hetzner-api-dyndns-records-webinterface/internal/web/server.go

package web

import (
	"context"
	"crypto/subtle"
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io/fs"
	"log/slog"
	"net"
	"net/http"
	"net/netip"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"time"

	"golang.org/x/net/idna"

	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/config"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/model"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/scheduler"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/secure"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/store"
)

//go:embed templates/*.html static/*
var embeddedAssets embed.FS

type Server struct {
	config    config.Config
	store     *store.Store
	cipher    *secure.Cipher
	scheduler *scheduler.Scheduler
	logger    *slog.Logger
	templates map[string]*template.Template
	limiter   *loginLimiter
}

type viewData struct {
	Title            string
	Page             string
	Mode             string
	CSRF             string
	Flash            *flashMessage
	Now              time.Time
	User             model.User
	IsAdmin          bool
	Dashboard        model.Dashboard
	Zones            []model.Zone
	Zone             model.Zone
	Targets          []model.Target
	ArchivedTargets  []model.Target
	CNAMERecords     []model.CNAMERecord
	Settings         model.Settings
	Token            string
	Form             map[string]string
	Users            []model.User
	ManagedUser      model.User
	AccessZones      []accessZone
	UpdaterEnabled   bool
	CanCreateTargets bool
	ManageTargetIDs  map[int64]bool
	ErrorTargets     []model.Target
	ErrorZones       []model.Zone
	ErrorRuns        []model.UpdateRun
	ErrorCount       int
}

type flashMessage struct {
	Message string
	Kind    string
}

type accessZone struct {
	Zone             model.Zone
	Targets          []model.Target
	DomainGranted    bool
	DomainManaged    bool
	CanCreateTargets bool
	GrantedTargetIDs map[int64]bool
	ManagedTargetIDs map[int64]bool
}

func New(cfg config.Config, database *store.Store, cipher *secure.Cipher, schedule *scheduler.Scheduler, logger *slog.Logger) (*Server, error) {
	templates, err := loadTemplates()
	if err != nil {
		return nil, err
	}
	return &Server{config: cfg, store: database, cipher: cipher, scheduler: schedule, logger: logger, templates: templates, limiter: newLoginLimiter()}, nil
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	static, _ := fs.Sub(embeddedAssets, "static")
	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServerFS(static)))
	mux.HandleFunc("GET /healthz", s.health)
	mux.HandleFunc("GET /readyz", s.ready)
	mux.HandleFunc("GET /setup", s.setupPage)
	mux.HandleFunc("POST /setup", s.setup)
	mux.HandleFunc("GET /login", s.loginPage)
	mux.HandleFunc("POST /login", s.login)
	mux.Handle("POST /logout", s.authenticated(s.logout))
	mux.Handle("GET /", s.authenticated(s.dashboard))
	mux.Handle("GET /domains", s.authenticated(s.domains))
	mux.Handle("GET /domains/new", s.adminOnly(s.domainNew))
	mux.Handle("POST /domains", s.adminOnly(s.domainCreate))
	mux.Handle("GET /domains/{id}", s.authenticated(s.domainDetail))
	mux.Handle("POST /domains/{id}/import", s.adminOnly(s.domainImport))
	mux.Handle("POST /domains/{id}/ttl", s.adminOnly(s.domainTTLSave))
	mux.Handle("POST /domains/{id}/remove", s.adminOnly(s.domainRemove))
	mux.Handle("POST /domains/{id}/delete", s.adminOnly(s.domainDelete))
	mux.Handle("POST /domains/{id}/token", s.adminOnly(s.domainToken))
	mux.Handle("POST /targets", s.authenticated(s.targetCreate))
	mux.Handle("POST /targets/{id}/save", s.authenticated(s.targetSave))
	mux.Handle("POST /targets/{id}/delete", s.adminOnly(s.targetDelete))
	mux.Handle("POST /targets/{id}/archive", s.adminOnly(s.targetArchive))
	mux.Handle("POST /targets/{id}/restore", s.adminOnly(s.targetRestore))
	mux.Handle("POST /cnames", s.adminOnly(s.cnameCreate))
	mux.Handle("POST /cnames/{id}/save", s.adminOnly(s.cnameSave))
	mux.Handle("POST /cnames/{id}/remove", s.adminOnly(s.cnameRemove))
	mux.Handle("POST /cnames/{id}/delete", s.adminOnly(s.cnameDelete))
	mux.Handle("GET /settings", s.adminOnly(s.settingsPage))
	mux.Handle("POST /settings", s.adminOnly(s.settingsSave))
	mux.Handle("POST /run", s.adminOnly(s.runNow))
	mux.Handle("GET /errors", s.adminOnly(s.errorsPage))
	mux.Handle("POST /errors/clear", s.adminOnly(s.errorsClear))
	mux.Handle("GET /security", s.authenticated(s.securityPage))
	mux.Handle("POST /security/password", s.authenticated(s.passwordChange))
	mux.Handle("GET /users", s.adminOnly(s.usersPage))
	mux.Handle("GET /users/new", s.adminOnly(s.userNewPage))
	mux.Handle("POST /users", s.adminOnly(s.userCreate))
	mux.Handle("GET /users/{id}", s.adminOnly(s.userDetail))
	mux.Handle("POST /users/{id}/access", s.adminOnly(s.userAccessSave))
	mux.Handle("POST /users/{id}/state", s.adminOnly(s.userStateSave))
	mux.Handle("POST /users/{id}/password", s.adminOnly(s.userPasswordReset))
	mux.Handle("GET /api/v1/status", s.adminOnly(s.statusAPI))
	mux.Handle("GET /api/v1/scheduler", s.authenticated(s.schedulerAPI))
	return s.securityHeaders(mux)
}

func (s *Server) health(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte("ok\n"))
}

func (s *Server) ready(w http.ResponseWriter, r *http.Request) {
	if _, err := s.store.GetSettings(r.Context()); err != nil {
		http.Error(w, "database unavailable", http.StatusServiceUnavailable)
		return
	}
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	_, _ = w.Write([]byte("ready\n"))
}

func (s *Server) setupPage(w http.ResponseWriter, r *http.Request) {
	exists, err := s.store.HasAdmin(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	if exists {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	s.render(w, "setup", viewData{Title: "Ersteinrichtung", Page: "setup", Mode: s.config.Mode, CSRF: s.publicCSRF(w, r), Now: time.Now(), Form: map[string]string{"username": "admin", "display_name": "Administrator"}})
}

func (s *Server) setup(w http.ResponseWriter, r *http.Request) {
	exists, err := s.store.HasAdmin(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	if exists {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validPublicCSRF(r) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	form := map[string]string{"username": strings.TrimSpace(r.FormValue("username")), "display_name": strings.TrimSpace(r.FormValue("display_name"))}
	username, usernameErr := normalizeUsername(form["username"])
	if usernameErr != nil {
		s.renderError(w, "setup", usernameErr.Error(), s.publicCSRF(w, r), form)
		return
	}
	if form["display_name"] == "" || len([]rune(form["display_name"])) > 80 {
		s.renderError(w, "setup", "Bitte einen Anzeigenamen mit höchstens 80 Zeichen angeben.", s.publicCSRF(w, r), form)
		return
	}
	password, confirm := r.FormValue("password"), r.FormValue("confirm_password")
	if password != confirm {
		s.renderError(w, "setup", "Die Passwörter stimmen nicht überein.", s.publicCSRF(w, r), form)
		return
	}
	hash, err := secure.HashPassword(password)
	if err != nil {
		s.renderError(w, "setup", err.Error(), s.publicCSRF(w, r), form)
		return
	}
	if err := s.store.CreateAdmin(r.Context(), username, form["display_name"], hash); err != nil {
		if strings.Contains(err.Error(), "UNIQUE") || strings.Contains(err.Error(), "constraint") {
			http.Redirect(w, r, "/login", http.StatusSeeOther)
			return
		}
		s.serverError(w, err)
		return
	}
	admin, _, err := s.store.GetUserByUsername(r.Context(), username)
	if err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "admin.setup", "Admin-Zugang eingerichtet")
	if err := s.startSession(w, r.Context(), admin); err != nil {
		s.serverError(w, err)
		return
	}
	s.redirectNotice(w, r, "/", "Ersteinrichtung abgeschlossen.")
}

func (s *Server) loginPage(w http.ResponseWriter, r *http.Request) {
	exists, err := s.store.HasAdmin(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	if !exists {
		http.Redirect(w, r, "/setup", http.StatusSeeOther)
		return
	}
	if session, _ := s.session(r.Context(), r); session != nil {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}
	s.render(w, "login", viewData{Title: "Anmelden", Page: "login", Mode: s.config.Mode, CSRF: s.publicCSRF(w, r), Flash: notice(r), Now: time.Now()})
}

func (s *Server) login(w http.ResponseWriter, r *http.Request) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validPublicCSRF(r) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	clientIP := remoteIP(r)
	if !s.limiter.Allow(clientIP) {
		s.renderError(w, "login", "Zu viele Anmeldeversuche. Bitte warte kurz.", s.publicCSRF(w, r), map[string]string{})
		return
	}
	username, usernameErr := normalizeUsername(r.FormValue("username"))
	user, hash, err := s.store.GetUserByUsername(r.Context(), username)
	if usernameErr != nil || err != nil || !user.Active || !secure.VerifyPassword(hash, r.FormValue("password")) {
		s.limiter.Fail(clientIP)
		_ = s.store.AddAudit(r.Context(), "auth.failed", "Fehlgeschlagene Anmeldung")
		s.renderError(w, "login", "Passwort nicht korrekt.", s.publicCSRF(w, r), map[string]string{})
		return
	}
	s.limiter.Reset(clientIP)
	if err := s.startSession(w, r.Context(), user); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.MarkUserLoggedIn(r.Context(), user.ID)
	_ = s.store.AddAudit(r.Context(), "auth.login", "Angemeldet: "+user.Username)
	s.redirectNotice(w, r, "/", "Angemeldet.")
}

func (s *Server) logout(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	_ = s.store.DeleteSession(r.Context(), session.TokenHash)
	s.clearSession(w)
	s.redirectNotice(w, r, "/login", "Abgemeldet.")
}

func (s *Server) dashboard(w http.ResponseWriter, r *http.Request, session *model.Session) {
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	user := userFromSession(session)
	zones, err := s.zonesForSession(r.Context(), session)
	if err != nil {
		s.serverError(w, err)
		return
	}
	active, _ := s.activeTargetsForSession(r.Context(), session)
	var runs []model.UpdateRun
	var events []model.AuditEvent
	errorCount := 0
	if session.Role == "admin" {
		runs, _ = s.store.RecentRuns(r.Context(), 6)
		events, _ = s.store.RecentAudit(r.Context(), 6)
		errorCount, _ = s.store.CountErrors(r.Context())
	}
	s.render(w, "dashboard", viewData{Title: "Übersicht", Page: "dashboard", CSRF: session.CSRFToken, Flash: notice(r), Now: time.Now(), User: user, IsAdmin: session.Role == "admin", Dashboard: model.Dashboard{Settings: settings, Zones: zones, ActiveTargets: active, RecentRuns: runs, RecentEvents: events, NextRunAt: s.scheduler.NextRunAt(), SchedulerRunning: s.scheduler.IsRunning(), ErrorCount: errorCount}})
}

func (s *Server) domains(w http.ResponseWriter, r *http.Request, session *model.Session) {
	zones, err := s.zonesForSession(r.Context(), session)
	if err != nil {
		s.serverError(w, err)
		return
	}
	s.render(w, "domains", viewData{Title: "Domains", Page: "domains", CSRF: session.CSRFToken, Flash: notice(r), Zones: zones, User: userFromSession(session), IsAdmin: session.Role == "admin", Now: time.Now()})
}

func (s *Server) domainNew(w http.ResponseWriter, r *http.Request, session *model.Session) {
	s.render(w, "domain_new", viewData{Title: "Domain verbinden", Page: "domains", CSRF: session.CSRFToken, User: userFromSession(session), IsAdmin: true, Now: time.Now(), Form: map[string]string{}})
}

func (s *Server) domainCreate(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	form := map[string]string{"label": strings.TrimSpace(r.FormValue("label")), "zone": strings.TrimSpace(r.FormValue("zone"))}
	token := strings.TrimSpace(r.FormValue("token"))
	zoneName, err := normalizeZone(form["zone"])
	if err != nil || token == "" {
		if err == nil {
			err = errors.New("Hetzner API-Token ist erforderlich")
		}
		s.renderError(w, "domain_new", err.Error(), session.CSRFToken, form)
		return
	}
	zones, err := s.scheduler.ValidateToken(r.Context(), token)
	if err != nil {
		s.renderError(w, "domain_new", "Der API-Token konnte nicht validiert werden: "+safeMessage(err), session.CSRFToken, form)
		return
	}
	providerID := ""
	for _, candidate := range zones {
		if strings.EqualFold(strings.TrimSuffix(candidate.Name, "."), zoneName) {
			providerID = candidate.ID
			break
		}
	}
	if providerID == "" {
		s.renderError(w, "domain_new", "Die Zone ist mit diesem Token nicht erreichbar. Prüfe den Domainnamen oder das Hetzner-Projekt.", session.CSRFToken, form)
		return
	}
	if form["label"] == "" {
		form["label"] = "Hetzner · " + zoneName
	}
	fingerprint := s.cipher.Fingerprint(token)
	credential, err := s.store.FindCredentialByFingerprint(r.Context(), fingerprint)
	if err != nil {
		s.serverError(w, err)
		return
	}
	if credential == nil {
		ciphertext, nonce, encryptErr := s.cipher.Encrypt(token)
		if encryptErr != nil {
			s.serverError(w, encryptErr)
			return
		}
		created, createErr := s.store.CreateCredential(r.Context(), form["label"], ciphertext, nonce, fingerprint)
		if createErr != nil {
			s.serverError(w, createErr)
			return
		}
		credential = &created
	}
	zone, err := s.store.CreateZone(r.Context(), credential.ID, providerID, zoneName)
	if err != nil {
		s.renderError(w, "domain_new", "Domain konnte nicht hinzugefügt werden: "+safeMessage(err), session.CSRFToken, form)
		return
	}
	imported, importErr := s.scheduler.SyncZone(r.Context(), zone.ID)
	if importErr != nil {
		s.logger.Warn("initial zone import failed", "zone", zone.Name, "error", importErr)
	}
	_ = s.store.AddAudit(r.Context(), "zone.connected", "Domain verbunden: "+zone.Name)
	noticeText := fmt.Sprintf("%s verbunden; %d A-/AAAA-Ziele und die vorhandenen CNAMEs importiert.", zone.Name, imported)
	if importErr != nil {
		noticeText = zone.Name + " verbunden, der Import kann jetzt manuell erneut gestartet werden."
	}
	s.redirectNotice(w, r, "/domains/"+strconv.FormatInt(zone.ID, 10), noticeText)
}

func (s *Server) domainDetail(w http.ResponseWriter, r *http.Request, session *model.Session) {
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if !s.canAccessZone(r.Context(), session, zoneID) {
		http.NotFound(w, r)
		return
	}
	var targets []model.Target
	if session.Role == "admin" {
		targets, err = s.store.ListTargets(r.Context(), zoneID)
	} else {
		targets, err = s.store.ListAccessibleTargets(r.Context(), session.UserID, zoneID)
	}
	if err != nil {
		s.serverError(w, err)
		return
	}
	var archivedTargets []model.Target
	if session.Role == "admin" {
		archivedTargets, err = s.store.ListArchivedTargets(r.Context(), zoneID)
		if err != nil {
			s.serverError(w, err)
			return
		}
	}
	var cnameRecords []model.CNAMERecord
	if session.Role == "admin" {
		cnameRecords, err = s.store.ListCNAMERecords(r.Context(), zoneID)
		if err != nil {
			s.serverError(w, err)
			return
		}
	}
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	canCreateTargets := session.Role == "admin"
	manageTargetIDs := make(map[int64]bool, len(targets))
	if session.Role == "admin" {
		for _, target := range targets {
			manageTargetIDs[target.ID] = true
		}
	} else {
		grants, grantErr := s.store.ListAccessGrants(r.Context(), session.UserID)
		if grantErr != nil {
			s.serverError(w, grantErr)
			return
		}
		domainManaged := false
		for _, grant := range grants {
			if grant.ZoneID != zoneID {
				continue
			}
			if grant.TargetID == nil {
				domainManaged = grant.CanManageTargets
				canCreateTargets = grant.CanCreateTargets
			} else if grant.CanManageTargets {
				manageTargetIDs[*grant.TargetID] = true
			}
		}
		if domainManaged {
			for _, target := range targets {
				manageTargetIDs[target.ID] = true
			}
		}
	}
	s.render(w, "domain_detail", viewData{Title: zone.Name, Page: "domains", CSRF: session.CSRFToken, Flash: notice(r), Zone: zone, Targets: targets, ArchivedTargets: archivedTargets, CNAMERecords: cnameRecords, Settings: settings, CanCreateTargets: canCreateTargets, ManageTargetIDs: manageTargetIDs, User: userFromSession(session), IsAdmin: session.Role == "admin", Now: time.Now()})
}

func (s *Server) domainImport(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	imported, err := s.scheduler.SyncZone(r.Context(), zoneID)
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), "Import fehlgeschlagen: "+safeMessage(err), "error")
		return
	}
	s.redirectNotice(w, r, domainURL(zoneID), fmt.Sprintf("Import abgeschlossen: %d neue A-/AAAA-Ziele; CNAMEs wurden synchronisiert.", imported))
}

func (s *Server) domainTTLSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	ttl, err := parseTTL(r.FormValue("ttl"))
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	targets, err := s.store.ListTargets(r.Context(), zoneID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	cnames, err := s.store.ListCNAMERecords(r.Context(), zoneID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	changed, err := s.scheduler.SyncZoneTTL(r.Context(), zoneID, targets, cnames, ttl)
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), "TTL konnte nicht für alle Records gesetzt werden: "+safeMessage(err), "error")
		return
	}
	if err := s.store.UpdateZoneTargetTTLs(r.Context(), zoneID, ttl); err != nil {
		_, _ = s.scheduler.SyncZone(r.Context(), zoneID)
		s.serverError(w, err)
		return
	}
	if err := s.store.UpdateZoneCNAMERecordTTLs(r.Context(), zoneID, ttl); err != nil {
		_, _ = s.scheduler.SyncZone(r.Context(), zoneID)
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "zone.ttl.updated", fmt.Sprintf("%s: TTL für %d verwaltete Records auf %d Sekunden gesetzt durch %s", zone.Name, len(targets)+len(cnames), ttl, session.Username))
	s.redirectNotice(w, r, domainURL(zoneID), fmt.Sprintf("TTL für %d verwaltete Records auf %d Sekunden gesetzt (%d RRsets bei Hetzner geändert).", len(targets)+len(cnames), ttl, changed))
}

func (s *Server) domainRemove(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if err := s.store.DeleteZone(r.Context(), zoneID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "zone.removed", "Verwaltung beendet: "+zone.Name)
	s.redirectNotice(w, r, "/domains", "Die lokale Verwaltung für "+zone.Name+" wurde entfernt; Hetzner-DNS-Records bleiben erhalten.")
}

func (s *Server) domainDelete(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	targets, err := s.store.ListTargets(r.Context(), zoneID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	archivedTargets, err := s.store.ListArchivedTargets(r.Context(), zoneID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	targets = append(targets, archivedTargets...)
	cnames, err := s.store.ListCNAMERecords(r.Context(), zoneID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	deleted, err := s.scheduler.DeleteZoneRecords(r.Context(), zoneID, targets, cnames)
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), "Domain konnte nicht vollständig gelöscht werden: "+safeMessage(err), "error")
		return
	}
	if err := s.store.DeleteZone(r.Context(), zoneID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "zone.deleted", fmt.Sprintf("Domain vollständig gelöscht: %s, %d Hetzner-RRsets entfernt durch %s", zone.Name, deleted, session.Username))
	s.redirectNotice(w, r, "/domains", fmt.Sprintf("%s und alle Einträge der WebUI wurden gelöscht; %d zugehörige Hetzner-RRsets wurden entfernt.", zone.Name, deleted))
}

func (s *Server) domainToken(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, ok := pathID(w, r)
	if !ok {
		return
	}
	hash, err := s.store.PasswordHash(r.Context(), session.UserID)
	if err != nil || !secure.VerifyPassword(hash, r.FormValue("password")) {
		s.redirectNotice(w, r, domainURL(zoneID), "Passwort nicht korrekt; Token bleibt verborgen.", "error")
		return
	}
	zone, credential, err := s.store.GetZoneWithCredential(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	token, err := s.cipher.Decrypt(credential.Ciphertext, credential.Nonce)
	if err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.SetSessionReauth(r.Context(), session.ID, time.Now().UTC().Add(5*time.Minute))
	_ = s.store.AddAudit(r.Context(), "credential.revealed", "API-Token angezeigt: "+zone.Name)
	s.render(w, "token", viewData{Title: "API-Token anzeigen", Page: "domains", CSRF: session.CSRFToken, Zone: zone, Token: token, User: userFromSession(session), IsAdmin: true, Now: time.Now()})
}

func (s *Server) targetCreate(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, err := strconv.ParseInt(r.FormValue("zone_id"), 10, 64)
	if err != nil || zoneID < 1 {
		http.Error(w, "Ungültige Domain", http.StatusBadRequest)
		return
	}
	if session.Role != "admin" {
		allowed, permissionErr := s.store.CanCreateTarget(r.Context(), session.UserID, zoneID)
		if permissionErr != nil {
			s.serverError(w, permissionErr)
			return
		}
		if !allowed {
			http.NotFound(w, r)
			return
		}
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	recordName, fqdn, err := normalizeRecord(r.FormValue("record_name"), zone.Name)
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	if session.Role != "admin" && recordName == "@" {
		s.redirectNotice(w, r, domainURL(zoneID), "Mitglieder dürfen nur Subdomains, nicht den Root-Record anlegen.", "error")
		return
	}
	updateIPv4, updateIPv6 := checked(r, "update_ipv4"), checked(r, "update_ipv6")
	if updateIPv6 && !settings.IPv6Enabled {
		s.redirectNotice(w, r, domainURL(zoneID), "IPv6 ist global deaktiviert und kann für dieses Ziel nicht aktiviert werden.", "error")
		return
	}
	ttl, err := parseTTL(r.FormValue("ttl"))
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	description := strings.TrimSpace(r.FormValue("description"))
	if len([]rune(description)) > 512 {
		s.redirectNotice(w, r, domainURL(zoneID), "Die Beschreibung darf höchstens 512 Zeichen haben.", "error")
		return
	}
	activeRequested := checked(r, "active")
	active := targetDynDNSActive(activeRequested, updateIPv4, updateIPv6)
	activeAutoDisabled := activeRequested && !active
	staticIPv4, staticIPv6 := "", ""
	if !active {
		staticIPv4, staticIPv6, err = parseStaticTargetIPs(r, updateIPv4, updateIPv6)
		if err != nil {
			s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
			return
		}
	}
	target, err := s.store.CreateTarget(r.Context(), model.Target{ZoneID: zoneID, RecordName: recordName, FQDN: fqdn, UpdateIPv4: updateIPv4, UpdateIPv6: updateIPv6, Active: active, StaticIPv4: staticIPv4, StaticIPv6: staticIPv6, Description: description, TTL: ttl})
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), "Ziel konnte nicht angelegt werden: "+safeMessage(err), "error")
		return
	}
	if !target.Active && hasStaticIP(target) {
		updated, status, syncErr := s.scheduler.SyncStaticTarget(r.Context(), target)
		if syncErr != nil {
			_ = s.store.UpdateTargetResult(r.Context(), target.ID, "Fehler", safeMessage(syncErr), false)
			s.redirectNotice(w, r, domainURL(zoneID), "Ziel angelegt, aber die feste IP konnte nicht bei Hetzner gesetzt werden: "+safeMessage(syncErr), "error")
			return
		}
		_ = s.store.UpdateTargetResult(r.Context(), target.ID, status, "", updated)
	}
	_ = s.store.AddAudit(r.Context(), "target.created", "DynDNS-Ziel angelegt: "+target.FQDN+" durch "+session.Username)
	triggered := target.Active && s.triggerUpdateIfEnabled(r.Context())
	noticeText := "Ziel angelegt."
	if activeAutoDisabled {
		noticeText += " DynDNS wurde deaktiviert, weil keine IP-Familie ausgewählt ist."
	}
	if !target.Active && hasStaticIP(target) {
		noticeText += " Feste IP gespeichert."
	}
	s.redirectNotice(w, r, domainURL(zoneID), noticeText+activeNotice(target.Active, triggered))
}

func (s *Server) targetSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	targetID, ok := pathID(w, r)
	if !ok {
		return
	}
	target, err := s.store.GetTarget(r.Context(), targetID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if !s.canAccessTarget(r.Context(), session, target) {
		http.NotFound(w, r)
		return
	}
	if session.Role != "admin" {
		allowed, permissionErr := s.store.CanManageTarget(r.Context(), session.UserID, target.ZoneID, target.ID)
		if permissionErr != nil {
			s.serverError(w, permissionErr)
			return
		}
		if !allowed {
			http.NotFound(w, r)
			return
		}
	}
	if !target.ArchivedAt.IsZero() {
		http.NotFound(w, r)
		return
	}
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	wasActive := target.Active
	previousIPv4, previousIPv6, previousTTL := target.UpdateIPv4, target.UpdateIPv6, target.TTL
	if session.Role == "admin" {
		target.UpdateIPv4 = checked(r, "update_ipv4")
		if checked(r, "update_ipv6") && !settings.IPv6Enabled {
			s.redirectNotice(w, r, domainURL(target.ZoneID), "IPv6 ist global deaktiviert und kann für dieses Ziel nicht aktiviert werden.", "error")
			return
		}
		target.UpdateIPv6 = checked(r, "update_ipv6")
	}
	if !settings.IPv6Enabled {
		target.UpdateIPv6 = false
		target.StaticIPv6 = ""
	}
	activeRequested := checked(r, "active")
	target.Active = targetDynDNSActive(activeRequested, target.UpdateIPv4, target.UpdateIPv6)
	activeAutoDisabled := activeRequested && !target.Active
	target.Description = strings.TrimSpace(r.FormValue("description"))
	ttl, err := parseEditableTTL(r.FormValue("ttl"), target.TTL)
	if err != nil {
		s.redirectNotice(w, r, domainURL(target.ZoneID), err.Error(), "error")
		return
	}
	target.TTL = ttl
	if len([]rune(target.Description)) > 512 {
		s.redirectNotice(w, r, domainURL(target.ZoneID), "Die Beschreibung darf höchstens 512 Zeichen haben.", "error")
		return
	}
	if target.Active {
		target.StaticIPv4, target.StaticIPv6 = "", ""
	} else {
		target.StaticIPv4, target.StaticIPv6, err = parseStaticTargetIPs(r, target.UpdateIPv4, target.UpdateIPv6)
		if err != nil {
			s.redirectNotice(w, r, domainURL(target.ZoneID), err.Error(), "error")
			return
		}
	}
	deleted, err := s.scheduler.DeleteTargetFamilies(r.Context(), target, previousIPv4 && !target.UpdateIPv4, previousIPv6 && !target.UpdateIPv6)
	if err != nil {
		s.redirectNotice(w, r, domainURL(target.ZoneID), "A-/AAAA-Record konnte nicht bei Hetzner gelöscht werden: "+safeMessage(err), "error")
		return
	}
	if previousTTL != target.TTL && (target.Active || !hasStaticIP(target)) {
		if err := s.scheduler.SyncTargetTTL(r.Context(), target); err != nil {
			s.redirectNotice(w, r, domainURL(target.ZoneID), "TTL konnte nicht bei Hetzner aktualisiert werden: "+safeMessage(err), "error")
			return
		}
	}
	if err := s.store.UpdateTarget(r.Context(), target); err != nil {
		s.serverError(w, err)
		return
	}
	if !target.Active && hasStaticIP(target) {
		updated, status, syncErr := s.scheduler.SyncStaticTarget(r.Context(), target)
		if syncErr != nil {
			_ = s.store.UpdateTargetResult(r.Context(), target.ID, "Fehler", safeMessage(syncErr), false)
			s.redirectNotice(w, r, domainURL(target.ZoneID), "Feste IP konnte nicht bei Hetzner gesetzt werden: "+safeMessage(syncErr), "error")
			return
		}
		_ = s.store.UpdateTargetResult(r.Context(), target.ID, status, "", updated)
	} else if target.Active {
		if err := s.scheduler.SyncTargetComment(r.Context(), target); err != nil {
			s.logger.Warn("sync target comment", "target", target.FQDN, "error", err)
		}
	}
	_ = s.store.AddAudit(r.Context(), "target.updated", "DynDNS-Ziel geändert: "+target.FQDN+" durch "+session.Username)
	needsUpdate := target.Active && (!wasActive || previousIPv4 != target.UpdateIPv4 || previousIPv6 != target.UpdateIPv6 || previousTTL != target.TTL)
	triggered := needsUpdate && s.triggerUpdateIfEnabled(r.Context())
	noticeText := "Ziel gespeichert."
	if activeAutoDisabled {
		noticeText += " DynDNS wurde deaktiviert, weil keine IP-Familie ausgewählt ist."
	}
	if deleted > 0 {
		noticeText += " A-/AAAA-Record entfernt."
	}
	s.redirectNotice(w, r, domainURL(target.ZoneID), noticeText+activeNotice(needsUpdate, triggered))
}

func (s *Server) targetDelete(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	targetID, ok := pathID(w, r)
	if !ok {
		return
	}
	target, err := s.store.GetTarget(r.Context(), targetID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	deleted, err := s.scheduler.DeleteTargetFamilies(r.Context(), target, true, true)
	if err != nil {
		s.redirectNotice(w, r, domainURL(target.ZoneID), "Ziel konnte nicht vollständig gelöscht werden: "+safeMessage(err), "error")
		return
	}
	if err := s.store.DeleteTarget(r.Context(), target.ID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "target.deleted", "Ziel vollständig gelöscht: "+target.FQDN+" durch "+session.Username)
	s.redirectNotice(w, r, domainURL(target.ZoneID), fmt.Sprintf("Ziel gelöscht; %d A-/AAAA-Record(s) bei Hetzner entfernt.", deleted))
}

func (s *Server) targetArchive(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	targetID, ok := pathID(w, r)
	if !ok {
		return
	}
	target, err := s.store.GetTarget(r.Context(), targetID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if !target.ArchivedAt.IsZero() {
		s.redirectNotice(w, r, domainURL(target.ZoneID), "Die Verknüpfung ist bereits getrennt.", "info")
		return
	}
	if err := s.store.ArchiveTarget(r.Context(), target.ID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "target.archived", "DynDNS-Verknüpfung getrennt: "+target.FQDN+" durch "+session.Username)
	s.redirectNotice(w, r, domainURL(target.ZoneID), "Verknüpfung getrennt. Der Hetzner-DNS-Record wurde nicht verändert.")
}

func (s *Server) targetRestore(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	targetID, ok := pathID(w, r)
	if !ok {
		return
	}
	target, err := s.store.GetTarget(r.Context(), targetID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if target.ArchivedAt.IsZero() {
		s.redirectNotice(w, r, domainURL(target.ZoneID), "Das Ziel ist bereits verknüpft.", "info")
		return
	}
	if err := s.store.RestoreTarget(r.Context(), target.ID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "target.restored", "DynDNS-Verknüpfung wiederhergestellt: "+target.FQDN+" durch "+session.Username)
	s.redirectNotice(w, r, domainURL(target.ZoneID), "Verknüpfung wiederhergestellt. Das Ziel bleibt zunächst deaktiviert.")
}

func (s *Server) cnameCreate(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	zoneID, err := strconv.ParseInt(r.FormValue("zone_id"), 10, 64)
	if err != nil || zoneID < 1 {
		http.Error(w, "Ungültige Domain", http.StatusBadRequest)
		return
	}
	zone, err := s.store.GetZone(r.Context(), zoneID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	recordName, fqdn, err := normalizeRecord(r.FormValue("record_name"), zone.Name)
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	if recordName == "@" {
		s.redirectNotice(w, r, domainURL(zoneID), "Ein CNAME kann nicht als Root-Record angelegt werden.", "error")
		return
	}
	destination, err := normalizeCNAMEDestination(r.FormValue("destination"))
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	ttl, err := parseTTL(r.FormValue("ttl"))
	if err != nil {
		s.redirectNotice(w, r, domainURL(zoneID), err.Error(), "error")
		return
	}
	description := strings.TrimSpace(r.FormValue("description"))
	if len([]rune(description)) > 512 {
		s.redirectNotice(w, r, domainURL(zoneID), "Die Beschreibung darf höchstens 512 Zeichen haben.", "error")
		return
	}
	record := model.CNAMERecord{ZoneID: zoneID, Active: checked(r, "active"), RecordName: recordName, FQDN: fqdn, Destination: destination, Description: description, TTL: ttl}
	if record.Active {
		if err := s.scheduler.CreateCNAME(r.Context(), record); err != nil {
			s.redirectNotice(w, r, domainURL(zoneID), "CNAME konnte nicht angelegt werden: "+safeMessage(err), "error")
			return
		}
	}
	created, err := s.store.CreateCNAMERecord(r.Context(), record)
	if err != nil {
		_, _ = s.scheduler.SyncZone(r.Context(), zoneID)
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "cname.created", "CNAME angelegt: "+created.FQDN+" → "+created.Destination+" durch "+session.Username)
	noticeText := "CNAME angelegt."
	if !record.Active {
		noticeText += " Der Hetzner-Record bleibt deaktiviert."
	}
	s.redirectNotice(w, r, domainURL(zoneID), noticeText)
}

func (s *Server) cnameSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	recordID, ok := pathID(w, r)
	if !ok {
		return
	}
	previous, err := s.store.GetCNAMERecord(r.Context(), recordID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	record := previous
	record.Active = checked(r, "active")
	record.Destination, err = normalizeCNAMEDestination(r.FormValue("destination"))
	if err != nil {
		s.redirectNotice(w, r, domainURL(record.ZoneID), err.Error(), "error")
		return
	}
	record.TTL, err = parseEditableTTL(r.FormValue("ttl"), previous.TTL)
	if err != nil {
		s.redirectNotice(w, r, domainURL(record.ZoneID), err.Error(), "error")
		return
	}
	record.Description = strings.TrimSpace(r.FormValue("description"))
	if len([]rune(record.Description)) > 512 {
		s.redirectNotice(w, r, domainURL(record.ZoneID), "Die Beschreibung darf höchstens 512 Zeichen haben.", "error")
		return
	}
	var providerErr error
	switch {
	case previous.Active && !record.Active:
		providerErr = s.scheduler.DeleteCNAME(r.Context(), previous)
	case !previous.Active && record.Active:
		providerErr = s.scheduler.CreateCNAME(r.Context(), record)
	case previous.Active && record.Active:
		providerErr = s.scheduler.UpdateCNAME(r.Context(), previous, record)
	}
	if providerErr != nil {
		s.redirectNotice(w, r, domainURL(record.ZoneID), "CNAME konnte nicht gespeichert werden: "+safeMessage(providerErr), "error")
		return
	}
	if err := s.store.UpdateCNAMERecord(r.Context(), record); err != nil {
		_, _ = s.scheduler.SyncZone(r.Context(), record.ZoneID)
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "cname.updated", fmt.Sprintf("CNAME geändert: %s, aktiv=%t durch %s", record.FQDN, record.Active, session.Username))
	state := "deaktiviert."
	if record.Active {
		state = "aktiviert."
	}
	s.redirectNotice(w, r, domainURL(record.ZoneID), "CNAME gespeichert und "+state)
}

func (s *Server) cnameDelete(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	recordID, ok := pathID(w, r)
	if !ok {
		return
	}
	record, err := s.store.GetCNAMERecord(r.Context(), recordID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	deleted, err := s.scheduler.DeleteZoneRecords(r.Context(), record.ZoneID, nil, []model.CNAMERecord{record})
	if err != nil {
		s.redirectNotice(w, r, domainURL(record.ZoneID), "CNAME konnte nicht vollständig gelöscht werden: "+safeMessage(err), "error")
		return
	}
	if err := s.store.DeleteCNAMERecord(r.Context(), record.ID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "cname.deleted", "CNAME vollständig gelöscht: "+record.FQDN+" durch "+session.Username)
	s.redirectNotice(w, r, domainURL(record.ZoneID), fmt.Sprintf("CNAME vollständig gelöscht; %d Hetzner-RRset entfernt.", deleted))
}

func (s *Server) cnameRemove(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	recordID, ok := pathID(w, r)
	if !ok {
		return
	}
	record, err := s.store.GetCNAMERecord(r.Context(), recordID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if err := s.store.DeleteCNAMERecord(r.Context(), record.ID); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "cname.removed", "CNAME nur aus WebUI entfernt: "+record.FQDN+" durch "+session.Username)
	s.redirectNotice(w, r, domainURL(record.ZoneID), "CNAME aus der WebUI entfernt; der Hetzner-Record blieb unverändert.")
}

func (s *Server) settingsPage(w http.ResponseWriter, r *http.Request, session *model.Session) {
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	s.render(w, "settings", viewData{Title: "Einstellungen", Page: "settings", CSRF: session.CSRFToken, Flash: notice(r), Settings: settings, User: userFromSession(session), IsAdmin: true, Now: time.Now()})
}

func (s *Server) settingsSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	interval, err := strconv.Atoi(r.FormValue("interval"))
	if err != nil || interval < 60 || interval > 86400 {
		s.redirectNotice(w, r, "/settings", "Das Intervall muss zwischen 60 und 86.400 Sekunden liegen.", "error")
		return
	}
	updaterEnabled, ipv6Enabled := checked(r, "updater_enabled"), checked(r, "ipv6_enabled")
	current, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	ipv4, ipv6 := lines(r.FormValue("ipv4_endpoints")), lines(r.FormValue("ipv6_endpoints"))
	if len(ipv4) == 0 {
		s.redirectNotice(w, r, "/settings", "Für IPv4 ist mindestens ein HTTPS-Endpoint erforderlich.", "error")
		return
	}
	if len(ipv6) == 0 {
		ipv6 = current.IPv6Endpoints
	}
	if ipv6Enabled && len(ipv6) == 0 {
		s.redirectNotice(w, r, "/settings", "Für aktiviertes IPv6 ist mindestens ein HTTPS-Endpoint erforderlich.", "error")
		return
	}
	if err := s.scheduler.ValidateEndpoints(r.Context(), ipv4); err != nil {
		s.redirectNotice(w, r, "/settings", "IPv4-Endpoint ungültig: "+safeMessage(err), "error")
		return
	}
	if ipv6Enabled {
		if err := s.scheduler.ValidateEndpoints(r.Context(), ipv6); err != nil {
			s.redirectNotice(w, r, "/settings", "IPv6-Endpoint ungültig: "+safeMessage(err), "error")
			return
		}
	}
	deletedIPv6 := 0
	if !ipv6Enabled {
		deletedIPv6, err = s.scheduler.DisableIPv6(r.Context())
		if err != nil {
			s.redirectNotice(w, r, "/settings", "IPv6 konnte nicht vollständig deaktiviert werden: "+safeMessage(err), "error")
			return
		}
	}
	if err := s.store.UpdateSettings(r.Context(), interval, updaterEnabled, ipv6Enabled, ipv4, ipv6); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "settings.updated", fmt.Sprintf("Updater geändert: Dienst=%t, IPv6=%t, Intervall=%ds, entfernte AAAA=%d", updaterEnabled, ipv6Enabled, interval, deletedIPv6))
	s.scheduler.Trigger()
	noticeText := "Einstellungen gespeichert."
	if !ipv6Enabled {
		noticeText += fmt.Sprintf(" %d AAAA-Record(s) entfernt und IPv6 bei allen Zielen deaktiviert.", deletedIPv6)
	}
	s.redirectNotice(w, r, "/settings", noticeText)
}

func (s *Server) runNow(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	if !settings.UpdaterEnabled {
		s.redirectNotice(w, r, "/settings", "Der Updater ist deaktiviert. Aktiviere zuerst den Dienst.", "info")
		return
	}
	s.scheduler.Trigger()
	s.redirectNotice(w, r, "/", "Aktualisierung gestartet.")
}

func (s *Server) errorsPage(w http.ResponseWriter, r *http.Request, session *model.Session) {
	targets, err := s.store.ListTargetsWithErrors(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	zones, err := s.store.ListZonesWithErrors(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	runs, err := s.store.FailedRuns(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	s.render(w, "errors", viewData{Title: "Fehler", Page: "errors", CSRF: session.CSRFToken, Flash: notice(r), User: userFromSession(session), IsAdmin: true, ErrorTargets: targets, ErrorZones: zones, ErrorRuns: runs, ErrorCount: len(targets) + len(zones) + len(runs), Now: time.Now()})
}

func (s *Server) errorsClear(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	if err := s.store.ClearErrors(r.Context()); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "errors.cleared", "Fehlerliste geleert durch "+session.Username)
	s.redirectNotice(w, r, "/errors", "Fehlerliste geleert.")
}

func (s *Server) securityPage(w http.ResponseWriter, r *http.Request, session *model.Session) {
	s.render(w, "security", viewData{Title: "Sicherheit", Page: "security", CSRF: session.CSRFToken, Flash: notice(r), Mode: s.config.Mode, User: userFromSession(session), IsAdmin: session.Role == "admin", Now: time.Now()})
}

func (s *Server) passwordChange(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	hash, err := s.store.PasswordHash(r.Context(), session.UserID)
	if err != nil || !secure.VerifyPassword(hash, r.FormValue("current_password")) {
		s.redirectNotice(w, r, "/security", "Aktuelles Passwort ist nicht korrekt.", "error")
		return
	}
	if r.FormValue("new_password") != r.FormValue("confirm_password") {
		s.redirectNotice(w, r, "/security", "Die neuen Passwörter stimmen nicht überein.", "error")
		return
	}
	newHash, err := secure.HashPassword(r.FormValue("new_password"))
	if err != nil {
		s.redirectNotice(w, r, "/security", err.Error(), "error")
		return
	}
	if err := s.store.UpdatePassword(r.Context(), session.UserID, newHash); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.DeleteOtherSessions(r.Context(), session.UserID, session.ID)
	_ = s.store.AddAudit(r.Context(), "security.password_changed", "Passwort geändert: "+session.Username)
	s.redirectNotice(w, r, "/security", "Passwort geändert; andere eigene Sitzungen wurden abgemeldet.")
}

func (s *Server) statusAPI(w http.ResponseWriter, r *http.Request, _ *model.Session) {
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	active, _ := s.store.CountActiveTargets(r.Context())
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"last_ipv4": settings.LastIPv4, "last_ipv6": settings.LastIPv6, "last_run_at": settings.LastRunAt, "last_run_status": settings.LastRunStatus,
		"next_run_at": s.scheduler.NextRunAt(), "active_targets": active, "running": s.scheduler.IsRunning(), "enabled": settings.UpdaterEnabled, "ipv6_enabled": settings.IPv6Enabled,
	})
}

func (s *Server) schedulerAPI(w http.ResponseWriter, r *http.Request, _ *model.Session) {
	settings, err := s.store.GetSettings(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"next_run_unix": unixSeconds(s.scheduler.NextRunAt()),
		"running":       s.scheduler.IsRunning(),
		"enabled":       settings.UpdaterEnabled,
	})
}

func (s *Server) usersPage(w http.ResponseWriter, r *http.Request, session *model.Session) {
	users, err := s.store.ListUsers(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	s.render(w, "users", viewData{Title: "Benutzer", Page: "users", CSRF: session.CSRFToken, Flash: notice(r), User: userFromSession(session), IsAdmin: true, Users: users, Now: time.Now()})
}

func (s *Server) userNewPage(w http.ResponseWriter, r *http.Request, session *model.Session) {
	s.render(w, "user_new", viewData{Title: "Benutzer anlegen", Page: "users", CSRF: session.CSRFToken, User: userFromSession(session), IsAdmin: true, Form: map[string]string{"role": "member"}, Now: time.Now()})
}

func (s *Server) userCreate(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	form := map[string]string{"username": strings.TrimSpace(r.FormValue("username")), "display_name": strings.TrimSpace(r.FormValue("display_name")), "role": r.FormValue("role")}
	username, err := normalizeUsername(form["username"])
	if err != nil {
		s.renderUserNewError(w, session, err.Error(), form)
		return
	}
	if form["display_name"] == "" || len([]rune(form["display_name"])) > 80 {
		s.renderUserNewError(w, session, "Bitte einen Anzeigenamen mit höchstens 80 Zeichen angeben.", form)
		return
	}
	if form["role"] != "admin" && form["role"] != "member" {
		s.renderUserNewError(w, session, "Ungültige Rolle.", form)
		return
	}
	if r.FormValue("password") != r.FormValue("confirm_password") {
		s.renderUserNewError(w, session, "Die Passwörter stimmen nicht überein.", form)
		return
	}
	hash, err := secure.HashPassword(r.FormValue("password"))
	if err != nil {
		s.renderUserNewError(w, session, err.Error(), form)
		return
	}
	user, err := s.store.CreateUser(r.Context(), username, form["display_name"], hash, form["role"])
	if err != nil {
		s.renderUserNewError(w, session, "Benutzer konnte nicht angelegt werden: "+safeMessage(err), form)
		return
	}
	_ = s.store.AddAudit(r.Context(), "user.created", "Benutzer angelegt: "+user.Username+" durch "+session.Username)
	s.redirectNotice(w, r, "/users/"+strconv.FormatInt(user.ID, 10), "Benutzer angelegt. Weise jetzt Domains oder einzelne Hosts zu.")
}

func (s *Server) userDetail(w http.ResponseWriter, r *http.Request, session *model.Session) {
	userID, ok := pathID(w, r)
	if !ok {
		return
	}
	managedUser, err := s.store.GetUser(r.Context(), userID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	zones, err := s.store.ListZones(r.Context())
	if err != nil {
		s.serverError(w, err)
		return
	}
	grants, err := s.store.ListAccessGrants(r.Context(), userID)
	if err != nil {
		s.serverError(w, err)
		return
	}
	domainGrants := make(map[int64]bool)
	domainManaged := make(map[int64]bool)
	createTargetGrants := make(map[int64]bool)
	targetGrants := make(map[int64]bool)
	managedTargetGrants := make(map[int64]bool)
	for _, grant := range grants {
		if grant.TargetID == nil {
			domainGrants[grant.ZoneID] = true
			domainManaged[grant.ZoneID] = grant.CanManageTargets
			createTargetGrants[grant.ZoneID] = grant.CanCreateTargets
		} else {
			targetGrants[*grant.TargetID] = true
			managedTargetGrants[*grant.TargetID] = grant.CanManageTargets
		}
	}
	accessZones := make([]accessZone, 0, len(zones))
	for _, zone := range zones {
		targets, targetErr := s.store.ListTargets(r.Context(), zone.ID)
		if targetErr != nil {
			s.serverError(w, targetErr)
			return
		}
		accessZones = append(accessZones, accessZone{Zone: zone, Targets: targets, DomainGranted: domainGrants[zone.ID], DomainManaged: domainManaged[zone.ID], CanCreateTargets: createTargetGrants[zone.ID], GrantedTargetIDs: targetGrants, ManagedTargetIDs: managedTargetGrants})
	}
	s.render(w, "user_detail", viewData{Title: managedUser.DisplayName, Page: "users", CSRF: session.CSRFToken, Flash: notice(r), User: userFromSession(session), IsAdmin: true, ManagedUser: managedUser, AccessZones: accessZones, Now: time.Now()})
}

func (s *Server) userAccessSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	userID, ok := pathID(w, r)
	if !ok {
		return
	}
	managedUser, err := s.store.GetUser(r.Context(), userID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if managedUser.IsAdmin() {
		s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Admins haben immer vollständigen Zugriff; Einzelrechte sind nicht nötig.", "info")
		return
	}
	selection := store.AccessSelection{}
	for key, values := range r.Form {
		if len(values) == 0 || values[0] == "" {
			continue
		}
		if raw, found := strings.CutPrefix(key, "zone_"); found {
			if id, parseErr := strconv.ParseInt(raw, 10, 64); parseErr == nil && id > 0 {
				selection.ZoneIDs = append(selection.ZoneIDs, id)
			}
		}
		if raw, found := strings.CutPrefix(key, "target_"); found {
			if id, parseErr := strconv.ParseInt(raw, 10, 64); parseErr == nil && id > 0 {
				selection.TargetIDs = append(selection.TargetIDs, id)
			}
		}
		if raw, found := strings.CutPrefix(key, "manage_zone_"); found {
			if id, parseErr := strconv.ParseInt(raw, 10, 64); parseErr == nil && id > 0 {
				selection.ManageZoneIDs = append(selection.ManageZoneIDs, id)
			}
		}
		if raw, found := strings.CutPrefix(key, "manage_target_"); found {
			if id, parseErr := strconv.ParseInt(raw, 10, 64); parseErr == nil && id > 0 {
				selection.ManageTargetIDs = append(selection.ManageTargetIDs, id)
			}
		}
		if raw, found := strings.CutPrefix(key, "create_zone_"); found {
			if id, parseErr := strconv.ParseInt(raw, 10, 64); parseErr == nil && id > 0 {
				selection.CreateTargetZoneIDs = append(selection.CreateTargetZoneIDs, id)
			}
		}
	}
	if err := s.store.ReplaceAccessGrants(r.Context(), userID, selection); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.AddAudit(r.Context(), "user.access_updated", "Zugriffe geändert: "+managedUser.Username+" durch "+session.Username)
	s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Zugriffsrechte gespeichert.")
}

func (s *Server) userStateSave(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	userID, ok := pathID(w, r)
	if !ok {
		return
	}
	managedUser, err := s.store.GetUser(r.Context(), userID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	displayName := strings.TrimSpace(r.FormValue("display_name"))
	role, active := r.FormValue("role"), checked(r, "active")
	if displayName == "" || len([]rune(displayName)) > 80 || (role != "admin" && role != "member") {
		s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Benutzerdaten sind ungültig.", "error")
		return
	}
	if managedUser.IsAdmin() && (role != "admin" || !active) {
		count, countErr := s.store.CountActiveAdmins(r.Context())
		if countErr != nil {
			s.serverError(w, countErr)
			return
		}
		if count <= 1 {
			s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Der letzte aktive Admin kann nicht deaktiviert oder herabgestuft werden.", "error")
			return
		}
	}
	if err := s.store.UpdateUserState(r.Context(), userID, displayName, role, active); err != nil {
		s.serverError(w, err)
		return
	}
	if role != managedUser.Role || active != managedUser.Active {
		_ = s.store.DeleteUserSessions(r.Context(), userID)
	}
	_ = s.store.AddAudit(r.Context(), "user.state_updated", "Benutzer geändert: "+managedUser.Username+" durch "+session.Username)
	s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Benutzerstatus gespeichert.")
}

func (s *Server) userPasswordReset(w http.ResponseWriter, r *http.Request, session *model.Session) {
	if err := s.parseForm(w, r); err != nil {
		return
	}
	if !s.validSessionCSRF(r, session) {
		http.Error(w, "Ungültige Anfrage", http.StatusForbidden)
		return
	}
	userID, ok := pathID(w, r)
	if !ok {
		return
	}
	managedUser, err := s.store.GetUser(r.Context(), userID)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if r.FormValue("password") != r.FormValue("confirm_password") {
		s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Die Passwörter stimmen nicht überein.", "error")
		return
	}
	hash, err := secure.HashPassword(r.FormValue("password"))
	if err != nil {
		s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), err.Error(), "error")
		return
	}
	if err := s.store.SetUserPassword(r.Context(), userID, hash); err != nil {
		s.serverError(w, err)
		return
	}
	_ = s.store.DeleteUserSessions(r.Context(), userID)
	_ = s.store.AddAudit(r.Context(), "user.password_reset", "Passwort zurückgesetzt: "+managedUser.Username+" durch "+session.Username)
	s.redirectNotice(w, r, "/users/"+strconv.FormatInt(userID, 10), "Passwort zurückgesetzt; der Benutzer muss sich neu anmelden.")
}

func (s *Server) authenticated(next func(http.ResponseWriter, *http.Request, *model.Session)) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		session, err := s.session(r.Context(), r)
		if err != nil {
			s.serverError(w, err)
			return
		}
		if session == nil {
			s.redirectNotice(w, r, "/login", "Bitte melde dich an.", "info")
			return
		}
		next(w, r, session)
	})
}

func (s *Server) adminOnly(next func(http.ResponseWriter, *http.Request, *model.Session)) http.Handler {
	return s.authenticated(func(w http.ResponseWriter, r *http.Request, session *model.Session) {
		if session.Role != "admin" {
			http.Error(w, "Diese Aktion erfordert Administratorrechte.", http.StatusForbidden)
			return
		}
		next(w, r, session)
	})
}

func (s *Server) zonesForSession(ctx context.Context, session *model.Session) ([]model.Zone, error) {
	if session.Role == "admin" {
		return s.store.ListZones(ctx)
	}
	return s.store.ListAccessibleZones(ctx, session.UserID)
}

func (s *Server) activeTargetsForSession(ctx context.Context, session *model.Session) (int, error) {
	if session.Role == "admin" {
		return s.store.CountActiveTargets(ctx)
	}
	return s.store.CountActiveAccessibleTargets(ctx, session.UserID)
}

func (s *Server) canAccessZone(ctx context.Context, session *model.Session, zoneID int64) bool {
	if session.Role == "admin" {
		return true
	}
	allowed, err := s.store.CanAccessZone(ctx, session.UserID, zoneID)
	return err == nil && allowed
}

func (s *Server) canAccessTarget(ctx context.Context, session *model.Session, target model.Target) bool {
	if session.Role == "admin" {
		return true
	}
	allowed, err := s.store.CanAccessTarget(ctx, session.UserID, target.ZoneID, target.ID)
	return err == nil && allowed
}

func userFromSession(session *model.Session) model.User {
	return model.User{ID: session.UserID, Username: session.Username, DisplayName: session.DisplayName, Role: session.Role, Active: true}
}

func (s *Server) session(ctx context.Context, r *http.Request) (*model.Session, error) {
	cookie, err := r.Cookie("dyndns_session")
	if err != nil || cookie.Value == "" {
		return nil, nil
	}
	return s.store.GetSession(ctx, secure.HashToken(cookie.Value))
}

func (s *Server) startSession(w http.ResponseWriter, ctx context.Context, user model.User) error {
	token, err := secure.RandomToken(32)
	if err != nil {
		return err
	}
	csrf, err := secure.RandomToken(32)
	if err != nil {
		return err
	}
	_, err = s.store.CreateSession(ctx, model.Session{UserID: user.ID, TokenHash: secure.HashToken(token), CSRFToken: csrf, ExpiresAt: time.Now().UTC().Add(s.config.SessionTTL)})
	if err != nil {
		return err
	}
	http.SetCookie(w, &http.Cookie{Name: "dyndns_session", Value: token, Path: "/", MaxAge: int(s.config.SessionTTL.Seconds()), HttpOnly: true, Secure: s.config.CookieSecure, SameSite: http.SameSiteStrictMode})
	return nil
}

func (s *Server) clearSession(w http.ResponseWriter) {
	http.SetCookie(w, &http.Cookie{Name: "dyndns_session", Value: "", Path: "/", MaxAge: -1, HttpOnly: true, Secure: s.config.CookieSecure, SameSite: http.SameSiteStrictMode})
}

func (s *Server) publicCSRF(w http.ResponseWriter, r *http.Request) string {
	if cookie, err := r.Cookie("dyndns_public_csrf"); err == nil && len(cookie.Value) >= 32 {
		return cookie.Value
	}
	token, err := secure.RandomToken(24)
	if err != nil {
		return ""
	}
	http.SetCookie(w, &http.Cookie{Name: "dyndns_public_csrf", Value: token, Path: "/", MaxAge: 3600, HttpOnly: true, Secure: s.config.CookieSecure, SameSite: http.SameSiteStrictMode})
	return token
}

func (s *Server) validPublicCSRF(r *http.Request) bool {
	cookie, err := r.Cookie("dyndns_public_csrf")
	if err != nil || cookie.Value == "" {
		return false
	}
	return subtle.ConstantTimeCompare([]byte(cookie.Value), []byte(r.FormValue("csrf"))) == 1
}

func (s *Server) validSessionCSRF(r *http.Request, session *model.Session) bool {
	return subtle.ConstantTimeCompare([]byte(session.CSRFToken), []byte(r.FormValue("csrf"))) == 1
}

func (s *Server) parseForm(w http.ResponseWriter, r *http.Request) error {
	r.Body = http.MaxBytesReader(w, r.Body, 64<<10)
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Ungültige Formulardaten", http.StatusBadRequest)
		return err
	}
	return nil
}

func (s *Server) triggerUpdateIfEnabled(ctx context.Context) bool {
	settings, err := s.store.GetSettings(ctx)
	if err != nil || !settings.UpdaterEnabled {
		return false
	}
	s.scheduler.Trigger()
	return true
}

func (s *Server) render(w http.ResponseWriter, name string, data viewData) {
	if data.Mode == "" {
		data.Mode = s.config.Mode
	}
	if data.Page != "setup" && data.Page != "login" {
		if settings, err := s.store.GetSettings(context.Background()); err == nil {
			data.UpdaterEnabled = settings.UpdaterEnabled
		}
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	if err := s.templates[name].ExecuteTemplate(w, name, data); err != nil {
		s.logger.Error("render template", "template", name, "error", err)
	}
}

func (s *Server) renderError(w http.ResponseWriter, name, message, csrf string, form map[string]string) {
	s.render(w, name, viewData{Title: "Eingabe prüfen", Page: name, Mode: s.config.Mode, CSRF: csrf, Flash: newFlash(message, "error"), Form: form, Now: time.Now()})
}

func (s *Server) renderUserNewError(w http.ResponseWriter, session *model.Session, message string, form map[string]string) {
	s.render(w, "user_new", viewData{Title: "Benutzer anlegen", Page: "users", CSRF: session.CSRFToken, Flash: newFlash(message, "error"), Form: form, User: userFromSession(session), IsAdmin: true, Now: time.Now()})
}

func (s *Server) serverError(w http.ResponseWriter, err error) {
	s.logger.Error("request failed", "error", err)
	http.Error(w, "Interner Fehler. Details stehen nicht in der Oberfläche.", http.StatusInternalServerError)
}

func (s *Server) redirectNotice(w http.ResponseWriter, r *http.Request, target, message string, kinds ...string) {
	kind := "success"
	if len(kinds) > 0 {
		kind = kinds[0]
	}
	location, err := url.Parse(target)
	if err != nil {
		s.serverError(w, err)
		return
	}
	query := location.Query()
	query.Set("notice", strings.TrimSpace(message))
	query.Set("notice_kind", normalizeFlashKind(kind))
	location.RawQuery = query.Encode()
	http.Redirect(w, r, location.String(), http.StatusSeeOther)
}

func (s *Server) securityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Security-Policy", "default-src 'self'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; img-src 'self' data:; object-src 'none'; script-src 'self'; style-src 'self'")
		w.Header().Set("Referrer-Policy", "no-referrer")
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=()")
		next.ServeHTTP(w, r)
	})
}

func loadTemplates() (map[string]*template.Template, error) {
	pages := []string{"setup", "login", "dashboard", "domains", "domain_new", "domain_detail", "settings", "errors", "security", "token", "users", "user_new", "user_detail"}
	functions := template.FuncMap{
		"formatTime": func(value time.Time) string {
			if value.IsZero() {
				return "–"
			}
			return value.Local().Format("02.01.2006 · 15:04")
		},
		"formatEndpoints": func(values []string) string { return strings.Join(values, "\n") },
		"unixSeconds":     unixSeconds,
		"initial": func(value string) string {
			for _, character := range strings.TrimSpace(value) {
				return strings.ToUpper(string(character))
			}
			return "U"
		},
		"statusClass":  statusClass,
		"ttlOptions":   func() []int { return []int{60, 300, 600, 1800, 3600, 86400} },
		"supportedTTL": supportedTTL,
		"families": func(target model.Target) string {
			var result []string
			if target.UpdateIPv4 {
				result = append(result, "A")
			}
			if target.UpdateIPv6 {
				result = append(result, "AAAA")
			}
			return strings.Join(result, " + ")
		},
	}
	result := make(map[string]*template.Template, len(pages))
	for _, page := range pages {
		templateSet, err := template.New("layout").Funcs(functions).ParseFS(embeddedAssets, "templates/layout.html", "templates/"+page+".html")
		if err != nil {
			return nil, fmt.Errorf("parse %s template: %w", page, err)
		}
		result[page] = templateSet
	}
	return result, nil
}

func unixSeconds(value time.Time) int64 {
	if value.IsZero() {
		return 0
	}
	return value.Unix()
}

func pathID(w http.ResponseWriter, r *http.Request) (int64, bool) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil || id < 1 {
		http.Error(w, "Ungültige Kennung", http.StatusBadRequest)
		return 0, false
	}
	return id, true
}

func normalizeZone(raw string) (string, error) {
	zone, err := idna.Lookup.ToASCII(strings.TrimSuffix(strings.ToLower(strings.TrimSpace(raw)), "."))
	if err != nil || strings.Count(zone, ".") < 1 || len(zone) > 253 {
		return "", errors.New("Bitte eine gültige Domain angeben, z. B. example.de")
	}
	return zone, nil
}

func normalizeUsername(raw string) (string, error) {
	username := strings.ToLower(strings.TrimSpace(raw))
	if len(username) < 3 || len(username) > 40 {
		return "", errors.New("Benutzername muss 3 bis 40 Zeichen lang sein")
	}
	for _, character := range username {
		if !(character >= 'a' && character <= 'z') && !(character >= '0' && character <= '9') && character != '_' && character != '-' && character != '.' {
			return "", errors.New("Benutzername darf nur Kleinbuchstaben, Zahlen, Punkt, Bindestrich und Unterstrich enthalten")
		}
	}
	return username, nil
}

func normalizeRecord(raw, zone string) (string, string, error) {
	value := strings.TrimSuffix(strings.ToLower(strings.TrimSpace(raw)), ".")
	if value == "" || value == "@" {
		return "@", zone, nil
	}
	if strings.HasSuffix(value, "."+zone) {
		value = strings.TrimSuffix(value, "."+zone)
	}
	value, err := idna.Lookup.ToASCII(value)
	if err != nil || value == "" || len(value) > 253 || strings.HasPrefix(value, ".") || strings.HasSuffix(value, ".") {
		return "", "", errors.New("Bitte eine gültige Subdomain angeben")
	}
	for _, label := range strings.Split(value, ".") {
		if len(label) == 0 || len(label) > 63 || strings.HasPrefix(label, "-") || strings.HasSuffix(label, "-") {
			return "", "", errors.New("Bitte eine gültige Subdomain angeben")
		}
	}
	return value, value + "." + zone, nil
}

func normalizeCNAMEDestination(raw string) (string, error) {
	value := strings.TrimSuffix(strings.ToLower(strings.TrimSpace(raw)), ".")
	value, err := idna.Lookup.ToASCII(value)
	if err != nil || value == "" || value == "@" || len(value) > 253 || strings.HasPrefix(value, ".") || strings.HasSuffix(value, ".") || net.ParseIP(value) != nil {
		return "", errors.New("Bitte ein gültiges CNAME-Ziel als Domain angeben")
	}
	for _, label := range strings.Split(value, ".") {
		if len(label) == 0 || len(label) > 63 || strings.HasPrefix(label, "-") || strings.HasSuffix(label, "-") {
			return "", errors.New("Bitte ein gültiges CNAME-Ziel als Domain angeben")
		}
	}
	return value + ".", nil
}

func parseStaticTargetIPs(r *http.Request, updateIPv4, updateIPv6 bool) (string, string, error) {
	staticIPv4, staticIPv6 := "", ""
	var err error
	if updateIPv4 {
		if strings.TrimSpace(r.FormValue("static_ipv4")) == "" {
			return "", "", errors.New("Für IPv4 ist bei deaktiviertem DynDNS eine feste IPv4-Adresse erforderlich")
		}
		staticIPv4, err = normalizeStaticIP(r.FormValue("static_ipv4"), 4)
		if err != nil {
			return "", "", err
		}
	}
	if updateIPv6 {
		if strings.TrimSpace(r.FormValue("static_ipv6")) == "" {
			return "", "", errors.New("Für IPv6 ist bei deaktiviertem DynDNS eine feste IPv6-Adresse erforderlich")
		}
		staticIPv6, err = normalizeStaticIP(r.FormValue("static_ipv6"), 6)
		if err != nil {
			return "", "", err
		}
	}
	return staticIPv4, staticIPv6, nil
}

func targetDynDNSActive(requested, updateIPv4, updateIPv6 bool) bool {
	return requested && (updateIPv4 || updateIPv6)
}

func normalizeStaticIP(raw string, family int) (string, error) {
	value := strings.TrimSpace(raw)
	if value == "" {
		return "", nil
	}
	address, err := netip.ParseAddr(value)
	if err != nil {
		return "", fmt.Errorf("Bitte eine gültige IPv%d-Adresse angeben", family)
	}
	address = address.Unmap()
	if (family == 4 && !address.Is4()) || (family == 6 && !address.Is6()) {
		return "", fmt.Errorf("Bitte eine gültige IPv%d-Adresse angeben", family)
	}
	return address.String(), nil
}

func hasStaticIP(target model.Target) bool {
	return target.StaticIPv4 != "" || target.StaticIPv6 != ""
}

func parseTTL(raw string) (int, error) {
	ttl, err := strconv.Atoi(strings.TrimSpace(raw))
	if err != nil || !supportedTTL(ttl) {
		return 0, errors.New("TTL muss 60, 300, 600, 1800, 3600 oder 86400 Sekunden betragen")
	}
	return ttl, nil
}

func parseEditableTTL(raw string, current int) (int, error) {
	ttl, err := parseTTL(raw)
	if err == nil {
		return ttl, nil
	}
	preserved, parseErr := strconv.Atoi(strings.TrimSpace(raw))
	if parseErr == nil && preserved == current && preserved >= 60 {
		return preserved, nil
	}
	return 0, err
}

func supportedTTL(ttl int) bool {
	switch ttl {
	case 60, 300, 600, 1800, 3600, 86400:
		return true
	default:
		return false
	}
}

func lines(raw string) []string {
	seen := make(map[string]bool)
	var result []string
	for _, line := range strings.FieldsFunc(raw, func(r rune) bool { return r == '\n' || r == '\r' || r == ',' }) {
		line = strings.TrimSpace(line)
		if line != "" && !seen[line] {
			seen[line] = true
			result = append(result, line)
		}
	}
	return result
}

func checked(r *http.Request, key string) bool {
	return r.FormValue(key) == "on" || r.FormValue(key) == "true" || r.FormValue(key) == "1"
}
func domainURL(id int64) string { return "/domains/" + strconv.FormatInt(id, 10) }
func activeNotice(updateNeeded, triggered bool) string {
	if triggered {
		return " Die Aktualisierung wurde direkt gestartet."
	}
	if updateNeeded {
		return " Der Updater ist deaktiviert; die Synchronisierung startet nach dem Aktivieren des Dienstes."
	}
	return ""
}
func notice(r *http.Request) *flashMessage {
	return newFlash(r.URL.Query().Get("notice"), r.URL.Query().Get("notice_kind"))
}
func newFlash(message, kind string) *flashMessage {
	message = strings.TrimSpace(message)
	if message == "" {
		return nil
	}
	return &flashMessage{Message: message, Kind: normalizeFlashKind(kind)}
}
func normalizeFlashKind(kind string) string {
	switch strings.ToLower(strings.TrimSpace(kind)) {
	case "success":
		return "success"
	case "error":
		return "error"
	default:
		return "info"
	}
}
func safeMessage(err error) string {
	if err == nil {
		return ""
	}
	message := strings.TrimSpace(err.Error())
	if len(message) > 240 {
		return message[:240]
	}
	return message
}
func statusClass(value string) string {
	value = strings.ToLower(value)
	switch {
	case strings.Contains(value, "ok"), strings.Contains(value, "unverändert"), strings.Contains(value, "aktualisiert"), strings.Contains(value, "angelegt"):
		return "status-good"
	case strings.Contains(value, "error"), strings.Contains(value, "fehler"), strings.Contains(value, "partial"):
		return "status-bad"
	default:
		return "status-warn"
	}
}
func remoteIP(r *http.Request) string {
	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return "unknown"
	}
	if address, err := netip.ParseAddr(host); err == nil {
		return address.String()
	}
	return "unknown"
}

type loginLimiter struct {
	mu       sync.Mutex
	attempts map[string][]time.Time
}

func newLoginLimiter() *loginLimiter { return &loginLimiter{attempts: make(map[string][]time.Time)} }
func (l *loginLimiter) Allow(ip string) bool {
	l.mu.Lock()
	defer l.mu.Unlock()
	cutoff := time.Now().Add(-15 * time.Minute)
	values := l.attempts[ip]
	kept := values[:0]
	for _, value := range values {
		if value.After(cutoff) {
			kept = append(kept, value)
		}
	}
	l.attempts[ip] = kept
	return len(kept) < 5
}
func (l *loginLimiter) Fail(ip string) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.attempts[ip] = append(l.attempts[ip], time.Now())
}
func (l *loginLimiter) Reset(ip string) {
	l.mu.Lock()
	defer l.mu.Unlock()
	delete(l.attempts, ip)
}