package profilemanager

import (
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"net"
	"net/url"
	"os"
	"os/user"
	"path/filepath"
	"reflect"
	"runtime"
	"slices"
	"strings"
	"time"

	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"

	log "github.com/sirupsen/logrus"

	"github.com/netbirdio/netbird/client/iface"
	"github.com/netbirdio/netbird/client/internal/routemanager/dynamic"
	"github.com/netbirdio/netbird/client/mdm"
	"github.com/netbirdio/netbird/client/ssh"
	mgm "github.com/netbirdio/netbird/shared/management/client"
	"github.com/netbirdio/netbird/shared/management/domain"
	"github.com/netbirdio/netbird/util"
)

const (
	// managementLegacyPortString is the port that was used before by the Management gRPC server.
	// It is used for backward compatibility now.
	managementLegacyPortString = "33073"
	// DefaultManagementURL points to the NetBird's cloud management endpoint
	DefaultManagementURL = "https://api.netbird.io:443"
	// oldDefaultManagementURL points to the NetBird's old cloud management endpoint
	oldDefaultManagementURL = "https://api.wiretrustee.com:443"
	// DefaultAdminURL points to NetBird's cloud management console
	DefaultAdminURL = "https://app.netbird.io:443"
)

// mgmProber is the subset of management client needed for URL migration probes.
type mgmProber interface {
	HealthCheck() error
	Close() error
}

// newMgmProber creates a management client for probing URL reachability.
// Overridden in tests to avoid real network calls.
var newMgmProber = func(ctx context.Context, addr string, key wgtypes.Key, tlsEnabled bool) (mgmProber, error) {
	return mgm.NewClient(ctx, addr, key, tlsEnabled)
}

var DefaultInterfaceBlacklist = []string{
	iface.WgInterfaceDefault, "wt", "utun", "tun0", "zt", "ZeroTier", "wg", "ts",
	"Tailscale", "tailscale", "docker", "veth", "br-", "lo",
}

// ConfigInput carries configuration changes to the client
type ConfigInput struct {
	ManagementURL                 string
	AdminURL                      string
	ConfigPath                    string
	StateFilePath                 string
	PreSharedKey                  *string
	ServerSSHAllowed              *bool
	RemoteJobsAllowed             *bool
	EnableSSHRoot                 *bool
	EnableSSHSFTP                 *bool
	EnableSSHLocalPortForwarding  *bool
	EnableSSHRemotePortForwarding *bool
	DisableSSHAuth                *bool
	SSHJWTCacheTTL                *int
	NATExternalIPs                []string
	CustomDNSAddress              []byte
	RosenpassEnabled              *bool
	RosenpassPermissive           *bool
	InterfaceName                 *string
	WireguardPort                 *int
	NetworkMonitor                *bool
	DisableAutoConnect            *bool
	ExtraIFaceBlackList           []string
	DNSRouteInterval              *time.Duration
	ClientCertPath                string
	ClientCertKeyPath             string

	DisableClientRoutes *bool
	DisableServerRoutes *bool
	DisableDNS          *bool
	DisableFirewall     *bool
	BlockLANAccess      *bool
	BlockInbound        *bool
	DisableIPv6         *bool
	SyncMessageVersion  *int

	DisableNotifications *bool

	DNSLabels domain.List

	MTU *uint16

	LocalMetricsEnabled *bool
	LocalMetricsAddress *string
}

// Config Configuration type
type Config struct {
	// Name is the human-readable profile name shown in CLI/UI listings.
	// It is independent of the profile's on-disk filename (which is the ID).
	Name string

	// Wireguard private key of local peer
	PrivateKey                    string
	PreSharedKey                  string
	ManagementURL                 *url.URL
	AdminURL                      *url.URL
	WgIface                       string
	WgPort                        int
	NetworkMonitor                *bool
	IFaceBlackList                []string
	DisableIPv6Discovery          bool
	RosenpassEnabled              bool
	RosenpassPermissive           bool
	ServerSSHAllowed              *bool
	RemoteJobsAllowed             *bool
	EnableSSHRoot                 *bool
	EnableSSHSFTP                 *bool
	EnableSSHLocalPortForwarding  *bool
	EnableSSHRemotePortForwarding *bool
	DisableSSHAuth                *bool
	SSHJWTCacheTTL                *int

	DisableClientRoutes bool
	DisableServerRoutes bool
	DisableDNS          bool
	DisableFirewall     bool
	BlockLANAccess      bool
	BlockInbound        bool
	DisableIPv6         bool
	SyncMessageVersion  *int

	DisableNotifications *bool

	DNSLabels domain.List

	// LocalMetricsEnabled enables the local Prometheus /metrics endpoint.
	LocalMetricsEnabled bool
	// LocalMetricsAddress is the listen address of the local /metrics endpoint.
	LocalMetricsAddress string

	// SSHKey is a private SSH key in a PEM format
	SSHKey string

	// ExternalIP mappings, if different from the host interface IP
	//
	//   External IP must not be behind a CGNAT and port-forwarding for incoming UDP packets from WgPort on ExternalIP
	//   to WgPort on host interface IP must be present. This can take form of single port-forwarding rule, 1:1 DNAT
	//   mapping ExternalIP to host interface IP, or a NAT DMZ to host interface IP.
	//
	//   A single mapping will take the form of: external[/internal]
	//    external (required): either the external IP address or "stun" to use STUN to determine the external IP address
	//    internal (optional): either the internal/interface IP address or an interface name
	//
	//   examples:
	//      "12.34.56.78"          => all interfaces IPs will be mapped to external IP of 12.34.56.78
	//      "12.34.56.78/eth0"     => IPv4 assigned to interface eth0 will be mapped to external IP of 12.34.56.78
	//      "12.34.56.78/10.1.2.3" => interface IP 10.1.2.3 will be mapped to external IP of 12.34.56.78

	NATExternalIPs []string
	// CustomDNSAddress sets the DNS resolver listening address in format ip:port
	CustomDNSAddress string

	// DisableAutoConnect determines whether the client should not start with the service
	// it's set to false by default due to backwards compatibility
	DisableAutoConnect bool

	// DNSRouteInterval is the interval in which the DNS routes are updated
	DNSRouteInterval time.Duration
	// Path to a certificate used for mTLS authentication
	ClientCertPath string

	// Path to corresponding private key of ClientCertPath
	ClientCertKeyPath string

	ClientCertKeyPair *tls.Certificate `json:"-"`

	// LazyConnection is the MDM-managed lazy-connection override ("on"/"off"/"").
	// Runtime-only: re-derived from MDM policy on each load, never persisted.
	LazyConnection string `json:"-"`

	// DebugBundleUploadURL is the MDM-managed debug-bundle upload URL override.
	// When set, it takes precedence over the management-supplied upload URL for
	// remote debug bundle jobs. Runtime-only: re-derived from MDM policy on each
	// load, never persisted.
	DebugBundleUploadURL string `json:"-"`

	MTU uint16

	// policy is the MDM policy that produced the currently-set values
	// for any MDM-enforced fields. Set by ApplyMDMPolicy on every
	// invocation. Never persisted to disk. Callers query enforcement
	// state via Policy() and the mdm.Policy API (HasKey, ManagedKeys,
	// IsEmpty).
	policy *mdm.Policy `json:"-"`
}

// ApplyMDMPolicy overlays the supplied MDM Policy on top of the current
// Config values and records it as Policy(). The overlay is not reversible:
// an empty Policy only clears the enforcement metadata, so resolve the base
// Config again (from disk or JSON) before applying a changed policy, the way
// the lifecycle owners do on every load.
func (config *Config) ApplyMDMPolicy(policy *mdm.Policy) {
	if config == nil {
		return
	}
	config.applyMDMPolicy(policy)
}

// Policy returns the MDM policy applied to this Config. Returns a non-nil
// empty Policy when MDM enforcement is inactive; callers can always invoke
// HasKey / ManagedKeys / IsEmpty without a nil check.
func (config *Config) Policy() *mdm.Policy {
	if config == nil || config.policy == nil {
		return mdm.NewPolicy(nil)
	}
	return config.policy
}

var ConfigDirOverride string

func getConfigDir() (string, error) {
	if ConfigDirOverride != "" {
		return ConfigDirOverride, nil
	}

	base, err := baseConfigDir()
	if err != nil {
		return "", err
	}

	configDir := filepath.Join(base, "netbird")
	// Under sudo this is the invoking user's directory and strictly read-only:
	// anything root creates in it would be root-owned and break the user's own
	// runs. Reads of a missing directory fall through to defaults.
	if sudoActive() {
		return configDir, nil
	}
	if err := os.MkdirAll(configDir, 0o755); err != nil {
		return "", err
	}
	return configDir, nil
}

func baseConfigDir() (string, error) {
	if u, ok := sudoInvokingUser(); ok {
		return userBaseConfigDir(u)
	}
	// Fail closed instead of falling through to root's own config directory:
	// reading root's active-profile and email state for what is actually the
	// invoking user's invocation is the very confusion this resolution exists
	// to prevent.
	if sudoActive() {
		return "", fmt.Errorf("resolve sudo invoking user %q: refusing to fall back to root's config directory", os.Getenv(envSudoUser))
	}
	if runtime.GOOS == "darwin" {
		if u, err := user.Current(); err == nil && u.HomeDir != "" {
			return filepath.Join(u.HomeDir, "Library", "Application Support"), nil
		}
	}
	return os.UserConfigDir()
}

func getConfigDirForUser(username string) (string, error) {
	if ConfigDirOverride != "" {
		return ConfigDirOverride, nil
	}

	username = sanitizeProfileName(username)

	configDir := filepath.Join(DefaultConfigPathDir, username)
	if _, err := os.Stat(configDir); os.IsNotExist(err) {
		if err := os.MkdirAll(configDir, 0700); err != nil {
			return "", err
		}
	}

	return configDir, nil
}

func fileExists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return false, err
}

// newConfigSkeleton returns the field values a brand-new profile config starts
// from, before apply() fills in the rest. Shared with the dry-run baseline so
// the two cannot disagree about what "a new config" means.
func newConfigSkeleton() *Config {
	return &Config{
		// defaults to false only for new (post 0.26) configurations
		ServerSSHAllowed: util.False(),
		// Remote jobs are an explicit opt-in and default off, including for
		// legacy configs (a nil value materializes to false at connect time).
		RemoteJobsAllowed: util.False(),
		WgPort:            iface.DefaultWgPort,
	}
}

// resolveUnsetDefaults is the single place where an optional field that carries
// no value gets one, and the only place that states what each of those defaults
// is. apply() runs it before it compares anything, and that ordering is the
// point: with the values named, every comparison below it diffs values instead
// of presence.
//
// Presence-based comparison is what broke `netbird up` for a client configured
// through the environment. These fields mean "the effective default" when they
// hold nothing — every consumer already reads a nil as the value resolved here,
// the SSH toggles in engine_ssh.go and the network monitor in
// createEngineConfig — so naming them changes nothing about what runs. But
// while they stayed nil, an input restating the default read as a change, and
// since the CLI sends every flag whose value came from an environment variable
// on each `netbird up`, a client with NB_ENABLE_SSH_ROOT=false restated it
// every time and the update-settings gate refused it.
//
// Filling a field in is not a settings change, so a caller measuring change
// must not read the returned bool as one: see WouldChange, which runs a pass
// for this and discards its verdict.
//
// ServerSSHAllowed is the one field whose default depends on the config's age.
// A brand-new profile gets false from newConfigSkeleton, which runs before
// this, so what is resolved here is only the legacy case: a config written by a
// version that had no such field keeps SSH on, for backwards compatibility.
func (config *Config) resolveUnsetDefaults() (updated bool) {
	// Fields that default to false on every platform.
	for _, field := range []**bool{
		&config.EnableSSHRoot,
		&config.EnableSSHSFTP,
		&config.EnableSSHLocalPortForwarding,
		&config.EnableSSHRemotePortForwarding,
		&config.DisableSSHAuth,
		// Remote jobs are an explicit opt-in: unlike SSH, a pre-existing config
		// with no value defaults to disabled rather than being turned on.
		&config.RemoteJobsAllowed,
	} {
		if *field == nil {
			*field = util.False()
			updated = true
		}
	}

	if config.DisableNotifications == nil {
		log.Infof("setting notifications to disabled by default")
		config.DisableNotifications = util.True()
		updated = true
	}

	if config.SSHJWTCacheTTL == nil {
		// A zero TTL disables the JWT cache, which is what no value meant.
		config.SSHJWTCacheTTL = new(int)
		updated = true
	}

	if config.NetworkMonitor == nil {
		// network monitoring is on by default on windows and darwin clients
		enabled := runtime.GOOS == "windows" || runtime.GOOS == "darwin"
		config.NetworkMonitor = &enabled
		updated = true
	}

	if config.ServerSSHAllowed == nil {
		if runtime.GOOS == "android" {
			// default to disabled SSH on Android for security
			log.Infof("setting SSH server to false by default on Android")
			config.ServerSSHAllowed = util.False()
		} else {
			// enables SSH for configs from old versions to preserve backwards compatibility
			log.Infof("falling back to enabled SSH server for pre-existing configuration")
			config.ServerSSHAllowed = util.True()
		}
		updated = true
	}

	return updated
}

// createNewConfig resolves a new config in memory, with no identity: whoever
// needs the peer's keys calls EnsureIdentity and persists the result, so a read
// that lands on a missing file cannot hand back a config carrying keys that
// nothing will ever write down.
func createNewConfig(input ConfigInput) (*Config, error) {
	config := newConfigSkeleton()

	if _, err := config.apply(input); err != nil {
		return nil, err
	}

	return config, nil
}

// createProvisionedConfig is createNewConfig plus the peer's identity, for the
// callers that go on to persist the config or to connect with it.
func createProvisionedConfig(input ConfigInput) (*Config, error) {
	config, err := createNewConfig(input)
	if err != nil {
		return nil, err
	}

	if _, err := config.EnsureIdentity(); err != nil {
		return nil, err
	}

	return config, nil
}

// EnsureIdentity generates the keys that identify this peer if the config does
// not carry them yet, reporting whether it had to generate any.
//
// It is deliberately not part of apply(). Everything apply() fills in is a
// default it can recompute on the next read, but a generated key is not: it
// has to be persisted, or the peer comes back with a different WireGuard
// identity and re-registers. Having apply() generate keys is what forced every
// read of a config to write it back — so identity provisioning is its own step
// now, and the callers that perform it write the result out explicitly.
func (config *Config) EnsureIdentity() (bool, error) {
	generated := false

	if config.PrivateKey == "" {
		log.Infof("generated new Wireguard key")
		config.PrivateKey = generateKey()
		generated = true
	}

	if config.SSHKey == "" {
		log.Infof("generated new SSH key")
		pem, err := ssh.GeneratePrivateKey(ssh.ED25519)
		if err != nil {
			return generated, err
		}
		config.SSHKey = string(pem)
		generated = true
	}

	return generated, nil
}

func (config *Config) apply(input ConfigInput) (updated bool, err error) {
	if config.Name != "" {
		sanitized, err := sanitizeDisplayName(config.Name)
		if err != nil {
			return false, fmt.Errorf("invalid profile name: %w", err)
		}
		if sanitized != config.Name {
			config.Name = sanitized
			updated = true
		}
	}

	// Every optional field gets its value here, before anything below compares
	// one. See resolveUnsetDefaults for why that ordering is the point.
	if config.resolveUnsetDefaults() {
		updated = true
	}

	if config.ManagementURL == nil {
		log.Infof("using default Management URL %s", DefaultManagementURL)
		config.ManagementURL, err = parseURL("Management URL", DefaultManagementURL)
		if err != nil {
			return false, err
		}
	}
	// The comparison is on the endpoint the URL addresses, not on its
	// spelling: the same endpoint can be written several ways (an implicit
	// :443, a trailing slash, a different host case), and treating an
	// equivalent URL as new would rewrite the config and report a settings
	// change where the configuration does not actually change.
	if input.ManagementURL != "" {
		URL, err := parseURL("Management URL", input.ManagementURL)
		if err != nil {
			return false, err
		}
		if !SameServiceURL(URL, config.ManagementURL) {
			log.Infof("new Management URL provided, updated to %#v (old value %#v)",
				URL.String(), config.ManagementURL.String())
			config.ManagementURL = URL
			updated = true
		}
	}

	if config.AdminURL == nil {
		log.Infof("using default Admin URL %s", DefaultAdminURL)
		config.AdminURL, err = parseURL("Admin URL", DefaultAdminURL)
		if err != nil {
			return false, err
		}
	}
	// The admin panel is opened, not dialed, so unlike the Management URL its
	// path is part of what identifies it: a panel served under /netbird is not
	// the one served at the root.
	if input.AdminURL != "" {
		newURL, err := parseURL("Admin Panel URL", input.AdminURL)
		if err != nil {
			return updated, err
		}
		if !SameServiceURLIncludingPath(newURL, config.AdminURL) {
			log.Infof("new Admin Panel URL provided, updated to %#v (old value %#v)",
				newURL.String(), config.AdminURL.String())
			config.AdminURL = newURL
			updated = true
		}
	}

	if input.WireguardPort != nil && *input.WireguardPort != config.WgPort {
		log.Infof("updating Wireguard port %d (old value %d)",
			*input.WireguardPort, config.WgPort)
		config.WgPort = *input.WireguardPort
		updated = true
	}

	if input.InterfaceName != nil && *input.InterfaceName != config.WgIface {
		log.Infof("updating Wireguard interface %#v (old value %#v)",
			*input.InterfaceName, config.WgIface)
		config.WgIface = *input.InterfaceName
		updated = true
	} else if config.WgIface == "" {
		config.WgIface = iface.WgInterfaceDefault
		log.Infof("using default Wireguard interface %s", config.WgIface)
		updated = true
	}

	if input.NATExternalIPs != nil && !reflect.DeepEqual(config.NATExternalIPs, input.NATExternalIPs) {
		log.Infof("updating NAT External IP [ %s ] (old value: [ %s ])",
			strings.Join(input.NATExternalIPs, " "),
			strings.Join(config.NATExternalIPs, " "))
		config.NATExternalIPs = input.NATExternalIPs
		updated = true
	}

	if input.PreSharedKey != nil && *input.PreSharedKey != config.PreSharedKey {
		log.Infof("new pre-shared key provided, replacing old key")
		config.PreSharedKey = *input.PreSharedKey
		updated = true
	}

	if input.RosenpassEnabled != nil && *input.RosenpassEnabled != config.RosenpassEnabled {
		log.Infof("switching Rosenpass to %t", *input.RosenpassEnabled)
		config.RosenpassEnabled = *input.RosenpassEnabled
		updated = true
	}

	if input.RosenpassPermissive != nil && *input.RosenpassPermissive != config.RosenpassPermissive {
		log.Infof("switching Rosenpass permissive to %t", *input.RosenpassPermissive)
		config.RosenpassPermissive = *input.RosenpassPermissive
		updated = true
	}

	if input.LocalMetricsEnabled != nil && *input.LocalMetricsEnabled != config.LocalMetricsEnabled {
		log.Infof("switching local metrics to %t", *input.LocalMetricsEnabled)
		config.LocalMetricsEnabled = *input.LocalMetricsEnabled
		updated = true
	}

	if input.LocalMetricsAddress != nil && *input.LocalMetricsAddress != config.LocalMetricsAddress {
		log.Infof("switching local metrics address to %s", *input.LocalMetricsAddress)
		config.LocalMetricsAddress = *input.LocalMetricsAddress
		updated = true
	}

	if input.NetworkMonitor != nil && *input.NetworkMonitor != *config.NetworkMonitor {
		log.Infof("switching Network Monitor to %t", *input.NetworkMonitor)
		config.NetworkMonitor = input.NetworkMonitor
		updated = true
	}

	if input.CustomDNSAddress != nil && string(input.CustomDNSAddress) != config.CustomDNSAddress {
		log.Infof("updating custom DNS address %#v (old value %#v)",
			string(input.CustomDNSAddress), config.CustomDNSAddress)
		config.CustomDNSAddress = string(input.CustomDNSAddress)
		updated = true
	}

	if len(config.IFaceBlackList) == 0 {
		log.Infof("filling in interface blacklist with defaults: [ %s ]",
			strings.Join(DefaultInterfaceBlacklist, " "))
		config.IFaceBlackList = append(config.IFaceBlackList, DefaultInterfaceBlacklist...)
		updated = true
	}

	if len(input.ExtraIFaceBlackList) > 0 {
		for _, iFace := range util.SliceDiff(input.ExtraIFaceBlackList, config.IFaceBlackList) {
			log.Infof("adding new entry to interface blacklist: %s", iFace)
			config.IFaceBlackList = append(config.IFaceBlackList, iFace)
			updated = true
		}
	}

	if input.DisableAutoConnect != nil && *input.DisableAutoConnect != config.DisableAutoConnect {
		if *input.DisableAutoConnect {
			log.Infof("turning off automatic connection on startup")
		} else {
			log.Infof("enabling automatic connection on startup")
		}
		config.DisableAutoConnect = *input.DisableAutoConnect
		updated = true
	}

	if input.ServerSSHAllowed != nil && *input.ServerSSHAllowed != *config.ServerSSHAllowed {
		if *input.ServerSSHAllowed {
			log.Infof("enabling SSH server")
		} else {
			log.Infof("disabling SSH server")
		}
		config.ServerSSHAllowed = input.ServerSSHAllowed
		updated = true
	}

	if input.RemoteJobsAllowed != nil && *input.RemoteJobsAllowed != *config.RemoteJobsAllowed {
		if *input.RemoteJobsAllowed {
			log.Infof("enabling remote jobs")
		} else {
			log.Infof("disabling remote jobs")
		}
		config.RemoteJobsAllowed = input.RemoteJobsAllowed
		updated = true
	}

	if input.EnableSSHRoot != nil && *input.EnableSSHRoot != *config.EnableSSHRoot {
		if *input.EnableSSHRoot {
			log.Infof("enabling SSH root login")
		} else {
			log.Infof("disabling SSH root login")
		}
		config.EnableSSHRoot = input.EnableSSHRoot
		updated = true
	}

	if input.EnableSSHSFTP != nil && *input.EnableSSHSFTP != *config.EnableSSHSFTP {
		if *input.EnableSSHSFTP {
			log.Infof("enabling SSH SFTP subsystem")
		} else {
			log.Infof("disabling SSH SFTP subsystem")
		}
		config.EnableSSHSFTP = input.EnableSSHSFTP
		updated = true
	}

	if input.EnableSSHLocalPortForwarding != nil && *input.EnableSSHLocalPortForwarding != *config.EnableSSHLocalPortForwarding {
		if *input.EnableSSHLocalPortForwarding {
			log.Infof("enabling SSH local port forwarding")
		} else {
			log.Infof("disabling SSH local port forwarding")
		}
		config.EnableSSHLocalPortForwarding = input.EnableSSHLocalPortForwarding
		updated = true
	}

	if input.EnableSSHRemotePortForwarding != nil && *input.EnableSSHRemotePortForwarding != *config.EnableSSHRemotePortForwarding {
		if *input.EnableSSHRemotePortForwarding {
			log.Infof("enabling SSH remote port forwarding")
		} else {
			log.Infof("disabling SSH remote port forwarding")
		}
		config.EnableSSHRemotePortForwarding = input.EnableSSHRemotePortForwarding
		updated = true
	}

	if input.DisableSSHAuth != nil && *input.DisableSSHAuth != *config.DisableSSHAuth {
		if *input.DisableSSHAuth {
			log.Infof("disabling SSH authentication")
		} else {
			log.Infof("enabling SSH authentication")
		}
		config.DisableSSHAuth = input.DisableSSHAuth
		updated = true
	}

	if input.SSHJWTCacheTTL != nil && *input.SSHJWTCacheTTL != *config.SSHJWTCacheTTL {
		log.Infof("updating SSH JWT cache TTL to %d seconds", *input.SSHJWTCacheTTL)
		config.SSHJWTCacheTTL = input.SSHJWTCacheTTL
		updated = true
	}

	if input.DNSRouteInterval != nil && *input.DNSRouteInterval != config.DNSRouteInterval {
		log.Infof("updating DNS route interval to %s (old value %s)",
			input.DNSRouteInterval.String(), config.DNSRouteInterval.String())
		config.DNSRouteInterval = *input.DNSRouteInterval
		updated = true
	} else if config.DNSRouteInterval == 0 {
		config.DNSRouteInterval = dynamic.DefaultInterval
		log.Infof("using default DNS route interval %s", config.DNSRouteInterval)
		updated = true
	}

	if input.DisableClientRoutes != nil && *input.DisableClientRoutes != config.DisableClientRoutes {
		if *input.DisableClientRoutes {
			log.Infof("disabling client routes")
		} else {
			log.Infof("enabling client routes")
		}
		config.DisableClientRoutes = *input.DisableClientRoutes
		updated = true
	}

	if input.DisableServerRoutes != nil && *input.DisableServerRoutes != config.DisableServerRoutes {
		if *input.DisableServerRoutes {
			log.Infof("disabling server routes")
		} else {
			log.Infof("enabling server routes")
		}
		config.DisableServerRoutes = *input.DisableServerRoutes
		updated = true
	}

	if input.DisableDNS != nil && *input.DisableDNS != config.DisableDNS {
		if *input.DisableDNS {
			log.Infof("disabling DNS configuration")
		} else {
			log.Infof("enabling DNS configuration")
		}
		config.DisableDNS = *input.DisableDNS
		updated = true
	}

	if input.DisableFirewall != nil && *input.DisableFirewall != config.DisableFirewall {
		if *input.DisableFirewall {
			log.Infof("disabling firewall configuration")
		} else {
			log.Infof("enabling firewall configuration")
		}
		config.DisableFirewall = *input.DisableFirewall
		updated = true
	}

	if input.BlockLANAccess != nil && *input.BlockLANAccess != config.BlockLANAccess {
		if *input.BlockLANAccess {
			log.Infof("blocking LAN access")
		} else {
			log.Infof("allowing LAN access")
		}
		config.BlockLANAccess = *input.BlockLANAccess
		updated = true
	}

	if input.BlockInbound != nil && *input.BlockInbound != config.BlockInbound {
		if *input.BlockInbound {
			log.Infof("blocking inbound connections")
		} else {
			log.Infof("allowing inbound connections")
		}
		config.BlockInbound = *input.BlockInbound
		updated = true
	}

	if input.DisableIPv6 != nil && *input.DisableIPv6 != config.DisableIPv6 {
		log.Infof("setting IPv6 overlay disabled=%v", *input.DisableIPv6)
		config.DisableIPv6 = *input.DisableIPv6
		updated = true
	}

	// Assigning the pointer, not writing through it: a config that carries no
	// version yet would otherwise be a nil dereference, and a panic inside a
	// request handler is not a way to fail.
	if input.SyncMessageVersion != nil && (config.SyncMessageVersion == nil || *input.SyncMessageVersion != *config.SyncMessageVersion) {
		log.Infof("setting SyncMessageVersion to %v", *input.SyncMessageVersion)
		config.SyncMessageVersion = input.SyncMessageVersion
		updated = true
	}

	if input.DisableNotifications != nil && *input.DisableNotifications != *config.DisableNotifications {
		if *input.DisableNotifications {
			log.Infof("disabling notifications")
		} else {
			log.Infof("enabling notifications")
		}
		config.DisableNotifications = input.DisableNotifications
		updated = true
	}

	// Compared, not just assigned: restating the path a config already holds
	// changes nothing, and reporting it as an update makes a caller that
	// re-sends its own configuration look like one asking to change it.
	if input.ClientCertKeyPath != "" && input.ClientCertKeyPath != config.ClientCertKeyPath {
		config.ClientCertKeyPath = input.ClientCertKeyPath
		updated = true
	}

	if input.ClientCertPath != "" && input.ClientCertPath != config.ClientCertPath {
		config.ClientCertPath = input.ClientCertPath
		updated = true
	}

	if config.ClientCertPath != "" && config.ClientCertKeyPath != "" {
		cert, err := tls.LoadX509KeyPair(config.ClientCertPath, config.ClientCertKeyPath)
		if err != nil {
			log.Error("Failed to load mTLS cert/key pair: ", err)
		} else {
			config.ClientCertKeyPair = &cert
			log.Info("Loaded client mTLS cert/key pair")
		}
	}

	if input.DNSLabels != nil && !slices.Equal(config.DNSLabels, input.DNSLabels) {
		log.Infof("updating DNS labels [ %s ] (old value: [ %s ])",
			input.DNSLabels.SafeString(),
			config.DNSLabels.SafeString())
		config.DNSLabels = input.DNSLabels
		updated = true
	}

	if input.MTU != nil && *input.MTU != config.MTU {
		log.Infof("updating MTU to %d (old value %d)", *input.MTU, config.MTU)
		config.MTU = *input.MTU
		updated = true
	} else if config.MTU == 0 {
		config.MTU = iface.DefaultMTU
		log.Infof("using default MTU %d", config.MTU)
		updated = true
	}

	// Initialise the MDM overlay to "no enforcement" so Config.Policy()
	// never returns a stale or nil policy on a freshly applied Config.
	// Lifecycle owners that want to enforce a real MDM policy invoke
	// Config.ApplyMDMPolicy(loader.Load()) after this returns.
	config.applyMDMPolicy(mdm.NewPolicy(nil))

	return updated, nil
}

// applyMDMPolicy overlays MDM-supplied values on top of the resolved Config.
// The provided Policy is also stored on the Config so callers can later query
// which fields are enforced. Invalid values (e.g. malformed URLs) are logged
// and skipped to avoid bricking the client; the field keeps its previous
// resolved value but is still marked as managed (Policy.HasKey returns true
// for the key, so per-field rejection of user writes still applies).
func (config *Config) applyMDMPolicy(policy *mdm.Policy) {
	config.policy = policy

	// DebugBundleUploadURL is a runtime-only override re-derived from MDM on
	// every apply. Resolve it unconditionally (before the IsEmpty early return)
	// so a policy that drops the key, becomes empty, or carries an invalid
	// value can never leave a previously-enforced upload target active on a
	// reused Config instance.
	config.DebugBundleUploadURL = mdmDebugBundleUploadURL(policy)

	if policy.IsEmpty() {
		return
	}

	// Helper: log the application of a single MDM-managed key. Values for
	// keys in mdm.SecretKeys are redacted.
	logApplied := func(key string, displayValue any) {
		if _, secret := mdm.SecretKeys[key]; secret {
			log.Infof("MDM override %s = ********** (secret)", key)
			return
		}
		log.Infof("MDM override %s = %v", key, displayValue)
	}

	if v, ok := policy.GetString(mdm.KeyManagementURL); ok {
		if u, err := parseURL("Management URL", v); err != nil {
			log.Warnf("MDM management URL %q invalid: %v; keeping previous value", v, err)
		} else {
			config.ManagementURL = u
			logApplied(mdm.KeyManagementURL, u.String())
		}
	}

	if v, ok := policy.GetString(mdm.KeyPreSharedKey); ok {
		// Defensive: refuse the redaction mask in case it round-tripped
		// through a manifest by mistake.
		if !isPreSharedKeyHidden(&v) {
			config.PreSharedKey = v
			logApplied(mdm.KeyPreSharedKey, "")
		}
	}

	// applyBool collapses the per-key "read + set + log" boilerplate
	// for every plain bool MDM key into a single helper. Keeps the
	// outer function's cognitive complexity below SonarCube's
	// threshold; functional behaviour is identical to the inlined
	// branches it replaces.
	applyBool := func(key string, setter func(bool)) {
		v, ok := policy.GetBool(key)
		if !ok {
			return
		}
		setter(v)
		logApplied(key, v)
	}

	applyBool(mdm.KeyAllowServerSSH, func(v bool) { bv := v; config.ServerSSHAllowed = &bv })
	applyBool(mdm.KeyRemoteJobsAllowed, func(v bool) { bv := v; config.RemoteJobsAllowed = &bv })
	applyBool(mdm.KeyDisableClientRoutes, func(v bool) { config.DisableClientRoutes = v })
	applyBool(mdm.KeyDisableServerRoutes, func(v bool) { config.DisableServerRoutes = v })
	applyBool(mdm.KeyBlockInbound, func(v bool) { config.BlockInbound = v })
	applyBool(mdm.KeyDisableAutoConnect, func(v bool) { config.DisableAutoConnect = v })
	applyBool(mdm.KeyRosenpassEnabled, func(v bool) { config.RosenpassEnabled = v })
	applyBool(mdm.KeyRosenpassPermissive, func(v bool) { config.RosenpassPermissive = v })
	applyBool(mdm.KeyEnableLocalMetrics, func(v bool) { config.LocalMetricsEnabled = v })

	if v, ok := policy.GetString(mdm.KeyLocalMetricsAddress); ok {
		config.LocalMetricsAddress = v
		logApplied(mdm.KeyLocalMetricsAddress, v)
	}

	if v, ok := policy.GetInt(mdm.KeyWireguardPort); ok {
		// REG_DWORD is 32-bit; UDP port range is 1-65535. Clamp at the
		// upper bound and reject obviously-invalid values to avoid the
		// engine binding to an unusable port if the admin pushes garbage.
		if v >= 1 && v <= 65535 {
			config.WgPort = int(v)
			logApplied(mdm.KeyWireguardPort, v)
		} else {
			log.Warnf("MDM wireguard port %d out of range [1,65535]; keeping previous value", v)
		}
	}

	if v, ok := policy.GetBool(mdm.KeyLazyConnection); ok {
		state := "off"
		if v {
			state = "on"
		}
		config.LazyConnection = state
		logApplied(mdm.KeyLazyConnection, state)
	}

}

// ValidateBundleUploadURL sanity-checks a debug-bundle upload URL. An empty
// value is accepted — the executor falls back to the default upload service. A
// non-empty value must be a well-formed https URL with a host; a malformed
// value or a plaintext scheme is rejected. It deliberately does not constrain
// which host may receive the bundle. This is the single source of truth for the
// rule, shared by the remote-job executor (client/internal) and the MDM policy
// override below so the two validation paths cannot drift.
func ValidateBundleUploadURL(raw string) error {
	if raw == "" {
		return nil
	}
	parsed, err := url.Parse(raw)
	if err != nil {
		return fmt.Errorf("parse upload URL: %w", err)
	}
	// Hostname(), not Host: an authority like ":443" is non-empty but has no
	// host, and would fail the actual upload.
	if parsed.Scheme != "https" || parsed.Hostname() == "" {
		return fmt.Errorf("upload URL must be an https URL with a host")
	}
	return nil
}

// mdmDebugBundleUploadURL resolves the MDM-enforced debug-bundle upload URL
// override from the policy, returning the empty string when the policy does
// not carry a valid KeyBundleUploadURL. An absent or invalid value fails
// closed to "" so it falls back to the management-supplied or default upload
// target rather than a previously-enforced one. The URL is never logged: it
// can embed credentials or signed query tokens (KeyBundleUploadURL is in
// mdm.SecretKeys).
func mdmDebugBundleUploadURL(policy *mdm.Policy) string {
	v, ok := policy.GetString(mdm.KeyBundleUploadURL)
	if !ok || v == "" {
		return ""
	}
	// Must be a well-formed https URL with a host, matching the client's
	// remote-job upload-URL validation (shared validator, single source of truth).
	if err := ValidateBundleUploadURL(v); err != nil {
		log.Warnf("MDM debug bundle upload URL is invalid (must be an https URL with a host); ignoring the override")
		return ""
	}
	log.Infof("MDM override %s = ********** (secret)", mdm.KeyBundleUploadURL)
	return v
}

// parseURL parses and validates the URL for the named service. The URL
// must use the http or https scheme; if no port is present, ":443" is
// appended for https or ":80" for http. The serviceName parameter is
// used to contextualise error messages. On success returns the parsed
// *url.URL; on failure returns a non-nil error.
// ParseServiceURL normalises a service URL exactly as the config layer does when
// it stores one, so callers comparing a requested URL against a stored one do not
// have to reimplement the scheme validation and default-port handling.
func ParseServiceURL(serviceName, serviceURL string) (*url.URL, error) {
	return parseURL(serviceName, serviceURL)
}

// SameServiceURL reports whether two service URLs address the same endpoint:
// same scheme, same host compared case-insensitively as DNS names are, and
// same effective port, where an absent port means the scheme's default.
//
// This is the one comparison every caller deciding "did this URL change?" must
// use. A string comparison answers a different question: "https://host",
// "https://host/" and "https://HOST:443" are one endpoint written three ways,
// and reading them as three values makes a client that restates its own
// management URL look like a client asking to be repointed. A nil operand
// matches only another nil one.
//
// The path plays no part: a management URL is dialed, and only its host and
// port are. util.SameServiceURL is this comparison plus the path, which is
// what SameServiceURLIncludingPath needs and delegates to.
func SameServiceURL(a, b *url.URL) bool {
	if a == nil || b == nil {
		return a == b
	}

	return strings.EqualFold(a.Scheme, b.Scheme) &&
		strings.EqualFold(a.Hostname(), b.Hostname()) &&
		util.ServiceURLPort(a) == util.ServiceURLPort(b)
}

// SameServiceURLIncludingPath is SameServiceURL plus everything a URL carries
// past its endpoint: path, query, fragment and userinfo.
//
// Use it for a URL that gets opened rather than dialed. The admin panel can
// live under a path, so two URLs with the same endpoint and different paths are
// two different panels — where for a URL the client dials over gRPC only the
// endpoint is ever used. Equivalent spellings still compare equal: a missing
// path and "/" are the same root, and so is a trailing slash on any path.
func SameServiceURLIncludingPath(a, b *url.URL) bool {
	if a == nil || b == nil {
		return a == b
	}

	return util.SameServiceURL(a, b) &&
		a.RawQuery == b.RawQuery &&
		a.Fragment == b.Fragment &&
		a.User.String() == b.User.String()
}

func parseURL(serviceName, serviceURL string) (*url.URL, error) {
	parsedMgmtURL, err := url.ParseRequestURI(serviceURL)
	if err != nil {
		log.Errorf("failed parsing %s URL %s: [%s]", serviceName, serviceURL, err.Error())
		return nil, err
	}

	if parsedMgmtURL.Scheme != "https" && parsedMgmtURL.Scheme != "http" {
		return nil, fmt.Errorf(
			"invalid %s URL provided %s. Supported format [http|https]://[host]:[port]",
			serviceName, serviceURL)
	}

	if parsedMgmtURL.Port() == "" {
		switch parsedMgmtURL.Scheme {
		case "https":
			parsedMgmtURL.Host += ":443"
		case "http":
			parsedMgmtURL.Host += ":80"
		default:
			log.Infof("unable to determine a default port for schema %s in URL %s", parsedMgmtURL.Scheme, serviceURL)
		}
	}

	return parsedMgmtURL, err
}

// generateKey generates a new Wireguard private key
func generateKey() string {
	key, err := wgtypes.GeneratePrivateKey()
	if err != nil {
		panic(err)
	}
	return key.String()
}

// don't overwrite pre-shared key if we receive asterisks from UI
func isPreSharedKeyHidden(preSharedKey *string) bool {
	if preSharedKey != nil && *preSharedKey == "**********" {
		return true
	}
	return false
}

// WouldChange reports whether applying input would modify any field the
// config persists, leaving the receiver untouched. It is the dry-run half of
// UpdateConfig and reuses the very same diff logic (Config.apply), so a
// caller asking "is this a settings change?" cannot drift from what an
// actual update would do, nor go stale when a new field is added.
//
// A redacted pre-shared key is collapsed to "unset" exactly as
// UpdateOrCreateConfig does, so a UI that round-trips the mask is not read as
// a request for a new key.
//
// A nil receiver means the profile holds no config yet, so the baseline is the
// config the daemon would create for it: input values matching those defaults
// change nothing, anything else does.
func (config *Config) WouldChange(input ConfigInput) (bool, error) {
	probe := config.clone()
	if probe == nil {
		baseline, err := newDryRunBaseline(input.ConfigPath)
		if err != nil {
			return true, fmt.Errorf("build default config baseline: %w", err)
		}
		probe = baseline
	}

	// Normalize before measuring. apply() reports two different things through
	// one bool: an input that changed a value, and a field it had to fill in
	// because the config carried none. Only the first is a settings change, so
	// the filling-in gets a pass of its own whose verdict is discarded, and the
	// pass that answers the caller runs against a config with nothing left to
	// fill in.
	//
	// Readers already hand out normalized configs — readConfig applies an empty
	// input for this very reason — so this is normally a no-op. But a gate that
	// refuses a request must not depend on where its caller got the config
	// from, and it must not start reading "this profile predates a field" as
	// "the caller asked for a change" the day someone adds one.
	if _, err := probe.apply(ConfigInput{ConfigPath: input.ConfigPath}); err != nil {
		return true, fmt.Errorf("normalize the config to diff against: %w", err)
	}

	if isPreSharedKeyHidden(input.PreSharedKey) {
		input.PreSharedKey = nil
	}

	return probe.apply(input)
}

// newDryRunBaseline builds the config a brand-new profile would start from, for
// a dry run to compare an input against. It is createNewConfig without the
// identity: this config exists only to be compared against and thrown away, and
// no ConfigInput field maps to either key.
func newDryRunBaseline(configPath string) (*Config, error) {
	baseline := newConfigSkeleton()

	if _, err := baseline.apply(ConfigInput{ConfigPath: configPath}); err != nil {
		return nil, err
	}

	return baseline, nil
}

// clone returns a copy of the config that apply can be run against without the
// original observing the writes, or nil for a nil receiver. Only what apply
// mutates in place needs detaching, which is the slices it replaces or appends
// to: every pointer field it touches is reassigned rather than written through,
// and ClientCertKeyPair is only overwritten.
func (config *Config) clone() *Config {
	if config == nil {
		return nil
	}

	probe := *config
	probe.IFaceBlackList = slices.Clone(config.IFaceBlackList)
	probe.NATExternalIPs = slices.Clone(config.NATExternalIPs)
	probe.DNSLabels = slices.Clone(config.DNSLabels)
	return &probe
}

// UpdateConfig update existing configuration according to input configuration and return with the configuration
func UpdateConfig(input ConfigInput) (*Config, error) {
	configExists, err := fileExists(input.ConfigPath)
	if err != nil {
		return nil, fmt.Errorf("failed to check if config file exists: %w", err)
	}
	if !configExists {
		return nil, fmt.Errorf("config file %s does not exist", input.ConfigPath)
	}

	// A UI that round-trips the mask GetConfig hands it back is asking to keep
	// the stored key, not to set the mask as the new one. UpdateOrCreateConfig
	// and DirectUpdateOrCreateConfig already collapse it; this one did not, so
	// the same round-trip through SetConfig replaced the key with asterisks.
	if isPreSharedKeyHidden(input.PreSharedKey) {
		input.PreSharedKey = nil
	}

	return update(input)
}

// UpdateOrCreateConfig reads existing config or generates a new one
func UpdateOrCreateConfig(input ConfigInput) (*Config, error) {
	configExists, err := fileExists(input.ConfigPath)
	if err != nil {
		return nil, fmt.Errorf("failed to check if config file exists: %w", err)
	}
	if !configExists {
		log.Infof("generating new config %s", input.ConfigPath)
		cfg, err := createProvisionedConfig(input)
		if err != nil {
			return nil, err
		}
		err = util.WriteJsonWithRestrictedPermission(context.Background(), input.ConfigPath, cfg)
		return cfg, err
	}

	if isPreSharedKeyHidden(input.PreSharedKey) {
		input.PreSharedKey = nil
	}
	err = util.EnforcePermission(input.ConfigPath)
	if err != nil {
		log.Errorf("failed to enforce permission on config dir: %v", err)
	}
	return update(input)
}

func update(input ConfigInput) (*Config, error) {
	config := &Config{}

	if _, err := util.ReadJson(input.ConfigPath, config); err != nil {
		return nil, err
	}

	// A write path is a provisioning point: a stored profile can legitimately
	// carry no identity (a mobile logout clears the keys in place), and the
	// next config write is what has to mint a new one. Reads leave that alone.
	identityGenerated, err := config.EnsureIdentity()
	if err != nil {
		return nil, err
	}

	updated, err := config.apply(input)
	if err != nil {
		return nil, err
	}

	if updated || identityGenerated {
		if err := util.WriteJson(context.Background(), input.ConfigPath, config); err != nil {
			return nil, err
		}
	}

	return config, nil
}

// GetExistingConfig reads and returns the config if it exists on disk. Fails otherwise.
func GetExistingConfig(configPath string) (*Config, error) {
	return readConfig(configPath, false)
}

// UpdateOldManagementURL checks whether client can switch to the new Management URL with port 443 and the management domain.
// If it can switch, then it updates the config and returns a new one. Otherwise, it returns the provided config.
// The check is performed only for the NetBird's managed version.
func UpdateOldManagementURL(ctx context.Context, config *Config, configPath string) (*Config, error) {
	defaultManagementURL, err := parseURL("Management URL", DefaultManagementURL)
	if err != nil {
		return nil, err
	}

	parsedOldDefaultManagementURL, err := parseURL("Management URL", oldDefaultManagementURL)
	if err != nil {
		return nil, err
	}

	if config.ManagementURL.Hostname() != defaultManagementURL.Hostname() &&
		config.ManagementURL.Hostname() != parsedOldDefaultManagementURL.Hostname() {
		// only do the check for the NetBird's managed version
		return config, nil
	}

	var mgmTlsEnabled bool
	if config.ManagementURL.Scheme == "https" {
		mgmTlsEnabled = true
	}

	if !mgmTlsEnabled {
		// only do the check for HTTPs scheme (the hosted version of the Management service is always HTTPs)
		return config, nil
	}

	if config.ManagementURL.Port() != managementLegacyPortString &&
		config.ManagementURL.Hostname() == defaultManagementURL.Hostname() {
		return config, nil
	}

	newURL, err := parseURL("Management URL", fmt.Sprintf("%s://%s", config.ManagementURL.Scheme, net.JoinHostPort(defaultManagementURL.Hostname(), "443")))
	if err != nil {
		return nil, err
	}
	// here we check whether we could switch from the legacy 33073 port to the new 443
	log.Infof("attempting to switch from the legacy Management URL %s to the new one %s",
		config.ManagementURL.String(), newURL.String())
	key, err := wgtypes.ParseKey(config.PrivateKey)
	if err != nil {
		log.Infof("couldn't switch to the new Management %s", newURL.String())
		return config, err
	}

	client, err := newMgmProber(ctx, newURL.Host, key, mgmTlsEnabled)
	if err != nil {
		log.Infof("couldn't switch to the new Management %s", newURL.String())
		return config, err
	}
	defer func() {
		if err := client.Close(); err != nil {
			log.Warnf("failed to close the Management service client %v", err)
		}
	}()

	// gRPC check
	if err = client.HealthCheck(); err != nil {
		log.Infof("couldn't switch to the new Management %s", newURL.String())
		return nil, err
	}

	// everything is alright => update the config
	newConfig, err := UpdateConfig(ConfigInput{
		ManagementURL: newURL.String(),
		ConfigPath:    configPath,
	})
	if err != nil {
		log.Infof("couldn't switch to the new Management %s", newURL.String())
		return config, fmt.Errorf("failed updating config file: %v", err)
	}
	log.Infof("successfully switched to the new Management URL: %s", newURL.String())

	return newConfig, nil
}

// CreateInMemoryConfig generate a new config but do not write out it to the store.
// It carries an identity: callers connect with what they get back.
func CreateInMemoryConfig(input ConfigInput) (*Config, error) {
	return createProvisionedConfig(input)
}

// ReadOrGenerateConfig reads the profile config at configPath if it exists, or
// generates one in memory from the defaults.
func ReadOrGenerateConfig(configPath string) (*Config, error) {
	return readConfig(configPath, true)
}

// readConfig reads the profile config at configPath. createIfMissing resolves a
// default config in memory when the file is absent, rather than erroring.
//
// Reads are pure. This used to write the config back whenever apply() had to
// fill in a default the file was missing, which quietly made every reader a
// writer: a gate deciding whether to refuse a request, a UI listing profiles,
// a mobile getter reading a single preference.
func readConfig(configPath string, createIfMissing bool) (*Config, error) {
	configExists, err := fileExists(configPath)
	if err != nil {
		return nil, fmt.Errorf("failed to check if config file exists: %w", err)
	}

	if configExists {
		err := util.EnforcePermission(configPath)
		if err != nil {
			log.Errorf("failed to enforce permission on config dir: %v", err)
		}

		config := &Config{}
		if _, err := util.ReadJson(configPath, config); err != nil {
			return nil, err
		}
		// initialize through apply() without changes
		if _, err := config.apply(ConfigInput{}); err != nil {
			return nil, err
		}

		return config, nil
	} else if !createIfMissing {
		return nil, fmt.Errorf("config file %s does not exist", configPath)
	}

	return createNewConfig(ConfigInput{ConfigPath: configPath})
}

// WriteOutConfig write put the prepared config to the given path
func WriteOutConfig(path string, config *Config) error {
	return util.WriteJson(context.Background(), path, config)
}

// DirectWriteOutConfig writes config directly without atomic temp file operations.
// Use this on platforms where atomic writes are blocked (e.g., tvOS sandbox).
func DirectWriteOutConfig(path string, config *Config) error {
	return util.DirectWriteJson(context.Background(), path, config)
}

// DirectUpdateOrCreateConfig is like UpdateOrCreateConfig but uses direct (non-atomic) writes.
// Use this on platforms where atomic writes are blocked (e.g., tvOS sandbox).
func DirectUpdateOrCreateConfig(input ConfigInput) (*Config, error) {
	configExists, err := fileExists(input.ConfigPath)
	if err != nil {
		return nil, fmt.Errorf("failed to check if config file exists: %w", err)
	}
	if !configExists {
		log.Infof("generating new config %s", input.ConfigPath)
		cfg, err := createProvisionedConfig(input)
		if err != nil {
			return nil, err
		}
		err = util.DirectWriteJson(context.Background(), input.ConfigPath, cfg)
		return cfg, err
	}

	if isPreSharedKeyHidden(input.PreSharedKey) {
		input.PreSharedKey = nil
	}

	// Enforce permissions on existing config files (same as UpdateOrCreateConfig)
	if err := util.EnforcePermission(input.ConfigPath); err != nil {
		log.Errorf("failed to enforce permission on config file: %v", err)
	}

	return directUpdate(input)
}

func directUpdate(input ConfigInput) (*Config, error) {
	config := &Config{}

	if _, err := util.ReadJson(input.ConfigPath, config); err != nil {
		return nil, err
	}

	// Same provisioning point as update(); see the note there.
	identityGenerated, err := config.EnsureIdentity()
	if err != nil {
		return nil, err
	}

	updated, err := config.apply(input)
	if err != nil {
		return nil, err
	}

	if updated || identityGenerated {
		if err := util.DirectWriteJson(context.Background(), input.ConfigPath, config); err != nil {
			return nil, err
		}
	}

	return config, nil
}

// ConfigToJSON serializes a Config struct to a JSON string.
// This is useful for exporting config to alternative storage mechanisms
// (e.g., UserDefaults on tvOS where file writes are blocked).
func ConfigToJSON(config *Config) (string, error) {
	bs, err := json.MarshalIndent(config, "", "    ")
	if err != nil {
		return "", err
	}
	return string(bs), nil
}

// ConfigFromJSON deserializes a JSON string to a Config struct.
// This is useful for restoring config from alternative storage mechanisms.
// After unmarshaling, defaults are applied to ensure the config is fully
// initialized.
//
// The peer identity is deliberately none of its business, in either direction.
// It does not generate one: a read cannot hand back keys that nothing will
// write down (see ReadOrGenerateConfig). Nor does it refuse a document that
// carries none, because a config legitimately has no identity between a logout
// and the next login — mobile logout clears both keys in place — and this is
// also the deserializer the iOS SDK copies a config through. Whoever goes on
// to connect is where an absent identity has to be answered.
func ConfigFromJSON(jsonStr string) (*Config, error) {
	config := &Config{}
	err := json.Unmarshal([]byte(jsonStr), config)
	if err != nil {
		return nil, err
	}

	// Apply defaults to ensure required fields are initialized.
	// This mirrors what readConfig does after loading from file.
	if _, err := config.apply(ConfigInput{}); err != nil {
		return nil, fmt.Errorf("failed to apply defaults to config: %w", err)
	}

	return config, nil
}