package node

import (
	"crypto/sha256"
	"crypto/subtle"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"net/http"
	"os"
	"path/filepath"
	"sync"
	"time"
)

type Invitation struct {
	ID         string `json:"id"`
	Endpoint   string `json:"endpoint"`
	ExpiresAt  int64  `json:"expires_at"`
	SecretHash string `json:"secret_hash,omitempty"`
}
type CoreBinding struct {
	BindingID string `json:"binding_id"`
	CoreID    string `json:"core_id"`
	CoreName  string `json:"core_name"`
	Endpoint  string `json:"endpoint"`
	CAPEM     string `json:"ca_pem"`
	ClientPEM string `json:"client_pem"`
	Receipt   string `json:"receipt,omitempty"`
	OfferHash string `json:"offer_hash,omitempty"`
	ExpiresAt int64  `json:"expires_at"`
}
type PairState struct {
	Schema      string        `json:"schema"`
	Phase       string        `json:"phase"`
	Invitation  *Invitation   `json:"invitation,omitempty"`
	Binding     *CoreBinding  `json:"binding,omitempty"`
	Revocations []CoreBinding `json:"revocations,omitempty"`
}
type Pairing struct {
	Sensors          *Sensors
	DeviceEnrollment *DeviceEnrollment
	mu               sync.Mutex
	path             string
	store            *Store
	state            PairState
	now              func() time.Time
	inventory        func() Inventory
	version          string
	lastSeen         int64
	connection       string
	listenError      string
	failureWindow    int64
	failures         int
	clients          map[string]*http.Client
}

func OpenPairing(store *Store, dir, version string, inventory func() Inventory) (*Pairing, error) {
	p := &Pairing{store: store, path: filepath.Join(dir, "core-binding.json"), now: time.Now, inventory: inventory, version: version, connection: "offline", clients: make(map[string]*http.Client), state: PairState{Schema: PairSchema, Phase: "unpaired"}}
	data, e := os.ReadFile(p.path)
	if os.IsNotExist(e) {
		return p, nil
	}
	if e != nil {
		return nil, e
	}
	info, e := os.Lstat(p.path)
	if e != nil || !info.Mode().IsRegular() || info.Mode().Perm()&0077 != 0 || len(data) > 65536 {
		return nil, errors.New("invalid Core binding permissions or size")
	}
	if json.Unmarshal(data, &p.state) != nil || p.state.Schema != PairSchema {
		return nil, errors.New("invalid Core binding; recovery required")
	}
	switch p.state.Phase {
	case "unpaired", "inviting", "pending", "paired", "revoked":
	default:
		return nil, errors.New("unknown Core binding state")
	}
	if (p.state.Phase == "pending" || p.state.Phase == "paired") && p.state.Binding == nil {
		return nil, errors.New("incomplete Core binding")
	}
	if (p.state.Phase == "inviting" || p.state.Phase == "pending") && p.state.Invitation == nil {
		return nil, errors.New("incomplete invitation")
	}
	if (p.state.Phase == "paired" || p.state.Phase == "revoked") && p.state.Invitation != nil {
		next := p.state
		next.Invitation = nil
		if e := p.save(next); e != nil {
			return nil, e
		}
	}
	return p, nil
}
func savePrivateJSON(path string, value any) error {
	data, e := json.Marshal(value)
	if e != nil {
		return e
	}
	f, e := os.CreateTemp(filepath.Dir(path), ".binding-*")
	if e != nil {
		return e
	}
	defer os.Remove(f.Name())
	if _, e = f.Write(data); e != nil {
		f.Close()
		return e
	}
	if e = f.Sync(); e != nil {
		f.Close()
		return e
	}
	if e = f.Close(); e != nil {
		return e
	}
	if e = os.Rename(f.Name(), path); e != nil {
		return e
	}
	dir, e := os.Open(filepath.Dir(path))
	if e != nil {
		return e
	}
	defer dir.Close()
	return dir.Sync()
}
func (p *Pairing) save(next PairState) error {
	if e := savePrivateJSON(p.path, next); e != nil {
		return e
	}
	p.state = next
	return nil
}
func digest(value string) string { h := sha256.Sum256([]byte(value)); return hex.EncodeToString(h[:]) }
func (p *Pairing) expire() error {
	if (p.state.Phase == "inviting" && p.state.Invitation.ExpiresAt <= p.now().Unix()) || (p.state.Phase == "pending" && p.state.Binding.ExpiresAt <= p.now().Unix()) {
		return p.save(PairState{Schema: PairSchema, Phase: "unpaired", Revocations: p.state.Revocations})
	}
	return nil
}
func (p *Pairing) status() map[string]any {
	p.mu.Lock()
	defer p.mu.Unlock()
	_ = p.expire()
	id, _ := p.store.Public()
	out := map[string]any{"phase": p.state.Phase, "node_id": id, "connection": p.connection, "last_seen": p.lastSeen, "notice": p.listenError, "addresses": p.addresses(), "pending_revocations": len(p.state.Revocations)}
	if i := p.state.Invitation; i != nil {
		out["invitation"] = map[string]any{"id": i.ID, "endpoint": i.Endpoint, "expires_at": i.ExpiresAt}
	}
	if b := p.state.Binding; b != nil {
		out["binding"] = map[string]any{"binding_id": b.BindingID, "core_id": b.CoreID, "core_name": b.CoreName, "endpoint": b.Endpoint}
	}
	return out
}
func (p *Pairing) addresses() []string {
	result := []string{}
	for _, network := range p.inventory().Networks {
		if !network.Up {
			continue
		}
		for _, alias := range network.Addresses {
			address := alias
			for i, c := range address {
				if c == '/' {
					address = address[:i]
					break
				}
			}
			if PrivateAddress(address) {
				result = append(result, address)
			}
		}
	}
	return result
}
func (p *Pairing) invite(address string) (map[string]any, error) {
	p.mu.Lock()
	defer p.mu.Unlock()
	if e := p.expire(); e != nil {
		return nil, e
	}
	if p.state.Phase == "paired" || p.state.Phase == "pending" {
		return nil, errors.New("Сначала отмените текущую привязку")
	}
	found := false
	for _, a := range p.addresses() {
		if a == address {
			found = true
		}
	}
	if !found {
		return nil, errors.New("Выберите доступный частный адрес этого БК")
	}
	secret := token()
	i := &Invitation{ID: token(), Endpoint: "https://" + address + ":" + PairPort, ExpiresAt: p.now().Add(10 * time.Minute).Unix(), SecretHash: digest(secret)}
	if e := p.save(PairState{Schema: PairSchema, Phase: "inviting", Invitation: i, Revocations: p.state.Revocations}); e != nil {
		return nil, e
	}
	p.connection = "offline"
	p.lastSeen = 0
	id, _ := p.store.Public()
	code, _ := json.Marshal(map[string]any{"schema": PairSchema, "node_id": id, "id": i.ID, "endpoint": i.Endpoint, "expires_at": i.ExpiresAt, "secret": secret})
	return map[string]any{"code": "MCN1." + base64.RawURLEncoding.EncodeToString(code), "expires_at": i.ExpiresAt}, nil
}
func (p *Pairing) cancel() error {
	p.mu.Lock()
	defer p.mu.Unlock()
	revocations := append([]CoreBinding(nil), p.state.Revocations...)
	if p.state.Binding != nil {
		if len(revocations) >= 8 {
			return errors.New("Дождитесь доставки предыдущих отзывов доверия")
		}
		revocations = append(revocations, *p.state.Binding)
	}
	p.connection = "offline"
	p.listenError = ""
	p.lastSeen = 0
	return p.save(PairState{Schema: PairSchema, Phase: "unpaired", Revocations: revocations})
}
func (p *Pairing) checkInvitation(id, secret string) bool {
	now := p.now().Unix()
	if now-p.failureWindow >= 60 {
		p.failureWindow = now
		p.failures = 0
	}
	if p.failures >= 32 {
		return false
	}
	i := p.state.Invitation
	if i == nil || i.ID != id || i.ExpiresAt <= now || subtle.ConstantTimeCompare([]byte(i.SecretHash), []byte(digest(secret))) != 1 {
		p.failures++
		return false
	}
	return true
}