package drivers

import (
	"cmp"
	"context"
	"errors"
	"fmt"
	"math"
	"math/rand/v2"
	"net/http"
	"os"
	"path/filepath"
	"slices"
	"sort"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/google/uuid"

	internalInstance "github.com/lxc/incus/v6/internal/instance"
	"github.com/lxc/incus/v6/internal/server/backup"
	"github.com/lxc/incus/v6/internal/server/db"
	dbCluster "github.com/lxc/incus/v6/internal/server/db/cluster"
	"github.com/lxc/incus/v6/internal/server/device"
	deviceConfig "github.com/lxc/incus/v6/internal/server/device/config"
	"github.com/lxc/incus/v6/internal/server/device/nictype"
	"github.com/lxc/incus/v6/internal/server/instance"
	"github.com/lxc/incus/v6/internal/server/instance/instancetype"
	"github.com/lxc/incus/v6/internal/server/instance/operationlock"
	"github.com/lxc/incus/v6/internal/server/lifecycle"
	"github.com/lxc/incus/v6/internal/server/locking"
	"github.com/lxc/incus/v6/internal/server/operations"
	"github.com/lxc/incus/v6/internal/server/project"
	"github.com/lxc/incus/v6/internal/server/state"
	storagePools "github.com/lxc/incus/v6/internal/server/storage"
	internalUtil "github.com/lxc/incus/v6/internal/util"
	"github.com/lxc/incus/v6/shared/api"
	"github.com/lxc/incus/v6/shared/logger"
	"github.com/lxc/incus/v6/shared/resources"
	"github.com/lxc/incus/v6/shared/revert"
	"github.com/lxc/incus/v6/shared/subprocess"
	"github.com/lxc/incus/v6/shared/util"
)

// Track last autorestart of an instance.
var (
	instancesLastRestart   = map[int][10]time.Time{}
	muInstancesLastRestart sync.Mutex
)

// ErrExecCommandNotFound indicates the command is not found.
var ErrExecCommandNotFound = api.StatusErrorf(http.StatusBadRequest, "Command not found")

// ErrExecCommandNotExecutable indicates the command is not executable.
var ErrExecCommandNotExecutable = api.StatusErrorf(http.StatusBadRequest, "Command not executable")

// ErrInstanceIsStopped indicates that the instance is stopped.
var ErrInstanceIsStopped error = api.StatusErrorf(http.StatusBadRequest, "The instance is already stopped")

// muNUMA is used to serialize NUMA node selection.
var muNUMA sync.Mutex

// deviceManager is an interface that allows managing device lifecycle.
type deviceManager interface {
	deviceAdd(dev device.Device, instanceRunning bool) error
	deviceRemove(dev device.Device, instanceRunning bool) error
	deviceStart(dev device.Device, instanceRunning bool) (*deviceConfig.RunConfig, error)
	deviceStop(dev device.Device, instanceRunning bool, stopHookNetnsPath string) error
}

// common provides structure common to all instance types.
type common struct {
	op    *operations.Operation
	state *state.State

	architecture    int
	creationDate    time.Time
	dbType          instancetype.Type
	description     string
	ephemeral       bool
	expandedConfig  map[string]string
	expandedDevices deviceConfig.Devices
	expiryDate      time.Time
	id              int
	lastUsedDate    time.Time
	localConfig     map[string]string
	localDevices    deviceConfig.Devices
	logger          logger.Logger
	name            string
	node            string
	profiles        []api.Profile
	project         api.Project
	isSnapshot      bool
	stateful        bool

	// Cached handles.
	// Do not use these variables directly, instead use their associated get functions so they
	// will be initialized on demand.
	storagePool storagePools.Pool

	// volatileSetPersistDisable indicates whether the VolatileSet function should persist changes to the DB.
	volatileSetPersistDisable bool
}

//
// SECTION: property getters
//

// Architecture returns the instance's architecture.
func (d *common) Architecture() int {
	return d.architecture
}

// CreationDate returns the instance's creation date.
func (d *common) CreationDate() time.Time {
	return d.creationDate
}

// Type returns the instance's type.
func (d *common) Type() instancetype.Type {
	return d.dbType
}

// Description returns the instance's description.
func (d *common) Description() string {
	return d.description
}

// IsEphemeral returns whether the instanc is ephemeral or not.
func (d *common) IsEphemeral() bool {
	return d.ephemeral
}

// ExpandedConfig returns instance's expanded config.
func (d *common) ExpandedConfig() map[string]string {
	return d.expandedConfig
}

// ExpandedDevices returns instance's expanded device config.
func (d *common) ExpandedDevices() deviceConfig.Devices {
	return d.expandedDevices
}

// ExpiryDate returns when this snapshot expires.
func (d *common) ExpiryDate() time.Time {
	if d.isSnapshot {
		return d.expiryDate
	}

	// Return zero time if the instance is not a snapshot.
	return time.Time{}
}

func (d *common) shouldAutoRestart() bool {
	if !util.IsTrue(d.expandedConfig["boot.autorestart"]) {
		return false
	}

	muInstancesLastRestart.Lock()
	defer muInstancesLastRestart.Unlock()

	// Check if the instance was ever auto-restarted.
	timestamps, ok := instancesLastRestart[d.id]
	if !ok || len(timestamps) == 0 {
		// If not, record it and allow the auto-restart.
		instancesLastRestart[d.id] = [10]time.Time{time.Now()}
		return true
	}

	// If it has been auto-restarted, look for the oldest non-zero timestamp.
	oldestIndex := 0
	validTimestamps := 0
	for i, timestamp := range timestamps {
		if timestamp.IsZero() {
			// We found an unused slot, lets use it.
			timestamps[i] = time.Now()
			instancesLastRestart[d.id] = timestamps
			return true
		}

		validTimestamps++

		if timestamp.Before(timestamps[oldestIndex]) {
			oldestIndex = i
		}
	}

	// Check if the oldest restart was more than a minute ago.
	if timestamps[oldestIndex].Before(time.Now().Add(-1 * time.Minute)) {
		// Remove the old timestamp and replace it with ours.
		timestamps[oldestIndex] = time.Now()
		instancesLastRestart[d.id] = timestamps
		return true
	}

	// If not and all slots are used
	return false
}

// ID gets instances's ID.
func (d *common) ID() int {
	return d.id
}

// LastUsedDate returns the instance's last used date.
func (d *common) LastUsedDate() time.Time {
	return d.lastUsedDate
}

// LocalConfig returns the instance's local config.
func (d *common) LocalConfig() map[string]string {
	return d.localConfig
}

// LocalDevices returns the instance's local device config.
func (d *common) LocalDevices() deviceConfig.Devices {
	return d.localDevices
}

// Name returns the instance's name.
func (d *common) Name() string {
	return d.name
}

// CloudInitID returns the cloud-init instance-id.
func (d *common) CloudInitID() string {
	id := d.LocalConfig()["volatile.cloud-init.instance-id"]
	if id != "" {
		return id
	}

	return d.name
}

// Location returns instance's location.
func (d *common) Location() string {
	return d.node
}

// Profiles returns the instance's profiles.
func (d *common) Profiles() []api.Profile {
	return d.profiles
}

// Project returns instance's project.
func (d *common) Project() api.Project {
	return d.project
}

// IsSnapshot returns whether instance is snapshot or not.
func (d *common) IsSnapshot() bool {
	return d.isSnapshot
}

// IsStateful returns whether instance is stateful or not.
func (d *common) IsStateful() bool {
	return d.stateful
}

// Operation returns the instance's current operation.
func (d *common) Operation() *operations.Operation {
	return d.op
}

//
// SECTION: general functions
//

// Backups returns a list of backups.
func (d *common) Backups() ([]backup.InstanceBackup, error) {
	var backupNames []string

	// Get all the backups
	err := d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		var err error
		backupNames, err = tx.GetInstanceBackups(ctx, d.project.Name, d.name)
		return err
	})
	if err != nil {
		return nil, err
	}

	// Build the backup list
	backups := []backup.InstanceBackup{}
	for _, backupName := range backupNames {
		backup, err := instance.BackupLoadByName(d.state, d.project.Name, backupName)
		if err != nil {
			return nil, err
		}

		backups = append(backups, *backup)
	}

	return backups, nil
}

// DeferTemplateApply records a template trigger to apply on next instance start.
func (d *common) DeferTemplateApply(trigger instance.TemplateTrigger) error {
	// Avoid over-writing triggers that have already been set.
	if d.localConfig["volatile.apply_template"] != "" {
		return nil
	}

	err := d.VolatileSet(map[string]string{"volatile.apply_template": string(trigger)})
	if err != nil {
		return fmt.Errorf("Failed to set apply_template volatile key: %w", err)
	}

	return nil
}

// MACPattern computes the most specific MAC address pattern for this instance.
func (d *common) MACPattern() string {
	macPattern, ok := d.project.Config["network.hwaddr_pattern"]
	if !ok {
		return d.state.GlobalConfig.NetworkHWAddrPattern()
	}

	return macPattern
}

// SetOperation sets the current operation.
func (d *common) SetOperation(op *operations.Operation) {
	d.op = op
}

// Snapshots returns a list of snapshots.
func (d *common) Snapshots() ([]instance.Instance, error) {
	if d.isSnapshot {
		return []instance.Instance{}, nil
	}

	var snapshotArgs map[int]db.InstanceArgs

	// Get all the snapshots for instance.
	err := d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		filter := dbCluster.InstanceSnapshotFilter{
			Project:  &d.project.Name,
			Instance: &d.name,
		}

		dbSnapshots, err := dbCluster.GetInstanceSnapshots(ctx, tx.Tx(), filter)
		if err != nil {
			return err
		}

		dbInstances := make([]dbCluster.Instance, len(dbSnapshots))
		for i, s := range dbSnapshots {
			dbInstances[i] = s.ToInstance(d.name, d.node, d.dbType, d.architecture)
		}

		snapshotArgs, err = tx.InstancesToInstanceArgs(ctx, false, dbInstances...)
		if err != nil {
			return err
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	// Allow storage to pre-fetch snapshot details using bulk queries.
	pool, err := d.getStoragePool()
	if err != nil {
		return nil, err
	}

	err = pool.CacheInstanceSnapshots(d)
	if err != nil {
		return nil, err
	}

	snapshots := make([]instance.Instance, 0, len(snapshotArgs))
	for _, snapshotArg := range snapshotArgs {
		// Populate profile info that was already loaded.
		snapshotArg.Profiles = d.profiles

		snapInst, err := instance.Load(d.state, snapshotArg, d.project)
		if err != nil {
			return nil, err
		}

		// Set the storage pool to the pre-loaded one (for caching).
		snapLXC, ok := snapInst.(*lxc)
		if ok {
			snapLXC.storagePool = pool
		}

		snapQEMU, ok := snapInst.(*qemu)
		if ok {
			snapQEMU.storagePool = pool
		}

		// Pass through the current operation.
		snapInst.SetOperation(d.op)

		snapshots = append(snapshots, instance.Instance(snapInst))
	}

	sort.SliceStable(snapshots, func(i, j int) bool {
		iCreation := snapshots[i].CreationDate()
		jCreation := snapshots[j].CreationDate()

		// Prefer sorting by creation date.
		if iCreation.Before(jCreation) {
			return true
		}

		// But if creation date is the same, then sort by ID.
		if iCreation.Equal(jCreation) && snapshots[i].ID() < snapshots[j].ID() {
			return true
		}

		return false
	})

	return snapshots, nil
}

// VolatileSet sets one or more volatile config keys.
func (d *common) VolatileSet(changes map[string]string) error {
	// Quick check.
	for key := range changes {
		if !strings.HasPrefix(key, internalInstance.ConfigVolatilePrefix) {
			return errors.New("Only volatile keys can be modified with VolatileSet")
		}
	}

	// Update the database if required.
	if !d.volatileSetPersistDisable {
		var err error
		if d.isSnapshot {
			err = d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
				return tx.UpdateInstanceSnapshotConfig(d.id, changes)
			})
		} else {
			err = d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
				return tx.UpdateInstanceConfig(d.id, changes)
			})
		}

		if err != nil {
			return fmt.Errorf("Failed to set volatile config: %w", err)
		}
	}

	// Apply the change locally.
	for key, value := range changes {
		if value == "" {
			delete(d.expandedConfig, key)
			delete(d.localConfig, key)
			continue
		}

		d.expandedConfig[key] = value
		d.localConfig[key] = value
	}

	return nil
}

//
// SECTION: path getters
//

// ConsoleBufferLogPath returns the instance's console buffer log path.
func (d *common) ConsoleBufferLogPath() string {
	return filepath.Join(d.LogPath(), "console.log")
}

// DevicesPath returns the instance's devices path.
func (d *common) DevicesPath() string {
	name := project.Instance(d.project.Name, d.name)
	return internalUtil.VarPath("devices", name)
}

// LogPath returns the instance's log path.
func (d *common) LogPath() string {
	name := project.Instance(d.project.Name, d.name)
	return internalUtil.LogPath(name)
}

// RunPath returns the instance's runtime path.
func (d *common) RunPath() string {
	name := project.Instance(d.project.Name, d.name)
	return internalUtil.RunPath(name)
}

// Path returns the instance's path.
func (d *common) Path() string {
	return storagePools.InstancePath(d.dbType, d.project.Name, d.name, d.isSnapshot)
}

// ExecOutputPath returns the instance's exec output path.
func (d *common) ExecOutputPath() string {
	return filepath.Join(d.Path(), "exec-output")
}

// RootfsPath returns the instance's rootfs path.
func (d *common) RootfsPath() string {
	return filepath.Join(d.Path(), "rootfs")
}

// ShmountsPath returns the instance's shared mounts path.
func (d *common) ShmountsPath() string {
	name := project.Instance(d.project.Name, d.name)
	return internalUtil.VarPath("shmounts", name)
}

// StatePath returns the instance's state path.
func (d *common) StatePath() string {
	return filepath.Join(d.Path(), "state")
}

// TemplatesPath returns the instance's templates path.
func (d *common) TemplatesPath() string {
	return filepath.Join(d.Path(), "templates")
}

// StoragePool returns the storage pool name.
func (d *common) StoragePool() (string, error) {
	pool, err := d.getStoragePool()
	if err != nil {
		return "", err
	}

	return pool.Name(), nil
}

//
// SECTION: internal functions
//

// deviceVolatileReset resets a device's volatile data when its removed or updated in such a way
// that it is removed then added immediately afterwards.
func (d *common) deviceVolatileReset(devName string, oldConfig, newConfig deviceConfig.Device) error {
	volatileClear := make(map[string]string)
	devicePrefix := fmt.Sprintf("volatile.%s.", devName)

	newNICType, err := nictype.NICType(d.state, d.project.Name, newConfig)
	if err != nil {
		return err
	}

	oldNICType, err := nictype.NICType(d.state, d.project.Name, oldConfig)
	if err != nil {
		return err
	}

	// If the device type has changed, remove all old volatile keys.
	// This will occur if the newConfig is empty (i.e the device is actually being removed) or
	// if the device type is being changed but keeping the same name.
	if newConfig["type"] != oldConfig["type"] || newNICType != oldNICType {
		for k := range d.localConfig {
			if !strings.HasPrefix(k, devicePrefix) {
				continue
			}

			volatileClear[k] = ""
		}

		return d.VolatileSet(volatileClear)
	}

	// If the device type remains the same, then just remove any volatile keys that have
	// the same key name present in the new config (i.e the new config is replacing the
	// old volatile key).
	for k := range d.localConfig {
		if !strings.HasPrefix(k, devicePrefix) {
			continue
		}

		devKey := strings.TrimPrefix(k, devicePrefix)
		_, found := newConfig[devKey]
		if found {
			volatileClear[k] = ""
		}
	}

	return d.VolatileSet(volatileClear)
}

// deviceVolatileGetFunc returns a function that retrieves a named device's volatile config and
// removes its device prefix from the keys.
func (d *common) deviceVolatileGetFunc(devName string) func() map[string]string {
	return func() map[string]string {
		volatile := make(map[string]string)
		prefix := fmt.Sprintf("volatile.%s.", devName)
		for k, v := range d.localConfig {
			after, ok := strings.CutPrefix(k, prefix)
			if ok {
				volatile[after] = v
			}
		}
		return volatile
	}
}

// deviceVolatileSetFunc returns a function that can be called to save a named device's volatile
// config using keys that do not have the device's name prefixed.
func (d *common) deviceVolatileSetFunc(devName string) func(save map[string]string) error {
	return func(save map[string]string) error {
		volatileSave := make(map[string]string)
		for k, v := range save {
			volatileSave[fmt.Sprintf("volatile.%s.%s", devName, k)] = v
		}

		return d.VolatileSet(volatileSave)
	}
}

// expandConfig applies the config of each profile in order, followed by the local config.
func (d *common) expandConfig() error {
	d.expandedConfig = db.ExpandInstanceConfig(d.localConfig, d.profiles)
	d.expandedDevices = db.ExpandInstanceDevices(d.localDevices, d.profiles)

	return nil
}

// restartCommon handles the common part of instance restarts.
func (d *common) restartCommon(inst instance.Instance, timeout time.Duration) error {
	// Setup a new operation for the stop/shutdown phase.
	op, err := operationlock.Create(d.Project().Name, d.Name(), d.op, operationlock.ActionRestart, true, true)
	if err != nil {
		return fmt.Errorf("Create restart operation: %w", err)
	}

	// Handle ephemeral instances.
	ephemeral := inst.IsEphemeral()

	ctxMap := logger.Ctx{
		"action":    "shutdown",
		"created":   d.creationDate,
		"ephemeral": ephemeral,
		"used":      d.lastUsedDate,
		"timeout":   timeout,
	}

	d.logger.Info("Restarting instance", ctxMap)

	if ephemeral {
		// Unset ephemeral flag
		args := db.InstanceArgs{
			Architecture: inst.Architecture(),
			Config:       inst.LocalConfig(),
			Description:  inst.Description(),
			Devices:      inst.LocalDevices(),
			Ephemeral:    false,
			Profiles:     inst.Profiles(),
			Project:      inst.Project().Name,
			Type:         inst.Type(),
			Snapshot:     inst.IsSnapshot(),
		}

		err := inst.Update(args, false)
		if err != nil {
			return err
		}

		// On function return, set the flag back on
		defer func() {
			args.Ephemeral = ephemeral
			_ = inst.Update(args, false)
		}()
	}

	if timeout == 0 {
		err := inst.Stop(false)
		if err != nil {
			op.Done(err)
			return err
		}
	} else {
		if inst.IsFrozen() {
			err = errors.New("Instance is not running")
			op.Done(err)
			return err
		}

		err := inst.Shutdown(timeout)
		if err != nil {
			op.Done(err)
			return err
		}
	}

	// Setup a new operation for the start phase.
	op, err = operationlock.CreateWaitGet(d.Project().Name, d.Name(), d.op, operationlock.ActionRestart, nil, true, false)
	if err != nil {
		if errors.Is(err, operationlock.ErrNonReusuableSucceeded) {
			// An existing matching operation has now succeeded, return.
			return nil
		}

		return fmt.Errorf("Create restart (for start) operation: %w", err)
	}

	err = inst.Start(false)
	if err != nil {
		op.Done(err)
		return err
	}

	d.logger.Info("Restarted instance", ctxMap)
	d.state.Events.SendLifecycle(d.project.Name, lifecycle.InstanceRestarted.Event(d, nil))

	return nil
}

// rebuildCommon handles the common part of instance rebuilds.
func (d *common) rebuildCommon(inst instance.Instance, img *api.Image, op *operations.Operation) error {
	instLocalConfig := d.localConfig

	// Reset the "image.*" keys.
	for k := range instLocalConfig {
		if strings.HasPrefix(k, "image.") {
			delete(instLocalConfig, k)
		}
	}

	delete(instLocalConfig, "volatile.base_image")
	if img != nil {
		for k, v := range img.Properties {
			instLocalConfig[fmt.Sprintf("image.%s", k)] = v
		}

		instLocalConfig["volatile.base_image"] = img.Fingerprint
		instLocalConfig["volatile.uuid.generation"] = instLocalConfig["volatile.uuid"]
	}

	// Reset relevant volatile keys.
	delete(instLocalConfig, "volatile.idmap.next")
	delete(instLocalConfig, "volatile.last_state.idmap")

	pool, err := d.getStoragePool()
	if err != nil {
		return err
	}

	err = pool.DeleteInstance(inst, op)
	if err != nil {
		return err
	}

	// Rebuild as empty if there is no image provided.
	if img == nil {
		err = pool.CreateInstance(inst, nil)
		if err != nil {
			return err
		}
	} else {
		err = pool.CreateInstanceFromImage(inst, img.Fingerprint, op)
		if err != nil {
			return err
		}
	}

	err = d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		err = dbCluster.UpdateInstanceConfig(ctx, tx.Tx(), int64(inst.ID()), instLocalConfig)
		if err != nil {
			return err
		}

		if img != nil {
			err = tx.UpdateImageLastUseDate(ctx, inst.Project().Name, img.Fingerprint, time.Now().UTC())
			if err != nil {
				return err
			}
		}

		return nil
	})
	if err != nil {
		return err
	}

	d.localConfig = instLocalConfig
	return nil
}

// runHooks executes the callback functions returned from a function.
func (d *common) runHooks(hooks []func() error) error {
	// Run any post start hooks.
	for _, hook := range hooks {
		err := hook()
		if err != nil {
			return err
		}
	}

	return nil
}

// snapshot handles the common part of the snapshotting process.
func (d *common) snapshotCommon(inst instance.Instance, name string, expiry time.Time, stateful bool) error {
	reverter := revert.New()
	defer reverter.Fail()

	// Setup the arguments.
	args := db.InstanceArgs{
		Project:      inst.Project().Name,
		Architecture: inst.Architecture(),
		Config:       inst.LocalConfig(),
		Description:  inst.Description(),
		Type:         inst.Type(),
		Snapshot:     true,
		Devices:      inst.LocalDevices(),
		Ephemeral:    inst.IsEphemeral(),
		Name:         inst.Name() + internalInstance.SnapshotDelimiter + name,
		Profiles:     inst.Profiles(),
		Stateful:     stateful,
		ExpiryDate:   expiry,
	}

	// Create the snapshot.
	snap, snapInstOp, cleanup, err := instance.CreateInternal(d.state, args, d.op, true, true)
	if err != nil {
		return fmt.Errorf("Failed creating instance snapshot record %q: %w", name, err)
	}

	reverter.Add(cleanup)
	defer snapInstOp.Done(err)

	pool, err := storagePools.LoadByInstance(d.state, snap)
	if err != nil {
		return err
	}

	err = pool.CreateInstanceSnapshot(snap, inst, d.op)
	if err != nil {
		return fmt.Errorf("Create instance snapshot: %w", err)
	}

	reverter.Add(func() { _ = snap.Delete(true) })

	// Mount volume for backup.yaml writing.
	_, err = pool.MountInstance(inst, d.op)
	if err != nil {
		return fmt.Errorf("Create instance snapshot (mount source): %w", err)
	}

	defer func() { _ = pool.UnmountInstance(inst, d.op) }()

	// Attempt to update backup.yaml for instance.
	err = inst.UpdateBackupFile()
	if err != nil {
		return err
	}

	reverter.Success()

	return nil
}

// updateProgress updates the operation metadata with a new progress string.
func (d *common) updateProgress(progress string) {
	if d.op == nil {
		return
	}

	meta := d.op.Metadata()
	if meta == nil {
		meta = make(map[string]any)
	}

	if meta["container_progress"] != progress {
		_ = d.op.ExtendMetadata(map[string]any{"container_progress": progress})
	}
}

// insertConfigkey function attempts to insert the instance config key into the database. If the insert fails
// then the database is queried to check whether another query inserted the same key. If the key is still
// unpopulated then the insert querty is retried until it succeeds or a retry limit is reached.
// If the insert succeeds or the key is found to have been populated then the value of the key is returned.
func (d *common) insertConfigkey(key string, value string) (string, error) {
	err := d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		err := tx.CreateInstanceConfig(ctx, d.id, map[string]string{key: value})
		if err == nil {
			return nil
		}

		// Check if something else filled it in behind our back.
		existingValue, errCheckExists := tx.GetInstanceConfig(ctx, d.id, key)
		if errCheckExists != nil {
			return err
		}

		value = existingValue

		return nil
	})
	if err != nil {
		return "", err
	}

	return value, nil
}

// isRunningStatusCode returns if instance is running from status code.
func (d *common) isRunningStatusCode(statusCode api.StatusCode) bool {
	return statusCode != api.Error && statusCode != api.Stopped
}

// isStartableStatusCode returns an error if the status code means the instance cannot be started currently.
func (d *common) isStartableStatusCode(statusCode api.StatusCode) error {
	if d.isRunningStatusCode(statusCode) {
		return errors.New("The instance is already running")
	}

	// If the instance process exists but is crashed, don't allow starting until its been cleaned up, as it
	// would likely fail to start anyway or leave the old process untracked.
	if statusCode == api.Error {
		return fmt.Errorf("The instance cannot be started as in %s status", statusCode)
	}

	return nil
}

// getStartupSnapNameAndExpiry returns the name and expiry for a snapshot to be taken at startup.
func (d *common) getStartupSnapNameAndExpiry(inst instance.Instance) (string, *time.Time, error) {
	schedule := strings.ToLower(d.expandedConfig["snapshots.schedule"])
	if schedule == "" {
		return "", nil, nil
	}

	triggers := strings.Split(schedule, ", ")
	if !slices.Contains(triggers, "@startup") {
		return "", nil, nil
	}

	expiry, err := internalInstance.GetExpiry(time.Now(), d.expandedConfig["snapshots.expiry"])
	if err != nil {
		return "", nil, err
	}

	name, err := instance.NextSnapshotName(d.state, inst, "snap%d")
	if err != nil {
		return "", nil, err
	}

	return name, &expiry, nil
}

// validateStartup checks any constraints that would prevent start up from succeeding under normal circumstances.
func (d *common) validateStartup(stateful bool, statusCode api.StatusCode) error {
	// Because the root disk is special and is mounted before the root disk device is setup we duplicate the
	// pre-start check here before the isStartableStatusCode check below so that if there is a problem loading
	// the instance status because the storage pool isn't available we don't mask the StatusServiceUnavailable
	// error with an ERROR status code from the instance check instead.
	_, rootDiskConf, err := internalInstance.GetRootDiskDevice(d.expandedDevices.CloneNative())
	if err != nil {
		return err
	}

	if !storagePools.IsAvailable(rootDiskConf["pool"]) {
		return api.StatusErrorf(http.StatusServiceUnavailable, "Storage pool %q unavailable on this server", rootDiskConf["pool"])
	}

	// Validate architecture.
	if !slices.Contains(d.state.OS.Architectures, d.architecture) {
		return errors.New("Requested architecture isn't supported by this host")
	}

	// Must happen before creating operation Start lock to avoid the status check returning Stopped due to the
	// existence of a Start operation lock.
	err = d.isStartableStatusCode(statusCode)
	if err != nil {
		return err
	}

	return nil
}

// onStopOperationSetup creates or picks up the relevant operation. This is used in the stopns and stop hooks to
// ensure that a lock on their activities is held before the instance process is stopped. This prevents a start
// request run at the same time from overlapping with the stop process.
// Returns the operation (with the instance initiated marker set if the operation was created).
func (d *common) onStopOperationSetup(target string) (*operationlock.InstanceOperation, error) {
	var err error

	// Pick up the existing stop operation lock created in Start(), Restart(), Shutdown() or Stop() functions.
	// If there is another ongoing operation that isn't in our inheritable list, wait until that has finished
	// before proceeding to run the hook.
	op := operationlock.Get(d.Project().Name, d.Name())
	if op != nil && !op.ActionMatch(operationlock.ActionStart, operationlock.ActionRestart, operationlock.ActionStop, operationlock.ActionRestore, operationlock.ActionMigrate) {
		d.logger.Debug("Waiting for existing operation lock to finish before running hook", logger.Ctx{"action": op.Action()})
		_ = op.Wait(context.Background())
		op = nil
	}

	if op == nil {
		d.logger.Debug("Instance initiated stop", logger.Ctx{"action": target})

		action := operationlock.ActionStop
		if target == "reboot" {
			action = operationlock.ActionRestart
		}

		op, err = operationlock.Create(d.Project().Name, d.Name(), d.op, action, false, false)
		if err != nil {
			return nil, fmt.Errorf("Failed creating %q operation: %w", action, err)
		}

		op.SetInstanceInitiated(true)
	} else {
		d.logger.Debug("Instance operation lock inherited for stop", logger.Ctx{"action": op.Action()})
	}

	return op, nil
}

// warningsDelete deletes any persistent warnings for the instance.
func (d *common) warningsDelete() error {
	err := d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		return dbCluster.DeleteWarnings(ctx, tx.Tx(), dbCluster.TypeInstance, d.ID())
	})
	if err != nil {
		return fmt.Errorf("Failed deleting persistent warnings: %w", err)
	}

	return nil
}

// canMigrate determines if the given instance can be migrated and what kind of migration to attempt.
func (d *common) canMigrate(inst instance.Instance) string {
	// Check policy for the instance.
	config := d.ExpandedConfig()
	val, ok := config["cluster.evacuate"]
	if !ok {
		val = "auto"
	}

	// If not using auto, just return the migration type.
	if val != "auto" {
		return val
	}

	// Look at attached devices.
	for _, entry := range d.ExpandedDevices().Sorted() {
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			logger.Warn("Instance will not be migrated due to a device error", logger.Ctx{"project": inst.Project().Name, "instance": inst.Name(), "device": dev.Name(), "err": err})
			return "stop"
		}

		if !dev.CanMigrate() {
			logger.Warn("Instance will not be migrated because its device cannot be migrated", logger.Ctx{"project": inst.Project().Name, "instance": inst.Name(), "device": dev.Name()})
			return "stop"
		}
	}

	// Check if set up for live migration.
	// Limit automatic live-migration to virtual machines for now.
	if inst.Type() == instancetype.VM && util.IsTrue(config["migration.stateful"]) {
		return "live-migrate"
	}

	return "migrate"
}

// recordLastState records last power and used time into local config and database config.
func (d *common) recordLastState() error {
	var err error

	// Record power state.
	d.localConfig["volatile.last_state.power"] = instance.PowerStateRunning
	d.expandedConfig["volatile.last_state.power"] = instance.PowerStateRunning

	// Database updates
	return d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		// Record power state.
		err = tx.UpdateInstancePowerState(d.id, instance.PowerStateRunning)
		if err != nil {
			err = fmt.Errorf("Error updating instance power state: %w", err)
			return err
		}

		// Update time instance last started time.
		err = tx.UpdateInstanceLastUsedDate(d.id, time.Now().UTC())
		if err != nil {
			err = fmt.Errorf("Error updating instance last used: %w", err)
			return err
		}

		return nil
	})
}

func (d *common) setCoreSched(pids []int) error {
	if !d.state.OS.CoreScheduling {
		return nil
	}

	args := []string{
		"forkcoresched",
		"0",
	}

	for _, pid := range pids {
		args = append(args, strconv.Itoa(pid))
	}

	_, err := subprocess.RunCommand(d.state.OS.ExecPath, args...)
	return err
}

// getRootDiskDevice gets the name and configuration of the root disk device of an instance.
func (d *common) getRootDiskDevice() (string, map[string]string, error) {
	devices := d.ExpandedDevices()
	if d.IsSnapshot() {
		parentName, _, _ := api.GetParentAndSnapshotName(d.name)

		// Load the parent.
		storageInstance, err := instance.LoadByProjectAndName(d.state, d.project.Name, parentName)
		if err != nil {
			return "", nil, err
		}

		devices = storageInstance.ExpandedDevices()
	}

	// Retrieve the instance's storage pool.
	name, configuration, err := internalInstance.GetRootDiskDevice(devices.CloneNative())
	if err != nil {
		return "", nil, err
	}

	return name, configuration, nil
}

// resetInstanceID generates a new UUID and puts it in volatile.
func (d *common) resetInstanceID() error {
	err := d.VolatileSet(map[string]string{"volatile.cloud-init.instance-id": uuid.New().String()})
	if err != nil {
		return fmt.Errorf("Failed to set volatile.cloud-init.instance-id: %w", err)
	}

	return nil
}

// needsNewInstanceID checks the changed data in an Update call to determine if a new instance-id is necessary.
func (d *common) needsNewInstanceID(changedConfig []string, oldExpandedDevices deviceConfig.Devices) bool {
	// Look for cloud-init related config changes.
	for _, key := range []string{
		"cloud-init.vendor-data",
		"cloud-init.user-data",
		"cloud-init.network-config",
		"user.vendor-data",
		"user.user-data",
		"user.network-config",
	} {
		if slices.Contains(changedConfig, key) {
			return true
		}
	}

	// Look for changes in network interface names.
	getNICNames := func(devs deviceConfig.Devices) []string {
		names := make([]string, 0, len(devs))
		for devName, dev := range devs {
			if dev["type"] != "nic" {
				continue
			}

			if dev["name"] != "" {
				names = append(names, dev["name"])
				continue
			}

			configKey := fmt.Sprintf("volatile.%s.name", devName)
			volatileName := d.localConfig[configKey]
			if volatileName != "" {
				names = append(names, dev["name"])
				continue
			}

			names = append(names, devName)
		}

		return names
	}

	oldNames := getNICNames(oldExpandedDevices)
	newNames := getNICNames(d.expandedDevices)

	for _, entry := range oldNames {
		if !slices.Contains(newNames, entry) {
			return true
		}
	}

	for _, entry := range newNames {
		if !slices.Contains(oldNames, entry) {
			return true
		}
	}

	return false
}

// getStoragePool returns the current storage pool handle. To avoid a DB lookup each time this
// function is called, the handle is cached internally in the struct.
func (d *common) getStoragePool() (storagePools.Pool, error) {
	if d.storagePool != nil {
		return d.storagePool, nil
	}

	var poolName string

	err := d.state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		var err error

		poolName, err = tx.GetInstancePool(ctx, d.Project().Name, d.Name())
		if err != nil {
			return fmt.Errorf("Failed getting instance pool: %w", err)
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	pool, err := storagePools.LoadByName(d.state, poolName)
	if err != nil {
		return nil, err
	}

	d.storagePool = pool

	return d.storagePool, nil
}

// deviceLoad instantiates and validates a new device and returns it along with enriched config.
func (d *common) deviceLoad(inst instance.Instance, deviceName string, rawConfig deviceConfig.Device) (device.Device, error) {
	var configCopy deviceConfig.Device
	var err error

	// Create copy of config and load some fields from volatile if device is nic or infiniband.
	if slices.Contains([]string{"nic", "infiniband"}, rawConfig["type"]) {
		configCopy, err = inst.FillNetworkDevice(deviceName, rawConfig)
		if err != nil {
			return nil, err
		}
	} else {
		// Otherwise copy the config so it cannot be modified by device.
		configCopy = rawConfig.Clone()
	}

	dev, err := device.New(inst, d.state, deviceName, configCopy, d.deviceVolatileGetFunc(deviceName), d.deviceVolatileSetFunc(deviceName))

	// If validation fails with unsupported device type then don't return the device for use.
	if errors.Is(err, device.ErrUnsupportedDevType) {
		return nil, err
	}

	// Return device even if error occurs as caller may still attempt to use device for stop and remove.
	return dev, err
}

// deviceAdd loads a new device and calls its Add() function.
func (d *common) deviceAdd(dev device.Device, instanceRunning bool) error {
	l := d.logger.AddContext(logger.Ctx{"device": dev.Name(), "type": dev.Config()["type"]})
	l.Debug("Adding device")

	if instanceRunning && !dev.CanHotPlug() {
		return errors.New("Device cannot be added when instance is running")
	}

	return dev.Add()
}

// deviceRemove loads a new device and calls its Remove() function.
func (d *common) deviceRemove(dev device.Device, instanceRunning bool) error {
	l := d.logger.AddContext(logger.Ctx{"device": dev.Name(), "type": dev.Config()["type"]})
	l.Debug("Removing device")

	if instanceRunning && !dev.CanHotPlug() {
		return errors.New("Device cannot be removed when instance is running")
	}

	return dev.Remove()
}

// devicesAdd adds devices to instance.
func (d *common) devicesAdd(inst instance.Instance, instanceRunning bool) (revert.Hook, error) {
	reverter := revert.New()
	defer reverter.Fail()

	for _, entry := range d.expandedDevices.Sorted() {
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			// If device conflicts with another device then do not call the deviceAdd function below
			// as this could cause the original device to be disrupted (such as allowing conflicting
			// static NIC DHCP leases to be created). Instead just log an error.
			// This will allow instances to be created with conflicting devices (such as when copying
			// or restoring a backup) and allows the user to manually fix the conflicts in order to
			// allow the instance to start.
			if api.StatusErrorCheck(err, http.StatusConflict) {
				d.logger.Error("Failed add validation for device, skipping add action", logger.Ctx{"device": entry.Name, "err": err})

				continue
			}

			// Clear any volatile key that could have been set during validation.
			_ = d.deviceVolatileReset(entry.Name, entry.Config, nil)

			return nil, fmt.Errorf("Failed add validation for device %q: %w", entry.Name, err)
		}

		err = d.deviceAdd(dev, instanceRunning)
		if err != nil {
			return nil, fmt.Errorf("Failed to add device %q: %w", dev.Name(), err)
		}

		reverter.Add(func() { _ = d.deviceRemove(dev, instanceRunning) })
	}

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

	return cleanup, nil
}

// devicesRegister calls the Register() function on all of the instance's devices.
func (d *common) devicesRegister(inst instance.Instance) {
	for _, entry := range d.ExpandedDevices().Sorted() {
		err := device.Register(inst, d.state, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			d.logger.Error("Failed to register device", logger.Ctx{"err": err, "device": entry.Name})
			continue
		}
	}
}

// devicesUpdate applies device changes to an instance.
func (d *common) devicesUpdate(inst instance.Instance, removeDevices deviceConfig.Devices, addDevices deviceConfig.Devices, updateDevices deviceConfig.Devices, oldExpandedDevices deviceConfig.Devices, instanceRunning bool, userRequested bool) error {
	reverter := revert.New()
	defer reverter.Fail()

	dm, ok := inst.(deviceManager)
	if !ok {
		return errors.New("Instance is not compatible with deviceManager interface")
	}

	// Remove devices in reverse order to how they were added.
	for _, entry := range removeDevices.Reversed() {
		l := d.logger.AddContext(logger.Ctx{"device": entry.Name, "userRequested": userRequested})
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			// Just log an error, but still allow the device to be removed if usable device returned.
			l.Error("Failed remove validation for device", logger.Ctx{"err": err})
		}

		// If a device was returned from deviceLoad even if validation fails, then try to stop and remove.
		if dev != nil {
			if instanceRunning {
				err = dm.deviceStop(dev, instanceRunning, "")
				if err != nil {
					return fmt.Errorf("Failed to stop device %q: %w", dev.Name(), err)
				}
			}

			err = d.deviceRemove(dev, instanceRunning)
			if err != nil && !errors.Is(err, device.ErrUnsupportedDevType) {
				return fmt.Errorf("Failed to remove device %q: %w", dev.Name(), err)
			}
		}

		// Check whether we are about to add the same device back with updated config and
		// if not, or if the device type has changed, then remove all volatile keys for
		// this device (as its an actual removal or a device type change).
		err = d.deviceVolatileReset(entry.Name, entry.Config, addDevices[entry.Name])
		if err != nil {
			return fmt.Errorf("Failed to reset volatile data for device %q: %w", entry.Name, err)
		}
	}

	// Add devices in sorted order, this ensures that device mounts are added in path order.
	for _, entry := range addDevices.Sorted() {
		l := d.logger.AddContext(logger.Ctx{"device": entry.Name, "userRequested": userRequested})
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			if userRequested {
				// Clear any volatile key that could have been set during validation.
				_ = d.deviceVolatileReset(entry.Name, entry.Config, nil)

				return fmt.Errorf("Failed add validation for device %q: %w", entry.Name, err)
			}

			// If update is non-user requested (i.e from a snapshot restore), there's nothing we can
			// do to fix the config and we don't want to prevent the snapshot restore so log and allow.
			l.Error("Failed add validation for device, skipping as non-user requested", logger.Ctx{"err": err})

			continue
		}

		err = d.deviceAdd(dev, instanceRunning)
		if err != nil {
			if userRequested {
				return fmt.Errorf("Failed to add device %q: %w", dev.Name(), err)
			}

			// If update is non-user requested (i.e from a snapshot restore), there's nothing we can
			// do to fix the config and we don't want to prevent the snapshot restore so log and allow.
			l.Error("Failed to add device, skipping as non-user requested", logger.Ctx{"err": err})
		}

		reverter.Add(func() { _ = d.deviceRemove(dev, instanceRunning) })

		if instanceRunning {
			err = dev.PreStartCheck()
			if err != nil {
				return fmt.Errorf("Failed pre-start check for device %q: %w", dev.Name(), err)
			}

			_, err := dm.deviceStart(dev, instanceRunning)
			if err != nil && !errors.Is(err, device.ErrUnsupportedDevType) {
				return fmt.Errorf("Failed to start device %q: %w", dev.Name(), err)
			}

			reverter.Add(func() { _ = dm.deviceStop(dev, instanceRunning, "") })
		}

		// For the root disk, call Update as its size may change.
		// Update will invoke applyQuota, which resizes the disk if necessary.
		if internalInstance.IsRootDiskDevice(dev.Config()) {
			err = dev.Update(oldExpandedDevices, instanceRunning)
			if err != nil {
				return fmt.Errorf("Failed to update device %q: %w", dev.Name(), err)
			}
		}
	}

	for _, entry := range updateDevices.Sorted() {
		l := d.logger.AddContext(logger.Ctx{"device": entry.Name, "userRequested": userRequested})
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			if userRequested {
				return fmt.Errorf("Failed update validation for device %q: %w", entry.Name, err)
			}

			// If update is non-user requested (i.e from a snapshot restore), there's nothing we can
			// do to fix the config and we don't want to prevent the snapshot restore so log and allow.
			// By not calling dev.Update on validation error we avoid potentially disrupting another
			// existing device if this device conflicts with it (such as allowing conflicting static
			// NIC DHCP leases to be created).
			l.Error("Failed update validation for device, removing device", logger.Ctx{"err": err})

			// If a device was returned from deviceLoad when validation fails, then try to stop and
			// remove it. This is to prevent devices being left in a state that is different to the
			// invalid non-user requested config that has been applied to DB. The safest thing to do
			// is to cleanup the device and wait for the config to be corrected.
			if dev != nil {
				if instanceRunning {
					err = dm.deviceStop(dev, instanceRunning, "")
					if err != nil {
						l.Error("Failed to stop device after update validation failed", logger.Ctx{"err": err})
					}
				}

				err = d.deviceRemove(dev, instanceRunning)
				if err != nil && !errors.Is(err, device.ErrUnsupportedDevType) {
					l.Error("Failed to remove device after update validation failed", logger.Ctx{"err": err})
				}
			}

			continue
		}

		err = dev.Update(oldExpandedDevices, instanceRunning)
		if err != nil {
			return fmt.Errorf("Failed to update device %q: %w", dev.Name(), err)
		}
	}

	reverter.Success()

	return nil
}

// devicesRemove runs device removal function for each device.
func (d *common) devicesRemove(inst instance.Instance) {
	for _, entry := range d.expandedDevices.Reversed() {
		dev, err := d.deviceLoad(inst, entry.Name, entry.Config)
		if err != nil {
			if errors.Is(err, device.ErrUnsupportedDevType) {
				continue // Skip unsupported device (allows for mixed instance type profiles).
			}

			// Just log an error, but still allow the device to be removed if usable device returned.
			d.logger.Error("Failed remove validation for device", logger.Ctx{"device": entry.Name, "err": err})
		}

		// If a usable device was returned from deviceLoad try to remove anyway, even if validation fails.
		// This allows for the scenario where a new version has additional validation restrictions
		// than older versions and we still need to allow previously valid devices to be stopped even if
		// they are no longer considered valid.
		if dev != nil {
			err = d.deviceRemove(dev, false)
			if err != nil {
				d.logger.Error("Failed to remove device", logger.Ctx{"device": dev.Name(), "err": err})
			}
		}
	}
}

// updateBackupFileLock acquires the update backup file lock that protects concurrent access to actions that will call UpdateBackupFile() as part of their operation.
func (d *common) updateBackupFileLock(ctx context.Context) (locking.UnlockFunc, error) {
	parentName, _, _ := api.GetParentAndSnapshotName(d.Name())
	return locking.Lock(ctx, fmt.Sprintf("instance_updatebackupfile_%s_%s", d.Project().Name, parentName))
}

// deleteSnapshots calls the deleteFunc on each of the instance's snapshots in reverse order.
func (d *common) deleteSnapshots(deleteFunc func(snapInst instance.Instance) error) error {
	snapInsts, err := d.Snapshots()
	if err != nil {
		return err
	}

	snapInstsCount := len(snapInsts)

	for k := range snapInsts {
		// Delete the snapshots in reverse order.
		k = snapInstsCount - 1 - k
		err = deleteFunc(snapInsts[k])
		if err != nil {
			return fmt.Errorf("Failed deleting snapshot %q: %w", snapInsts[k].Name(), err)
		}
	}

	return nil
}

// balanceNUMANodes looks at all other instances and picks the least used NUMA node(s).
func (d *common) balanceNUMANodes() error {
	muNUMA.Lock()
	defer muNUMA.Unlock()

	// Get the CPU information.
	cpu, err := resources.GetCPU()
	if err != nil {
		return err
	}

	// Get a list of NUMA nodes.
	nodes := []uint64{}
	for _, cpuSocket := range cpu.Sockets {
		for _, cpuCore := range cpuSocket.Cores {
			for _, cpuThread := range cpuCore.Threads {
				if !slices.Contains(nodes, cpuThread.NUMANode) {
					nodes = append(nodes, cpuThread.NUMANode)
				}
			}
		}
	}

	// Shortcut on single-node systems.
	if len(nodes) == 1 {
		return d.VolatileSet(map[string]string{"volatile.cpu.nodes": fmt.Sprintf("%d", nodes[0])})
	}

	// Get all local instances.
	insts, err := instance.LoadNodeAll(d.state, instancetype.Any)
	if err != nil {
		return err
	}

	// Record current NUMA assignment (number of instance).
	numaUsage := map[int64]int{}
	for _, inst := range insts {
		conf := inst.ExpandedConfig()

		// Ignore ourselves.
		if inst.ID() == d.id {
			continue
		}

		// Ignore instances without any NUMA pinning.
		if conf["limits.cpu.nodes"] == "" {
			continue
		}

		// Parse the used NUMA nodes.
		nodes := conf["limits.cpu.nodes"]
		if nodes == "balanced" {
			nodes = conf["volatile.cpu.nodes"]
		}

		numaNodeSet, err := resources.ParseNumaNodeSet(nodes)
		if err != nil {
			continue
		}

		for _, numaNode := range numaNodeSet {
			numaUsage[numaNode]++
		}
	}

	// Sort NUMA nodes by usage.
	slices.SortFunc(nodes, func(i, j uint64) int {
		return cmp.Compare(numaUsage[int64(i)], numaUsage[int64(j)])
	})

	// If `limits.cpu` is greater than the number of CPUs per NUMA node,
	// then figure out how many NUMA nodes to use.
	conf := d.ExpandedConfig()
	cpusPerNumaNode := int(cpu.Total) / len(nodes)

	limitsCPU, err := strconv.Atoi(conf["limits.cpu"])
	if err == nil && limitsCPU > cpusPerNumaNode {
		numaNodesToUse := int(math.Ceil(float64(limitsCPU) / float64(cpusPerNumaNode)))

		selectedNumaNodes := make([]string, numaNodesToUse)
		for i, node := range nodes[:numaNodesToUse] {
			selectedNumaNodes[i] = strconv.FormatUint(node, 10)
		}

		joinedNumaNodes := strings.Join(selectedNumaNodes, ",")
		return d.VolatileSet(map[string]string{"volatile.cpu.nodes": joinedNumaNodes})
	}

	return d.VolatileSet(map[string]string{"volatile.cpu.nodes": fmt.Sprintf("%d", nodes[0])})
}

// Gets the process starting time.
func (d *common) processStartedAt(pid int) (time.Time, error) {
	if pid < 1 {
		return time.Time{}, fmt.Errorf("Invalid PID %q", pid)
	}

	file, err := os.Stat(fmt.Sprintf("/proc/%d", pid))
	if err != nil {
		return time.Time{}, err
	}

	linuxInfo, ok := file.Sys().(*syscall.Stat_t)
	if !ok {
		return time.Time{}, errors.New("Bad stat type")
	}

	return time.Unix(int64(linuxInfo.Ctim.Sec), int64(linuxInfo.Ctim.Nsec)), nil
}

// ETag returns the instance configuration ETag data for pre-condition validation.
func (d *common) ETag() []any {
	if d.IsSnapshot() {
		return []any{d.expiryDate}
	}

	// Prepare the ETag
	etag := []any{d.architecture, d.ephemeral, d.profiles, d.localDevices.Sorted()}

	configKeys := make([]string, 0, len(d.localConfig))
	for k := range d.localConfig {
		configKeys = append(configKeys, k)
	}

	sort.Strings(configKeys)

	for _, k := range configKeys {
		etag = append(etag, fmt.Sprintf("%s=%s", k, d.localConfig[k]))
	}

	return etag
}

// ClearLimitsCPUNodes clears the "volatile.cpu.nodes" configuration if necessary.
func (d *common) ClearLimitsCPUNodes(changedConfig []string) {
	if !slices.Contains(changedConfig, "limits.cpu.nodes") {
		return
	}

	value := d.expandedConfig["limits.cpu.nodes"]
	if value == "balanced" {
		return
	}

	d.localConfig["volatile.cpu.nodes"] = ""
}

// setOOMPriority applies the OOM score adjustment to the instance.
func (d *common) setOOMPriority(pid int) error {
	oomPriority := d.expandedConfig["limits.memory.oom_priority"]

	score := int64(0)
	var err error
	if oomPriority != "" {
		score, err = strconv.ParseInt(oomPriority, 10, 64)
		if err != nil {
			return fmt.Errorf("Invalid OOM priority value %q: %w", oomPriority, err)
		}
	}

	if pid <= 0 {
		return fmt.Errorf("Failed to set OOM priority: instance not running or PID not found")
	}

	err = os.WriteFile(fmt.Sprintf("/proc/%d/oom_score_adj", pid), []byte(fmt.Sprintf("%d", score)), 0o644)
	if err != nil {
		return fmt.Errorf("Failed to set OOM priority: %w", err)
	}

	return nil
}

// selinuxContext returns the SELinux context for the instance.
func (d *common) selinuxContext(baseContext string) (string, error) {
	// Get all local instances.
	instances, err := instance.LoadNodeAll(d.state, instancetype.Any)
	if err != nil {
		return "", fmt.Errorf("Failed loading local instances: %w", err)
	}

	// Get all current values.
	seContexts := make([]string, 0, len(instances))
	for _, inst := range instances {
		if !inst.IsRunning() {
			continue
		}

		val, err := os.ReadFile(filepath.Join("/proc", strconv.Itoa(inst.InitPID()), "attr", "current"))
		if err != nil {
			return "", err
		}

		seContexts = append(seContexts, strings.TrimSuffix(string(val), "\x00"))
	}

	// Generate a random set of categories.
	for {
		c1 := rand.IntN(1023)
		c2 := rand.IntN(1023)

		if c1 == c2 {
			continue
		}

		seContext := baseContext + ":c" + strconv.Itoa(c1) + ",c" + strconv.Itoa(c2)
		if slices.Contains(seContexts, seContext) {
			continue
		}

		return seContext, nil
	}
}
