package server

import (
	"bytes"
	"context"
	"crypto/sha256"
	"embed"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"heckel.io/ntfy/user"
	"io"
	"net"
	"net/http"
	"net/netip"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"heckel.io/ntfy/log"

	"github.com/emersion/go-smtp"
	"github.com/gorilla/websocket"
	"golang.org/x/sync/errgroup"
	"heckel.io/ntfy/util"
)

/*
TODO
--

- HIGH Rate limiting: dailyLimitToRate is wrong? + TESTS
- HIGH Rate limiting: Sensitive endpoints (account/login/change-password/...)
- MEDIUM: Races with v.user (see publishSyncEventAsync test)
- MEDIUM: Reservation (UI): Show "This topic is reserved" error message when trying to reserve a reserved topic (Thorben)
- MEDIUM: Reservation (UI): Ask for confirmation when removing reservation (deadcade)
- MEDIUM: Reservation table delete button: dialog "keep or delete messages?"
- LOW: UI: Flickering upgrade banner when logging in
- LOW: JS constants
- LOW: Payments reconciliation process

Limits & rate limiting:
	users without tier: should the stats be persisted? are they meaningful? -> test that the visitor is based on the IP address!
	when ResetStats() is run, reset messagesLimiter (and others)?
	Delete visitor when tier is changed to refresh rate limiters

Make sure account endpoints make sense for admins

Tests:
- Payment endpoints (make mocks)
- test that the visitor is based on the IP address when a user has no tier
*/

// Server is the main server, providing the UI and API for ntfy
type Server struct {
	config            *Config
	httpServer        *http.Server
	httpsServer       *http.Server
	unixListener      net.Listener
	smtpServer        *smtp.Server
	smtpServerBackend *smtpBackend
	smtpSender        mailer
	topics            map[string]*topic
	visitors          map[string]*visitor // ip:<ip> or user:<user>
	firebaseClient    *firebaseClient
	messages          int64
	userManager       *user.Manager                        // Might be nil!
	messageCache      *messageCache                        // Database that stores the messages
	fileCache         *fileCache                           // File system based cache that stores attachments
	stripe            stripeAPI                            // Stripe API, can be replaced with a mock
	priceCache        *util.LookupCache[map[string]string] // Stripe price ID -> formatted price
	closeChan         chan bool
	mu                sync.Mutex
}

// handleFunc extends the normal http.HandlerFunc to be able to easily return errors
type handleFunc func(http.ResponseWriter, *http.Request, *visitor) error

var (
	// If changed, don't forget to update Android App and auth_sqlite.go
	topicRegex             = regexp.MustCompile(`^[-_A-Za-z0-9]{1,64}$`)               // No /!
	topicPathRegex         = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}$`)              // Regex must match JS & Android app!
	externalTopicPathRegex = regexp.MustCompile(`^/[^/]+\.[^/]+/[-_A-Za-z0-9]{1,64}$`) // Extended topic path, for web-app, e.g. /example.com/mytopic
	jsonPathRegex          = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/json$`)
	ssePathRegex           = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/sse$`)
	rawPathRegex           = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/raw$`)
	wsPathRegex            = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/ws$`)
	authPathRegex          = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/auth$`)
	publishPathRegex       = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}/(publish|send|trigger)$`)

	webConfigPath                                        = "/config.js"
	accountPath                                          = "/account"
	matrixPushPath                                       = "/_matrix/push/v1/notify"
	apiHealthPath                                        = "/v1/health"
	apiTiers                                             = "/v1/tiers"
	apiAccountPath                                       = "/v1/account"
	apiAccountTokenPath                                  = "/v1/account/token"
	apiAccountPasswordPath                               = "/v1/account/password"
	apiAccountSettingsPath                               = "/v1/account/settings"
	apiAccountSubscriptionPath                           = "/v1/account/subscription"
	apiAccountReservationPath                            = "/v1/account/reservation"
	apiAccountBillingPortalPath                          = "/v1/account/billing/portal"
	apiAccountBillingWebhookPath                         = "/v1/account/billing/webhook"
	apiAccountBillingSubscriptionPath                    = "/v1/account/billing/subscription"
	apiAccountBillingSubscriptionCheckoutSuccessTemplate = "/v1/account/billing/subscription/success/{CHECKOUT_SESSION_ID}"
	apiAccountBillingSubscriptionCheckoutSuccessRegex    = regexp.MustCompile(`/v1/account/billing/subscription/success/(.+)$`)
	apiAccountReservationSingleRegex                     = regexp.MustCompile(`/v1/account/reservation/([-_A-Za-z0-9]{1,64})$`)
	apiAccountSubscriptionSingleRegex                    = regexp.MustCompile(`^/v1/account/subscription/([-_A-Za-z0-9]{16})$`)
	staticRegex                                          = regexp.MustCompile(`^/static/.+`)
	docsRegex                                            = regexp.MustCompile(`^/docs(|/.*)$`)
	fileRegex                                            = regexp.MustCompile(`^/file/([-_A-Za-z0-9]{1,64})(?:\.[A-Za-z0-9]{1,16})?$`)
	disallowedTopics                                     = []string{"docs", "static", "file", "app", "account", "settings", "pricing", "signup", "login", "reset-password"} // If updated, also update in Android and web app
	urlRegex                                             = regexp.MustCompile(`^https?://`)

	//go:embed site
	webFs        embed.FS
	webFsCached  = &util.CachingEmbedFS{ModTime: time.Now(), FS: webFs}
	webSiteDir   = "/site"
	webHomeIndex = "/home.html" // Landing page, only if "web-root: home"
	webAppIndex  = "/app.html"  // React app

	//go:embed docs
	docsStaticFs     embed.FS
	docsStaticCached = &util.CachingEmbedFS{ModTime: time.Now(), FS: docsStaticFs}
)

const (
	firebaseControlTopic     = "~control"                // See Android if changed
	firebasePollTopic        = "~poll"                   // See iOS if changed
	emptyMessageBody         = "triggered"               // Used if message body is empty
	newMessageBody           = "New message"             // Used in poll requests as generic message
	defaultAttachmentMessage = "You received a file: %s" // Used if message body is empty, and there is an attachment
	encodingBase64           = "base64"                  // Used mainly for binary UnifiedPush messages
	jsonBodyBytesLimit       = 16384
)

// WebSocket constants
const (
	wsWriteWait  = 2 * time.Second
	wsBufferSize = 1024
	wsReadLimit  = 64 // We only ever receive PINGs
	wsPongWait   = 15 * time.Second
)

// New instantiates a new Server. It creates the cache and adds a Firebase
// subscriber (if configured).
func New(conf *Config) (*Server, error) {
	var mailer mailer
	if conf.SMTPSenderAddr != "" {
		mailer = &smtpSender{config: conf}
	}
	var stripe stripeAPI
	if conf.StripeSecretKey != "" {
		stripe = newStripeAPI()
	}
	messageCache, err := createMessageCache(conf)
	if err != nil {
		return nil, err
	}
	topics, err := messageCache.Topics()
	if err != nil {
		return nil, err
	}
	var fileCache *fileCache
	if conf.AttachmentCacheDir != "" {
		fileCache, err = newFileCache(conf.AttachmentCacheDir, conf.AttachmentTotalSizeLimit)
		if err != nil {
			return nil, err
		}
	}
	var userManager *user.Manager
	if conf.AuthFile != "" {
		userManager, err = user.NewManager(conf.AuthFile, conf.AuthStartupQueries, conf.AuthDefault)
		if err != nil {
			return nil, err
		}
	}
	var firebaseClient *firebaseClient
	if conf.FirebaseKeyFile != "" {
		sender, err := newFirebaseSender(conf.FirebaseKeyFile)
		if err != nil {
			return nil, err
		}
		firebaseClient = newFirebaseClient(sender, userManager)
	}
	s := &Server{
		config:         conf,
		messageCache:   messageCache,
		fileCache:      fileCache,
		firebaseClient: firebaseClient,
		smtpSender:     mailer,
		topics:         topics,
		userManager:    userManager,
		visitors:       make(map[string]*visitor),
		stripe:         stripe,
	}
	s.priceCache = util.NewLookupCache(s.fetchStripePrices, conf.StripePriceCacheDuration)
	return s, nil
}

func createMessageCache(conf *Config) (*messageCache, error) {
	if conf.CacheDuration == 0 {
		return newNopCache()
	} else if conf.CacheFile != "" {
		return newSqliteCache(conf.CacheFile, conf.CacheStartupQueries, conf.CacheDuration, conf.CacheBatchSize, conf.CacheBatchTimeout, false)
	}
	return newMemCache()
}

// Run executes the main server. It listens on HTTP (+ HTTPS, if configured), and starts
// a manager go routine to print stats and prune messages.
func (s *Server) Run() error {
	var listenStr string
	if s.config.ListenHTTP != "" {
		listenStr += fmt.Sprintf(" %s[http]", s.config.ListenHTTP)
	}
	if s.config.ListenHTTPS != "" {
		listenStr += fmt.Sprintf(" %s[https]", s.config.ListenHTTPS)
	}
	if s.config.ListenUnix != "" {
		listenStr += fmt.Sprintf(" %s[unix]", s.config.ListenUnix)
	}
	if s.config.SMTPServerListen != "" {
		listenStr += fmt.Sprintf(" %s[smtp]", s.config.SMTPServerListen)
	}
	log.Info("Listening on%s, ntfy %s, log level is %s", listenStr, s.config.Version, log.CurrentLevel().String())
	mux := http.NewServeMux()
	mux.HandleFunc("/", s.handle)
	errChan := make(chan error)
	s.mu.Lock()
	s.closeChan = make(chan bool)
	if s.config.ListenHTTP != "" {
		s.httpServer = &http.Server{Addr: s.config.ListenHTTP, Handler: mux}
		go func() {
			errChan <- s.httpServer.ListenAndServe()
		}()
	}
	if s.config.ListenHTTPS != "" {
		s.httpsServer = &http.Server{Addr: s.config.ListenHTTPS, Handler: mux}
		go func() {
			errChan <- s.httpsServer.ListenAndServeTLS(s.config.CertFile, s.config.KeyFile)
		}()
	}
	if s.config.ListenUnix != "" {
		go func() {
			var err error
			s.mu.Lock()
			os.Remove(s.config.ListenUnix)
			s.unixListener, err = net.Listen("unix", s.config.ListenUnix)
			if err != nil {
				s.mu.Unlock()
				errChan <- err
				return
			}
			defer s.unixListener.Close()
			if s.config.ListenUnixMode > 0 {
				if err := os.Chmod(s.config.ListenUnix, s.config.ListenUnixMode); err != nil {
					s.mu.Unlock()
					errChan <- err
					return
				}
			}
			s.mu.Unlock()
			httpServer := &http.Server{Handler: mux}
			errChan <- httpServer.Serve(s.unixListener)
		}()
	}
	if s.config.SMTPServerListen != "" {
		go func() {
			errChan <- s.runSMTPServer()
		}()
	}
	s.mu.Unlock()
	go s.runManager()
	go s.runStatsResetter()
	go s.runDelayedSender()
	go s.runFirebaseKeepaliver()

	return <-errChan
}

// Stop stops HTTP (+HTTPS) server and all managers
func (s *Server) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.httpServer != nil {
		s.httpServer.Close()
	}
	if s.httpsServer != nil {
		s.httpsServer.Close()
	}
	if s.unixListener != nil {
		s.unixListener.Close()
	}
	if s.smtpServer != nil {
		s.smtpServer.Close()
	}
	close(s.closeChan)
}

func (s *Server) handle(w http.ResponseWriter, r *http.Request) {
	v, err := s.visitor(r) // Note: Always returns v, even when error is returned
	if err == nil {
		log.Debug("%s Dispatching request", logHTTPPrefix(v, r))
		if log.IsTrace() {
			log.Trace("%s Entire request (headers and body):\n%s", logHTTPPrefix(v, r), renderHTTPRequest(r))
		}
		err = s.handleInternal(w, r, v)
	}
	if err != nil {
		if websocket.IsWebSocketUpgrade(r) {
			isNormalError := strings.Contains(err.Error(), "i/o timeout")
			if isNormalError {
				log.Debug("%s WebSocket error (this error is okay, it happens a lot): %s", logHTTPPrefix(v, r), err.Error())
			} else {
				log.Info("%s WebSocket error: %s", logHTTPPrefix(v, r), err.Error())
			}
			return // Do not attempt to write to upgraded connection
		}
		if matrixErr, ok := err.(*errMatrix); ok {
			writeMatrixError(w, r, v, matrixErr)
			return
		}
		httpErr, ok := err.(*errHTTP)
		if !ok {
			httpErr = errHTTPInternalError
		}
		isNormalError := httpErr.HTTPCode == http.StatusNotFound || httpErr.HTTPCode == http.StatusBadRequest
		if isNormalError {
			log.Debug("%s Connection closed with HTTP %d (ntfy error %d): %s", logHTTPPrefix(v, r), httpErr.HTTPCode, httpErr.Code, err.Error())
		} else {
			log.Info("%s Connection closed with HTTP %d (ntfy error %d): %s", logHTTPPrefix(v, r), httpErr.HTTPCode, httpErr.Code, err.Error())
		}
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
		w.WriteHeader(httpErr.HTTPCode)
		io.WriteString(w, httpErr.JSON()+"\n")
	}
}

func (s *Server) handleInternal(w http.ResponseWriter, r *http.Request, v *visitor) error {
	if r.Method == http.MethodGet && r.URL.Path == "/" {
		return s.ensureWebEnabled(s.handleHome)(w, r, v)
	} else if r.Method == http.MethodHead && r.URL.Path == "/" {
		return s.ensureWebEnabled(s.handleEmpty)(w, r, v)
	} else if r.Method == http.MethodGet && r.URL.Path == apiHealthPath {
		return s.handleHealth(w, r, v)
	} else if r.Method == http.MethodGet && r.URL.Path == webConfigPath {
		return s.ensureWebEnabled(s.handleWebConfig)(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountPath {
		return s.ensureUserManager(s.handleAccountCreate)(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountTokenPath {
		return s.ensureUser(s.handleAccountTokenIssue)(w, r, v)
	} else if r.Method == http.MethodGet && r.URL.Path == apiAccountPath {
		return s.handleAccountGet(w, r, v) // Allowed by anonymous
	} else if r.Method == http.MethodDelete && r.URL.Path == apiAccountPath {
		return s.ensureUser(s.withAccountSync(s.handleAccountDelete))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountPasswordPath {
		return s.ensureUser(s.handleAccountPasswordChange)(w, r, v)
	} else if r.Method == http.MethodPatch && r.URL.Path == apiAccountTokenPath {
		return s.ensureUser(s.handleAccountTokenExtend)(w, r, v)
	} else if r.Method == http.MethodDelete && r.URL.Path == apiAccountTokenPath {
		return s.ensureUser(s.handleAccountTokenDelete)(w, r, v)
	} else if r.Method == http.MethodPatch && r.URL.Path == apiAccountSettingsPath {
		return s.ensureUser(s.withAccountSync(s.handleAccountSettingsChange))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountSubscriptionPath {
		return s.ensureUser(s.withAccountSync(s.handleAccountSubscriptionAdd))(w, r, v)
	} else if r.Method == http.MethodPatch && apiAccountSubscriptionSingleRegex.MatchString(r.URL.Path) {
		return s.ensureUser(s.withAccountSync(s.handleAccountSubscriptionChange))(w, r, v)
	} else if r.Method == http.MethodDelete && apiAccountSubscriptionSingleRegex.MatchString(r.URL.Path) {
		return s.ensureUser(s.withAccountSync(s.handleAccountSubscriptionDelete))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountReservationPath {
		return s.ensureUser(s.withAccountSync(s.handleAccountReservationAdd))(w, r, v)
	} else if r.Method == http.MethodDelete && apiAccountReservationSingleRegex.MatchString(r.URL.Path) {
		return s.ensureUser(s.withAccountSync(s.handleAccountReservationDelete))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountBillingSubscriptionPath {
		return s.ensurePaymentsEnabled(s.ensureUser(s.handleAccountBillingSubscriptionCreate))(w, r, v) // Account sync via incoming Stripe webhook
	} else if r.Method == http.MethodGet && apiAccountBillingSubscriptionCheckoutSuccessRegex.MatchString(r.URL.Path) {
		return s.ensurePaymentsEnabled(s.ensureUserManager(s.handleAccountBillingSubscriptionCreateSuccess))(w, r, v) // No user context!
	} else if r.Method == http.MethodPut && r.URL.Path == apiAccountBillingSubscriptionPath {
		return s.ensurePaymentsEnabled(s.ensureStripeCustomer(s.handleAccountBillingSubscriptionUpdate))(w, r, v) // Account sync via incoming Stripe webhook
	} else if r.Method == http.MethodDelete && r.URL.Path == apiAccountBillingSubscriptionPath {
		return s.ensurePaymentsEnabled(s.ensureStripeCustomer(s.handleAccountBillingSubscriptionDelete))(w, r, v) // Account sync via incoming Stripe webhook
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountBillingPortalPath {
		return s.ensurePaymentsEnabled(s.ensureStripeCustomer(s.handleAccountBillingPortalSessionCreate))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == apiAccountBillingWebhookPath {
		return s.ensurePaymentsEnabled(s.ensureUserManager(s.handleAccountBillingWebhook))(w, r, v) // This request comes from Stripe!
	} else if r.Method == http.MethodGet && r.URL.Path == apiTiers {
		return s.ensurePaymentsEnabled(s.handleBillingTiersGet)(w, r, v)
	} else if r.Method == http.MethodGet && r.URL.Path == matrixPushPath {
		return s.handleMatrixDiscovery(w)
	} else if r.Method == http.MethodGet && staticRegex.MatchString(r.URL.Path) {
		return s.ensureWebEnabled(s.handleStatic)(w, r, v)
	} else if r.Method == http.MethodGet && docsRegex.MatchString(r.URL.Path) {
		return s.ensureWebEnabled(s.handleDocs)(w, r, v)
	} else if (r.Method == http.MethodGet || r.Method == http.MethodHead) && fileRegex.MatchString(r.URL.Path) && s.config.AttachmentCacheDir != "" {
		return s.limitRequests(s.handleFile)(w, r, v)
	} else if r.Method == http.MethodOptions {
		return s.ensureWebEnabled(s.handleOptions)(w, r, v)
	} else if (r.Method == http.MethodPut || r.Method == http.MethodPost) && r.URL.Path == "/" {
		return s.limitRequests(s.transformBodyJSON(s.authorizeTopicWrite(s.handlePublish)))(w, r, v)
	} else if r.Method == http.MethodPost && r.URL.Path == matrixPushPath {
		return s.limitRequests(s.transformMatrixJSON(s.authorizeTopicWrite(s.handlePublishMatrix)))(w, r, v)
	} else if (r.Method == http.MethodPut || r.Method == http.MethodPost) && topicPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicWrite(s.handlePublish))(w, r, v)
	} else if r.Method == http.MethodGet && publishPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicWrite(s.handlePublish))(w, r, v)
	} else if r.Method == http.MethodGet && jsonPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicRead(s.handleSubscribeJSON))(w, r, v)
	} else if r.Method == http.MethodGet && ssePathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicRead(s.handleSubscribeSSE))(w, r, v)
	} else if r.Method == http.MethodGet && rawPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicRead(s.handleSubscribeRaw))(w, r, v)
	} else if r.Method == http.MethodGet && wsPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicRead(s.handleSubscribeWS))(w, r, v)
	} else if r.Method == http.MethodGet && authPathRegex.MatchString(r.URL.Path) {
		return s.limitRequests(s.authorizeTopicRead(s.handleTopicAuth))(w, r, v)
	} else if r.Method == http.MethodGet && (topicPathRegex.MatchString(r.URL.Path) || externalTopicPathRegex.MatchString(r.URL.Path)) {
		return s.ensureWebEnabled(s.handleTopic)(w, r, v)
	}
	return errHTTPNotFound
}

func (s *Server) handleHome(w http.ResponseWriter, r *http.Request, v *visitor) error {
	if s.config.WebRootIsApp {
		r.URL.Path = webAppIndex
	} else {
		r.URL.Path = webHomeIndex
	}
	return s.handleStatic(w, r, v)
}

func (s *Server) handleTopic(w http.ResponseWriter, r *http.Request, v *visitor) error {
	unifiedpush := readBoolParam(r, false, "x-unifiedpush", "unifiedpush", "up") // see PUT/POST too!
	if unifiedpush {
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
		_, err := io.WriteString(w, `{"unifiedpush":{"version":1}}`+"\n")
		return err
	}
	r.URL.Path = webAppIndex
	return s.handleStatic(w, r, v)
}

func (s *Server) handleEmpty(_ http.ResponseWriter, _ *http.Request, _ *visitor) error {
	return nil
}

func (s *Server) handleTopicAuth(w http.ResponseWriter, _ *http.Request, _ *visitor) error {
	return s.writeJSON(w, newSuccessResponse())
}

func (s *Server) handleHealth(w http.ResponseWriter, _ *http.Request, _ *visitor) error {
	response := &apiHealthResponse{
		Healthy: true,
	}
	return s.writeJSON(w, response)
}

func (s *Server) handleWebConfig(w http.ResponseWriter, _ *http.Request, _ *visitor) error {
	appRoot := "/"
	if !s.config.WebRootIsApp {
		appRoot = "/app"
	}
	response := &apiConfigResponse{
		BaseURL:            "", // Will translate to window.location.origin
		AppRoot:            appRoot,
		EnableLogin:        s.config.EnableLogin,
		EnableSignup:       s.config.EnableSignup,
		EnablePayments:     s.config.StripeSecretKey != "",
		EnableReservations: s.config.EnableReservations,
		DisallowedTopics:   disallowedTopics,
	}
	b, err := json.MarshalIndent(response, "", "  ")
	if err != nil {
		return err
	}
	w.Header().Set("Content-Type", "text/javascript")
	_, err = io.WriteString(w, fmt.Sprintf("// Generated server configuration\nvar config = %s;\n", string(b)))
	return err
}

func (s *Server) handleStatic(w http.ResponseWriter, r *http.Request, _ *visitor) error {
	r.URL.Path = webSiteDir + r.URL.Path
	util.Gzip(http.FileServer(http.FS(webFsCached))).ServeHTTP(w, r)
	return nil
}

func (s *Server) handleDocs(w http.ResponseWriter, r *http.Request, _ *visitor) error {
	util.Gzip(http.FileServer(http.FS(docsStaticCached))).ServeHTTP(w, r)
	return nil
}

func (s *Server) handleFile(w http.ResponseWriter, r *http.Request, v *visitor) error {
	if s.config.AttachmentCacheDir == "" {
		return errHTTPInternalError
	}
	matches := fileRegex.FindStringSubmatch(r.URL.Path)
	if len(matches) != 2 {
		return errHTTPInternalErrorInvalidPath
	}
	messageID := matches[1]
	file := filepath.Join(s.config.AttachmentCacheDir, messageID)
	stat, err := os.Stat(file)
	if err != nil {
		return errHTTPNotFound
	}
	if r.Method == http.MethodGet {
		if err := v.BandwidthLimiter().Allow(stat.Size()); err != nil {
			return errHTTPTooManyRequestsLimitAttachmentBandwidth
		}
	}
	w.Header().Set("Content-Length", fmt.Sprintf("%d", stat.Size()))
	w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
	if r.Method == http.MethodGet {
		f, err := os.Open(file)
		if err != nil {
			return err
		}
		defer f.Close()
		_, err = io.Copy(util.NewContentTypeWriter(w, r.URL.Path), f)
		return err
	}
	return nil
}

func (s *Server) handleMatrixDiscovery(w http.ResponseWriter) error {
	if s.config.BaseURL == "" {
		return errHTTPInternalErrorMissingBaseURL
	}
	return writeMatrixDiscoveryResponse(w)
}

func (s *Server) handlePublishWithoutResponse(r *http.Request, v *visitor) (*message, error) {
	t, err := s.topicFromPath(r.URL.Path)
	if err != nil {
		return nil, err
	}
	if err := v.MessageAllowed(); err != nil {
		return nil, errHTTPTooManyRequestsLimitMessages
	}
	body, err := util.Peek(r.Body, s.config.MessageLimit)
	if err != nil {
		return nil, err
	}
	m := newDefaultMessage(t.ID, "")
	cache, firebase, email, unifiedpush, err := s.parsePublishParams(r, v, m)
	if err != nil {
		return nil, err
	}
	if m.PollID != "" {
		m = newPollRequestMessage(t.ID, m.PollID)
	}
	if v.user != nil {
		m.User = v.user.ID
	}
	m.Expires = time.Now().Add(v.Limits().MessagesExpiryDuration).Unix()
	if err := s.handlePublishBody(r, v, m, body, unifiedpush); err != nil {
		return nil, err
	}
	if m.Message == "" {
		m.Message = emptyMessageBody
	}
	delayed := m.Time > time.Now().Unix()
	log.Debug("%s Received message: event=%s, user=%s, body=%d byte(s), delayed=%t, firebase=%t, cache=%t, up=%t, email=%s",
		logMessagePrefix(v, m), m.Event, m.User, len(m.Message), delayed, firebase, cache, unifiedpush, email)
	if log.IsTrace() {
		log.Trace("%s Message body: %s", logMessagePrefix(v, m), util.MaybeMarshalJSON(m))
	}
	if !delayed {
		if err := t.Publish(v, m); err != nil {
			return nil, err
		}
		if s.firebaseClient != nil && firebase {
			go s.sendToFirebase(v, m)
		}
		if s.smtpSender != nil && email != "" {
			v.IncrementEmails()
			go s.sendEmail(v, m, email)
		}
		if s.config.UpstreamBaseURL != "" {
			go s.forwardPollRequest(v, m)
		}
	} else {
		log.Debug("%s Message delayed, will process later", logMessagePrefix(v, m))
	}
	if cache {
		log.Debug("%s Adding message to cache", logMessagePrefix(v, m))
		if err := s.messageCache.AddMessage(m); err != nil {
			return nil, err
		}
	}
	v.IncrementMessages()
	if s.userManager != nil && v.user != nil {
		s.userManager.EnqueueStats(v.user)
	}
	s.mu.Lock()
	s.messages++
	s.mu.Unlock()
	return m, nil
}

func (s *Server) handlePublish(w http.ResponseWriter, r *http.Request, v *visitor) error {
	m, err := s.handlePublishWithoutResponse(r, v)
	if err != nil {
		return err
	}
	return s.writeJSON(w, m)
}

func (s *Server) handlePublishMatrix(w http.ResponseWriter, r *http.Request, v *visitor) error {
	_, err := s.handlePublishWithoutResponse(r, v)
	if err != nil {
		return &errMatrix{pushKey: r.Header.Get(matrixPushKeyHeader), err: err}
	}
	return writeMatrixSuccess(w)
}

func (s *Server) sendToFirebase(v *visitor, m *message) {
	log.Debug("%s Publishing to Firebase", logMessagePrefix(v, m))
	if err := s.firebaseClient.Send(v, m); err != nil {
		if err == errFirebaseTemporarilyBanned {
			log.Debug("%s Unable to publish to Firebase: %v", logMessagePrefix(v, m), err.Error())
		} else {
			log.Warn("%s Unable to publish to Firebase: %v", logMessagePrefix(v, m), err.Error())
		}
	}
}

func (s *Server) sendEmail(v *visitor, m *message, email string) {
	log.Debug("%s Sending email to %s", logMessagePrefix(v, m), email)
	if err := s.smtpSender.Send(v, m, email); err != nil {
		log.Warn("%s Unable to send email to %s: %v", logMessagePrefix(v, m), email, err.Error())
	}
}

func (s *Server) forwardPollRequest(v *visitor, m *message) {
	topicURL := fmt.Sprintf("%s/%s", s.config.BaseURL, m.Topic)
	topicHash := fmt.Sprintf("%x", sha256.Sum256([]byte(topicURL)))
	forwardURL := fmt.Sprintf("%s/%s", s.config.UpstreamBaseURL, topicHash)
	log.Debug("%s Publishing poll request to %s", logMessagePrefix(v, m), forwardURL)
	req, err := http.NewRequest("POST", forwardURL, strings.NewReader(""))
	if err != nil {
		log.Warn("%s Unable to publish poll request: %v", logMessagePrefix(v, m), err.Error())
		return
	}
	req.Header.Set("X-Poll-ID", m.ID)
	var httpClient = &http.Client{
		Timeout: time.Second * 10,
	}
	response, err := httpClient.Do(req)
	if err != nil {
		log.Warn("%s Unable to publish poll request: %v", logMessagePrefix(v, m), err.Error())
		return
	} else if response.StatusCode != http.StatusOK {
		log.Warn("%s Unable to publish poll request, unexpected HTTP status: %d", logMessagePrefix(v, m), response.StatusCode)
		return
	}
}

func (s *Server) parsePublishParams(r *http.Request, v *visitor, m *message) (cache bool, firebase bool, email string, unifiedpush bool, err error) {
	cache = readBoolParam(r, true, "x-cache", "cache")
	firebase = readBoolParam(r, true, "x-firebase", "firebase")
	m.Title = readParam(r, "x-title", "title", "t")
	m.Click = readParam(r, "x-click", "click")
	icon := readParam(r, "x-icon", "icon")
	filename := readParam(r, "x-filename", "filename", "file", "f")
	attach := readParam(r, "x-attach", "attach", "a")
	if attach != "" || filename != "" {
		m.Attachment = &attachment{}
	}
	if filename != "" {
		m.Attachment.Name = filename
	}
	if attach != "" {
		if !urlRegex.MatchString(attach) {
			return false, false, "", false, errHTTPBadRequestAttachmentURLInvalid
		}
		m.Attachment.URL = attach
		if m.Attachment.Name == "" {
			u, err := url.Parse(m.Attachment.URL)
			if err == nil {
				m.Attachment.Name = path.Base(u.Path)
				if m.Attachment.Name == "." || m.Attachment.Name == "/" {
					m.Attachment.Name = ""
				}
			}
		}
		if m.Attachment.Name == "" {
			m.Attachment.Name = "attachment"
		}
	}
	if icon != "" {
		if !urlRegex.MatchString(icon) {
			return false, false, "", false, errHTTPBadRequestIconURLInvalid
		}
		m.Icon = icon
	}
	email = readParam(r, "x-email", "x-e-mail", "email", "e-mail", "mail", "e")
	if email != "" {
		if err := v.EmailAllowed(); err != nil {
			return false, false, "", false, errHTTPTooManyRequestsLimitEmails
		}
	}
	if s.smtpSender == nil && email != "" {
		return false, false, "", false, errHTTPBadRequestEmailDisabled
	}
	messageStr := strings.ReplaceAll(readParam(r, "x-message", "message", "m"), "\\n", "\n")
	if messageStr != "" {
		m.Message = messageStr
	}
	m.Priority, err = util.ParsePriority(readParam(r, "x-priority", "priority", "prio", "p"))
	if err != nil {
		return false, false, "", false, errHTTPBadRequestPriorityInvalid
	}
	tagsStr := readParam(r, "x-tags", "tags", "tag", "ta")
	if tagsStr != "" {
		m.Tags = make([]string, 0)
		for _, s := range util.SplitNoEmpty(tagsStr, ",") {
			m.Tags = append(m.Tags, strings.TrimSpace(s))
		}
	}
	delayStr := readParam(r, "x-delay", "delay", "x-at", "at", "x-in", "in")
	if delayStr != "" {
		if !cache {
			return false, false, "", false, errHTTPBadRequestDelayNoCache
		}
		if email != "" {
			return false, false, "", false, errHTTPBadRequestDelayNoEmail // we cannot store the email address (yet)
		}
		delay, err := util.ParseFutureTime(delayStr, time.Now())
		if err != nil {
			return false, false, "", false, errHTTPBadRequestDelayCannotParse
		} else if delay.Unix() < time.Now().Add(s.config.MinDelay).Unix() {
			return false, false, "", false, errHTTPBadRequestDelayTooSmall
		} else if delay.Unix() > time.Now().Add(s.config.MaxDelay).Unix() {
			return false, false, "", false, errHTTPBadRequestDelayTooLarge
		}
		m.Time = delay.Unix()
		m.Sender = v.ip // Important for rate limiting
	}
	actionsStr := readParam(r, "x-actions", "actions", "action")
	if actionsStr != "" {
		m.Actions, err = parseActions(actionsStr)
		if err != nil {
			return false, false, "", false, wrapErrHTTP(errHTTPBadRequestActionsInvalid, err.Error())
		}
	}
	unifiedpush = readBoolParam(r, false, "x-unifiedpush", "unifiedpush", "up") // see GET too!
	if unifiedpush {
		firebase = false
		unifiedpush = true
	}
	m.PollID = readParam(r, "x-poll-id", "poll-id")
	if m.PollID != "" {
		unifiedpush = false
		cache = false
		email = ""
	}
	return cache, firebase, email, unifiedpush, nil
}

// handlePublishBody consumes the PUT/POST body and decides whether the body is an attachment or the message.
//
//  1. curl -X POST -H "Poll: 1234" ntfy.sh/...
//     If a message is flagged as poll request, the body does not matter and is discarded
//  2. curl -T somebinarydata.bin "ntfy.sh/mytopic?up=1"
//     If body is binary, encode as base64, if not do not encode
//  3. curl -H "Attach: http://example.com/file.jpg" ntfy.sh/mytopic
//     Body must be a message, because we attached an external URL
//  4. curl -T short.txt -H "Filename: short.txt" ntfy.sh/mytopic
//     Body must be attachment, because we passed a filename
//  5. curl -T file.txt ntfy.sh/mytopic
//     If file.txt is <= 4096 (message limit) and valid UTF-8, treat it as a message
//  6. curl -T file.txt ntfy.sh/mytopic
//     If file.txt is > message limit, treat it as an attachment
func (s *Server) handlePublishBody(r *http.Request, v *visitor, m *message, body *util.PeekedReadCloser, unifiedpush bool) error {
	if m.Event == pollRequestEvent { // Case 1
		return s.handleBodyDiscard(body)
	} else if unifiedpush {
		return s.handleBodyAsMessageAutoDetect(m, body) // Case 2
	} else if m.Attachment != nil && m.Attachment.URL != "" {
		return s.handleBodyAsTextMessage(m, body) // Case 3
	} else if m.Attachment != nil && m.Attachment.Name != "" {
		return s.handleBodyAsAttachment(r, v, m, body) // Case 4
	} else if !body.LimitReached && utf8.Valid(body.PeekedBytes) {
		return s.handleBodyAsTextMessage(m, body) // Case 5
	}
	return s.handleBodyAsAttachment(r, v, m, body) // Case 6
}

func (s *Server) handleBodyDiscard(body *util.PeekedReadCloser) error {
	_, err := io.Copy(io.Discard, body)
	_ = body.Close()
	return err
}

func (s *Server) handleBodyAsMessageAutoDetect(m *message, body *util.PeekedReadCloser) error {
	if utf8.Valid(body.PeekedBytes) {
		m.Message = string(body.PeekedBytes) // Do not trim
	} else {
		m.Message = base64.StdEncoding.EncodeToString(body.PeekedBytes)
		m.Encoding = encodingBase64
	}
	return nil
}

func (s *Server) handleBodyAsTextMessage(m *message, body *util.PeekedReadCloser) error {
	if !utf8.Valid(body.PeekedBytes) {
		return errHTTPBadRequestMessageNotUTF8
	}
	if len(body.PeekedBytes) > 0 { // Empty body should not override message (publish via GET!)
		m.Message = strings.TrimSpace(string(body.PeekedBytes)) // Truncates the message to the peek limit if required
	}
	if m.Attachment != nil && m.Attachment.Name != "" && m.Message == "" {
		m.Message = fmt.Sprintf(defaultAttachmentMessage, m.Attachment.Name)
	}
	return nil
}

func (s *Server) handleBodyAsAttachment(r *http.Request, v *visitor, m *message, body *util.PeekedReadCloser) error {
	if s.fileCache == nil || s.config.BaseURL == "" || s.config.AttachmentCacheDir == "" {
		return errHTTPBadRequestAttachmentsDisallowed
	}
	vinfo, err := v.Info()
	if err != nil {
		return err
	}
	attachmentExpiry := time.Now().Add(vinfo.Limits.AttachmentExpiryDuration).Unix()
	if m.Time > attachmentExpiry {
		return errHTTPBadRequestAttachmentsExpiryBeforeDelivery
	}
	contentLengthStr := r.Header.Get("Content-Length")
	if contentLengthStr != "" { // Early "do-not-trust" check, hard limit see below
		contentLength, err := strconv.ParseInt(contentLengthStr, 10, 64)
		if err == nil && (contentLength > vinfo.Stats.AttachmentTotalSizeRemaining || contentLength > vinfo.Limits.AttachmentFileSizeLimit) {
			return errHTTPEntityTooLargeAttachment
		}
	}
	if m.Attachment == nil {
		m.Attachment = &attachment{}
	}
	var ext string
	m.Sender = v.ip // Important for attachment rate limiting
	m.Attachment.Expires = attachmentExpiry
	m.Attachment.Type, ext = util.DetectContentType(body.PeekedBytes, m.Attachment.Name)
	m.Attachment.URL = fmt.Sprintf("%s/file/%s%s", s.config.BaseURL, m.ID, ext)
	if m.Attachment.Name == "" {
		m.Attachment.Name = fmt.Sprintf("attachment%s", ext)
	}
	if m.Message == "" {
		m.Message = fmt.Sprintf(defaultAttachmentMessage, m.Attachment.Name)
	}
	limiters := []util.Limiter{
		v.BandwidthLimiter(),
		util.NewFixedLimiter(vinfo.Limits.AttachmentFileSizeLimit),
		util.NewFixedLimiter(vinfo.Stats.AttachmentTotalSizeRemaining),
	}
	m.Attachment.Size, err = s.fileCache.Write(m.ID, body, limiters...)
	if err == util.ErrLimitReached {
		return errHTTPEntityTooLargeAttachment
	} else if err != nil {
		return err
	}
	return nil
}

func (s *Server) handleSubscribeJSON(w http.ResponseWriter, r *http.Request, v *visitor) error {
	encoder := func(msg *message) (string, error) {
		var buf bytes.Buffer
		if err := json.NewEncoder(&buf).Encode(&msg); err != nil {
			return "", err
		}
		return buf.String(), nil
	}
	return s.handleSubscribeHTTP(w, r, v, "application/x-ndjson", encoder)
}

func (s *Server) handleSubscribeSSE(w http.ResponseWriter, r *http.Request, v *visitor) error {
	encoder := func(msg *message) (string, error) {
		var buf bytes.Buffer
		if err := json.NewEncoder(&buf).Encode(&msg); err != nil {
			return "", err
		}
		if msg.Event != messageEvent {
			return fmt.Sprintf("event: %s\ndata: %s\n", msg.Event, buf.String()), nil // Browser's .onmessage() does not fire on this!
		}
		return fmt.Sprintf("data: %s\n", buf.String()), nil
	}
	return s.handleSubscribeHTTP(w, r, v, "text/event-stream", encoder)
}

func (s *Server) handleSubscribeRaw(w http.ResponseWriter, r *http.Request, v *visitor) error {
	encoder := func(msg *message) (string, error) {
		if msg.Event == messageEvent { // only handle default events
			return strings.ReplaceAll(msg.Message, "\n", " ") + "\n", nil
		}
		return "\n", nil // "keepalive" and "open" events just send an empty line
	}
	return s.handleSubscribeHTTP(w, r, v, "text/plain", encoder)
}

func (s *Server) handleSubscribeHTTP(w http.ResponseWriter, r *http.Request, v *visitor, contentType string, encoder messageEncoder) error {
	log.Debug("%s HTTP stream connection opened", logHTTPPrefix(v, r))
	defer log.Debug("%s HTTP stream connection closed", logHTTPPrefix(v, r))
	if err := v.SubscriptionAllowed(); err != nil {
		return errHTTPTooManyRequestsLimitSubscriptions
	}
	defer v.RemoveSubscription()
	topics, topicsStr, err := s.topicsFromPath(r.URL.Path)
	if err != nil {
		return err
	}
	poll, since, scheduled, filters, err := parseSubscribeParams(r)
	if err != nil {
		return err
	}
	var wlock sync.Mutex
	defer func() {
		// Hack: This is the fix for a horrible data race that I have not been able to figure out in quite some time.
		// It appears to be happening when the Go HTTP code reads from the socket when closing the request (i.e. AFTER
		// this function returns), and causes a data race with the ResponseWriter. Locking wlock here silences the
		// data race detector. See https://github.com/binwiederhier/ntfy/issues/338#issuecomment-1163425889.
		wlock.TryLock()
	}()
	sub := func(v *visitor, msg *message) error {
		if !filters.Pass(msg) {
			return nil
		}
		m, err := encoder(msg)
		if err != nil {
			return err
		}
		wlock.Lock()
		defer wlock.Unlock()
		if _, err := w.Write([]byte(m)); err != nil {
			return err
		}
		if fl, ok := w.(http.Flusher); ok {
			fl.Flush()
		}
		return nil
	}
	w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
	w.Header().Set("Content-Type", contentType+"; charset=utf-8")                    // Android/Volley client needs charset!
	if poll {
		return s.sendOldMessages(topics, since, scheduled, v, sub)
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	subscriberIDs := make([]int, 0)
	for _, t := range topics {
		subscriberIDs = append(subscriberIDs, t.Subscribe(sub, v.MaybeUserID(), cancel))
	}
	defer func() {
		for i, subscriberID := range subscriberIDs {
			topics[i].Unsubscribe(subscriberID) // Order!
		}
	}()
	if err := sub(v, newOpenMessage(topicsStr)); err != nil { // Send out open message
		return err
	}
	if err := s.sendOldMessages(topics, since, scheduled, v, sub); err != nil {
		return err
	}
	for {
		select {
		case <-ctx.Done():
			return nil
		case <-r.Context().Done():
			return nil
		case <-time.After(s.config.KeepaliveInterval):
			log.Trace("%s Sending keepalive message", logHTTPPrefix(v, r))
			v.Keepalive()
			if err := sub(v, newKeepaliveMessage(topicsStr)); err != nil { // Send keepalive message
				return err
			}
		}
	}
}

func (s *Server) handleSubscribeWS(w http.ResponseWriter, r *http.Request, v *visitor) error {
	if strings.ToLower(r.Header.Get("Upgrade")) != "websocket" {
		return errHTTPBadRequestWebSocketsUpgradeHeaderMissing
	}
	if err := v.SubscriptionAllowed(); err != nil {
		return errHTTPTooManyRequestsLimitSubscriptions
	}
	defer v.RemoveSubscription()
	log.Debug("%s WebSocket connection opened", logHTTPPrefix(v, r))
	defer log.Debug("%s WebSocket connection closed", logHTTPPrefix(v, r))
	topics, topicsStr, err := s.topicsFromPath(r.URL.Path)
	if err != nil {
		return err
	}
	poll, since, scheduled, filters, err := parseSubscribeParams(r)
	if err != nil {
		return err
	}
	upgrader := &websocket.Upgrader{
		ReadBufferSize:  wsBufferSize,
		WriteBufferSize: wsBufferSize,
		CheckOrigin: func(r *http.Request) bool {
			return true // We're open for business!
		},
	}
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		return err
	}
	defer conn.Close()

	// Subscription connections can be canceled externally, see topic.CancelSubscribers
	cancelCtx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Use errgroup to run WebSocket reader and writer in Go routines
	var wlock sync.Mutex
	g, gctx := errgroup.WithContext(cancelCtx)
	g.Go(func() error {
		pongWait := s.config.KeepaliveInterval + wsPongWait
		conn.SetReadLimit(wsReadLimit)
		if err := conn.SetReadDeadline(time.Now().Add(pongWait)); err != nil {
			return err
		}
		conn.SetPongHandler(func(appData string) error {
			log.Trace("%s Received WebSocket pong", logHTTPPrefix(v, r))
			return conn.SetReadDeadline(time.Now().Add(pongWait))
		})
		for {
			_, _, err := conn.NextReader()
			if err != nil {
				return err
			}
			select {
			case <-gctx.Done():
				return nil
			default:
			}
		}
	})
	g.Go(func() error {
		ping := func() error {
			wlock.Lock()
			defer wlock.Unlock()
			if err := conn.SetWriteDeadline(time.Now().Add(wsWriteWait)); err != nil {
				return err
			}
			log.Trace("%s Sending WebSocket ping", logHTTPPrefix(v, r))
			return conn.WriteMessage(websocket.PingMessage, nil)
		}
		for {
			select {
			case <-gctx.Done():
				return nil
			case <-cancelCtx.Done():
				log.Trace("%s Cancel received, closing subscriber connection", logHTTPPrefix(v, r))
				conn.Close()
				return &websocket.CloseError{Code: websocket.CloseNormalClosure, Text: "subscription was canceled"}
			case <-time.After(s.config.KeepaliveInterval):
				v.Keepalive()
				if err := ping(); err != nil {
					return err
				}
			}
		}
	})
	sub := func(v *visitor, msg *message) error {
		if !filters.Pass(msg) {
			return nil
		}
		wlock.Lock()
		defer wlock.Unlock()
		if err := conn.SetWriteDeadline(time.Now().Add(wsWriteWait)); err != nil {
			return err
		}
		return conn.WriteJSON(msg)
	}
	w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
	if poll {
		return s.sendOldMessages(topics, since, scheduled, v, sub)
	}
	subscriberIDs := make([]int, 0)
	for _, t := range topics {
		subscriberIDs = append(subscriberIDs, t.Subscribe(sub, v.MaybeUserID(), cancel))
	}
	defer func() {
		for i, subscriberID := range subscriberIDs {
			topics[i].Unsubscribe(subscriberID) // Order!
		}
	}()
	if err := sub(v, newOpenMessage(topicsStr)); err != nil { // Send out open message
		return err
	}
	if err := s.sendOldMessages(topics, since, scheduled, v, sub); err != nil {
		return err
	}
	err = g.Wait()
	if err != nil && websocket.IsCloseError(err, websocket.CloseNormalClosure, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
		log.Trace("%s WebSocket connection closed: %s", logHTTPPrefix(v, r), err.Error())
		return nil // Normal closures are not errors; note: "1006 (abnormal closure)" is treated as normal, because people disconnect a lot
	}
	return err
}

func parseSubscribeParams(r *http.Request) (poll bool, since sinceMarker, scheduled bool, filters *queryFilter, err error) {
	poll = readBoolParam(r, false, "x-poll", "poll", "po")
	scheduled = readBoolParam(r, false, "x-scheduled", "scheduled", "sched")
	since, err = parseSince(r, poll)
	if err != nil {
		return
	}
	filters, err = parseQueryFilters(r)
	if err != nil {
		return
	}
	return
}

// sendOldMessages selects old messages from the messageCache and calls sub for each of them. It uses since as the
// marker, returning only messages that are newer than the marker.
func (s *Server) sendOldMessages(topics []*topic, since sinceMarker, scheduled bool, v *visitor, sub subscriber) error {
	if since.IsNone() {
		return nil
	}
	messages := make([]*message, 0)
	for _, t := range topics {
		topicMessages, err := s.messageCache.Messages(t.ID, since, scheduled)
		if err != nil {
			return err
		}
		messages = append(messages, topicMessages...)
	}
	sort.Slice(messages, func(i, j int) bool {
		return messages[i].Time < messages[j].Time
	})
	for _, m := range messages {
		if err := sub(v, m); err != nil {
			return err
		}
	}
	return nil
}

// parseSince returns a timestamp identifying the time span from which cached messages should be received.
//
// Values in the "since=..." parameter can be either a unix timestamp or a duration (e.g. 12h), or
// "all" for all messages.
func parseSince(r *http.Request, poll bool) (sinceMarker, error) {
	since := readParam(r, "x-since", "since", "si")

	// Easy cases (empty, all, none)
	if since == "" {
		if poll {
			return sinceAllMessages, nil
		}
		return sinceNoMessages, nil
	} else if since == "all" {
		return sinceAllMessages, nil
	} else if since == "none" {
		return sinceNoMessages, nil
	}

	// ID, timestamp, duration
	if validMessageID(since) {
		return newSinceID(since), nil
	} else if s, err := strconv.ParseInt(since, 10, 64); err == nil {
		return newSinceTime(s), nil
	} else if d, err := time.ParseDuration(since); err == nil {
		return newSinceTime(time.Now().Add(-1 * d).Unix()), nil
	}
	return sinceNoMessages, errHTTPBadRequestSinceInvalid
}

func (s *Server) handleOptions(w http.ResponseWriter, _ *http.Request, _ *visitor) error {
	w.Header().Set("Access-Control-Allow-Methods", "GET, PUT, POST, PATCH, DELETE")
	w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
	w.Header().Set("Access-Control-Allow-Headers", "*")                              // CORS, allow auth via JS // FIXME is this terrible?
	return nil
}

func (s *Server) topicFromPath(path string) (*topic, error) {
	parts := strings.Split(path, "/")
	if len(parts) < 2 {
		return nil, errHTTPBadRequestTopicInvalid
	}
	return s.topicFromID(parts[1])
}

func (s *Server) topicsFromPath(path string) ([]*topic, string, error) {
	parts := strings.Split(path, "/")
	if len(parts) < 2 {
		return nil, "", errHTTPBadRequestTopicInvalid
	}
	topicIDs := util.SplitNoEmpty(parts[1], ",")
	topics, err := s.topicsFromIDs(topicIDs...)
	if err != nil {
		return nil, "", errHTTPBadRequestTopicInvalid
	}
	return topics, parts[1], nil
}

func (s *Server) topicsFromIDs(ids ...string) ([]*topic, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	topics := make([]*topic, 0)
	for _, id := range ids {
		if util.Contains(disallowedTopics, id) {
			return nil, errHTTPBadRequestTopicDisallowed
		}
		if _, ok := s.topics[id]; !ok {
			if len(s.topics) >= s.config.TotalTopicLimit {
				return nil, errHTTPTooManyRequestsLimitTotalTopics
			}
			s.topics[id] = newTopic(id)
		}
		topics = append(topics, s.topics[id])
	}
	return topics, nil
}

func (s *Server) topicFromID(id string) (*topic, error) {
	topics, err := s.topicsFromIDs(id)
	if err != nil {
		return nil, err
	}
	return topics[0], nil
}

func (s *Server) execManager() {
	log.Debug("Manager: Starting")
	defer log.Debug("Manager: Finished")

	// WARNING: Make sure to only selectively lock with the mutex, and be aware that this
	//          there is no mutex for the entire function.

	// Expire visitors from rate visitors map
	s.mu.Lock()
	staleVisitors := 0
	for ip, v := range s.visitors {
		if v.Stale() {
			log.Trace("Deleting stale visitor %s", v.ip)
			delete(s.visitors, ip)
			staleVisitors++
		}
	}
	s.mu.Unlock()
	log.Debug("Manager: Deleted %d stale visitor(s)", staleVisitors)

	// Delete expired user tokens and users
	if s.userManager != nil {
		if err := s.userManager.RemoveExpiredTokens(); err != nil {
			log.Warn("Error expiring user tokens: %s", err.Error())
		}
		if err := s.userManager.RemoveDeletedUsers(); err != nil {
			log.Warn("Error deleting soft-deleted users: %s", err.Error())
		}
	}

	// Delete expired attachments
	if s.fileCache != nil {
		ids, err := s.messageCache.AttachmentsExpired()
		if err != nil {
			log.Warn("Manager: Error retrieving expired attachments: %s", err.Error())
		} else if len(ids) > 0 {
			if log.IsDebug() {
				log.Debug("Manager: Deleting attachments %s", strings.Join(ids, ", "))
			}
			if err := s.fileCache.Remove(ids...); err != nil {
				log.Warn("Manager: Error deleting attachments: %s", err.Error())
			}
			if err := s.messageCache.MarkAttachmentsDeleted(ids...); err != nil {
				log.Warn("Manager: Error marking attachments deleted: %s", err.Error())
			}
		} else {
			log.Debug("Manager: No expired attachments to delete")
		}
	}

	// Prune messages
	log.Debug("Manager: Pruning messages")
	expiredMessageIDs, err := s.messageCache.MessagesExpired()
	if err != nil {
		log.Warn("Manager: Error retrieving expired messages: %s", err.Error())
	} else if len(expiredMessageIDs) > 0 {
		if err := s.fileCache.Remove(expiredMessageIDs...); err != nil {
			log.Warn("Manager: Error deleting attachments for expired messages: %s", err.Error())
		}
		if err := s.messageCache.DeleteMessages(expiredMessageIDs...); err != nil {
			log.Warn("Manager: Error marking attachments deleted: %s", err.Error())
		}
	} else {
		log.Debug("Manager: No expired messages to delete")
	}

	// Message count per topic
	var messages int
	messageCounts, err := s.messageCache.MessageCounts()
	if err != nil {
		log.Warn("Manager: Cannot get message counts: %s", err.Error())
		messageCounts = make(map[string]int) // Empty, so we can continue
	}
	for _, count := range messageCounts {
		messages += count
	}

	// Remove subscriptions without subscribers
	s.mu.Lock()
	var subscribers int
	for _, t := range s.topics {
		subs := t.SubscribersCount()
		log.Trace("- topic %s: %d subscribers", t.ID, subs)
		msgs, exists := messageCounts[t.ID]
		if subs == 0 && (!exists || msgs == 0) {
			log.Trace("Deleting empty topic %s", t.ID)
			delete(s.topics, t.ID)
			continue
		}
		subscribers += subs
	}
	s.mu.Unlock()

	// Mail stats
	var receivedMailTotal, receivedMailSuccess, receivedMailFailure int64
	if s.smtpServerBackend != nil {
		receivedMailTotal, receivedMailSuccess, receivedMailFailure = s.smtpServerBackend.Counts()
	}
	var sentMailTotal, sentMailSuccess, sentMailFailure int64
	if s.smtpSender != nil {
		sentMailTotal, sentMailSuccess, sentMailFailure = s.smtpSender.Counts()
	}

	// Print stats
	s.mu.Lock()
	messagesCount, topicsCount, visitorsCount := s.messages, len(s.topics), len(s.visitors)
	s.mu.Unlock()
	log.Info("Stats: %d messages published, %d in cache, %d topic(s) active, %d subscriber(s), %d visitor(s), %d mails received (%d successful, %d failed), %d mails sent (%d successful, %d failed)",
		messagesCount, messages, topicsCount, subscribers, visitorsCount,
		receivedMailTotal, receivedMailSuccess, receivedMailFailure,
		sentMailTotal, sentMailSuccess, sentMailFailure)
}

func (s *Server) runSMTPServer() error {
	s.smtpServerBackend = newMailBackend(s.config, s.handle)
	s.smtpServer = smtp.NewServer(s.smtpServerBackend)
	s.smtpServer.Addr = s.config.SMTPServerListen
	s.smtpServer.Domain = s.config.SMTPServerDomain
	s.smtpServer.ReadTimeout = 10 * time.Second
	s.smtpServer.WriteTimeout = 10 * time.Second
	s.smtpServer.MaxMessageBytes = 1024 * 1024 // Must be much larger than message size (headers, multipart, etc.)
	s.smtpServer.MaxRecipients = 1
	s.smtpServer.AllowInsecureAuth = true
	return s.smtpServer.ListenAndServe()
}

func (s *Server) runManager() {
	for {
		select {
		case <-time.After(s.config.ManagerInterval):
			s.execManager()
		case <-s.closeChan:
			return
		}
	}
}

// runStatsResetter runs once a day (usually midnight UTC) to reset all the visitor's message and
// email counters. The stats are used to display the counters in the web app, as well as for rate limiting.
func (s *Server) runStatsResetter() {
	for {
		runAt := util.NextOccurrenceUTC(s.config.VisitorStatsResetTime, time.Now())
		timer := time.NewTimer(time.Until(runAt))
		log.Debug("Stats resetter: Waiting until %v to reset visitor stats", runAt)
		select {
		case <-timer.C:
			s.resetStats()
		case <-s.closeChan:
			timer.Stop()
			return
		}
	}
}

func (s *Server) resetStats() {
	log.Info("Resetting all visitor stats (daily task)")
	s.mu.Lock()
	defer s.mu.Unlock() // Includes the database query to avoid races with other processes
	for _, v := range s.visitors {
		v.ResetStats()
	}
	if s.userManager != nil {
		if err := s.userManager.ResetStats(); err != nil {
			log.Warn("Failed to write to database: %s", err.Error())
		}
	}
}

func (s *Server) runFirebaseKeepaliver() {
	if s.firebaseClient == nil {
		return
	}
	v := newVisitor(s.config, s.messageCache, s.userManager, netip.IPv4Unspecified(), nil) // Background process, not a real visitor, uses IP 0.0.0.0
	for {
		select {
		case <-time.After(s.config.FirebaseKeepaliveInterval):
			s.sendToFirebase(v, newKeepaliveMessage(firebaseControlTopic))
		case <-time.After(s.config.FirebasePollInterval):
			s.sendToFirebase(v, newKeepaliveMessage(firebasePollTopic))
		case <-s.closeChan:
			return
		}
	}
}

func (s *Server) runDelayedSender() {
	for {
		select {
		case <-time.After(s.config.DelayedSenderInterval):
			if err := s.sendDelayedMessages(); err != nil {
				log.Warn("Error sending delayed messages: %s", err.Error())
			}
		case <-s.closeChan:
			return
		}
	}
}

func (s *Server) sendDelayedMessages() error {
	messages, err := s.messageCache.MessagesDue()
	if err != nil {
		return err
	}
	for _, m := range messages {
		var v *visitor
		if s.userManager != nil && m.User != "" {
			u, err := s.userManager.User(m.User)
			if err != nil {
				log.Warn("%s Error sending delayed message: %s", logMessagePrefix(v, m), err.Error())
				continue
			}
			v = s.visitorFromUser(u, m.Sender)
		} else {
			v = s.visitorFromIP(m.Sender)
		}
		if err := s.sendDelayedMessage(v, m); err != nil {
			log.Warn("%s Error sending delayed message: %s", logMessagePrefix(v, m), err.Error())
		}
	}
	return nil
}

func (s *Server) sendDelayedMessage(v *visitor, m *message) error {
	log.Debug("%s Sending delayed message", logMessagePrefix(v, m))
	s.mu.Lock()
	t, ok := s.topics[m.Topic] // If no subscribers, just mark message as published
	s.mu.Unlock()
	if ok {
		go func() {
			// We do not rate-limit messages here, since we've rate limited them in the PUT/POST handler
			if err := t.Publish(v, m); err != nil {
				log.Warn("%s Unable to publish message: %v", logMessagePrefix(v, m), err.Error())
			}
		}()
	}
	if s.firebaseClient != nil { // Firebase subscribers may not show up in topics map
		go s.sendToFirebase(v, m)
	}
	if s.config.UpstreamBaseURL != "" {
		go s.forwardPollRequest(v, m)
	}
	if err := s.messageCache.MarkPublished(m); err != nil {
		return err
	}
	return nil
}

func (s *Server) limitRequests(next handleFunc) handleFunc {
	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
		if util.ContainsIP(s.config.VisitorRequestExemptIPAddrs, v.ip) {
			return next(w, r, v)
		} else if err := v.RequestAllowed(); err != nil {
			return errHTTPTooManyRequestsLimitRequests
		}
		return next(w, r, v)
	}
}

// transformBodyJSON peeks the request body, reads the JSON, and converts it to headers
// before passing it on to the next handler. This is meant to be used in combination with handlePublish.
func (s *Server) transformBodyJSON(next handleFunc) handleFunc {
	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
		m, err := readJSONWithLimit[publishMessage](r.Body, s.config.MessageLimit*2) // 2x to account for JSON format overhead
		if err != nil {
			return err
		}
		if !topicRegex.MatchString(m.Topic) {
			return errHTTPBadRequestTopicInvalid
		}
		if m.Message == "" {
			m.Message = emptyMessageBody
		}
		r.URL.Path = "/" + m.Topic
		r.Body = io.NopCloser(strings.NewReader(m.Message))
		if m.Title != "" {
			r.Header.Set("X-Title", m.Title)
		}
		if m.Priority != 0 {
			r.Header.Set("X-Priority", fmt.Sprintf("%d", m.Priority))
		}
		if m.Tags != nil && len(m.Tags) > 0 {
			r.Header.Set("X-Tags", strings.Join(m.Tags, ","))
		}
		if m.Attach != "" {
			r.Header.Set("X-Attach", m.Attach)
		}
		if m.Filename != "" {
			r.Header.Set("X-Filename", m.Filename)
		}
		if m.Click != "" {
			r.Header.Set("X-Click", m.Click)
		}
		if m.Icon != "" {
			r.Header.Set("X-Icon", m.Icon)
		}
		if len(m.Actions) > 0 {
			actionsStr, err := json.Marshal(m.Actions)
			if err != nil {
				return errHTTPBadRequestMessageJSONInvalid
			}
			r.Header.Set("X-Actions", string(actionsStr))
		}
		if m.Email != "" {
			r.Header.Set("X-Email", m.Email)
		}
		if m.Delay != "" {
			r.Header.Set("X-Delay", m.Delay)
		}
		return next(w, r, v)
	}
}

func (s *Server) transformMatrixJSON(next handleFunc) handleFunc {
	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
		newRequest, err := newRequestFromMatrixJSON(r, s.config.BaseURL, s.config.MessageLimit)
		if err != nil {
			return err
		}
		if err := next(w, newRequest, v); err != nil {
			return &errMatrix{pushKey: newRequest.Header.Get(matrixPushKeyHeader), err: err}
		}
		return nil
	}
}

func (s *Server) authorizeTopicWrite(next handleFunc) handleFunc {
	return s.autorizeTopic(next, user.PermissionWrite)
}

func (s *Server) authorizeTopicRead(next handleFunc) handleFunc {
	return s.autorizeTopic(next, user.PermissionRead)
}

func (s *Server) autorizeTopic(next handleFunc, perm user.Permission) handleFunc {
	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
		if s.userManager == nil {
			return next(w, r, v)
		}
		topics, _, err := s.topicsFromPath(r.URL.Path)
		if err != nil {
			return err
		}
		for _, t := range topics {
			if err := s.userManager.Authorize(v.user, t.ID, perm); err != nil {
				log.Info("unauthorized: %s", err.Error())
				return errHTTPForbidden
			}
		}
		return next(w, r, v)
	}
}

// visitor creates or retrieves a rate.Limiter for the given visitor.
// Note that this function will always return a visitor, even if an error occurs.
func (s *Server) visitor(r *http.Request) (v *visitor, err error) {
	ip := extractIPAddress(r, s.config.BehindProxy)
	var u *user.User // may stay nil if no auth header!
	if u, err = s.authenticate(r); err != nil {
		log.Debug("authentication failed: %s", err.Error())
		err = errHTTPUnauthorized // Always return visitor, even when error occurs!
	}
	if u != nil {
		v = s.visitorFromUser(u, ip)
	} else {
		v = s.visitorFromIP(ip)
	}
	v.mu.Lock()
	v.user = u
	v.mu.Unlock()
	return v, err // Always return visitor, even when error occurs!
}

// authenticate a user based on basic auth username/password (Authorization: Basic ...), or token auth (Authorization: Bearer ...).
// The Authorization header can be passed as a header or the ?auth=... query param. The latter is required only to
// support the WebSocket JavaScript class, which does not support passing headers during the initial request. The auth
// query param is effectively double base64 encoded. Its format is base64(Basic base64(user:pass)).
func (s *Server) authenticate(r *http.Request) (user *user.User, err error) {
	value := strings.TrimSpace(r.Header.Get("Authorization"))
	queryParam := readQueryParam(r, "authorization", "auth")
	if queryParam != "" {
		a, err := base64.RawURLEncoding.DecodeString(queryParam)
		if err != nil {
			return nil, err
		}
		value = strings.TrimSpace(string(a))
	}
	if value == "" {
		return nil, nil
	} else if s.userManager == nil {
		return nil, errHTTPUnauthorized
	}
	if strings.HasPrefix(value, "Bearer") {
		return s.authenticateBearerAuth(value)
	}
	return s.authenticateBasicAuth(r, value)
}

func (s *Server) authenticateBasicAuth(r *http.Request, value string) (user *user.User, err error) {
	r.Header.Set("Authorization", value)
	username, password, ok := r.BasicAuth()
	if !ok {
		return nil, errors.New("invalid basic auth")
	}
	return s.userManager.Authenticate(username, password)
}

func (s *Server) authenticateBearerAuth(value string) (user *user.User, err error) {
	token := strings.TrimSpace(strings.TrimPrefix(value, "Bearer"))
	return s.userManager.AuthenticateToken(token)
}

func (s *Server) visitorFromID(visitorID string, ip netip.Addr, user *user.User) *visitor {
	s.mu.Lock()
	defer s.mu.Unlock()
	v, exists := s.visitors[visitorID]
	if !exists {
		s.visitors[visitorID] = newVisitor(s.config, s.messageCache, s.userManager, ip, user)
		return s.visitors[visitorID]
	}
	v.Keepalive()
	return v
}

func (s *Server) visitorFromIP(ip netip.Addr) *visitor {
	return s.visitorFromID(fmt.Sprintf("ip:%s", ip.String()), ip, nil)
}

func (s *Server) visitorFromUser(user *user.User, ip netip.Addr) *visitor {
	return s.visitorFromID(fmt.Sprintf("user:%s", user.ID), ip, user)
}

func (s *Server) writeJSON(w http.ResponseWriter, v any) error {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Access-Control-Allow-Origin", s.config.AccessControlAllowOrigin) // CORS, allow cross-origin requests
	if err := json.NewEncoder(w).Encode(v); err != nil {
		return err
	}
	return nil
}