package device

import (
	"context"
	"errors"
	"fmt"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"slices"
	"sort"
	"strings"
	"time"

	"golang.org/x/sys/unix"

	"github.com/lxc/incus/v6/internal/linux"
	"github.com/lxc/incus/v6/internal/server/instance"
	storageDrivers "github.com/lxc/incus/v6/internal/server/storage/drivers"
	"github.com/lxc/incus/v6/shared/idmap"
	"github.com/lxc/incus/v6/shared/revert"
	"github.com/lxc/incus/v6/shared/subprocess"
	"github.com/lxc/incus/v6/shared/util"
)

// RBDFormatPrefix is the prefix used in disk paths to identify RBD.
const RBDFormatPrefix = "rbd"

// RBDFormatSeparator is the field separate used in disk paths for RBD devices.
const RBDFormatSeparator = " "

// DiskParseRBDFormat parses an rbd formatted string, and returns the pool name, volume name, and map of options.
func DiskParseRBDFormat(rbd string) (string, string, map[string]string, error) {
	// Remove and check the prefix.
	prefix, rbd, _ := strings.Cut(rbd, RBDFormatSeparator)
	if prefix != RBDFormatPrefix {
		return "", "", nil, fmt.Errorf("Invalid rbd format, wrong prefix: %q", prefix)
	}

	// Split the path and options.
	path, rawOpts, _ := strings.Cut(rbd, RBDFormatSeparator)

	// Check for valid RBD path.
	pool, volume, validPath := strings.Cut(path, "/")
	if !validPath {
		return "", "", nil, fmt.Errorf("Invalid rbd format, missing pool and/or volume: %q", path)
	}

	// Parse options.
	opts := make(map[string]string)
	for _, o := range strings.Split(rawOpts, ":") {
		k, v, isValid := strings.Cut(o, "=")
		if !isValid {
			return "", "", nil, fmt.Errorf("Invalid rbd format, bad option: %q", o)
		}

		opts[k] = v
	}

	return pool, volume, opts, nil
}

// DiskGetRBDFormat returns a rbd formatted string with the given values.
func DiskGetRBDFormat(clusterName string, userName string, poolName string, volumeName string) string {
	// Resolve any symlinks to config path.
	confPath := fmt.Sprintf("/etc/ceph/%s.conf", clusterName)
	target, err := filepath.EvalSymlinks(confPath)
	if err == nil {
		confPath = target
	}

	// Configuration values containing :, @, or = can be escaped with a leading \ character.
	// According to https://docs.ceph.com/docs/hammer/rbd/qemu-rbd/#usage
	optEscaper := strings.NewReplacer(":", `\:`, "@", `\@`, "=", `\=`)
	opts := []string{
		fmt.Sprintf("id=%s", optEscaper.Replace(userName)),
		fmt.Sprintf("pool=%s", optEscaper.Replace(poolName)),
		fmt.Sprintf("cluster=%s", optEscaper.Replace(clusterName)),
		fmt.Sprintf("conf=%s", optEscaper.Replace(confPath)),
	}

	return fmt.Sprintf("%s%s%s/%s%s%s", RBDFormatPrefix, RBDFormatSeparator, optEscaper.Replace(poolName), optEscaper.Replace(volumeName), RBDFormatSeparator, strings.Join(opts, ":"))
}

// BlockFsDetect detects the type of block device.
func BlockFsDetect(dev string) (string, error) {
	out, err := subprocess.RunCommand("blkid", "-s", "TYPE", "-o", "value", dev)
	if err != nil {
		return "", err
	}

	return strings.TrimSpace(out), nil
}

// IsBlockdev returns boolean indicating whether device is block type.
func IsBlockdev(path string) bool {
	// Get a stat struct from the provided path.
	stat := unix.Stat_t{}
	err := unix.Stat(path, &stat)
	if err != nil {
		return false
	}

	// Check if it's a block device
	if stat.Mode&unix.S_IFMT == unix.S_IFBLK {
		return true
	}

	// Not a device
	return false
}

// DiskMount mounts a disk device.
func DiskMount(srcPath string, dstPath string, recursive bool, propagation string, mountOptions []string, fsName string) error {
	var err error

	flags, mountOptionsStr := linux.ResolveMountOptions(mountOptions)

	var readonly bool
	if slices.Contains(mountOptions, "ro") {
		readonly = true
	}

	// Detect the filesystem
	if fsName == "none" {
		flags |= unix.MS_BIND
	}

	if propagation != "" {
		switch propagation {
		case "private":
			flags |= unix.MS_PRIVATE
		case "shared":
			flags |= unix.MS_SHARED
		case "slave":
			flags |= unix.MS_SLAVE
		case "unbindable":
			flags |= unix.MS_UNBINDABLE
		case "rprivate":
			flags |= unix.MS_PRIVATE | unix.MS_REC
		case "rshared":
			flags |= unix.MS_SHARED | unix.MS_REC
		case "rslave":
			flags |= unix.MS_SLAVE | unix.MS_REC
		case "runbindable":
			flags |= unix.MS_UNBINDABLE | unix.MS_REC
		default:
			return fmt.Errorf("Invalid propagation mode %q", propagation)
		}
	}

	if recursive {
		flags |= unix.MS_REC
	}

	// Mount the filesystem
	err = unix.Mount(srcPath, dstPath, fsName, uintptr(flags), mountOptionsStr)
	if err != nil {
		return fmt.Errorf("Unable to mount %q at %q with filesystem %q: %w", srcPath, dstPath, fsName, err)
	}

	// Remount bind mounts in readonly mode if requested
	if readonly && flags&unix.MS_BIND == unix.MS_BIND {
		flags = unix.MS_RDONLY | unix.MS_BIND | unix.MS_REMOUNT
		err = unix.Mount("", dstPath, fsName, uintptr(flags), "")
		if err != nil {
			return fmt.Errorf("Unable to mount %q in readonly mode: %w", dstPath, err)
		}
	}

	flags = unix.MS_REC | unix.MS_SLAVE
	err = unix.Mount("", dstPath, "", uintptr(flags), "")
	if err != nil {
		return fmt.Errorf("Unable to make mount %q private: %w", dstPath, err)
	}

	return nil
}

// DiskMountClear unmounts and removes the mount path used for disk shares.
func DiskMountClear(mntPath string) error {
	if util.PathExists(mntPath) {
		if linux.IsMountPoint(mntPath) {
			err := storageDrivers.TryUnmount(mntPath, 0)
			if err != nil {
				return fmt.Errorf("Failed unmounting %q: %w", mntPath, err)
			}
		}

		err := os.Remove(mntPath)
		if err != nil {
			return fmt.Errorf("Failed removing %q: %w", mntPath, err)
		}
	}

	return nil
}

func diskCephRbdMap(clusterName string, userName string, poolName string, volumeName string) (string, error) {
	devPath, err := subprocess.RunCommand(
		"rbd",
		"--id", userName,
		"--cluster", clusterName,
		"--pool", poolName,
		"map",
		volumeName)
	if err != nil {
		return "", err
	}

	idx := strings.Index(devPath, "/dev/rbd")
	if idx < 0 {
		return "", errors.New("Failed to detect mapped device path")
	}

	devPath = devPath[idx:]
	return strings.TrimSpace(devPath), nil
}

func diskCephRbdUnmap(deviceName string) error {
	unmapImageName := deviceName
	busyCount := 0
again:
	_, err := subprocess.RunCommand(
		"rbd",
		"unmap",
		unmapImageName)
	if err != nil {
		var runError subprocess.RunError
		if errors.As(err, &runError) {
			var exitError *exec.ExitError
			if errors.As(runError.Unwrap(), &exitError) {
				if exitError.ExitCode() == 22 {
					// EINVAL (already unmapped)
					return nil
				}

				if exitError.ExitCode() == 16 {
					// EBUSY (currently in use)
					busyCount++
					if busyCount == 10 {
						return err
					}

					// Wait a second an try again
					time.Sleep(time.Second)
					goto again
				}
			}
		}

		return err
	}

	goto again
}

// diskCephfsOptions returns the mntSrcPath and fsOptions to use for mounting a cephfs share.
func diskCephfsOptions(clusterName string, userName string, fsName string, fsPath string) (string, []string, error) {
	// Get the FSID.
	fsid, err := storageDrivers.CephFsid(clusterName, userName)
	if err != nil {
		return "", nil, err
	}

	// Get the monitor list.
	monAddresses, err := storageDrivers.CephMonitors(clusterName, userName)
	if err != nil {
		return "", nil, err
	}

	// Get the keyring entry.
	secret, err := storageDrivers.CephKeyring(clusterName, userName)
	if err != nil {
		return "", nil, err
	}

	srcPath, fsOptions := storageDrivers.CephBuildMount(
		userName,
		secret,
		fsid,
		monAddresses,
		fsName,
		fsPath,
	)

	return srcPath, fsOptions, nil
}

// DiskVMVirtiofsdStart starts a new virtiofsd process.
// If the idmaps slice is supplied then the proxy process is run inside a user namespace using the supplied maps.
// Returns UnsupportedError error if the host system or instance does not support virtiosfd, returns normal error
// type if process cannot be started for other reasons.
// Returns revert function and listener file handle on success.
func DiskVMVirtiofsdStart(execPath string, inst instance.Instance, socketPath string, pidPath string, logPath string, sharePath string, idmaps []idmap.Entry, cacheOption string) (func(), net.Listener, error) {
	reverter := revert.New()
	defer reverter.Fail()

	if !filepath.IsAbs(sharePath) {
		return nil, nil, fmt.Errorf("Share path not absolute: %q", sharePath)
	}

	// Remove old socket if needed.
	_ = os.Remove(socketPath)

	// Locate virtiofsd.
	cmd, err := exec.LookPath("virtiofsd")
	if err != nil {
		if util.PathExists("/usr/lib/qemu/virtiofsd") {
			cmd = "/usr/lib/qemu/virtiofsd"
		} else if util.PathExists("/usr/libexec/virtiofsd") {
			cmd = "/usr/libexec/virtiofsd"
		} else if util.PathExists("/usr/lib/virtiofsd") {
			cmd = "/usr/lib/virtiofsd"
		}
	}

	if cmd == "" {
		return nil, nil, ErrMissingVirtiofsd
	}

	if util.IsTrue(inst.ExpandedConfig()["migration.stateful"]) {
		return nil, nil, UnsupportedError{"Stateful migration unsupported"}
	}

	if util.IsTrue(inst.ExpandedConfig()["security.sev"]) || util.IsTrue(inst.ExpandedConfig()["security.sev.policy.es"]) {
		return nil, nil, UnsupportedError{"SEV unsupported"}
	}

	// Trickery to handle paths > 107 chars.
	socketFileDir, err := os.Open(filepath.Dir(socketPath))
	if err != nil {
		return nil, nil, err
	}

	defer func() { _ = socketFileDir.Close() }()

	socketFile := fmt.Sprintf("/proc/self/fd/%d/%s", socketFileDir.Fd(), filepath.Base(socketPath))

	listener, err := net.Listen("unix", socketFile)
	if err != nil {
		return nil, nil, fmt.Errorf("Failed to create unix listener for virtiofsd: %w", err)
	}

	reverter.Add(func() {
		_ = listener.Close()
		_ = os.Remove(socketPath)
	})

	unixListener, ok := listener.(*net.UnixListener)
	if !ok {
		return nil, nil, errors.New("Failed getting UnixListener for virtiofsd")
	}

	unixFile, err := unixListener.File()
	if err != nil {
		return nil, nil, fmt.Errorf("Failed to getting unix listener file for virtiofsd: %w", err)
	}

	defer func() { _ = unixFile.Close() }()

	switch cacheOption {
	case "metadata":
		cacheOption = "metadata"
	case "unsafe":
		cacheOption = "always"
	default:
		cacheOption = "never"
	}

	// Start the virtiofsd process in non-daemon mode.
	args := []string{"--fd=3", fmt.Sprintf("--cache=%s", cacheOption), fmt.Sprintf("--shared-dir=%s", sharePath)}

	if len(idmaps) > 0 {
		idmapSet := &idmap.Set{Entries: idmaps}
		sort.Sort(idmapSet)

		var lastUID int64
		var lastGID int64

		for _, entry := range idmapSet.Entries {
			if entry.IsUID {
				args = append(args, fmt.Sprintf("--translate-uid=map:%d:%d:%d", entry.NSID, entry.HostID, entry.MapRange))

				args = append(args, fmt.Sprintf("--translate-uid=forbid-guest:%d:%d", lastUID, entry.NSID-lastUID))
				lastUID = entry.NSID + entry.MapRange
			}

			if entry.IsGID {
				args = append(args, fmt.Sprintf("--translate-gid=map:%d:%d:%d", entry.NSID, entry.HostID, entry.MapRange))

				args = append(args, fmt.Sprintf("--translate-gid=forbid-guest:%d:%d", lastGID, entry.NSID-lastGID))
				lastGID = entry.NSID + entry.MapRange
			}
		}

		if lastUID < 4294967295 {
			args = append(args, fmt.Sprintf("--translate-uid=forbid-guest:%d:%d", lastUID, 4294967295-lastUID))
		}

		if lastGID < 4294967295 {
			args = append(args, fmt.Sprintf("--translate-gid=forbid-guest:%d:%d", lastGID, 4294967295-lastGID))
		}
	} else {
		args = append(args, "--posix-acl")
	}

	proc, err := subprocess.NewProcess(cmd, args, logPath, logPath)
	if err != nil {
		return nil, nil, err
	}

	err = proc.StartWithFiles(context.Background(), []*os.File{unixFile})
	if err != nil {
		return nil, nil, fmt.Errorf("Failed to start virtiofsd: %w", err)
	}

	reverter.Add(func() { _ = proc.Stop() })

	err = proc.Save(pidPath)
	if err != nil {
		return nil, nil, fmt.Errorf("Failed to save virtiofsd state: %w", err)
	}

	cleanup := reverter.Clone().Fail
	reverter.Success()

	return cleanup, listener, err
}

// DiskVMVirtiofsdStop stops an existing virtiofsd process and cleans up.
func DiskVMVirtiofsdStop(socketPath string, pidPath string) error {
	if util.PathExists(pidPath) {
		proc, err := subprocess.ImportProcess(pidPath)
		if err != nil {
			return err
		}

		err = proc.Stop()
		// The virtiofsd process will terminate automatically once the VM has stopped.
		// We therefore should only return an error if it's still running and fails to stop.
		if err != nil && !errors.Is(err, subprocess.ErrNotRunning) {
			return err
		}

		// Remove PID file if needed.
		err = os.Remove(pidPath)
		if err != nil && !errors.Is(err, os.ErrNotExist) {
			return fmt.Errorf("Failed to remove PID file: %w", err)
		}
	}

	// Remove socket file if needed.
	err := os.Remove(socketPath)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return fmt.Errorf("Failed to remove socket file: %w", err)
	}

	return nil
}