package main

import (
	"crypto/rand"
	"crypto/sha256"
	"crypto/tls"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/smtp"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"sync"
	"time"

	"golang.org/x/crypto/bcrypt"
	"gopkg.in/yaml.v3"
	_ "github.com/mattn/go-sqlite3"
)

var passwordRE = regexp.MustCompile(`^[A-Za-z0-9]+$`)

// ============================================================
// Config
// ============================================================

type AdminUser struct {
	Username     string `yaml:"username"`
	PasswordHash string `yaml:"password_hash"`
}

type Config struct {
	Port  int          `yaml:"port"`
	Admin []AdminUser  `yaml:"admin"`
	mu    sync.Mutex
	path  string
}

func LoadConfig(dataDir string) (*Config, error) {
	path := filepath.Join(dataDir, "config.yml")
	cfg := &Config{
		Port:  47732,
		Admin: nil,
		path:  path,
	}
	data, err := os.ReadFile(path)
	if err == nil {
		if err := yaml.Unmarshal(data, cfg); err != nil {
			return nil, fmt.Errorf("parse config: %w", err)
		}
	}
	return cfg, nil
}

func (c *Config) Save() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	data, err := yaml.Marshal(c)
	if err != nil {
		return err
	}
	return os.WriteFile(c.path, data, 0640)
}

func (c *Config) SetAdmin(username, password string) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return err
	}
	user := AdminUser{Username: username, PasswordHash: string(hash)}
	// Replace existing or append.
	for i, u := range c.Admin {
		if u.Username == username {
			c.Admin[i] = user
			return c.saveLocked()
		}
	}
	c.Admin = append(c.Admin, user)
	return c.saveLocked()
}

func (c *Config) CheckAdmin(username, password string) bool {
	c.mu.Lock()
	defer c.mu.Unlock()
	for _, u := range c.Admin {
		if u.Username == username {
			if bcrypt.CompareHashAndPassword([]byte(u.PasswordHash), []byte(password)) == nil {
				return true
			}
		}
	}
	return false
}

func (c *Config) saveLocked() error {
	data, err := yaml.Marshal(c)
	if err != nil {
		return err
	}
	return os.WriteFile(c.path, data, 0640)
}

// ============================================================
// Token
// ============================================================

type tokenStore struct {
	mu     sync.Mutex
	tokens map[string]time.Time
}

func newTokenStore() *tokenStore {
	return &tokenStore{tokens: make(map[string]time.Time)}
}

func (ts *tokenStore) Create() string {
	ts.mu.Lock()
	defer ts.mu.Unlock()
	b := make([]byte, 16)
	rand.Read(b)
	tok := hex.EncodeToString(b)
	ts.tokens[tok] = time.Now().Add(24 * time.Hour)
	return tok
}

func (ts *tokenStore) Check(tok string) bool {
	ts.mu.Lock()
	defer ts.mu.Unlock()
	exp, ok := ts.tokens[tok]
	if !ok {
		return false
	}
	if time.Now().After(exp) {
		delete(ts.tokens, tok)
		return false
	}
	return true
}

// userTokenStore embeds tokenStore but also tracks the user_id per token.
type userTokenStore struct {
	mu     sync.Mutex
	tokens map[string]userTokenEntry
}

type userTokenEntry struct {
	UserID    string
	ExpiresAt time.Time
}

func newUserTokenStore() *userTokenStore {
	return &userTokenStore{tokens: make(map[string]userTokenEntry)}
}

func (uts *userTokenStore) Create(userID string) string {
	uts.mu.Lock()
	defer uts.mu.Unlock()
	b := make([]byte, 16)
	rand.Read(b)
	tok := hex.EncodeToString(b)
	uts.tokens[tok] = userTokenEntry{UserID: userID, ExpiresAt: time.Now().Add(24 * time.Hour)}
	return tok
}

func (uts *userTokenStore) Check(tok string) (string, bool) {
	uts.mu.Lock()
	defer uts.mu.Unlock()
	entry, ok := uts.tokens[tok]
	if !ok {
		return "", false
	}
	if time.Now().After(entry.ExpiresAt) {
		delete(uts.tokens, tok)
		return "", false
	}
	return entry.UserID, true
}

// ============================================================
// Server DB schema
// ============================================================

const serverSchema = `
CREATE TABLE IF NOT EXISTS server_devices (
    id TEXT PRIMARY KEY,
    name TEXT NOT NULL,
    api_key TEXT NOT NULL UNIQUE,
    last_seen TEXT,
    created_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS server_revisions (
    rev INTEGER PRIMARY KEY AUTOINCREMENT,
    op_id TEXT NOT NULL,
    device_id TEXT NOT NULL,
    created_at TEXT NOT NULL DEFAULT (datetime('now'))
);

CREATE TABLE IF NOT EXISTS server_ops (
    op_id TEXT PRIMARY KEY,
    device_id TEXT NOT NULL,
    entity_type TEXT NOT NULL,
    entity_id TEXT NOT NULL,
    op_type TEXT NOT NULL,
    payload_json TEXT NOT NULL,
    created_at TEXT NOT NULL,
    pushed_at TEXT NOT NULL DEFAULT (datetime('now'))
);

CREATE TABLE IF NOT EXISTS server_blobs (
    sha256 TEXT PRIMARY KEY,
    size INTEGER NOT NULL,
    created_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS server_smtp_config (
    key TEXT PRIMARY KEY,
    value TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS server_users (
    id TEXT PRIMARY KEY,
    username TEXT NOT NULL UNIQUE,
    email TEXT NOT NULL UNIQUE,
    password_hash TEXT NOT NULL,
    confirmed INTEGER NOT NULL DEFAULT 0,
    created_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS server_email_tokens (
    token TEXT PRIMARY KEY,
    user_id TEXT NOT NULL,
    purpose TEXT NOT NULL,
    expires_at TEXT NOT NULL,
    created_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS server_user_devices (
    user_id TEXT NOT NULL,
    device_id TEXT NOT NULL,
    PRIMARY KEY (user_id, device_id)
);
`

// ============================================================
// Server
// ============================================================

type Server struct {
	db         *sql.DB
	cfg        *Config
	tokens     *tokenStore
	userTokens *userTokenStore
	blobsDir   string
	mux        *http.ServeMux
}

func NewServer(dbPath, dataDir string, cfg *Config) (*Server, error) {
	db, err := sql.Open("sqlite3", fmt.Sprintf("file:%s?mode=rwc", dbPath))
	if err != nil {
		return nil, fmt.Errorf("open db: %w", err)
	}
	db.SetMaxOpenConns(1)

	// Run schema.
	for _, stmt := range strings.Split(serverSchema, ";") {
		stmt = strings.TrimSpace(stmt)
		if stmt == "" {
			continue
		}
		if _, err := db.Exec(stmt); err != nil {
			db.Close()
			return nil, fmt.Errorf("schema: %w", err)
		}
	}

	blobsDir := filepath.Join(dataDir, "blobs")
	if err := os.MkdirAll(blobsDir, 0750); err != nil {
		db.Close()
		return nil, err
	}

	s := &Server{
		db:         db,
		cfg:        cfg,
		tokens:     newTokenStore(),
		userTokens: newUserTokenStore(),
		blobsDir:   blobsDir,
	}
	s.mux = s.routes()
	return s, nil
}

func (s *Server) Close() error {
	return s.db.Close()
}

func (s *Server) ListenAndServe(addr string) error {
	return http.ListenAndServe(addr, s.mux)
}

// ============================================================
// Routes
// ============================================================

func (s *Server) routes() *http.ServeMux {
	mux := http.NewServeMux()
	mux.HandleFunc("/api/v1/health", s.handleHealth)
	mux.HandleFunc("/api/v1/device/register", s.handleDeviceRegister)
	mux.HandleFunc("/api/v1/sync/push", s.handleSyncPush)
	mux.HandleFunc("/api/v1/sync/pull", s.handleSyncPull)
	mux.HandleFunc("/api/v1/blobs/", s.handleBlobs)
	mux.HandleFunc("/api/v1/auth/register", s.handleRegister)
	mux.HandleFunc("/api/v1/auth/confirm", s.handleConfirm)
	mux.HandleFunc("/api/v1/auth/login", s.handleUserLogin)
	mux.HandleFunc("/api/v1/auth/forgot", s.handleForgot)
	mux.HandleFunc("/api/v1/auth/reset", s.handleReset)
	mux.HandleFunc("/api/v1/user/devices", s.handleUserDevices)
	mux.HandleFunc("/register", s.handleUserWebRegister)
	mux.HandleFunc("/login", s.handleUserWebLogin)
	mux.HandleFunc("/dashboard", s.handleUserDashboard)
	mux.HandleFunc("/logout", s.handleUserWebLogout)
	mux.HandleFunc("/admin/login", s.handleAdminLogin)
	mux.HandleFunc("/admin/dashboard", s.handleAdminDashboard)
	mux.HandleFunc("/admin/api/stats", s.handleAdminStats)
	mux.HandleFunc("/admin/", s.handleAdminAPI)
	mux.HandleFunc("/", s.handleNotFound)
	return mux
}

// ============================================================
// Helpers
// ============================================================

func jsonOK(w http.ResponseWriter, v interface{}) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(v)
}

func jsonErr(w http.ResponseWriter, code int, msg string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	json.NewEncoder(w).Encode(map[string]string{"error": msg})
}

func (s *Server) requireAPIKey(w http.ResponseWriter, r *http.Request) bool {
	key := r.Header.Get("Authorization")
	key = strings.TrimPrefix(key, "Bearer ")
	if key == "" {
		key = r.URL.Query().Get("api_key")
	}
	if key == "" {
		jsonErr(w, 401, "API key required")
		return false
	}
	var count int
	err := s.db.QueryRow("SELECT COUNT(*) FROM server_devices WHERE api_key=?", key).Scan(&count)
	if err != nil || count == 0 {
		jsonErr(w, 401, "invalid API key")
		return false
	}
	return true
}

func (s *Server) requireAdmin(w http.ResponseWriter, r *http.Request) bool {
	cookie, err := r.Cookie("session")
	if err != nil || !s.tokens.Check(cookie.Value) {
		http.Redirect(w, r, "/admin/login", http.StatusFound)
		return false
	}
	return true
}

// ============================================================
// SMTP Config
// ============================================================

func (s *Server) smtpGet(key string) string {
	var val string
	s.db.QueryRow("SELECT value FROM server_smtp_config WHERE key=?", key).Scan(&val)
	return val
}

func (s *Server) smtpSet(key, val string) error {
	_, err := s.db.Exec("INSERT OR REPLACE INTO server_smtp_config (key, value) VALUES (?, ?)", key, val)
	return err
}

func (s *Server) smtpSend(to, subject, body string) error {
	host := s.smtpGet("smtp_host")
	port := s.smtpGet("smtp_port")
	user := s.smtpGet("smtp_user")
	pass := s.smtpGet("smtp_pass")
	from := s.smtpGet("smtp_from")
	if host == "" || port == "" || from == "" {
		return fmt.Errorf("SMTP not configured")
	}
	addr := net.JoinHostPort(host, port)
	msg := []byte("From: " + from + "\r\n" +
		"To: " + to + "\r\n" +
		"Subject: " + subject + "\r\n" +
		"MIME-Version: 1.0\r\n" +
		"Content-Type: text/plain; charset=UTF-8\r\n" +
		"\r\n" + body + "\r\n")
	if user != "" {
		auth := smtp.PlainAuth("", user, pass, host)
		if port == "465" {
			tlsCfg := &tls.Config{ServerName: host}
			conn, err := tls.Dial("tcp", addr, tlsCfg)
			if err != nil {
				return err
			}
			cl, err := smtp.NewClient(conn, host)
			if err != nil {
				return err
			}
			defer cl.Close()
			if err := cl.Auth(auth); err != nil {
				return err
			}
			if err := cl.Mail(from); err != nil {
				return err
			}
			if err := cl.Rcpt(to); err != nil {
				return err
			}
			w, err := cl.Data()
			if err != nil {
				return err
			}
			_, err = w.Write(msg)
			if err != nil {
				return err
			}
			return w.Close()
		}
		return smtp.SendMail(addr, auth, from, []string{to}, msg)
	}
	return smtp.SendMail(addr, nil, from, []string{to}, msg)
}

// ============================================================
// User helpers
// ============================================================

func validatePassword(password string) string {
	if len(password) < 8 {
		return "Password must be at least 8 characters"
	}
	if !passwordRE.MatchString(password) {
		return "Password must contain only Latin letters and digits"
	}
	hasLetter := false
	hasDigit := false
	for _, ch := range password {
		if ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z' {
			hasLetter = true
		}
		if ch >= '0' && ch <= '9' {
			hasDigit = true
		}
	}
	if !hasLetter || !hasDigit {
		return "Password must contain both letters and digits"
	}
	return ""
}

func (s *Server) requireUser(w http.ResponseWriter, r *http.Request) (string, bool) {
	key := r.Header.Get("Authorization")
	key = strings.TrimPrefix(key, "Bearer ")
	if key == "" {
		jsonErr(w, 401, "authorization required")
		return "", false
	}
	userID, ok := s.userTokens.Check(key)
	if !ok {
		jsonErr(w, 401, "invalid or expired token")
		return "", false
	}
	return userID, true
}

// ============================================================
// Handlers
// ============================================================

func (s *Server) handleNotFound(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path == "/" {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Write([]byte("Verstak Sync Server\n"))
		return
	}
	jsonErr(w, 404, "not found")
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	jsonOK(w, map[string]interface{}{
		"status":  "ok",
		"version": "verstak-server/v1",
		"time":    time.Now().UTC().Format(time.RFC3339),
	})
}

func (s *Server) handleDeviceRegister(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		Name     string `json:"name"`
		Username string `json:"username"`
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}
	if req.Name == "" {
		jsonErr(w, 400, "name required")
		return
	}
	if req.Username == "" || req.Password == "" {
		jsonErr(w, 401, "username and password required")
		return
	}

	// Look up user by username or email.
	var userID, hash string
	var confirmed int
	err := s.db.QueryRow("SELECT id, password_hash, confirmed FROM server_users WHERE username=? OR email=?",
		req.Username, strings.ToLower(req.Username)).Scan(&userID, &hash, &confirmed)
	if err != nil {
		jsonErr(w, 401, "invalid credentials")
		return
	}
	if confirmed == 0 {
		jsonErr(w, 403, "email not confirmed")
		return
	}
	if bcrypt.CompareHashAndPassword([]byte(hash), []byte(req.Password)) != nil {
		jsonErr(w, 401, "invalid credentials")
		return
	}

	b := make([]byte, 20)
	rand.Read(b)
	apiKey := hex.EncodeToString(b)
	deviceID := apiKey[:12]
	now := time.Now().UTC().Format(time.RFC3339)

	_, err = s.db.Exec(
		"INSERT INTO server_devices (id, name, api_key, last_seen, created_at) VALUES (?, ?, ?, ?, ?)",
		deviceID, req.Name, apiKey, now, now,
	)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	// Link device to user.
	s.db.Exec("INSERT OR IGNORE INTO server_user_devices (user_id, device_id) VALUES (?, ?)", userID, deviceID)

	jsonOK(w, map[string]interface{}{
		"device_id": deviceID,
		"api_key":   apiKey,
	})
}

// ============================================================
// Auth / User handlers
// ============================================================

func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		Username string `json:"username"`
		Email    string `json:"email"`
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}
	if req.Username == "" || req.Email == "" || req.Password == "" {
		jsonErr(w, 400, "username, email and password required")
		return
	}
	if err := validatePassword(req.Password); err != "" {
		jsonErr(w, 400, err)
		return
	}
	if !strings.Contains(req.Email, "@") || !strings.Contains(req.Email, ".") {
		jsonErr(w, 400, "invalid email")
		return
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(req.Password), bcrypt.DefaultCost)
	if err != nil {
		jsonErr(w, 500, "internal error")
		return
	}
	now := time.Now().UTC().Format(time.RFC3339)
	id := make([]byte, 12)
	rand.Read(id)
	userID := hex.EncodeToString(id)
	_, err = s.db.Exec(
		"INSERT INTO server_users (id, username, email, password_hash, confirmed, created_at) VALUES (?, ?, ?, ?, 0, ?)",
		userID, req.Username, strings.ToLower(req.Email), string(hash), now,
	)
	if err != nil {
		if strings.Contains(err.Error(), "UNIQUE") {
			jsonErr(w, 409, "username or email already taken")
			return
		}
		jsonErr(w, 500, err.Error())
		return
	}
	// Confirmation token.
	tok := make([]byte, 24)
	rand.Read(tok)
	tokenStr := hex.EncodeToString(tok)
	exp := time.Now().Add(48 * time.Hour).UTC().Format(time.RFC3339)
	s.db.Exec("INSERT INTO server_email_tokens (token, user_id, purpose, expires_at, created_at) VALUES (?, ?, 'confirm', ?, ?)",
		tokenStr, userID, exp, now)
	// Try to send email.
	host := s.smtpGet("smtp_host")
	if host != "" {
		confirmURL := fmt.Sprintf("%s/confirm?token=%s", s.smtpGet("server_url"), tokenStr)
		if confirmURL == "" {
			confirmURL = fmt.Sprintf("/api/v1/auth/confirm?token=%s", tokenStr)
		}
		body := fmt.Sprintf("Welcome to Verstak Sync!\n\nPlease confirm your email by clicking:\n%s\n\nIf you did not register, ignore this message.", confirmURL)
		s.smtpSend(req.Email, "Confirm your Verstak Sync account", body)
	}
	jsonOK(w, map[string]string{"status": "confirmation_sent"})
}

func (s *Server) handleConfirm(w http.ResponseWriter, r *http.Request) {
	if r.Method != "GET" {
		jsonErr(w, 405, "GET required")
		return
	}
	tokenStr := r.URL.Query().Get("token")
	if tokenStr == "" {
		jsonErr(w, 400, "token required")
		return
	}
	var userID, expiresAt string
	err := s.db.QueryRow("SELECT user_id, expires_at FROM server_email_tokens WHERE token=? AND purpose='confirm'",
		tokenStr).Scan(&userID, &expiresAt)
	if err != nil {
		jsonErr(w, 400, "invalid or expired token")
		return
	}
	exp, err := time.Parse(time.RFC3339, expiresAt)
	if err != nil || time.Now().After(exp) {
		jsonErr(w, 400, "token expired")
		return
	}
	s.db.Exec("UPDATE server_users SET confirmed=1 WHERE id=?", userID)
	s.db.Exec("DELETE FROM server_email_tokens WHERE token=?", tokenStr)
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Write([]byte("<html><body><h1>Email confirmed</h1><p>You can now log in.</p></body></html>"))
}

func (s *Server) handleUserLogin(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}
	if req.Username == "" || req.Password == "" {
		jsonErr(w, 400, "username and password required")
		return
	}
	var userID, hash string
	var confirmed int
	err := s.db.QueryRow("SELECT id, password_hash, confirmed FROM server_users WHERE username=? OR email=?",
		req.Username, strings.ToLower(req.Username)).Scan(&userID, &hash, &confirmed)
	if err != nil {
		jsonErr(w, 401, "invalid credentials")
		return
	}
	if confirmed == 0 {
		jsonErr(w, 403, "email not confirmed")
		return
	}
	if bcrypt.CompareHashAndPassword([]byte(hash), []byte(req.Password)) != nil {
		jsonErr(w, 401, "invalid credentials")
		return
	}
	tok := s.userTokens.Create(userID)
	jsonOK(w, map[string]string{"token": tok, "user_id": userID})
}

func (s *Server) handleForgot(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		Email string `json:"email"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}
	if req.Email == "" {
		jsonErr(w, 400, "email required")
		return
	}
	var userID string
	err := s.db.QueryRow("SELECT id FROM server_users WHERE email=?", strings.ToLower(req.Email)).Scan(&userID)
	if err != nil {
		jsonOK(w, map[string]string{"status": "if email exists, reset link sent"})
		return
	}
	tok := make([]byte, 24)
	rand.Read(tok)
	tokenStr := hex.EncodeToString(tok)
	exp := time.Now().Add(1 * time.Hour).UTC().Format(time.RFC3339)
	now := time.Now().UTC().Format(time.RFC3339)
	s.db.Exec("INSERT INTO server_email_tokens (token, user_id, purpose, expires_at, created_at) VALUES (?, ?, 'reset', ?, ?)",
		tokenStr, userID, exp, now)
	host := s.smtpGet("smtp_host")
	if host != "" {
		resetURL := fmt.Sprintf("%s/reset?token=%s", s.smtpGet("server_url"), tokenStr)
		if resetURL == "" {
			resetURL = fmt.Sprintf("/api/v1/auth/reset?token=%s", tokenStr)
		}
		body := fmt.Sprintf("Reset your Verstak Sync password:\n\n%s\n\nThis link expires in 1 hour.", resetURL)
		s.smtpSend(req.Email, "Verstak Sync password reset", body)
	}
	jsonOK(w, map[string]string{"status": "if email exists, reset link sent"})
}

func (s *Server) handleReset(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		Token       string `json:"token"`
		NewPassword string `json:"new_password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}
	if req.Token == "" || req.NewPassword == "" {
		jsonErr(w, 400, "token and new_password required")
		return
	}
	if err := validatePassword(req.NewPassword); err != "" {
		jsonErr(w, 400, err)
		return
	}
	var userID, expiresAt string
	err := s.db.QueryRow("SELECT user_id, expires_at FROM server_email_tokens WHERE token=? AND purpose='reset'",
		req.Token).Scan(&userID, &expiresAt)
	if err != nil {
		jsonErr(w, 400, "invalid or expired token")
		return
	}
	exp, err := time.Parse(time.RFC3339, expiresAt)
	if err != nil || time.Now().After(exp) {
		jsonErr(w, 400, "token expired")
		return
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		jsonErr(w, 500, "internal error")
		return
	}
	s.db.Exec("UPDATE server_users SET password_hash=? WHERE id=?", string(hash), userID)
	s.db.Exec("DELETE FROM server_email_tokens WHERE token=?", req.Token)
	jsonOK(w, map[string]string{"status": "password reset"})
}

func (s *Server) handleUserDevices(w http.ResponseWriter, r *http.Request) {
	userID, ok := s.requireUser(w, r)
	if !ok {
		return
	}
	if r.Method != "GET" {
		jsonErr(w, 405, "GET required")
		return
	}
	rows, err := s.db.Query(`
		SELECT d.id, d.name, d.last_seen, d.created_at
		FROM server_devices d
		JOIN server_user_devices ud ON ud.device_id = d.id
		WHERE ud.user_id = ?
		ORDER BY d.created_at`, userID)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	defer rows.Close()
	type deviceDTO struct {
		ID        string `json:"id"`
		Name      string `json:"name"`
		LastSeen  string `json:"last_seen"`
		CreatedAt string `json:"created_at"`
	}
	var devices []deviceDTO
	for rows.Next() {
		var d deviceDTO
		var lastSeen sql.NullString
		if err := rows.Scan(&d.ID, &d.Name, &lastSeen, &d.CreatedAt); err != nil {
			continue
		}
		d.LastSeen = lastSeen.String
		devices = append(devices, d)
	}
	if devices == nil {
		devices = []deviceDTO{}
	}
	jsonOK(w, map[string]interface{}{"devices": devices})
}

func (s *Server) handleSyncPush(w http.ResponseWriter, r *http.Request) {
	if !s.requireAPIKey(w, r) {
		return
	}
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		DeviceID string `json:"device_id"`
		Ops      []struct {
			OpID        string `json:"op_id"`
			EntityType  string `json:"entity_type"`
			EntityID    string `json:"entity_id"`
			OpType      string `json:"op_type"`
			PayloadJSON string `json:"payload_json"`
			CreatedAt   string `json:"created_at"`
		} `json:"ops"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON: "+err.Error())
		return
	}

	var accepted []string
	for _, op := range req.Ops {
		if op.OpID == "" || op.EntityType == "" || op.EntityID == "" || op.OpType == "" {
			continue
		}
		_, err := s.db.Exec(
			`INSERT OR IGNORE INTO server_ops (op_id, device_id, entity_type, entity_id, op_type, payload_json, created_at)
			 VALUES (?, ?, ?, ?, ?, ?, ?)`,
			op.OpID, req.DeviceID, op.EntityType, op.EntityID, op.OpType, op.PayloadJSON, op.CreatedAt,
		)
		if err != nil {
			continue
		}
		// Assign revision.
		res, err := s.db.Exec(
			"INSERT INTO server_revisions (op_id, device_id) VALUES (?, ?)",
			op.OpID, req.DeviceID,
		)
		if err != nil {
			continue
		}
		rev, _ := res.LastInsertId()
		_ = rev
		accepted = append(accepted, op.OpID)
	}

	jsonOK(w, map[string]interface{}{
		"accepted": accepted,
		"count":    len(accepted),
	})
}

func (s *Server) handleSyncPull(w http.ResponseWriter, r *http.Request) {
	if !s.requireAPIKey(w, r) {
		return
	}
	if r.Method != "POST" {
		jsonErr(w, 405, "POST required")
		return
	}
	var req struct {
		SinceRevision int `json:"since_revision"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "invalid JSON")
		return
	}

	// Get current server revision.
	var serverRev int
	s.db.QueryRow("SELECT COALESCE(MAX(rev), 0) FROM server_revisions").Scan(&serverRev)

	// Get ops since the requested revision.
	rows, err := s.db.Query(`
		SELECT so.op_id, so.device_id, so.entity_type, so.entity_id, so.op_type, so.payload_json, so.created_at
		FROM server_ops so
		JOIN server_revisions sr ON sr.op_id = so.op_id
		WHERE sr.rev > ?
		ORDER BY sr.rev`, req.SinceRevision)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	defer rows.Close()

	type opDTO struct {
		OpID        string `json:"op_id"`
		DeviceID    string `json:"device_id"`
		EntityType  string `json:"entity_type"`
		EntityID    string `json:"entity_id"`
		OpType      string `json:"op_type"`
		PayloadJSON string `json:"payload_json"`
		CreatedAt   string `json:"created_at"`
	}
	var ops []opDTO
	for rows.Next() {
		var o opDTO
		if err := rows.Scan(&o.OpID, &o.DeviceID, &o.EntityType, &o.EntityID, &o.OpType, &o.PayloadJSON, &o.CreatedAt); err != nil {
			continue
		}
		ops = append(ops, o)
	}

	jsonOK(w, map[string]interface{}{
		"server_revision": serverRev,
		"ops":            ops,
	})
}

func (s *Server) handleBlobs(w http.ResponseWriter, r *http.Request) {
	if !s.requireAPIKey(w, r) {
		return
	}
	switch r.Method {
	case "POST":
		// Upload: accept multipart file, store by SHA-256.
		if err := r.ParseMultipartForm(200 << 20); err != nil {
			jsonErr(w, 400, "multipart error: "+err.Error())
			return
		}
		file, header, err := r.FormFile("file")
		if err != nil {
			jsonErr(w, 400, "file field required")
			return
		}
		defer file.Close()

		// Read content and compute SHA-256.
		data, err := io.ReadAll(file)
		if err != nil {
			jsonErr(w, 500, "read error")
			return
		}
		hash := sha256.Sum256(data)
		shaHex := hex.EncodeToString(hash[:])

		// Store at blobs/ab/cd/sha256.
		blobDir := filepath.Join(s.blobsDir, shaHex[:2], shaHex[2:4])
		if err := os.MkdirAll(blobDir, 0750); err != nil {
			jsonErr(w, 500, "mkdir error")
			return
		}
		blobPath := filepath.Join(blobDir, shaHex)
		if err := os.WriteFile(blobPath, data, 0640); err != nil {
			jsonErr(w, 500, "write error")
			return
		}
		_ = header

		// Record in blobs table.
		now := time.Now().UTC().Format(time.RFC3339)
		s.db.Exec("INSERT OR IGNORE INTO server_blobs (sha256, size, created_at) VALUES (?, ?, ?)",
			shaHex, len(data), now)

		jsonOK(w, map[string]interface{}{
			"sha256": shaHex,
			"size":   len(data),
		})

	case "GET":
		// Download: GET /api/v1/blobs/{sha256}
		shaHex := strings.TrimPrefix(r.URL.Path, "/api/v1/blobs/")
		if len(shaHex) != 64 {
			jsonErr(w, 400, "invalid SHA-256")
			return
		}
		blobPath := filepath.Join(s.blobsDir, shaHex[:2], shaHex[2:4], shaHex)
		if _, err := os.Stat(blobPath); os.IsNotExist(err) {
			jsonErr(w, 404, "blob not found")
			return
		}
		data, err := os.ReadFile(blobPath)
		if err != nil {
			jsonErr(w, 500, "read error")
			return
		}
		w.Header().Set("Content-Type", "application/octet-stream")
		w.Header().Set("Content-Disposition", "attachment; filename=\""+shaHex+"\"")
		w.Write(data)

	default:
		jsonErr(w, 405, "method not allowed")
	}
}

// ============================================================
// User web GUI
// ============================================================

func (s *Server) requireUserWeb(w http.ResponseWriter, r *http.Request) (string, bool) {
	cookie, err := r.Cookie("user_session")
	if err != nil {
		http.Redirect(w, r, "/login", http.StatusFound)
		return "", false
	}
	userID, ok := s.userTokens.Check(cookie.Value)
	if !ok {
		http.Redirect(w, r, "/login", http.StatusFound)
		return "", false
	}
	return userID, true
}

func (s *Server) handleUserWebRegister(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Write([]byte(userRegisterHTML))
	case "POST":
		if err := r.ParseForm(); err != nil {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(400)
			w.Write([]byte("<html><body><h1>400 Bad request</h1><a href='/register'>Back</a></body></html>"))
			return
		}
		username := r.FormValue("username")
		email := r.FormValue("email")
		password := r.FormValue("password")
		if username == "" || email == "" || password == "" {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(400)
			w.Write([]byte("<html><body><h1>All fields required</h1><a href='/register'>Back</a></body></html>"))
			return
		}
		if err := validatePassword(password); err != "" {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(400)
			w.Write([]byte("<html><body><h1>" + err + "</h1><a href='/register'>Back</a></body></html>"))
			return
		}
		hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
		if err != nil {
			w.WriteHeader(500)
			w.Write([]byte("<html><body><h1>Internal error</h1><a href='/register'>Back</a></body></html>"))
			return
		}
		now := time.Now().UTC().Format(time.RFC3339)
		id := make([]byte, 12)
		rand.Read(id)
		userID := hex.EncodeToString(id)
		_, err = s.db.Exec(
			"INSERT INTO server_users (id, username, email, password_hash, confirmed, created_at) VALUES (?, ?, ?, ?, 0, ?)",
			userID, username, strings.ToLower(email), string(hash), now,
		)
		if err != nil {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			if strings.Contains(err.Error(), "UNIQUE") {
				w.WriteHeader(409)
				w.Write([]byte("<html><body><h1>Username or email already taken</h1><a href='/register'>Back</a></body></html>"))
			} else {
				w.WriteHeader(500)
				w.Write([]byte("<html><body><h1>"+err.Error()+"</h1><a href='/register'>Back</a></body></html>"))
			}
			return
		}
		// Confirmation token.
		tok := make([]byte, 24)
		rand.Read(tok)
		tokenStr := hex.EncodeToString(tok)
		exp := time.Now().Add(48 * time.Hour).UTC().Format(time.RFC3339)
		s.db.Exec("INSERT INTO server_email_tokens (token, user_id, purpose, expires_at, created_at) VALUES (?, ?, 'confirm', ?, ?)",
			tokenStr, userID, exp, now)
		// Try to send email.
		host := s.smtpGet("smtp_host")
		if host != "" {
			confirmURL := fmt.Sprintf("%s/api/v1/auth/confirm?token=%s", s.smtpGet("server_url"), tokenStr)
			if confirmURL == fmt.Sprintf("/api/v1/auth/confirm?token=%s", tokenStr) {
				confirmURL = fmt.Sprintf("http://%s/api/v1/auth/confirm?token=%s", r.Host, tokenStr)
			}
			body := fmt.Sprintf("Welcome to Verstak Sync!\n\nPlease confirm your email by clicking:\n%s\n\nIf you did not register, ignore this message.", confirmURL)
			s.smtpSend(email, "Confirm your Verstak Sync account", body)
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Write([]byte("<html><body><h1>Registration successful</h1><p>Check your email to confirm (or if SMTP not configured, check server logs for the token).</p><a href='/login'>Log in</a></body></html>"))
	default:
		jsonErr(w, 405, "method not allowed")
	}
}

func (s *Server) handleUserWebLogin(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Write([]byte(userLoginHTML))
	case "POST":
		if err := r.ParseForm(); err != nil {
			jsonErr(w, 400, "bad form")
			return
		}
		username := r.FormValue("username")
		password := r.FormValue("password")
		var userID, hash string
		var confirmed int
		err := s.db.QueryRow("SELECT id, password_hash, confirmed FROM server_users WHERE username=? OR email=?",
			username, strings.ToLower(username)).Scan(&userID, &hash, &confirmed)
		if err != nil || confirmed == 0 || bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)) != nil {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(401)
			w.Write([]byte("<html><body><h1>401 Unauthorized</h1><a href='/login'>Try again</a></body></html>"))
			return
		}
		tok := s.userTokens.Create(userID)
		http.SetCookie(w, &http.Cookie{
			Name: "user_session", Value: tok, Path: "/",
			HttpOnly: true, SameSite: http.SameSiteLaxMode,
			MaxAge: 86400,
		})
		http.Redirect(w, r, "/dashboard", http.StatusFound)
	default:
		jsonErr(w, 405, "method not allowed")
	}
}

func (s *Server) handleUserDashboard(w http.ResponseWriter, r *http.Request) {
	userID, ok := s.requireUserWeb(w, r)
	if !ok {
		return
	}
	// Get username.
	var username string
	s.db.QueryRow("SELECT username FROM server_users WHERE id=?", userID).Scan(&username)

	// Get devices.
	rows, err := s.db.Query(`
		SELECT d.id, d.name, d.api_key, d.last_seen, d.created_at
		FROM server_devices d
		JOIN server_user_devices ud ON ud.device_id = d.id
		WHERE ud.user_id = ?
		ORDER BY d.created_at`, userID)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	defer rows.Close()

	type dev struct {
		ID, Name, APIKey, LastSeen, CreatedAt string
	}
	var devices []dev
	for rows.Next() {
		var d dev
		var lastSeen sql.NullString
		if err := rows.Scan(&d.ID, &d.Name, &d.APIKey, &lastSeen, &d.CreatedAt); err != nil {
			continue
		}
		d.LastSeen = lastSeen.String
		devices = append(devices, d)
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	// Build device rows HTML.
	deviceRows := ""
	if len(devices) == 0 {
		deviceRows = "<tr><td colspan='4' style='color:#666;text-align:center;padding:24px'>Нет подключённых устройств</td></tr>"
	} else {
		for _, d := range devices {
			lastSeen := d.LastSeen
			if lastSeen == "" {
				lastSeen = "—"
			}
			escKey := strings.ReplaceAll(d.APIKey, "'", "\\'")
			deviceRows += fmt.Sprintf(`<tr>
				<td>%s</td>
				<td class="key-cell" title="%s">%s</td>
				<td>%s</td>
				<td>
					<button class="btn copy-btn" onclick="copyKey('%s',this)">Копировать</button>
					<button class="btn btn-danger" onclick="delDevice('%s')">Отключить</button>
				</td>
			</tr>`, d.Name, d.APIKey, d.APIKey, lastSeen, escKey, d.ID)
		}
	}

	html := fmt.Sprintf(`<!DOCTYPE html>
<html lang="ru">
<head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Verstak Sync — %s</title>
<style>
body{font-family:sans-serif;background:#13131f;color:#e4e4ef;padding:24px;max-width:800px;margin:0 auto}
h1{border-bottom:1px solid #2a2a3c;padding-bottom:12px}
h2{margin-top:24px;font-size:16px}
table{width:100%;border-collapse:collapse;margin-top:8px}
th,td{text-align:left;padding:8px 12px;border-bottom:1px solid #2a2a3c}
th{font-size:12px;color:#888;text-transform:uppercase}
.key-cell{max-width:300px;overflow:hidden;text-overflow:ellipsis;font-family:monospace;font-size:12px;color:#b0b0c0}
.btn{font-family:inherit;font-size:12px;padding:6px 12px;border-radius:6px;border:1px solid #2a2a3c;background:#1a1a28;color:#ccc;cursor:pointer;display:inline-flex;align-items:center;gap:4px}
.btn:hover{background:#222233}
.btn-primary{background:#6366f1;border-color:#6366f1;color:#fff}
.btn-primary:hover{background:#4f46e5}
.btn-danger{color:#ff6b6b;border-color:#4a2222}
.btn-danger:hover{background:#3a2222}
.copy-btn{padding:2px 8px;font-size:11px}
input{font-family:inherit;font-size:14px;padding:8px 12px;border:1px solid #2a2a3c;background:#13131f;color:#e4e4ef;border-radius:6px;margin-right:8px;flex:1}
input:focus{outline:none;border-color:#6366f1}
.top{display:flex;justify-content:space-between;align-items:center}
a{color:#6366f1}
</style>
</head><body>
<div class="top">
<h1>Verstak Sync</h1>
<span>%s · <a href="/logout">Выйти</a></span>
</div>
<h2>Устройства</h2>
<table><tr><th>Устройство</th><th>API-ключ</th><th>Последняя активность</th><th></th></tr>%s</table>

<h2>Новое устройство</h2>
<form action="/api/v1/device/register" method="POST" style="display:flex;gap:8px;margin-top:8px"
      onsubmit="event.preventDefault();var f=this;fetch('/api/v1/device/register',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({name:f.name.value,username:'%s',password:document.getElementById('regpass').value})}).then(r=>r.json()).then(d=>{if(d.api_key){f.name.value='';location.reload()}else{alert(d.error||'error')}})">
<input name="name" placeholder="Название устройства" required>
<input type="hidden" id="regpass" value="">
<button class="btn btn-primary" type="button" onclick="var p=prompt('Ваш пароль:');if(p){document.getElementById('regpass').value=p;this.form.requestSubmit()}">Подключить</button>
</form>
<script>
function copyKey(key,btn){
  navigator.clipboard.writeText(key).then(()=>{
    var old=btn.textContent;btn.textContent='Скопировано';btn.style.color='#4ade80'
    setTimeout(function(){btn.textContent=old;btn.style.color=''},1500)
  })
}
function delDevice(id){
  if(!confirm('Отключить устройство?'))return
  fetch('/admin/api/keys/'+id,{method:'DELETE'}).then(()=>location.reload())
}
</script>
</body></html>`, username, username, deviceRows, username)
	w.Write([]byte(html))
}

func (s *Server) handleUserWebLogout(w http.ResponseWriter, r *http.Request) {
	http.SetCookie(w, &http.Cookie{
		Name: "user_session", Value: "", Path: "/",
		HttpOnly: true, MaxAge: -1,
	})
	http.Redirect(w, r, "/login", http.StatusFound)
}

// ============================================================
// Admin handlers
// ============================================================

func (s *Server) handleAdminLogin(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Write([]byte(adminLoginHTML))
	case "POST":
		if err := r.ParseForm(); err != nil {
			jsonErr(w, 400, "bad form")
			return
		}
		user := r.FormValue("username")
		pass := r.FormValue("password")
		if !s.cfg.CheckAdmin(user, pass) {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(401)
			w.Write([]byte("<html><body><h1>401 Unauthorized</h1><a href='/admin/login'>Try again</a></body></html>"))
			return
		}
		tok := s.tokens.Create()
		http.SetCookie(w, &http.Cookie{
			Name: "session", Value: tok, Path: "/admin",
			HttpOnly: true, SameSite: http.SameSiteLaxMode,
			MaxAge: 86400,
		})
		http.Redirect(w, r, "/admin/dashboard", http.StatusFound)
	default:
		jsonErr(w, 405, "method not allowed")
	}
}

func (s *Server) handleAdminDashboard(w http.ResponseWriter, r *http.Request) {
	if !s.requireAdmin(w, r) {
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	// Fetch data for dashboard.
	var deviceCount, opsCount int
	s.db.QueryRow("SELECT COUNT(*) FROM server_devices").Scan(&deviceCount)
	s.db.QueryRow("SELECT COUNT(*) FROM server_ops").Scan(&opsCount)

	// Load SMTP config for display.
	smtpHost := s.smtpGet("smtp_host")
	smtpPort := s.smtpGet("smtp_port")
	smtpUser := s.smtpGet("smtp_user")
	smtpFrom := s.smtpGet("smtp_from")
	srvURL := s.smtpGet("server_url")

	html := fmt.Sprintf(`<!DOCTYPE html>
<html lang="ru">
<head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Verstak Sync — Admin</title>
<style>
body{font-family:sans-serif;background:#13131f;color:#e4e4ef;padding:24px;max-width:860px;margin:0 auto}
a{color:#6366f1}
h1{border-bottom:1px solid #2a2a3c;padding-bottom:12px}
h2{margin-top:24px;font-size:16px}
.stat{background:#1a1a28;border:1px solid #2a2a3c;padding:12px 16px;border-radius:8px;margin:8px 0}
table{width:100%;border-collapse:collapse;margin-top:8px}
th,td{text-align:left;padding:8px 12px;border-bottom:1px solid #2a2a3c}
th{font-size:12px;color:#888;text-transform:uppercase}
.key-cell{max-width:360px;overflow:hidden;text-overflow:ellipsis;font-family:monospace;font-size:12px;color:#b0b0c0}
.btn{font-family:inherit;font-size:12px;padding:6px 12px;border-radius:6px;border:1px solid #2a2a3c;background:#1a1a28;color:#ccc;cursor:pointer;display:inline-flex;align-items:center;gap:4px}
.btn:hover{background:#222233}
.btn-primary{background:#6366f1;border-color:#6366f1;color:#fff}
.btn-primary:hover{background:#4f46e5}
.btn-danger{color:#ff6b6b;border-color:#4a2222}
.btn-danger:hover{background:#3a2222}
.copy-btn{padding:2px 8px;font-size:11px;margin-left:6px}
input{font-family:inherit;font-size:14px;padding:8px 12px;border:1px solid #2a2a3c;background:#13131f;color:#e4e4ef;border-radius:6px;margin:0;box-sizing:border-box}
input:focus{outline:none;border-color:#6366f1}
.form-row{display:flex;gap:8px;margin-bottom:8px;align-items:center}
.form-row label{font-size:12px;color:#888;min-width:80px;flex-shrink:0}
.form-row input{flex:1}
.toolbar{display:flex;gap:8px;margin:16px 0;flex-wrap:wrap}
.modal-overlay{position:fixed;inset:0;background:rgba(0,0,0,0.6);display:flex;align-items:center;justify-content:center;z-index:100}
.modal{background:#1a1a28;border:1px solid #2a2a3c;border-radius:12px;padding:24px;width:420px;max-width:90vw;position:relative;max-height:80vh;overflow-y:auto}
.modal h2{margin-top:0}
.modal-close{position:absolute;top:10px;right:14px;font-size:20px;cursor:pointer;background:none;border:none;color:#888}
.modal-close:hover{color:#e4e4ef}
pre{background:#13131f;border:1px solid #2a2a3c;border-radius:8px;padding:12px;overflow-x:auto;white-space:pre-wrap}
</style>
</head><body>
<h1>Verstak Sync Server</h1>
<div class="stat"><strong>Устройств:</strong> <span id="dev-count">0</span></div>
<div class="stat"><strong>Операций:</strong> <span id="op-count">0</span></div>

<div class="toolbar">
<button class="btn btn-primary" onclick="openSMTP()">Настройка SMTP</button>
<button class="btn" onclick="openHealth()">Health check</button>
</div>

<h2>API-ключи</h2>
<div id="keys"></div>
<script>
fetch('/admin/api/keys').then(r=>r.json()).then(keys=>{
  const div=document.getElementById('keys')
  if(!keys.length){div.innerHTML='<p>Нет ключей</p>';return}
  div.innerHTML='<table><tr><th>Устройство</th><th>API-ключ</th><th></th><th></th></tr>'+
    keys.map(k=>'<tr><td>'+k.name+'</td><td class="key-cell" title="'+k.api_key+'">'+k.api_key+'</td>'+
    '<td><button class="btn copy-btn" onclick="copyKey(\''+k.api_key+'\',this)">Копировать</button></td>'+
    '<td><button class="btn btn-danger" onclick="delKey(\''+k.id+'\')">Удалить</button></td></tr>').join('')+'</table>'
  document.getElementById('dev-count').textContent=keys.length
})
fetch('/admin/api/stats').then(r=>r.json()).then(stats=>{
  document.getElementById('op-count').textContent=stats.ops||'0'
})
function copyKey(key,btn){
  navigator.clipboard.writeText(key).then(()=>{
    var old=btn.textContent;btn.textContent='Скопировано';btn.style.color='#4ade80'
    setTimeout(function(){btn.textContent=old;btn.style.color=''},1500)
  })
}
function delKey(id){if(confirm('Удалить ключ?'))fetch('/admin/api/keys/'+id,{method:'DELETE'}).then(()=>location.reload())}
function openSMTP(){document.getElementById('smtp-modal').style.display='flex'}
function closeSMTP(e){if(!e||e.target.id==='smtp-modal')document.getElementById('smtp-modal').style.display='none'}
function openHealth(){var m=document.getElementById('health-modal');m.style.display='flex';document.getElementById('health-result').textContent='Загрузка...';fetch('/api/v1/health').then(function(r){return r.text()}).then(function(t){document.getElementById('health-result').textContent=t})}
function closeHealth(e){if(!e||e.target.id==='health-modal')document.getElementById('health-modal').style.display='none'}
</script>

<h3>Новый ключ</h3>
<form action="/admin/api/keys" method="POST" style="display:flex;gap:8px">
<input name="name" placeholder="Название устройства" required style="flex:1">
<button class="btn btn-primary">Создать</button>
</form>

<div id="smtp-modal" class="modal-overlay" style="display:none" onclick="closeSMTP(event)">
<div class="modal">
<button class="modal-close" onclick="closeSMTP()">&times;</button>
<h2>SMTP (для писем)</h2>
<form action="/admin/api/smtp" method="POST">
<div class="form-row"><label>Сервер</label><input name="smtp_host" value="` + smtpHost + `" placeholder="smtp.example.com"></div>
<div class="form-row"><label>Порт</label><input name="smtp_port" value="` + smtpPort + `" placeholder="587"></div>
<div class="form-row"><label>Логин</label><input name="smtp_user" value="` + smtpUser + `" placeholder="user@example.com"></div>
<div class="form-row"><label>Пароль</label><input type="password" name="smtp_pass" placeholder="••••••••"></div>
<div class="form-row"><label>От кого</label><input name="smtp_from" value="` + smtpFrom + `" placeholder="noreply@example.com"></div>
<div class="form-row"><label>URL сервера</label><input name="server_url" value="` + srvURL + `" placeholder="https://example.com:47732"></div>
<div style="margin-top:12px"><button class="btn btn-primary">Сохранить SMTP</button></div>
</form>
</div>
</div>

<div id="health-modal" class="modal-overlay" style="display:none" onclick="closeHealth(event)">
<div class="modal">
<button class="modal-close" onclick="closeHealth()">&times;</button>
<h2>Health check</h2>
<pre id="health-result">Загрузка...</pre>
</div>
</div>

</body></html>`)
	w.Write([]byte(html))
}

func (s *Server) handleAdminStats(w http.ResponseWriter, r *http.Request) {
	if !s.requireAdmin(w, r) {
		return
	}
	var opsCount int
	s.db.QueryRow("SELECT COUNT(*) FROM server_ops").Scan(&opsCount)
	jsonOK(w, map[string]int{"ops": opsCount})
}

func (s *Server) handleAdminAPI(w http.ResponseWriter, r *http.Request) {
	if !s.requireAdmin(w, r) {
		return
	}
	path := strings.TrimPrefix(r.URL.Path, "/admin")

	switch {
	case path == "/api/keys" && r.Method == "GET":
		rows, err := s.db.Query("SELECT id, name, api_key FROM server_devices ORDER BY created_at")
		if err != nil {
			jsonErr(w, 500, err.Error())
			return
		}
		defer rows.Close()
		var out []map[string]string
		for rows.Next() {
			var id, name, key string
			rows.Scan(&id, &name, &key)
			out = append(out, map[string]string{"id": id, "name": name, "api_key": key})
		}
		jsonOK(w, out)

	case path == "/api/keys" && r.Method == "POST":
		if err := r.ParseForm(); err != nil {
			jsonErr(w, 400, "bad form")
			return
		}
		name := r.FormValue("name")
		if name == "" {
			jsonErr(w, 400, "name required")
			return
		}
		b := make([]byte, 20)
		rand.Read(b)
		apiKey := hex.EncodeToString(b)
		now := time.Now().UTC().Format(time.RFC3339)
		_, err := s.db.Exec(
			"INSERT INTO server_devices (id, name, api_key, last_seen, created_at) VALUES (?, ?, ?, ?, ?)",
			apiKey[:12], name, apiKey, now, now,
		)
		if err != nil {
			jsonErr(w, 500, err.Error())
			return
		}
		http.Redirect(w, r, "/admin/dashboard", http.StatusFound)

	case strings.HasPrefix(path, "/api/keys/") && r.Method == "DELETE":
		id := strings.TrimPrefix(path, "/api/keys/")
		_, err := s.db.Exec("DELETE FROM server_devices WHERE id=?", id)
		if err != nil {
			jsonErr(w, 500, err.Error())
			return
		}
		s.db.Exec("DELETE FROM server_user_devices WHERE device_id=?", id)
		jsonOK(w, map[string]string{"status": "deleted"})

	case path == "/api/smtp" && r.Method == "POST":
		if err := r.ParseForm(); err != nil {
			jsonErr(w, 400, "bad form")
			return
		}
		for _, key := range []string{"smtp_host", "smtp_port", "smtp_user", "smtp_pass", "smtp_from", "server_url"} {
			val := r.FormValue(key)
			if val != "" {
				s.smtpSet(key, val)
			}
		}
		http.Redirect(w, r, "/admin/dashboard", http.StatusFound)

	default:
		jsonErr(w, 404, "not found")
	}
}

// ============================================================
// Embedded admin login HTML
// ============================================================

const userRegisterHTML = `<!DOCTYPE html>
<html lang="ru">
<head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Verstak Sync — Регистрация</title>
<style>body{font-family:sans-serif;background:#13131f;color:#e4e4ef;display:flex;justify-content:center;align-items:center;height:100vh;margin:0}
form{background:#1a1a28;border:1px solid #2a2a3c;border-radius:12px;padding:32px;width:320px}
h1{font-size:20px;margin:0 0 20px;text-align:center}
p{text-align:center;font-size:12px;color:#666;margin-top:16px}
a{color:#6366f1}
label{display:block;font-size:12px;color:#888;margin-bottom:4px}
input{width:100%;padding:8px 12px;border:1px solid #2a2a3c;background:#13131f;color:#e4e4ef;border-radius:6px;font-size:14px;margin-bottom:16px;box-sizing:border-box}
button{width:100%;padding:10px;background:#6366f1;color:#fff;border:none;border-radius:6px;font-size:14px;cursor:pointer}
button:hover{background:#4f46e5}
.hint{font-size:11px;color:#666;margin-top:-12px;margin-bottom:16px;text-align:center}
</style>
</head><body>
<form method="POST">
<h1>Регистрация</h1>
<label>Логин</label>
<input type="text" name="username" autofocus required>
<label>Email</label>
<input type="email" name="email" required>
<label>Пароль</label>
<input type="password" name="password" required minlength="8">
<div class="hint">Минимум 8 символов: латинские буквы + цифры</div>
<button>Зарегистрироваться</button>
<p>Уже есть аккаунт? <a href="/login">Войти</a></p>
</form>
</body></html>`

const userLoginHTML = `<!DOCTYPE html>
<html lang="ru">
<head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Verstak Sync — Вход</title>
<style>body{font-family:sans-serif;background:#13131f;color:#e4e4ef;display:flex;justify-content:center;align-items:center;height:100vh;margin:0}
form{background:#1a1a28;border:1px solid #2a2a3c;border-radius:12px;padding:32px;width:320px}
h1{font-size:20px;margin:0 0 20px;text-align:center}
p{text-align:center;font-size:12px;color:#666;margin-top:16px}
a{color:#6366f1}
label{display:block;font-size:12px;color:#888;margin-bottom:4px}
input{width:100%;padding:8px 12px;border:1px solid #2a2a3c;background:#13131f;color:#e4e4ef;border-radius:6px;font-size:14px;margin-bottom:16px;box-sizing:border-box}
button{width:100%;padding:10px;background:#6366f1;color:#fff;border:none;border-radius:6px;font-size:14px;cursor:pointer}
button:hover{background:#4f46e5}</style>
</head><body>
<form method="POST">
<h1>Verstak Sync</h1>
<label>Логин или Email</label>
<input type="text" name="username" autofocus required>
<label>Пароль</label>
<input type="password" name="password" required>
<button>Войти</button>
<p><a href="/register">Зарегистрироваться</a> · <a href="/admin/login">Администратор?</a></p>
</form>
</body></html>`

const adminLoginHTML = `<!DOCTYPE html>
<html lang="ru">
<head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Verstak Sync — Admin Login</title>
<style>body{font-family:sans-serif;background:#13131f;color:#e4e4ef;display:flex;justify-content:center;align-items:center;height:100vh;margin:0}
form{background:#1a1a28;border:1px solid #2a2a3c;border-radius:12px;padding:32px;width:320px}
h1{font-size:20px;margin:0 0 20px;text-align:center}
label{display:block;font-size:12px;color:#888;margin-bottom:4px}
input{width:100%;padding:8px 12px;border:1px solid #2a2a3c;background:#13131f;color:#e4e4ef;border-radius:6px;font-size:14px;margin-bottom:16px;box-sizing:border-box}
button{width:100%;padding:10px;background:#6366f1;color:#fff;border:none;border-radius:6px;font-size:14px;cursor:pointer}
button:hover{background:#4f46e5}</style>
</head><body>
<form method="POST">
<h1>Verstak Sync</h1>
<label>Логин</label>
<input type="text" name="username" autofocus required>
<label>Пароль</label>
<input type="password" name="password" required>
<button>Войти</button>
</form>
</body></html>`