package peer

import (
	"context"
	"fmt"
	"net"
	"net/netip"
	"slices"
	"strings"
	"time"

	log "github.com/sirupsen/logrus"

	"github.com/netbirdio/netbird/management/server/util"
	"github.com/netbirdio/netbird/shared/management/http/api"
)

// Peer capability constants mirror the proto enum values.
const (
	PeerCapabilitySourcePrefixes int32 = 1
	PeerCapabilityIPv6Overlay    int32 = 2
)

// Peer represents a machine connected to the network.
// The Peer is a WireGuard peer identified by a public key
type Peer struct {
	// ID is an internal ID of the peer
	ID string `gorm:"primaryKey"`
	// AccountID is a reference to Account that this object belongs
	AccountID string `json:"-" gorm:"index"`
	// WireGuard public key
	Key string // uniqueness index (check migrations)
	// IP address of the Peer
	IP netip.Addr `gorm:"serializer:json"` // uniqueness index per accountID (check migrations)
	// IPv6 overlay address of the Peer, zero value if IPv6 is not enabled for the account.
	IPv6 netip.Addr `gorm:"serializer:json"`
	// Meta is a Peer system meta data
	Meta PeerSystemMeta `gorm:"embedded;embeddedPrefix:meta_"`
	// ProxyMeta is metadata related to proxy peers
	ProxyMeta ProxyMeta `gorm:"embedded;embeddedPrefix:proxy_meta_"`
	// Name is peer's name (machine name)
	Name string `gorm:"index"`
	// DNSLabel is the parsed peer name for domain resolution. It is used to form an FQDN by appending the account's
	// domain to the peer label. e.g. peer-dns-label.netbird.cloud
	DNSLabel string // uniqueness index per accountID (check migrations)
	// Status peer's management connection status
	Status *PeerStatus `gorm:"embedded;embeddedPrefix:peer_status_"`
	// The user ID that registered the peer
	UserID string
	// SSHKey is a public SSH key of the peer
	SSHKey string
	// SSHEnabled indicates whether SSH server is enabled on the peer
	SSHEnabled bool
	// LoginExpirationEnabled indicates whether peer's login expiration is enabled and once expired the peer has to re-login.
	// Works with LastLogin
	LoginExpirationEnabled bool

	InactivityExpirationEnabled bool
	// LastLogin the time when peer performed last login operation
	LastLogin *time.Time
	// CreatedAt records the time the peer was created
	CreatedAt time.Time
	// Indicate ephemeral peer attribute
	Ephemeral bool `gorm:"index"`

	// Geo location based on connection IP
	Location Location `gorm:"embedded;embeddedPrefix:location_"`

	// ExtraDNSLabels is a list of additional DNS labels that can be used to resolve the peer
	ExtraDNSLabels []string `gorm:"serializer:json"`
	// AllowExtraDNSLabels indicates whether the peer allows extra DNS labels to be used for resolving the peer
	AllowExtraDNSLabels bool
}

type ProxyMeta struct {
	Embedded bool   `gorm:"index"`
	Cluster  string `gorm:"index"`
}

type PeerStatus struct { //nolint:revive
	// LastSeen is the last time the peer status was updated (i.e. the last
	// time we observed the peer being alive on a sync stream). Written by
	// the database (CURRENT_TIMESTAMP) — callers do not supply it.
	LastSeen time.Time
	// SessionStartedAt records when the currently-active sync stream began,
	// stored as Unix nanoseconds. It acts as the optimistic-locking token
	// for status updates: a stream is only allowed to mutate the peer's
	// status when its own token strictly exceeds the stored token (when connecting)
	// or matches it exactly (for disconnects). Zero means "no
	// active session". Integer nanoseconds are used so equality is
	// precision-safe across drivers, and so the predicates compose to a
	// single bigint comparison.
	SessionStartedAt int64 `gorm:"not null;default:0"`
	// Connected indicates whether peer is connected to the management service or not
	Connected bool
	// LoginExpired
	LoginExpired bool
	// RequiresApproval indicates whether peer requires approval or not
	RequiresApproval bool
}

// Location is a geo location information of a Peer based on public connection IP
type Location struct {
	ConnectionIP net.IP `gorm:"serializer:json"` // from grpc peer or reverse proxy headers depends on setup
	CountryCode  string
	CityName     string
	GeoNameID    uint // city level geoname id
}

// NetworkAddress is the IP address with network and MAC address of a network interface
type NetworkAddress struct {
	NetIP netip.Prefix `gorm:"serializer:json"`
	Mac   string
}

// Environment is a system environment information
type Environment struct {
	Cloud    string
	Platform string
}

// File is a file on the system.
type File struct {
	Path             string
	Exist            bool
	ProcessIsRunning bool
}

// Flags defines a set of options to control feature behavior
type Flags struct {
	RosenpassEnabled    bool
	RosenpassPermissive bool
	ServerSSHAllowed    bool

	DisableClientRoutes bool
	DisableServerRoutes bool
	DisableDNS          bool
	DisableFirewall     bool
	BlockLANAccess      bool
	BlockInbound        bool
	DisableIPv6         bool

	LazyConnectionEnabled bool
}

// PeerSystemMeta is a metadata of a Peer machine system
type PeerSystemMeta struct { //nolint:revive
	Hostname           string
	GoOS               string
	Kernel             string
	Core               string
	Platform           string
	OS                 string
	OSVersion          string
	WtVersion          string
	UIVersion          string
	KernelVersion      string
	NetworkAddresses   []NetworkAddress `gorm:"serializer:json"`
	SystemSerialNumber string
	SystemProductName  string
	SystemManufacturer string
	Environment        Environment `gorm:"serializer:json"`
	Flags              Flags       `gorm:"serializer:json"`
	Files              []File      `gorm:"serializer:json"`
	Capabilities       []int32     `gorm:"serializer:json"`
}

func (p PeerSystemMeta) isEqual(other PeerSystemMeta) bool {
	return len(metaDiff(p, other)) == 0
}

func (p PeerSystemMeta) isEmpty() bool {
	return p.Hostname == "" &&
		p.GoOS == "" &&
		p.Kernel == "" &&
		p.Core == "" &&
		p.Platform == "" &&
		p.OS == "" &&
		p.OSVersion == "" &&
		p.WtVersion == "" &&
		p.UIVersion == "" &&
		p.KernelVersion == "" &&
		len(p.NetworkAddresses) == 0 &&
		p.SystemSerialNumber == "" &&
		p.SystemProductName == "" &&
		p.SystemManufacturer == "" &&
		p.Environment.Cloud == "" &&
		p.Environment.Platform == "" &&
		len(p.Files) == 0
}

// AddedWithSSOLogin indicates whether this peer has been added with an SSO login by a user.
func (p *Peer) AddedWithSSOLogin() bool {
	return p.UserID != ""
}

// HasCapability reports whether the peer has the given capability.
func (p *Peer) HasCapability(capability int32) bool {
	return slices.Contains(p.Meta.Capabilities, capability)
}

// SupportsIPv6 reports whether the peer supports IPv6 overlay.
func (p *Peer) SupportsIPv6() bool {
	return !p.Meta.Flags.DisableIPv6 && p.HasCapability(PeerCapabilityIPv6Overlay)
}

// SupportsSourcePrefixes reports whether the peer reads SourcePrefixes.
func (p *Peer) SupportsSourcePrefixes() bool {
	return p.HasCapability(PeerCapabilitySourcePrefixes)
}

func capabilitiesEqual(a, b []int32) bool {
	if len(a) != len(b) {
		return false
	}
	set := make(map[int32]struct{}, len(a))
	for _, c := range a {
		set[c] = struct{}{}
	}
	for _, c := range b {
		if _, ok := set[c]; !ok {
			return false
		}
	}
	return true
}

// Copy copies Peer object
func (p *Peer) Copy() *Peer {
	peerStatus := p.Status
	if peerStatus != nil {
		peerStatus = p.Status.Copy()
	}
	return &Peer{
		ID:                          p.ID,
		AccountID:                   p.AccountID,
		Key:                         p.Key,
		IP:                          p.IP,
		IPv6:                        p.IPv6,
		Meta:                        p.Meta,
		Name:                        p.Name,
		DNSLabel:                    p.DNSLabel,
		Status:                      peerStatus,
		UserID:                      p.UserID,
		SSHKey:                      p.SSHKey,
		SSHEnabled:                  p.SSHEnabled,
		LoginExpirationEnabled:      p.LoginExpirationEnabled,
		LastLogin:                   p.LastLogin,
		CreatedAt:                   p.CreatedAt,
		Ephemeral:                   p.Ephemeral,
		ProxyMeta:                   p.ProxyMeta,
		Location:                    p.Location,
		InactivityExpirationEnabled: p.InactivityExpirationEnabled,
		ExtraDNSLabels:              slices.Clone(p.ExtraDNSLabels),
		AllowExtraDNSLabels:         p.AllowExtraDNSLabels,
	}
}

// UpdateMetaIfNew updates peer's system metadata and connection geo location if
// new information is provided. newLocation is the geo location resolved from the
// peer's current connection IP, or nil when there is nothing to apply (geo
// disabled, no real IP, or the IP is unchanged); the caller owns the expensive
// lookup and the same-IP guard. It returns a MetaDiff describing what changed;
// diff.Updated() reports whether the peer needs to be persisted.
func (p *Peer) UpdateMetaIfNew(ctx context.Context, meta PeerSystemMeta, newLocation *Location) MetaDiff {
	if meta.isEmpty() {
		return MetaDiff{}
	}

	versionChanged := p.Meta.WtVersion != meta.WtVersion

	// Avoid overwriting UIVersion if the update was triggered sole by the CLI client
	if meta.UIVersion == "" {
		meta.UIVersion = p.Meta.UIVersion
	}

	oldVersion := p.Meta.WtVersion

	diff := diffMeta(p.Meta, meta)
	if diff.Any() {
		p.Meta = meta
	}
	diff.VersionChanged = versionChanged

	locationInfo := ""
	if newLocation != nil {
		p.Location = *newLocation
		diff.LocationChanged = true
		locationInfo = fmt.Sprintf("location changed to %s, ", newLocation.ConnectionIP)
	}

	versionInfo := ""
	if diff.VersionChanged {
		versionInfo = fmt.Sprintf("version changed: %s -> %s, ", oldVersion, meta.WtVersion)
	}

	if diff.Any() || diff.VersionChanged || diff.LocationChanged {
		log.WithContext(ctx).
			Debugf("peer meta updated, %s%s%d field(s) changed: %s", versionInfo, locationInfo, len(diff.Changed), strings.Join(diff.Changed, ", "))
	}

	return diff
}

// MetaDiff records which PeerSystemMeta fields differ between two metas. Each bool
// maps to a single struct field, except Environment, which is split into Cloud and
// Platform. Changed holds the human-readable `field: <old> -> <new>` entries so the
// existing log line and isEqual can be derived from the same comparison.
//
// VersionChanged and LocationChanged sit outside the per-meta-field set:
// VersionChanged tracks the WireGuard client version specifically (compared before
// the UIVersion fixup, to signal client upgrades) and LocationChanged tracks the
// peer's connection geo location, which lives on Peer rather than PeerSystemMeta.
// Neither contributes an entry to Changed, so the field-coverage accounting stays
// driven purely by the PeerSystemMeta comparison.
type MetaDiff struct {
	Hostname            bool
	GoOS                bool
	Kernel              bool
	KernelVersion       bool
	Core                bool
	Platform            bool
	OS                  bool
	OSVersion           bool
	WtVersion           bool
	UIVersion           bool
	SystemSerialNumber  bool
	SystemProductName   bool
	SystemManufacturer  bool
	EnvironmentCloud    bool
	EnvironmentPlatform bool
	Flags               bool
	Capabilities        bool
	NetworkAddresses    bool
	Files               bool

	VersionChanged  bool
	LocationChanged bool

	Changed []string
}

// Any reports whether any PeerSystemMeta field changed.
func (d MetaDiff) Any() bool {
	return len(d.Changed) != 0
}

// Updated reports whether the peer needs to be persisted: any meta field changed
// or the geo location changed. The version flag alone does not imply a write,
// since a version change is also reflected in the WtVersion meta field.
func (d MetaDiff) Updated() bool {
	return d.Any() || d.LocationChanged || d.VersionChanged
}

func metaDiff(oldMeta, newMeta PeerSystemMeta) []string {
	return diffMeta(oldMeta, newMeta).Changed
}

// diffMeta compares two metas field by field, returning both a per-field flag set
// (for callers that need to know exactly what changed, e.g. matching against
// posture checks) and the human-readable Changed list. It is the single source of
// truth for meta comparison: isEqual reports equality as an empty diff, so the log
// line, the change decision, and the flags can never disagree.
func diffMeta(oldMeta, newMeta PeerSystemMeta) MetaDiff {
	var d MetaDiff
	add := func(field string, oldVal, newVal any) {
		d.Changed = append(d.Changed, fmt.Sprintf("%s: %v -> %v", field, oldVal, newVal))
	}

	if oldMeta.Hostname != newMeta.Hostname {
		d.Hostname = true
		add("hostname", oldMeta.Hostname, newMeta.Hostname)
	}
	if oldMeta.GoOS != newMeta.GoOS {
		d.GoOS = true
		add("goos", oldMeta.GoOS, newMeta.GoOS)
	}
	if oldMeta.Kernel != newMeta.Kernel {
		d.Kernel = true
		add("kernel", oldMeta.Kernel, newMeta.Kernel)
	}
	if oldMeta.KernelVersion != newMeta.KernelVersion {
		d.KernelVersion = true
		add("kernel_version", oldMeta.KernelVersion, newMeta.KernelVersion)
	}
	if oldMeta.Core != newMeta.Core {
		d.Core = true
		add("core", oldMeta.Core, newMeta.Core)
	}
	if oldMeta.Platform != newMeta.Platform {
		d.Platform = true
		add("platform", oldMeta.Platform, newMeta.Platform)
	}
	if oldMeta.OS != newMeta.OS {
		d.OS = true
		add("os", oldMeta.OS, newMeta.OS)
	}
	if oldMeta.OSVersion != newMeta.OSVersion {
		d.OSVersion = true
		add("os_version", oldMeta.OSVersion, newMeta.OSVersion)
	}
	if oldMeta.WtVersion != newMeta.WtVersion {
		d.WtVersion = true
		add("wt_version", oldMeta.WtVersion, newMeta.WtVersion)
	}
	if oldMeta.UIVersion != newMeta.UIVersion {
		d.UIVersion = true
		add("ui_version", oldMeta.UIVersion, newMeta.UIVersion)
	}
	if oldMeta.SystemSerialNumber != newMeta.SystemSerialNumber {
		d.SystemSerialNumber = true
		add("system_serial_number", oldMeta.SystemSerialNumber, newMeta.SystemSerialNumber)
	}
	if oldMeta.SystemProductName != newMeta.SystemProductName {
		d.SystemProductName = true
		add("system_product_name", oldMeta.SystemProductName, newMeta.SystemProductName)
	}
	if oldMeta.SystemManufacturer != newMeta.SystemManufacturer {
		d.SystemManufacturer = true
		add("system_manufacturer", oldMeta.SystemManufacturer, newMeta.SystemManufacturer)
	}
	if oldMeta.Environment.Cloud != newMeta.Environment.Cloud {
		d.EnvironmentCloud = true
		add("environment_cloud", oldMeta.Environment.Cloud, newMeta.Environment.Cloud)
	}
	if oldMeta.Environment.Platform != newMeta.Environment.Platform {
		d.EnvironmentPlatform = true
		add("environment_platform", oldMeta.Environment.Platform, newMeta.Environment.Platform)
	}
	if !oldMeta.Flags.isEqual(newMeta.Flags) {
		d.Flags = true
		add("flags", fmt.Sprintf("%+v", oldMeta.Flags), fmt.Sprintf("%+v", newMeta.Flags))
	}
	if !capabilitiesEqual(oldMeta.Capabilities, newMeta.Capabilities) {
		d.Capabilities = true
		add("capabilities", oldMeta.Capabilities, newMeta.Capabilities)
	}

	if !sameMultiset(oldMeta.NetworkAddresses, newMeta.NetworkAddresses) {
		d.NetworkAddresses = true
		add("network_addresses", fmt.Sprintf("%v", oldMeta.NetworkAddresses), fmt.Sprintf("%v", newMeta.NetworkAddresses))
	}

	if !sameMultiset(oldMeta.Files, newMeta.Files) {
		d.Files = true
		add("files", fmt.Sprintf("%v", oldMeta.Files), fmt.Sprintf("%v", newMeta.Files))
	}

	return d
}

// sameMultiset reports whether two slices contain the same elements with the
// same multiplicity, ignoring order. The element type is the comparison key, so
// every field participates in equality.
func sameMultiset[T comparable](a, b []T) bool {
	if len(a) != len(b) {
		return false
	}
	counts := make(map[T]int, len(a))
	for _, v := range a {
		counts[v]++
	}
	for _, v := range b {
		counts[v]--
		if counts[v] == 0 {
			delete(counts, v)
		}
	}
	return len(counts) == 0
}

// GetLastLogin returns the last login time of the peer.
func (p *Peer) GetLastLogin() time.Time {
	if p.LastLogin != nil {
		return *p.LastLogin
	}
	return time.Time{}

}

// MarkLoginExpired marks peer's status expired or not
func (p *Peer) MarkLoginExpired(expired bool) {
	newStatus := p.Status.Copy()
	newStatus.LoginExpired = expired
	if expired {
		newStatus.Connected = false
	}
	p.Status = newStatus
}

// SessionExpired indicates whether the peer's session has expired or not.
// If Peer.LastLogin plus the expiresIn duration has happened already; then session has expired.
// Return true if a session has expired, false otherwise, and time left to expiration (negative when expired).
// Session expiration can be disabled/enabled on a Peer level via Peer.LoginExpirationEnabled property.
// Session expiration can also be disabled/enabled globally on the Account level via Settings.PeerLoginExpirationEnabled.
// Only peers added by interactive SSO login can be expired.
func (p *Peer) SessionExpired(expiresIn time.Duration) (bool, time.Duration) {
	if !p.AddedWithSSOLogin() || !p.InactivityExpirationEnabled || p.Status.Connected {
		return false, 0
	}
	expiresAt := p.Status.LastSeen.Add(expiresIn)
	now := time.Now()
	timeLeft := expiresAt.Sub(now)
	return timeLeft <= 0, timeLeft
}

// LoginExpired indicates whether the peer's login has expired or not.
// If Peer.LastLogin plus the expiresIn duration has happened already; then login has expired.
// Return true if a login has expired, false otherwise, and time left to expiration (negative when expired).
// Login expiration can be disabled/enabled on a Peer level via Peer.LoginExpirationEnabled property.
// Login expiration can also be disabled/enabled globally on the Account level via Settings.PeerLoginExpirationEnabled.
// Only peers added by interactive SSO login can be expired.
func (p *Peer) LoginExpired(expiresIn time.Duration) (bool, time.Duration) {
	if !p.AddedWithSSOLogin() || !p.LoginExpirationEnabled {
		return false, 0
	}
	expiresAt := p.GetLastLogin().Add(expiresIn)
	now := time.Now()
	timeLeft := expiresAt.Sub(now)
	return timeLeft <= 0, timeLeft
}

// SessionExpiresAt returns the absolute UTC instant at which the peer's SSO
// session expires, derived from LastLogin and the account-level
// PeerLoginExpiration setting. Returns the zero value when login expiration
// does not apply (peer not SSO-registered, peer-level toggle off, or account
// expiry disabled). Callers should treat the zero value as "no deadline".
func (p *Peer) SessionExpiresAt(accountExpirationEnabled bool, expiresIn time.Duration) time.Time {
	if !accountExpirationEnabled || !p.AddedWithSSOLogin() || !p.LoginExpirationEnabled {
		return time.Time{}
	}
	last := p.GetLastLogin()
	if last.IsZero() {
		return time.Time{}
	}
	return last.Add(expiresIn).UTC()
}

// FQDN returns peers FQDN combined of the peer's DNS label and the system's DNS domain
func (p *Peer) FQDN(dnsDomain string) string {
	if dnsDomain == "" {
		return ""
	}
	return p.DNSLabel + "." + dnsDomain
}

// EventMeta returns activity event meta related to the peer
func (p *Peer) EventMeta(dnsDomain string) map[string]any {
	meta := map[string]any{"name": p.Name, "fqdn": p.FQDN(dnsDomain), "ip": p.IP, "created_at": p.CreatedAt,
		"location_city_name": p.Location.CityName, "location_country_code": p.Location.CountryCode,
		"location_geo_name_id": p.Location.GeoNameID, "location_connection_ip": p.Location.ConnectionIP}
	if p.IPv6.IsValid() {
		meta["ipv6"] = p.IPv6.String()
	}
	return meta
}

// Copy PeerStatus. SessionStartedAt must be propagated so clone-based
// callers (Peer.Copy, MarkLoginExpired, UpdateLastLogin) don't silently
// reset the fencing token to zero — that would let any subsequent
// SavePeerStatus write reopen the optimistic-lock window.
func (p *PeerStatus) Copy() *PeerStatus {
	return &PeerStatus{
		LastSeen:         p.LastSeen,
		SessionStartedAt: p.SessionStartedAt,
		Connected:        p.Connected,
		LoginExpired:     p.LoginExpired,
		RequiresApproval: p.RequiresApproval,
	}
}

// UpdateLastLogin and set login expired false
func (p *Peer) UpdateLastLogin() *Peer {
	p.LastLogin = util.ToPtr(time.Now().UTC())
	newStatus := p.Status.Copy()
	newStatus.LoginExpired = false
	p.Status = newStatus
	return p
}

func (p *Peer) FromAPITemporaryAccessRequest(a *api.PeerTemporaryAccessRequest) {
	p.Ephemeral = true
	p.Name = a.Name
	p.Key = a.WgPubKey
	p.Meta = PeerSystemMeta{
		Hostname:      a.Name,
		GoOS:          "js",
		OS:            "js",
		KernelVersion: "wasm",
	}
}

func (f Flags) isEqual(other Flags) bool {
	return f.RosenpassEnabled == other.RosenpassEnabled &&
		f.RosenpassPermissive == other.RosenpassPermissive &&
		f.ServerSSHAllowed == other.ServerSSHAllowed &&
		f.DisableClientRoutes == other.DisableClientRoutes &&
		f.DisableServerRoutes == other.DisableServerRoutes &&
		f.DisableDNS == other.DisableDNS &&
		f.DisableFirewall == other.DisableFirewall &&
		f.BlockLANAccess == other.BlockLANAccess &&
		f.BlockInbound == other.BlockInbound &&
		f.LazyConnectionEnabled == other.LazyConnectionEnabled &&
		f.DisableIPv6 == other.DisableIPv6
}