UidCont     int      `access:"r,w"`
	GidCont     int      `access:"r,w"`
	FileListUid []string `access:"r,w"`
	FileListGid []string `access:"r,w"`
}

type simpleUserInfo struct {
	name string
	uid  int
	gid  int
}

/*
sync the uids,gids from the host to the container
*/
func SyncUids(containerName string, showOnly bool) error {
	var userDb []completeUserInfo
	passwdName := "/etc/passwd"
	groupName := "/etc/group"

	// populate db with users from the host
	hostUsers, err := createPasswdMap(passwdName)
	if err != nil {
		wwlog.Error("Could not open "+passwdName)
		return err
	}
	for _, hostUser := range hostUsers {
		userDb = append(userDb, completeUserInfo{Name: hostUser.name,
			UidHost: hostUser.uid, GidHost: hostUser.gid, UidCont: -1, GidCont: -1})
	}

	// merge container users into db and track users that are only in the
	// container
	fullPath := RootFsDir(containerName)
	containerUsers, err := createPasswdMap(path.Join(fullPath, passwdName))
	if err != nil {
		wwlog.Error("Could not open "+path.Join(fullPath, passwdName))
		return err
	}
	var userOnlyCont []string
	for _, containerUser := range containerUsers {
		foundUser := false
		for idxHost, user := range userDb {
			if containerUser.name == user.Name {
				foundUser = true
				(&userDb[idxHost]).UidCont = containerUser.uid
				(&userDb[idxHost]).GidCont = containerUser.gid
			}
		}
		if !foundUser {
			userDb = append(userDb, completeUserInfo{Name: containerUser.name,
				UidHost: -1, GidHost: -1, UidCont: containerUser.uid, GidCont: containerUser.gid})
			wwlog.Warn("user: %s:%v:%v not present on host", containerUser.name, containerUser.uid, containerUser.gid)
			userOnlyCont = append(userOnlyCont, containerUser.name)
		}
	}

	// detect users in the host and container with conflicting uids
	for _, containerUser := range userDb {
		if (containerUser.UidCont == -1 || containerUser.UidHost != -1) {
			// containerUser is either not actually in the
			// container or is also in the host
			continue
		}
		for _, hostUser := range userDb {
			if hostUser.UidHost == containerUser.UidCont {
				wwlog.Warn("uid(%v) collision for host: %s and container: %s",
					containerUser.UidCont, hostUser.Name, containerUser.Name)
				return errors.New(fmt.Sprintf("user %s only present in container has same uid(%v) as user %s on host,\n"+
					"add this user to /etc/passwd on host", containerUser.Name, containerUser.UidCont, hostUser.Name))
			}
		}
	}

	if showOnly {
		wwlog.Info("uid/gid not synced, run \nwwctl container syncuser --write %s\nto synchronize uid/gids.", containerName)
		return nil
	}
	// create list of files which need changed ownerships in order to
	// change them later what avoid uid/gid collisions
	for idx, user := range userDb {
		if (user.UidHost != user.UidCont && user.UidHost != -1) ||
			(user.GidHost != user.GidCont && user.GidHost != -1 && user.UidHost != -1) {
			wwlog.Verbose(fmt.Sprintf("host %s:%v:%v <-> container %s:%v:%v",
				user.Name, user.UidHost, user.GidHost, user.Name, user.UidCont, user.GidCont))
			err = filepath.Walk(fullPath, func(filePath string, info fs.FileInfo, err error) error {
				// root is always good, if we fail to get UID/GID of a file
				var uid, gid int
				if stat, ok := info.Sys().(*syscall.Stat_t); ok {
					uid = int(stat.Uid)
					gid = int(stat.Gid)
				}
				if uid == user.UidCont {
					(&userDb[idx]).FileListUid = append((&userDb[idx]).FileListUid, filePath)
				}
				if gid == user.GidCont {
					(&userDb[idx]).FileListGid = append((&userDb[idx]).FileListGid, filePath)
				}
				return nil
			})
			if err != nil {
				return err
			}
		}
	}
	// change uids and gid of file
	for _, user := range userDb {
		if len(user.FileListUid) != 0 {
			//fmt.Printf("uidList(%s): %v\n", user.Name, user.FileListUid)
			for _, file := range user.FileListUid {
				fsInfo, err := os.Stat(file)
				if err != nil {
					return err
				}
				var gid int
				if stat, ok := fsInfo.Sys().(*syscall.Stat_t); ok {
					gid = int(stat.Gid)
				}
				wwlog.Debug("%s chown(%v,%v)", file, user.UidHost, gid)
				err = os.Chown(file, user.UidHost, gid)
				if err != nil {
					return err
				}
			}
		}
		if len(user.FileListGid) != 0 {
			//fmt.Printf("gidList(%s): %v\n", user.Name, user.FileListGid)
			for _, file := range user.FileListGid {
				fsInfo, err := os.Stat(file)
				if err != nil {
					return err
				}
				var uid int
				if stat, ok := fsInfo.Sys().(*syscall.Stat_t); ok {
					uid = int(stat.Uid)
				}
				wwlog.Debug("%s chown(%v,%v)", file, user.UidHost, uid)
				// only chown files and dirs
				if fsInfo.IsDir() && fsInfo.Mode().IsRegular() {
					err = os.Chown(file, uid, user.GidHost)
					if err != nil {
						return err
					}
				}
			}

		}

	}
	// get the entries for the passwd/group file before copy over
	passwdEntries, err := getEntires(path.Join(fullPath, passwdName), userOnlyCont)
	if err != nil {
		return err
	}
	// implicitly assuming that users/groups which only exists on the host have the same name
	groupEntries, err := getEntires(path.Join(fullPath, groupName), userOnlyCont)
	if err != nil {
		return err
	}
	if err = os.Remove(path.Join(fullPath, passwdName)); err != nil {
		return err
	}
	if err = os.Remove(path.Join(fullPath, groupName)); err != nil {
		return err
	}
	if err = util.CopyFile(passwdName, path.Join(fullPath, passwdName)); err != nil {
		return err
	}
	if err = util.CopyFile(groupName, path.Join(fullPath, groupName)); err != nil {
		return err
	}
	if err = util.AppendLines(path.Join(fullPath, passwdName), passwdEntries); err != nil {
		return err
	}
	if err = util.AppendLines(path.Join(fullPath, groupName), groupEntries); err != nil {
		return err
	}
	return nil

}

/*
creates simple user db []simpleUserInfo  for a /etc/{passwd|group} file
*/
func createPasswdMap(fileName string) ([]simpleUserInfo, error) {
	var nameDb []simpleUserInfo
	file, err := os.Open(fileName)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	fileScanner := bufio.NewScanner(file)
	for fileScanner.Scan() {
		line := fileScanner.Text()
		entries := strings.Split(line, ":")
		name := entries[0]
		uid, err := strconv.Atoi(entries[2])
		if err != nil {
			wwlog.Warn("could not parse uid(%s) for %s", entries[2], name)
		}
		gid, err := strconv.Atoi(entries[3])
		if err != nil {
			wwlog.Warn("could not parse gid(%s) for %s", entries[2], name)
		}
		if name != "" {
			nameDb = append(nameDb, simpleUserInfo{name: name, uid: uid, gid: gid})

		}
	}
	wwlog.Debug(fmt.Sprintf("created uid/gid map with %v entries from %s", len(nameDb), fileName))
	return nameDb, nil
}

/*
Creates a slice with the entries of of passwd for the given slice of user names
*/
func getEntires(fileName string, names []string) ([]string, error) {
	file, err := os.Open(fileName)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	var list []string
	fileScanner := bufio.NewScanner(file)
	for fileScanner.Scan() {
		line := fileScanner.Text()
		entries := strings.Split(line, ":")
		for _, name := range names {
			if entries[0] == name {
				list = append(list, line)
			}
		}
	}
	wwlog.Debug("file: %s, list: %v", fileName, list)
	return list, nil
}