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[onechat] / whatsapp.go

package main

import (
        "context"
        "crypto/sha256"
        "database/sql"
        "errors"
        "fmt"
        "log/slog"
        "net/url"
        "os"
        "path/filepath"
        "slices"
        "strings"
        "sync"
        "time"

        "go.mau.fi/whatsmeow"
        "go.mau.fi/whatsmeow/proto/waCompanionReg"
        "go.mau.fi/whatsmeow/proto/waE2E"
        "go.mau.fi/whatsmeow/store"
        "go.mau.fi/whatsmeow/store/sqlstore"
        "go.mau.fi/whatsmeow/types"
        "go.mau.fi/whatsmeow/types/events"
        waLog "go.mau.fi/whatsmeow/util/log"
        // The session store of the library opens SQLite with this pure Go
        // driver.
        _ "modernc.org/sqlite"
)

const (
        // whatsappDirName is the directory of the WhatsApp files in the data
        // directory.
        whatsappDirName = "whatsapp"

        // whatsappSessionFileName is the session database of the library in
        // whatsappDirName.
        whatsappSessionFileName = "session.db"

        // whatsappCommand starts the input lines of the WhatsApp commands, such
        // as "/whatsapp status".
        whatsappCommand = "/whatsapp"

        // whatsappUsage is the answer to a WhatsApp command that does not
        // exist.
        whatsappUsage = "Use /whatsapp pair PHONE, /whatsapp status, or /whatsapp unlink. PHONE is the number of your WhatsApp account with its country code, such as +15550001111."

        // whatsappPairSteps tells the user what to do with the pairing code,
        // which comes in the next message.
        whatsappPairSteps = "In WhatsApp on your phone, open Linked devices, tap Link a device, then tap Link with phone number instead, and enter the code of the next message. The code expires in about 2 minutes."

        // whatsappPairExpired is the answer when the pairing code expires.
        whatsappPairExpired = "The pairing code expired. Run /whatsapp pair PHONE again for a new code."

        // whatsappTimeLayout is the layout of the times in the answers.
        whatsappTimeLayout = "2006-01-02 15:04"

        // whatsappPairTimeout is the longest time of a pairing. The library
        // closes the pairing connection after about 160 seconds.
        whatsappPairTimeout = 3 * time.Minute

        // whatsappLogoutTimeout is the longest time of the logout call of an
        // unlink.
        whatsappLogoutTimeout = 30 * time.Second

        // whatsappOutageNoticeDelay is the delay from a disconnection to its
        // notice to the user.
        whatsappOutageNoticeDelay = 10 * time.Minute

        // whatsappRetryDelay is the first wait after a failed starting
        // connection.
        whatsappRetryDelay = 2 * time.Second

        // whatsappRetryLimit is the longest wait between starting connections.
        whatsappRetryLimit = 5 * time.Minute

        // whatsappRequests is the number of pair and unlink commands that can
        // wait for Run.
        whatsappRequests = 8

        // whatsappNotLinked is the answer of a WhatsApp tool without a link.
        whatsappNotLinked = "WhatsApp is not linked. Tell the user to run /whatsapp pair PHONE in the terminal or in Telegram."
)

// WhatsAppClient is the part of the WhatsApp client that the daemon uses. The
// real one is a *whatsmeow.Client from whatsappNewClient, and the tests use a
// fake.
type WhatsAppClient interface {
        ConnectContext(ctx context.Context) error
        Disconnect()
        GetQRChannel(ctx context.Context) (<-chan whatsmeow.QRChannelItem, error)
        PairPhone(ctx context.Context, phone string, showPushNotification bool, clientType whatsmeow.PairClientType, clientDisplayName string) (string, error)
        Logout(ctx context.Context) error
        GetJoinedGroups(ctx context.Context) ([]*types.GroupInfo, error)
        Download(ctx context.Context, message whatsmeow.DownloadableMessage) ([]byte, error)
        Upload(ctx context.Context, data []byte, mediaType whatsmeow.MediaType) (whatsmeow.UploadResponse, error)
        GenerateMessageID() types.MessageID
        SendMessage(ctx context.Context, to types.JID, message *waE2E.Message, extra ...whatsmeow.SendRequestExtra) (whatsmeow.SendResponse, error)
}

// openWhatsApp opens the WhatsApp session in the data directory dir. Without
// the session file, WhatsApp is not linked. The session gives full access to
// the account, so a file that another user can read is an error. The clock
// gives the times of the status, logger gets the failures, and newClient makes
// the client of a device with its event handler.
func openWhatsApp(ctx context.Context, dir string, clock func() time.Time, logger *slog.Logger, newClient func(device *store.Device, handle func(event any) bool) WhatsAppClient) (*WhatsApp, error) {
        w := &WhatsApp{
                ctx:       ctx,
                dir:       filepath.Join(dir, whatsappDirName),
                clock:     clock,
                logger:    logger,
                newClient: newClient,
                requests:  make(chan WhatsAppRequest, whatsappRequests),
                logouts:   make(chan struct{}, 1),
                groups:    newWhatsAppGroups(logger),
        }

        var err error

        w.state, err = openWhatsAppState(filepath.Join(w.dir, whatsappStateFileName))
        if err != nil {
                return nil, err
        }

        w.inbox = newWhatsAppInbox(w.state, clock, w.groups, &ImageStore{dir: filepath.Join(dir, imageDirName)}, logger)

        info, err := os.Stat(w.sessionPath())
        if errors.Is(err, os.ErrNotExist) {
                return w, nil
        }

        if err != nil {
                return nil, fmt.Errorf("read WhatsApp session: %w", err)
        }

        if info.Mode().Perm()&0o077 != 0 {
                return nil, fmt.Errorf("%s holds the WhatsApp session, so its mode must be 0600", filepath.Join(whatsappDirName, whatsappSessionFileName))
        }

        err = w.openSession(ctx)
        if err != nil {
                return nil, err
        }

        if w.device.ID != nil {
                w.linked = true
                w.inbox.waitForCatchup()

                w.own = whatsappOwnIDs(w.device.ID.User, w.device.LID.User)
        }

        return w, nil
}

// WhatsApp is the link of the daemon to the WhatsApp account of the user, as a
// linked device. The session database of the library in dir holds the keys of
// the device. Run keeps a linked device connected, and the library connects
// again by itself after a network failure.
//
// The commands pair and unlink go to Run as requests, and Run runs one at a
// time. A pairing runs in its own goroutine until its code expires, and a new
// pairing ends the one before. Its phone number and code go only to the answer
// of the client that asked. A logout from the phone comes as an event of the
// library, and Run deletes the session. The mutex protects the session, the
// client, and the state of the connection, which the event handler of the
// library changes from its own goroutines. The sessionMutex serializes session
// creation, close, removal, and snapshots. It is held before mutex, and stays
// held when removal releases mutex for client callbacks.
//
// ctx is the caller context until Run sets its context for library callbacks.
// The mutex protects it, so callbacks follow daemon cancellation.
//
// The inbox puts messages into batches and logs them, and groups holds the
// names of the groups. Both get a WhatsAppLink from link for each call, so they
// use the current device and client.
//
// The library logs nothing, because its log lines hold the ID of the own
// account, which is the phone number of the user. The own number and the own
// LID never go to the log of the agent or to the log of the daemon: redact
// removes them from the errors, and a batch shows the messages of the user as
// You and a mention of the user as @you. The IDs of the other chats go to the
// log, and those of private chats hold phone numbers, because the agent needs
// them to send.
type WhatsApp struct {
        ctx       context.Context
        dir       string
        clock     func() time.Time
        logger    *slog.Logger
        newClient func(device *store.Device, handle func(event any) bool) WhatsAppClient
        requests  chan WhatsAppRequest
        logouts   chan struct{}
        state     *WhatsAppState
        groups    *WhatsAppGroups
        inbox     *WhatsAppInbox
        routes    *Routes

        sessionMutex   sync.Mutex
        mutex          sync.Mutex
        container      *sqlstore.Container
        device         *store.Device
        client         WhatsAppClient
        linked         bool
        own            []string
        notify         func(Event)
        connected      bool
        retrying       bool
        connectedAt    time.Time
        disconnectedAt time.Time
        disconnections int
        noticed        bool
        timer          *time.Timer
        closed         bool
}

// Run connects a linked device, logs the closed batches in l, runs the pair and
// unlink commands, and handles a logout from the phone, until ctx ends. Its
// notes go to the log of l, and notify gets the notices for all clients. A
// failed first connection starts the same outage notice as a lost connection. A
// timer in the select retries it with a doubled wait from 2 seconds to 5
// minutes, without a retry goroutine or a wait that blocks commands or the
// inbox. A connection, unlink, logout, or ctx end stops retries. The library
// owns retries after a connection opens. Run returns the error of a write of
// the log or of the state file, which stops the daemon, because then messages
// would be lost.
func (w *WhatsApp) Run(ctx context.Context, l *TurnLoop, notify func(Event)) error {
        w.mutex.Lock()

        w.ctx = ctx
        w.notify = notify
        linked := w.linked
        w.retrying = linked
        w.mutex.Unlock()

        timer := time.NewTimer(whatsappRetryDelay)
        timer.Stop()
        defer timer.Stop()

        var retry <-chan time.Time

        delay := whatsappRetryDelay
        connect := func() {
                retry = nil
                if w.connect(ctx) {
                        timer.Reset(delay)

                        retry = timer.C
                        delay = min(2*delay, whatsappRetryLimit)
                }
        }

        stopRetry := func() {
                timer.Stop()

                retry = nil

                w.mutex.Lock()

                w.retrying = false
                w.mutex.Unlock()
        }

        var pairing sync.WaitGroup

        cancel := func() {}
        defer func() {
                cancel()
                pairing.Wait()
                w.close()
        }()

        if linked {
                connect()
        }

        for {
                err := w.inbox.deliver(ctx, l, w.link(), false)
                if err != nil {
                        return err
                }

                select {
                case <-ctx.Done():
                        return nil
                case err = <-w.inbox.failures:
                        return err
                case <-w.inbox.wake:
                case <-w.inbox.due():
                case <-retry:
                        connect()
                case <-w.logouts:
                        stopRetry()

                        err = w.loggedOut(ctx, l)
                        if err != nil {
                                return err
                        }
                case request := <-w.requests:
                        cancel()
                        pairing.Wait()

                        cancel = func() {}

                        switch {
                        case request.unlink:
                                stopRetry()

                                err = w.unlink(ctx, l, request.answer)
                                if err != nil {
                                        return err
                                }
                        case w.isLinked():
                                request.answer("WhatsApp is linked already. Run /whatsapp unlink first.")
                        default:
                                pairCtx, cancelPair := context.WithTimeout(ctx, whatsappPairTimeout)
                                cancel = cancelPair
                                pairing.Go(func() {
                                        defer cancelPair()

                                        w.pair(pairCtx, ctx, l, request.phone, request.answer)
                                })
                        }
                }
        }
}

// Command runs the WhatsApp command args, the text after /whatsapp, and gives
// each answer to answer. The answers go only to the client that sent the
// command.
func (w *WhatsApp) Command(args string, answer func(text string)) {
        fields := strings.Fields(args)
        request := WhatsAppRequest{
                answer: answer,
        }

        switch {
        case len(fields) == 1 && fields[0] == "status":
                answer(w.Status())

                return
        case len(fields) == 1 && fields[0] == "unlink":
                request.unlink = true
        case len(fields) >= 2 && fields[0] == "pair":
                phone, valid := whatsappPhone(strings.Join(fields[1:], ""))
                if !valid {
                        answer("PHONE must be the number of your WhatsApp account with its country code: 7 to 15 digits, such as +15550001111.")

                        return
                }

                request.phone = phone
        default:
                answer(whatsappUsage)

                return
        }

        select {
        case w.requests <- request:
        default:
                answer("Too many WhatsApp commands wait. Try again in a minute.")
        }
}

// Status returns the state of the link: not linked, linked and connected, or
// linked and disconnected, with the times of the connection and the routes.
// Route source IDs can hold the phone numbers of other chats.
func (w *WhatsApp) Status() string {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        routes := ""
        if w.routes != nil {
                listed := w.routes.List()
                if listed != "No routes." {
                        routes = "\nWhatsApp routes:\n" + listed
                }
        }

        switch {
        case !w.linked:
                return "WhatsApp is not linked. Run /whatsapp pair PHONE to link it." + routes
        case w.connected:
                return "WhatsApp is linked and connected since " + w.connectedAt.Format(whatsappTimeLayout) + "." + routes
        case w.disconnectedAt.IsZero():
                return "WhatsApp is linked and not connected yet." + routes
        case w.connectedAt.IsZero():
                return "WhatsApp is linked and disconnected since " + w.disconnectedAt.Format(whatsappTimeLayout) + "." + routes
        default:
                return "WhatsApp is linked and disconnected since " + w.disconnectedAt.Format(whatsappTimeLayout) + ". The last connection started at " + w.connectedAt.Format(whatsappTimeLayout) + "." + routes
        }
}

// BackupSession writes a consistent SQLite snapshot to path while the session
// cannot be created, closed, or removed. The source opens without creation
// permission. No session file means no linked state to copy.
func (w *WhatsApp) BackupSession(ctx context.Context, path string) (err error) {
        w.sessionMutex.Lock()
        defer w.sessionMutex.Unlock()

        w.mutex.Lock()
        defer w.mutex.Unlock()

        _, err = os.Stat(w.sessionPath())
        if errors.Is(err, os.ErrNotExist) {
                return nil
        }

        if err != nil {
                return fmt.Errorf("read session file: %w", err)
        }

        err = os.MkdirAll(filepath.Dir(path), 0o700)
        if err != nil {
                return fmt.Errorf("create session snapshot directory: %w", err)
        }

        address, err := whatsappSessionAddress(w.sessionPath())
        if err != nil {
                return fmt.Errorf("find session database: %w", err)
        }

        database, err := sql.Open("sqlite", address+"&mode=rw")
        if err != nil {
                return fmt.Errorf("open session snapshot source: %w", err)
        }

        defer func() {
                err = errors.Join(err, database.Close())
        }()

        _, err = database.ExecContext(ctx, "VACUUM INTO ?", path)
        if err != nil {
                return fmt.Errorf("snapshot session database: %w", err)
        }

        err = os.Chmod(path, 0o600)
        if err != nil {
                return fmt.Errorf("set session snapshot mode: %w", err)
        }

        return nil
}

// Close closes the session database.
func (w *WhatsApp) Close() error {
        w.sessionMutex.Lock()
        defer w.sessionMutex.Unlock()

        w.mutex.Lock()
        defer w.mutex.Unlock()

        if w.container == nil {
                return nil
        }

        err := w.container.Close()
        w.container = nil

        return err
}

// Find returns the answer of whatsapp_find for name, as whatsappFind says.
func (w *WhatsApp) Find(ctx context.Context, name string) (string, error) {
        return whatsappFind(ctx, w.link(), w.groups, name)
}

// Send returns the answer of whatsapp_send for text and an optional stored
// image to chat, with the durable send id that whatsappSend describes.
func (w *WhatsApp) Send(ctx context.Context, id, chat, text, image string) (string, error) {
        return whatsappSend(ctx, w.link(), w.groups, w.state, w.inbox.images, w.logger, w.clock, id, chat, text, image)
}

func (w *WhatsApp) sessionPath() string {
        return filepath.Join(w.dir, whatsappSessionFileName)
}

// openSession opens the session database and its first device. The caller holds
// the mutex, or no other goroutine uses w yet.
func (w *WhatsApp) openSession(ctx context.Context) error {
        address, err := whatsappSessionAddress(w.sessionPath())
        if err != nil {
                return err
        }

        container, err := sqlstore.New(ctx, "sqlite", address, waLog.Noop)
        if err != nil {
                return fmt.Errorf("open WhatsApp session: %w", err)
        }

        device, err := container.GetFirstDevice(ctx)
        if err != nil {
                return errors.Join(fmt.Errorf("read WhatsApp device: %w", err), container.Close())
        }

        w.container = container
        w.device = device

        return nil
}

func (w *WhatsApp) isLinked() bool {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        return w.linked
}

// link returns a copy of the link of the device: whether it is linked, the
// device, the client, whether it is connected, and the own IDs.
func (w *WhatsApp) link() WhatsAppLink {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        return WhatsAppLink{
                linked:    w.linked,
                device:    w.device,
                client:    w.client,
                connected: w.connected,
                own:       slices.Clone(w.own),
        }
}

// connect tries the starting connection of the linked device with one client.
// It returns whether Run must retry. A failed call starts the shared outage
// state and logs its redacted cause once, because a returned ConnectContext
// error does not emit Disconnected. Connected logs recovery after
// authentication.
func (w *WhatsApp) connect(ctx context.Context) bool {
        w.mutex.Lock()

        if ctx.Err() != nil || !w.linked || !w.retrying || w.closed {
                w.mutex.Unlock()

                return false
        }

        if w.client == nil {
                w.client = w.newClient(w.device, w.handle)
        }

        client := w.client
        w.mutex.Unlock()

        err := client.ConnectContext(ctx)

        w.mutex.Lock()

        if err == nil || ctx.Err() != nil || !w.retrying || !w.linked {
                w.retrying = false
                w.mutex.Unlock()

                return false
        }

        first := w.startOutage()
        cause := whatsappRedact(w.own, err.Error())
        w.mutex.Unlock()

        if first {
                w.logger.Warn("first connect failed, retrying", "err", cause)
        }

        return true
}

// startOutage starts the shared outage time and notice timer once. The caller
// holds the mutex. Its result tells whether this is the first failure.
func (w *WhatsApp) startOutage() bool {
        first := w.linked && (w.connected || w.disconnectedAt.IsZero())
        if first {
                w.disconnectedAt = w.clock()
                w.disconnections++
                disconnections := w.disconnections
                w.timer = time.AfterFunc(whatsappOutageNoticeDelay, func() {
                        w.disconnectedLong(disconnections)
                })
        }

        w.connected = false

        return first
}

// close ends the connection and the timer of the notice, and stops all notices.
func (w *WhatsApp) close() {
        w.mutex.Lock()

        w.closed = true
        if w.timer != nil {
                w.timer.Stop()
        }

        client := w.client
        w.client = nil
        w.mutex.Unlock()

        w.inbox.close()

        if client != nil {
                client.Disconnect()
        }
}

// loggedOut logs the open batches, deletes the session after a logout from the
// phone, notes it in the log of l, and tells all clients one time.
func (w *WhatsApp) loggedOut(ctx context.Context, l *TurnLoop) error {
        if !w.isLinked() {
                return nil
        }

        w.logger.Error("logged out by the phone, run /whatsapp pair PHONE")

        err := w.inbox.deliver(ctx, l, w.link(), true)
        if err != nil {
                return err
        }

        err = w.removeSession()
        if err != nil {
                w.logger.Error("session delete failed", "err", err)
        }

        err = l.note("WhatsApp was unlinked from the phone.")
        if err != nil {
                w.logger.Error("chat note failed", "err", err)
        }

        w.broadcast("WhatsApp was unlinked from the phone. Run /whatsapp pair PHONE to link it again.")

        return nil
}

// unlink logs the open batches, logs out the linked device, and deletes the
// session. When the logout call fails, as it does while WhatsApp is
// disconnected, the session is deleted all the same, and answer tells the user
// to remove the device in the phone. Its error is one of the log or the state
// file.
func (w *WhatsApp) unlink(ctx context.Context, l *TurnLoop, answer func(text string)) error {
        w.mutex.Lock()

        linked := w.linked
        client := w.client
        w.mutex.Unlock()

        if !linked {
                answer("WhatsApp is not linked.")

                return nil
        }

        err := w.inbox.deliver(ctx, l, w.link(), true)
        if err != nil {
                return err
        }

        var logoutErr error

        if client != nil {
                ctx, cancel := context.WithTimeout(ctx, whatsappLogoutTimeout)
                defer cancel()

                logoutErr = client.Logout(ctx)
        }

        err = w.removeSession()
        if err != nil {
                answer("The unlink failed: " + w.redact(err.Error()))

                return nil
        }

        w.logger.Info("unlinked")

        err = l.note("WhatsApp is unlinked.")
        if err != nil {
                w.logger.Error("chat note failed", "err", err)
        }

        if client == nil || logoutErr != nil {
                answer("WhatsApp is unlinked here, but the phone did not get the logout. In WhatsApp on your phone, open Linked devices and remove the device.")

                return nil
        }

        answer("WhatsApp is unlinked.")

        return nil
}

// removeSession ends the connection, closes the session database, and deletes
// its files. The session lock covers the cleanup after mutex is released, so a
// snapshot or a new session cannot open files that cleanup removes.
func (w *WhatsApp) removeSession() error {
        w.sessionMutex.Lock()
        defer w.sessionMutex.Unlock()

        w.mutex.Lock()

        client := w.client
        w.client = nil
        w.linked = false
        w.retrying = false
        w.own = nil
        w.connected = false
        w.disconnectedAt = time.Time{}
        if w.timer != nil {
                w.timer.Stop()
        }

        w.noticed = false
        container := w.container
        w.container = nil
        w.device = nil
        w.mutex.Unlock()

        w.inbox.stopCatchup()

        if client != nil {
                client.Disconnect()
        }

        var err error

        if container != nil {
                err = container.Close()
        }

        for _, suffix := range []string{"", "-wal", "-shm"} {
                removeErr := os.Remove(w.sessionPath() + suffix)
                if !errors.Is(removeErr, os.ErrNotExist) {
                        err = errors.Join(err, removeErr)
                }
        }

        return err
}

// pair links a new device to the account of phone with a pairing code. It gives
// the steps and the code to answer, and then the end of the pairing: the linked
// number, an expired code, or a failure. A pairing that a new one ends gives no
// answer. A link notes "WhatsApp is linked." in the log of l, with no number.
// The client of a pairing that does not link is disconnected.
//
// ctx limits the pairing, but the connection uses runCtx, the context of Run.
// The library keeps the context of the connection for its keep-alive, its event
// handler, and its reconnections, and after the link the server ends the stream
// and the library connects again. With ctx, the end of the pairing would stop
// that reconnection, and the linked device would never connect.
func (w *WhatsApp) pair(ctx, runCtx context.Context, l *TurnLoop, phone string, answer func(text string)) {
        device, err := w.newDevice(ctx)
        if err != nil {
                answer("The pairing failed: " + err.Error())

                return
        }

        client := w.newClient(device, w.handle)
        linked := false
        defer func() {
                if !linked {
                        client.Disconnect()
                }
        }()

        qr, err := client.GetQRChannel(ctx)
        if err == nil {
                err = client.ConnectContext(runCtx)
        }

        if err != nil {
                answer("The connection to WhatsApp failed: " + err.Error())

                return
        }

        select {
        case item, open := <-qr:
                if !open || item.Event != whatsmeow.QRChannelEventCode {
                        answer("WhatsApp did not start the pairing. Try again later.")

                        return
                }
        case <-ctx.Done():
                if errors.Is(ctx.Err(), context.DeadlineExceeded) {
                        answer("The connection to WhatsApp did not start the pairing in time. Try again later.")
                }

                return
        }

        // The server accepts only a display name of the form "Browser (OS)"
        // with a common browser and OS, and refuses the pairing otherwise.
        code, err := client.PairPhone(ctx, phone, true, whatsmeow.PairClientChrome, "Chrome (Linux)")
        if err != nil {
                answer("WhatsApp refused the pairing: " + err.Error() + ". Check the phone number and run /whatsapp pair PHONE again.")

                return
        }

        answer(whatsappPairSteps)
        answer(code)

        for {
                var item whatsmeow.QRChannelItem

                open := true
                select {
                case item, open = <-qr:
                case <-ctx.Done():
                        if errors.Is(ctx.Err(), context.DeadlineExceeded) {
                                answer(whatsappPairExpired)
                        }

                        return
                }

                switch {
                case !open || item.Event == whatsmeow.QRChannelTimeout.Event:
                        answer(whatsappPairExpired)

                        return
                case item.Event == whatsmeow.QRChannelEventCode:
                        continue
                case item.Event == whatsmeow.QRChannelSuccess.Event:
                        linked = true

                        w.linkedBy(client)
                        w.logger.Info("linked")

                        err = l.note("WhatsApp is linked.")
                        if err != nil {
                                w.logger.Error("chat note failed", "err", err)
                        }

                        answer("WhatsApp is linked to +" + phone + ".")

                        return
                default:
                        answer("The pairing failed: " + whatsappItemError(item) + ". Run /whatsapp pair PHONE again.")

                        return
                }
        }
}

// newDevice returns a new device in the session database. It makes the
// directory and the file of the session first, with their modes, when they do
// not exist.
func (w *WhatsApp) newDevice(ctx context.Context) (*store.Device, error) {
        w.sessionMutex.Lock()
        defer w.sessionMutex.Unlock()

        w.mutex.Lock()
        defer w.mutex.Unlock()

        if w.container == nil {
                err := os.MkdirAll(w.dir, 0o700)
                if err != nil {
                        return nil, fmt.Errorf("create WhatsApp directory: %w", err)
                }

                file, err := os.OpenFile(w.sessionPath(), os.O_CREATE|os.O_RDWR, 0o600)
                if err != nil {
                        return nil, fmt.Errorf("create WhatsApp session: %w", err)
                }

                err = file.Close()
                if err != nil {
                        return nil, fmt.Errorf("create WhatsApp session: %w", err)
                }

                err = w.openSession(ctx)
                if err != nil {
                        return nil, err
                }
        }

        w.device = w.container.NewDevice()

        return w.device, nil
}

// linkedBy makes client the client of the linked device.
func (w *WhatsApp) linkedBy(client WhatsAppClient) {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        w.client = client
        w.linked = true
}

// handle takes one event of the library and tells if it was handled. A message
// goes to the inbox. The names of the groups follow the events of the groups. A
// connection starts a catch-up of the inbox, which ends at OfflineSyncCompleted
// or after whatsappCatchupTimeout. A disconnection keeps the time of its start
// while Run or the library tries again. After whatsappOutageNoticeDelay of a
// disconnection, all clients get one notice, and they get one more when the
// connection comes back. A disconnection that the library does not try again
// gives a notice at once.
//
// The log of the daemon gets one line for each change of the connection of the
// linked device: connected, a failed first connection, a lost connection, and
// connected again with the length of the outage. The retries of the library and
// Run between them log nothing.
func (w *WhatsApp) handle(event any) bool {
        w.mutex.Lock()

        ctx := w.ctx
        w.mutex.Unlock()

        switch event := event.(type) {
        case *events.Message:
                return w.inbox.receive(ctx, w.link(), event)
        case *events.GroupInfo:
                if event.Name != nil {
                        w.groups.set(event.JID.String(), event.Name.Name)
                }

                return true
        case *events.JoinedGroup:
                w.groups.set(event.JID.String(), event.Name)

                return true
        case *events.OfflineSyncCompleted:
                w.inbox.endCatchup()

                return true
        case *events.Connected:
                w.inbox.startCatchup()
        }

        var notice, line string

        level := slog.LevelInfo

        var attrs []any

        w.mutex.Lock()

        switch event := event.(type) {
        case *events.PairSuccess:
                w.own = whatsappOwnIDs(event.ID.User, event.LID.User)
        case *events.Connected:
                switch {
                case !w.linked || w.connected:
                case w.disconnectedAt.IsZero():
                        line = "connected"
                default:
                        line = "connected again"
                        attrs = append(attrs, "after", w.clock().Sub(w.disconnectedAt))
                }

                w.connected = true
                w.retrying = false
                w.connectedAt = w.clock()
                if w.timer != nil {
                        w.timer.Stop()
                }

                if w.noticed {
                        w.noticed = false
                        notice = "WhatsApp is connected again."
                }
        case *events.Disconnected:
                connected := w.connected
                if w.startOutage() {
                        level = slog.LevelWarn
                        line = "disconnected, retrying"
                        if !connected {
                                line = "first connect failed, retrying"
                        }
                }
        case *events.LoggedOut:
                w.retrying = false
                select {
                case w.logouts <- struct{}{}:
                default:
                }
        case events.PermanentDisconnect:
                w.retrying = false
                if w.linked {
                        w.connected = false
                        w.noticed = true
                        notice = "WhatsApp is disconnected and does not connect again by itself: " + event.PermanentDisconnectDescription() + ". Restart the daemon to try again."
                        level = slog.LevelError
                        line = "disconnected for good, restart to retry"
                        attrs = append(attrs, "err", whatsappRedact(w.own, event.PermanentDisconnectDescription()))
                }
        }

        if w.closed {
                line = ""
        }

        w.mutex.Unlock()

        if line != "" {
                w.logger.Log(ctx, level, line, attrs...)
        }

        if notice != "" {
                w.broadcast(notice)
        }

        return true
}

// disconnectedLong gives the notice of a long disconnection, unless the
// disconnection with the number disconnections ended.
func (w *WhatsApp) disconnectedLong(disconnections int) {
        w.mutex.Lock()

        long := !w.closed && w.linked && !w.connected && !w.noticed && w.disconnections == disconnections
        if long {
                w.noticed = true
        }

        since := w.disconnectedAt
        w.mutex.Unlock()

        if long {
                w.broadcast("WhatsApp is disconnected since " + since.Format(whatsappTimeLayout) + ". OneChat tries again.")
        }
}

// broadcast gives text as a notice to all clients.
func (w *WhatsApp) broadcast(text string) {
        w.mutex.Lock()

        notify := w.notify
        closed := w.closed
        w.mutex.Unlock()

        if notify != nil && !closed {
                notify(Event{
                        Kind: "notice",
                        Text: text,
                })
        }
}

// redact replaces the own number and the own LID in text with OWN.
func (w *WhatsApp) redact(text string) string {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        return whatsappRedact(w.own, text)
}

// WhatsAppLink is a copy of the link of the device at one time, for the parts
// of WhatsApp that do not own it: the groups, the batches, find, and send.
type WhatsAppLink struct {
        linked    bool
        device    *store.Device
        client    WhatsAppClient
        connected bool
        own       []string
}

// WhatsAppRequest is a pair or unlink command for Run, with the function that
// gives its answers to the client that asked. A pairing has the phone number.
type WhatsAppRequest struct {
        phone  string
        unlink bool
        answer func(text string)
}

// whatsappSetDeviceProps sets the device properties that the library sends at
// the pairing. They are global values of the library, so the daemon sets them
// once before any client exists. The phone shows the linked device with the
// name OneChat and a desktop icon only when the platform type is known.
func whatsappSetDeviceProps() {
        store.SetOSInfo("OneChat", [3]uint32{0, 1, 0})

        store.DeviceProps.PlatformType = waCompanionReg.DeviceProps_DESKTOP.Enum()
}

// whatsappNewClient returns the client of the library for device, with handle
// as its event handler. Run owns failed starting connections of linked devices,
// so only an unlinked device enables the initial retry of the library for
// pairing. The library still retries a lost connection. The client acknowledges
// a message only after handle returns true, and downloads no old history.
func whatsappNewClient(device *store.Device, handle func(event any) bool) WhatsAppClient {
        client := whatsmeow.NewClient(device, waLog.Noop)
        client.InitialAutoReconnect = device.ID == nil
        client.SynchronousAck = true
        client.ManualHistorySyncDownload = true
        client.AddEventHandlerWithSuccessStatus(handle)

        return client
}

// whatsappContactName returns the name of the person jid: the full name, the
// first name, the business name, or the push name of the contact in the session
// of device, then push, the push name of a message, then the phone number. A
// LID gets its phone number from the LID map of the session.
func whatsappContactName(ctx context.Context, device *store.Device, jid types.JID, push string) string {
        jid = jid.ToNonAD()
        candidates := []types.JID{jid}
        phone := types.EmptyJID
        switch jid.Server {
        case types.DefaultUserServer:
                phone = jid
        case types.HiddenUserServer:
                mapped, err := device.LIDs.GetPNForLID(ctx, jid)
                if err == nil && !mapped.IsEmpty() {
                        phone = mapped
                        candidates = append(candidates, mapped)
                }
        }

        for _, candidate := range candidates {
                contact, err := device.Contacts.GetContact(ctx, candidate)
                if err != nil || !contact.Found {
                        continue
                }

                for _, name := range []string{contact.FullName, contact.FirstName, contact.BusinessName, contact.PushName} {
                        if name != "" {
                                return name
                        }
                }
        }

        switch {
        case push != "":
                return push
        case !phone.IsEmpty():
                return "+" + phone.User
        default:
                return jid.User
        }
}

// whatsappOwnIDs returns the own number and the own LID that are not empty.
func whatsappOwnIDs(ids ...string) []string {
        var own []string

        for _, id := range ids {
                if id != "" {
                        own = append(own, id)
                }
        }

        return own
}

// whatsappChatHash returns a short hash of chat for the daemon log, so that a
// log line can tell chats apart without a phone number.
func whatsappChatHash(chat types.JID) string {
        digest := sha256.Sum256([]byte(chat.ToNonAD().String()))

        return fmt.Sprintf("%x", digest[:6])
}

// whatsappRedact replaces each of the own IDs own in text with OWN.
func whatsappRedact(own []string, text string) string {
        for _, id := range own {
                text = strings.ReplaceAll(text, id, "OWN")
        }

        return text
}

// whatsappSessionAddress returns the SQLite address of the session database at
// path, with foreign keys on, as the library needs, and a wait for a busy
// database.
func whatsappSessionAddress(path string) (string, error) {
        path, err := filepath.Abs(path)
        if err != nil {
                return "", fmt.Errorf("find WhatsApp session: %w", err)
        }

        address := url.URL{
                Scheme:   "file",
                Path:     path,
                RawQuery: "_pragma=foreign_keys(1)&_pragma=busy_timeout(5000)",
        }

        return address.String(), nil
}

// whatsappCommandArgs returns the text after /whatsapp of a line of a WhatsApp
// command, or false for any other line.
func whatsappCommandArgs(line string) (string, bool) {
        line = strings.TrimSpace(line)
        if line == whatsappCommand {
                return "", true
        }

        args, found := strings.CutPrefix(line, whatsappCommand+" ")
        if !found {
                return "", false
        }

        return strings.TrimSpace(args), true
}

// whatsappPhone returns the digits of phone, a number with its country code and
// an optional + and dashes, and tells if it has the form of a number: 7 to 15
// digits, with no 0 first.
func whatsappPhone(phone string) (string, bool) {
        phone = strings.ReplaceAll(strings.TrimPrefix(phone, "+"), "-", "")
        valid := len(phone) >= 7 && len(phone) <= 15 && phone[0] != '0' && strings.Trim(phone, "0123456789") == ""

        return phone, valid
}

// whatsappItemError returns the error of a pairing item that is not a code, a
// success, or a timeout.
func whatsappItemError(item whatsmeow.QRChannelItem) string {
        if item.Error != nil {
                return item.Error.Error()
        }

        return item.Event
}