Convert WhatsApp events with pure functions

[onechat] / whatsapp.go

package main

import (
        "cmp"
        "context"
        "crypto/sha256"
        "encoding/hex"
        "errors"
        "fmt"
        "log"
        "maps"
        "net/url"
        "os"
        "path/filepath"
        "slices"
        "strings"
        "sync"
        "time"
        "unicode"

        "go.mau.fi/whatsmeow"
        "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"
        "golang.org/x/text/runes"
        "golang.org/x/text/transform"
        "golang.org/x/text/unicode/norm"

        // 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"

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

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

        // whatsappNoticeDelay is how long a disconnection lasts before the user
        // gets a notice.
        whatsappNoticeDelay = 10 * time.Minute

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

        // whatsappSource is the source of the work events of the batches.
        whatsappSource = "whatsapp"

        // whatsappLookupTime is the longest time of a read of the names in the
        // session database or of the groups from WhatsApp.
        whatsappLookupTime = 10 * time.Second

        // whatsappGroupsRefresh is the shortest time between two reads of the
        // groups from WhatsApp for a group with no name.
        whatsappGroupsRefresh = time.Minute

        // whatsappUnknownGroup is the name of a group whose name is not known.
        whatsappUnknownGroup = "A group with no known name"

        // whatsappCatchupLimit is the longest wait for the end of the catch-up
        // after a connection.
        whatsappCatchupLimit = time.Minute

        // whatsappGroupsAge is how long whatsapp_find uses the groups that it
        // read from WhatsApp.
        whatsappGroupsAge = time.Hour

        // whatsappFindMatches is the most matches of whatsapp_find.
        whatsappFindMatches = 20

        // 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."

        // whatsappSendTime is the longest time of a send.
        whatsappSendTime = 30 * time.Second

        // whatsappSendBytes is the most bytes of the text of a send.
        whatsappSendBytes = 65536

        // whatsappSendIDBytes is the most bytes of the ID of a send.
        whatsappSendIDBytes = 100

        // The states of a send record.
        whatsappSending = "sending"
        whatsappSent    = "sent"
        whatsappFailed  = "failed"

        // whatsappNamesNotReady is the answer of whatsapp_find before the names
        // arrive from the phone.
        whatsappNamesNotReady = "The names of the contacts and groups have not arrived from the phone yet. They come some minutes after the link. Try again later."
)

// 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)
        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 *log.Logger, newClient func(device *store.Device, handle func(event any) bool) WhatsAppClient) (*WhatsApp, error) {
        w := &WhatsApp{
                dir:          filepath.Join(dir, whatsappDirName),
                clock:        clock,
                logger:       logger,
                newClient:    newClient,
                noticeDelay:  whatsappNoticeDelay,
                catchupLimit: whatsappCatchupLimit,
                requests:     make(chan WhatsAppRequest, whatsappRequests),
                logouts:      make(chan struct{}, 1),
                wake:         make(chan struct{}, 1),
                failures:     make(chan error, 1),
                groupNames:   make(map[string]string),
        }

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

        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.catchingUp = true
                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 text messages go into batches, one chat at a time, as WhatsAppState says.
// Run logs each closed batch as a work message that starts with [WhatsApp], and
// a batch that needs the user wakes the turn loop.
//
// After each connection, the servers send the messages that came while the
// daemon was away, and then OfflineSyncCompleted. Until then, or until
// catchupLimit passes, the closed batches wait in the state file. At the end of
// the catch-up, Run closes all batches, logs them, and wakes the turn loop
// once, so the whole catch-up gives one turn and not one turn for each chat.
// The batches of the state file at the start wait for the first catch-up in the
// same way. The event handler acknowledges a message only after the state file
// holds it, so the servers send again a message that a crash lost. A batch
// leaves the state file only after its work message is durable in the log. A
// crash between the two makes the batch repeat once.
//
// 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 {
        dir          string
        clock        func() time.Time
        logger       *log.Logger
        newClient    func(device *store.Device, handle func(event any) bool) WhatsAppClient
        noticeDelay  time.Duration
        catchupLimit time.Duration
        requests     chan WhatsAppRequest
        logouts      chan struct{}
        wake         chan struct{}
        failures     chan error
        state        *WhatsAppState

        mutex          sync.Mutex
        container      *sqlstore.Container
        device         *store.Device
        client         WhatsAppClient
        linked         bool
        own            []string
        notify         func(Event)
        connected      bool
        connectedAt    time.Time
        disconnectedAt time.Time
        disconnections int
        noticed        bool
        timer          *time.Timer
        closed         bool
        groupNames     map[string]string
        groupsAt       time.Time
        groupsRead     time.Time
        catchingUp     bool
        caughtUp       bool
        catchups       int
        catchupTimer   *time.Timer
}

// 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 is logged, and the library tries again when the
// failure is one of the network. 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.notify = notify
        linked := w.linked
        w.mutex.Unlock()

        if linked {
                w.connect(ctx)
        }

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

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

                var due <-chan time.Time
                wait, open := w.state.Wait(time.Now())
                if open {
                        due = time.After(wait)
                }

                select {
                case <-ctx.Done():
                        return nil
                case err = <-w.failures:
                        return err
                case <-w.wake:
                case <-due:
                case <-w.logouts:
                        err = w.loggedOut(ctx, l)
                        if err != nil {
                                return err
                        }
                case request := <-w.requests:
                        cancel()
                        pairing.Wait()
                        cancel = func() {}

                        switch {
                        case request.unlink:
                                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, whatsappPairTime)
                                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. It never holds the
// phone number.
func (w *WhatsApp) Status() string {
        w.mutex.Lock()
        defer w.mutex.Unlock()

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

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

        if w.container == nil {
                return nil
        }

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

        return err
}

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
}

// connect makes the client of the linked device and connects it.
func (w *WhatsApp) connect(ctx context.Context) {
        w.mutex.Lock()
        w.client = w.newClient(w.device, w.handle)
        client := w.client
        w.mutex.Unlock()

        err := client.ConnectContext(ctx)
        if err != nil {
                w.logger.Printf("connect: %s", w.redact(err.Error()))
        }
}

// 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()
        }

        if w.catchupTimer != nil {
                w.catchupTimer.Stop()
        }

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

        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
        }

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

        err = w.removeSession()
        if err != nil {
                w.logger.Printf("delete the session after the logout: %v", err)
        }

        err = l.note("WhatsApp was unlinked from the phone.")
        if err != nil {
                w.logger.Printf("note the logout: %v", 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.deliver(ctx, l, true)
        if err != nil {
                return err
        }

        var logoutErr error
        if client != nil {
                ctx, cancel := context.WithTimeout(ctx, whatsappLogoutTime)
                defer cancel()

                logoutErr = client.Logout(ctx)
        }

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

        err = l.note("WhatsApp is unlinked.")
        if err != nil {
                w.logger.Printf("note the unlink: %v", 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
}

// deliver logs the closed batches in l in order, each as a work message of
// whatsappSource, and wakes the loop once with the batches that start a turn. A
// batch leaves the state file after its message is durable in the log. A group
// with no name gets its name from WhatsApp first. During a catch-up it logs
// nothing, and at its end it closes all batches first. With all, it closes and
// logs all batches also during a catch-up.
func (w *WhatsApp) deliver(ctx context.Context, l *TurnLoop, all bool) error {
        w.mutex.Lock()
        catchingUp := w.catchingUp
        caughtUp := w.caughtUp
        w.caughtUp = false
        w.mutex.Unlock()

        var err error
        switch {
        case all || caughtUp:
                err = w.state.CloseAll()
        case catchingUp:
                return nil
        default:
                _, err = w.state.CloseDue(time.Now())
        }

        if err != nil {
                return err
        }

        var turns []Message
        for _, batch := range w.state.Closed() {
                if batch.Chat.Group && batch.Chat.Name == "" {
                        batch.Chat.Name = w.groupName(ctx, batch.Chat.ID)
                }

                message, err := l.Work(whatsappSource, batch.Text(w.clock().Location()), "")
                if err != nil {
                        return fmt.Errorf("log a WhatsApp batch: %w", err)
                }

                // A stop of the daemon during the flush is no failure: the
                // batch stays in the state file and repeats once at the next
                // start.
                err = l.Flush(ctx)
                if ctx.Err() != nil {
                        return nil
                }

                if err != nil {
                        return fmt.Errorf("log a WhatsApp batch: %w", err)
                }

                err = w.state.Remove(batch.Number)
                if err != nil {
                        return err
                }

                if batch.Turn() {
                        turns = append(turns, message)
                }
        }

        l.Wake(turns...)

        return nil
}

// groupName returns the name of the group id, or whatsappUnknownGroup. A group
// that is not in the names of the groups reads the groups from WhatsApp again,
// at most once in whatsappGroupsRefresh.
func (w *WhatsApp) groupName(ctx context.Context, id string) string {
        w.mutex.Lock()
        name, found := w.groupNames[id]
        fresh := time.Since(w.groupsAt) < whatsappGroupsRefresh
        w.mutex.Unlock()

        if !found && !fresh {
                w.readGroups(ctx)

                w.mutex.Lock()
                name, found = w.groupNames[id]
                w.mutex.Unlock()
        }

        if !found || name == "" {
                return whatsappUnknownGroup
        }

        return name
}

// readGroups reads the names of the groups of the account from WhatsApp, and
// tells if it could. They stay in memory only.
func (w *WhatsApp) readGroups(ctx context.Context) bool {
        w.mutex.Lock()
        client := w.client
        w.mutex.Unlock()

        if client == nil {
                return false
        }

        ctx, cancel := context.WithTimeout(ctx, whatsappLookupTime)
        defer cancel()

        groups, err := client.GetJoinedGroups(ctx)
        if err != nil {
                w.logger.Printf("read the groups: %s", w.redact(err.Error()))
        }

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

        w.groupsAt = time.Now()
        if err != nil {
                return false
        }

        w.groupsRead = w.groupsAt
        for _, group := range groups {
                w.groupNames[group.JID.String()] = group.Name
        }

        return true
}

// Find returns the contacts and the groups whose name contains name, with no
// regard to case and accents, as lines "ID | name | contact" or "ID | name |
// group", sorted by name. It gives at most whatsappFindMatches lines and the
// number of the others. The contacts come from the session database, and the
// groups from WhatsApp, read again after whatsappGroupsAge. When the groups
// cannot be read and none are known, the answer says so. Before the names
// arrive from the phone, it says that they are not ready.
func (w *WhatsApp) Find(ctx context.Context, name string) (string, error) {
        w.mutex.Lock()
        linked := w.linked
        device := w.device
        own := slices.Clone(w.own)
        stale := time.Since(w.groupsRead) >= whatsappGroupsAge
        w.mutex.Unlock()

        if !linked {
                return whatsappNotLinked, nil
        }

        query := whatsappFold(name)
        if query == "" {
                return "", errors.New("name is empty: give a part of the name of the contact or the group")
        }

        contacts, err := device.Contacts.GetAllContacts(ctx)
        if err != nil {
                return "", fmt.Errorf("read the contacts: %s", w.redact(err.Error()))
        }

        read := !stale || w.readGroups(ctx)
        w.mutex.Lock()
        groups := maps.Clone(w.groupNames)
        w.mutex.Unlock()

        if len(contacts) == 0 && len(groups) == 0 {
                if !read {
                        return "The names are not known yet, and WhatsApp is disconnected, so the groups cannot be read. Try again later.", nil
                }

                return whatsappNamesNotReady, nil
        }

        var matches []WhatsAppMatch
        for jid, contact := range contacts {
                names := []string{contact.FullName, contact.FirstName, contact.BusinessName, contact.PushName}
                shown := slices.IndexFunc(names, func(name string) bool {
                        return name != ""
                })

                if slices.Contains(own, jid.User) || shown < 0 || !slices.ContainsFunc(names, func(name string) bool {
                        return strings.Contains(whatsappFold(name), query)
                }) {
                        continue
                }

                matches = append(matches, WhatsAppMatch{
                        id:   jid.ToNonAD().String(),
                        name: names[shown],
                        kind: "contact",
                })
        }

        for id, group := range groups {
                if strings.Contains(whatsappFold(group), query) {
                        matches = append(matches, WhatsAppMatch{
                                id:   id,
                                name: group,
                                kind: "group",
                        })
                }
        }

        return whatsappFindAnswer(name, matches, read || len(groups) > 0), nil
}

// removeSession ends the connection, closes the session database, and deletes
// its files.
func (w *WhatsApp) removeSession() error {
        w.mutex.Lock()
        client := w.client
        w.client = nil
        w.linked = false
        w.own = nil
        w.connected = false
        w.catchingUp = false
        if w.timer != nil {
                w.timer.Stop()
        }

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

        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
        }

        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)

                        err = l.note("WhatsApp is linked.")
                        if err != nil {
                                w.logger.Printf("note the link: %v", 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.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 receive. The names of the groups follow the events of the groups. A
// connection starts a catch-up, which ends at OfflineSyncCompleted or after
// catchupLimit. A disconnection keeps the time of its start while the library
// tries again. After noticeDelay 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.
func (w *WhatsApp) handle(event any) bool {
        message, isMessage := event.(*events.Message)
        if isMessage {
                return w.receive(message)
        }

        var notice string
        w.mutex.Lock()
        switch event := event.(type) {
        case *events.GroupInfo:
                if event.Name != nil {
                        w.groupNames[event.JID.String()] = event.Name.Name
                }
        case *events.JoinedGroup:
                w.groupNames[event.JID.String()] = event.Name
        case *events.PairSuccess:
                w.own = whatsappOwnIDs(event.ID.User, event.LID.User)
        case *events.Connected:
                w.connected = true
                w.connectedAt = w.clock()
                w.catchingUp = true
                w.catchups++
                catchups := w.catchups
                if w.catchupTimer != nil {
                        w.catchupTimer.Stop()
                }

                w.catchupTimer = time.AfterFunc(w.catchupLimit, func() {
                        w.caughtUpBy(catchups)
                })
                if w.timer != nil {
                        w.timer.Stop()
                }

                if w.noticed {
                        w.noticed = false
                        notice = "WhatsApp is connected again."
                }
        case *events.Disconnected:
                if w.linked && (w.connected || w.disconnectedAt.IsZero()) {
                        w.disconnectedAt = w.clock()
                        w.disconnections++
                        disconnections := w.disconnections
                        w.timer = time.AfterFunc(w.noticeDelay, func() {
                                w.disconnectedLong(disconnections)
                        })
                }

                w.connected = false
        case *events.OfflineSyncCompleted:
                w.endCatchup()
        case *events.LoggedOut:
                select {
                case w.logouts <- struct{}{}:
                default:
                }
        case events.PermanentDisconnect:
                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."
                }
        }
        w.mutex.Unlock()

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

        return true
}

// receive puts the text of event into its batch and wakes Run. It returns false
// when the state file cannot hold the message, so that the library does not
// acknowledge it, and Run stops the daemon. A message that is not text, or that
// the batches do not take, is handled with nothing to do.
func (w *WhatsApp) receive(event *events.Message) bool {
        ctx, cancel := context.WithTimeout(context.Background(), whatsappLookupTime)
        defer cancel()

        w.mutex.Lock()
        device := w.device
        own := slices.Clone(w.own)
        w.mutex.Unlock()

        chat, message, found := whatsappMessage(ctx, device, own, event)
        if !found {
                return true
        }

        _, err := w.state.Add(chat, message, time.Now())
        if err != nil {
                select {
                case w.failures <- err:
                default:
                }

                return false
        }

        select {
        case w.wake <- struct{}{}:
        default:
        }

        return true
}

// caughtUpBy ends the catch-up of the connection with the number catchups, when
// no later connection started a new one.
func (w *WhatsApp) caughtUpBy(catchups int) {
        w.mutex.Lock()
        defer w.mutex.Unlock()

        if w.catchups == catchups {
                w.endCatchup()
        }
}

// endCatchup ends a running catch-up and wakes Run, which logs all batches. The
// caller holds the mutex.
func (w *WhatsApp) endCatchup() {
        if !w.catchingUp {
                return
        }

        w.catchingUp = false
        w.caughtUp = true
        if w.catchupTimer != nil {
                w.catchupTimer.Stop()
        }

        select {
        case w.wake <- struct{}{}:
        default:
        }
}

// 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)
}

// Send sends text to chat, the ID of a private chat or a group, and returns the
// answer of the tool. id names the send: a call with an id that has a record
// gives the answer of the record and sends nothing, and the same id with
// another chat or text is an error. The record "sending" is durable before the
// send, so a stop of the daemon during the send gives an answer that the result
// is unknown, and not a second send. A disconnected WhatsApp sends nothing and
// makes no record.
func (w *WhatsApp) Send(ctx context.Context, id, chat, text string) (string, error) {
        w.mutex.Lock()
        linked := w.linked
        device := w.device
        client := w.client
        connected := w.connected
        own := slices.Clone(w.own)
        w.mutex.Unlock()

        if !linked {
                return whatsappNotLinked, nil
        }

        jid, err := whatsappSendCheck(id, chat, text, own)
        if err != nil {
                return "", err
        }

        digest := sha256.Sum256([]byte(text))
        record := WhatsAppSend{
                ID:     id,
                Chat:   chat,
                Digest: hex.EncodeToString(digest[:]),
                State:  whatsappSending,
                Time:   w.clock(),
        }

        held, found := w.state.Send(id)
        switch {
        case found && (held.Chat != record.Chat || held.Digest != record.Digest):
                return "", fmt.Errorf("the id %s belongs to another message: give a new id for each message", id)
        case found && held.State == whatsappSending:
                return "The send with this id started, but its result is unknown, because the daemon stopped during it. Ask the user to look at the chat in WhatsApp before you send the message again with a new id.", nil
        case found:
                return held.Answer + " This is the answer of the first call with this id: nothing was sent again.", nil
        case client == nil || !connected:
                return "", errors.New("WhatsApp is disconnected, so nothing was sent: try again later")
        }

        record.MessageID = client.GenerateMessageID()
        err = w.state.PutSend(record)
        if err != nil {
                return "", err
        }

        sendCtx, cancel := context.WithTimeout(ctx, whatsappSendTime)
        defer cancel()

        response, err := client.SendMessage(sendCtx, jid, &waE2E.Message{
                Conversation: new(text),
        }, whatsmeow.SendRequestExtra{
                ID: record.MessageID,
        })

        record.State = whatsappSent
        if err != nil {
                record.State = whatsappFailed
                record.Answer = "The send failed: " + w.redact(err.Error()) + "."
        } else {
                name := w.groupName(ctx, jid.String())
                if jid.Server != types.GroupServer {
                        name = whatsappContactName(ctx, device, jid, "")
                }

                record.Answer = "Sent to " + name + " at " + response.Timestamp.In(w.clock().Location()).Format("15:04") + "."
        }

        err = w.state.PutSend(record)
        if err != nil {
                return "", err
        }

        return record.Answer, nil
}

// WhatsAppMatch is one contact or group of Find.
type WhatsAppMatch struct {
        id   string
        name string
        kind 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)
}

// whatsappNewClient returns the client of the library for device, with handle
// as its event handler. The client tries again after a failed first connection,
// acknowledges a message only after handle returns true, and downloads no old
// history. The phone shows the device with the name OneChat.
func whatsappNewClient(device *store.Device, handle func(event any) bool) WhatsAppClient {
        store.SetOSInfo("OneChat", [3]uint32{0, 1, 0})
        client := whatsmeow.NewClient(device, waLog.Noop)
        client.InitialAutoReconnect = true
        client.SynchronousAck = true
        client.ManualHistorySyncDownload = true
        client.AddEventHandlerWithSuccessStatus(handle)

        return client
}

// whatsappMessage returns the chat and the batch message of event, or false
// when the batches do not take it. device is the linked device, and own holds
// the own IDs. The batches take the text of a private chat or a group, from
// another person or from the user. They do not take media, reactions, edits,
// deletions, view-once and disappearing messages, old history, status
// broadcasts, channels, and the chat of the user with itself.
//
// A mention of the user becomes @you, another mention @NAME when the name is
// known, and the own number and LID become OWN, so that they never go to the
// log.
func whatsappMessage(ctx context.Context, device *store.Device, own []string, event *events.Message) (WhatsAppChat, WhatsAppMessage, bool) {
        info := event.Info
        chatJID := info.Chat.ToNonAD()
        switch {
        case device == nil:
        case event.IsEdit, info.Edit != "", event.IsEphemeral, event.IsViewOnce, event.SourceWebMsg != nil:
        case chatJID.Server != types.DefaultUserServer && chatJID.Server != types.HiddenUserServer && chatJID.Server != types.GroupServer:
        case slices.Contains(own, chatJID.User):
        default:
                return whatsappText(ctx, device, own, event)
        }

        return WhatsAppChat{}, WhatsAppMessage{}, false
}

// whatsappText returns the chat and the batch message of event, a message that
// the batches take when it has text.
func whatsappText(ctx context.Context, device *store.Device, own []string, event *events.Message) (WhatsAppChat, WhatsAppMessage, bool) {
        info := event.Info
        text := event.Message.GetConversation()
        extended := event.Message.GetExtendedTextMessage()
        if text == "" {
                text = extended.GetText()
        }

        if strings.TrimSpace(text) == "" {
                return WhatsAppChat{}, WhatsAppMessage{}, false
        }

        contextInfo := extended.GetContextInfo()
        message := WhatsAppMessage{
                ID:   info.ID,
                Time: info.Timestamp,
                Mine: info.IsFromMe,
        }

        if !message.Mine {
                message.Sender = whatsappContactName(ctx, device, info.Sender, info.PushName)
        }

        for _, mentioned := range contextInfo.GetMentionedJID() {
                jid, err := types.ParseJID(mentioned)
                switch {
                case err != nil:
                case slices.Contains(own, jid.User):
                        message.Mention = true
                        text = strings.ReplaceAll(text, "@"+jid.User, "@you")
                default:
                        text = strings.ReplaceAll(text, "@"+jid.User, "@"+whatsappContactName(ctx, device, jid, ""))
                }
        }

        participant, err := types.ParseJID(contextInfo.GetParticipant())
        message.Reply = err == nil && slices.Contains(own, participant.User)

        message.Text = whatsappRedact(own, text)
        chatJID := info.Chat.ToNonAD()
        chat := WhatsAppChat{
                ID:    chatJID.String(),
                Group: chatJID.Server == types.GroupServer,
        }

        if !chat.Group {
                push := info.PushName
                if message.Mine {
                        push = ""
                }

                chat.Name = whatsappContactName(ctx, device, chatJID, push)
        }

        return chat, message, true
}

// 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
        }
}

// whatsappFold returns text in lower case with no accents and no space at its
// ends, so that names match with no regard to case and accents.
func whatsappFold(text string) string {
        folded, _, err := transform.String(transform.Chain(norm.NFD, runes.Remove(runes.In(unicode.Mn)), norm.NFC), text)
        if err != nil {
                folded = text
        }

        return strings.ToLower(strings.TrimSpace(folded))
}

// whatsappFindAnswer returns the answer of Find for name with matches. Without
// groups, the answer says that it has no groups.
func whatsappFindAnswer(name string, matches []WhatsAppMatch, groups bool) string {
        slices.SortFunc(matches, func(a, b WhatsAppMatch) int {
                return cmp.Or(strings.Compare(whatsappFold(a.name), whatsappFold(b.name)), strings.Compare(a.id, b.id))
        })

        var lines []string
        for _, match := range matches[:min(len(matches), whatsappFindMatches)] {
                lines = append(lines, match.id+" | "+match.name+" | "+match.kind)
        }

        if len(matches) == 0 {
                lines = append(lines, "No contact or group has a name with \""+name+"\".")
        }

        if len(matches) > whatsappFindMatches {
                lines = append(lines, fmt.Sprintf("%d more: give a longer part of the name.", len(matches)-whatsappFindMatches))
        }

        if !groups {
                lines = append(lines, "The groups are not in this answer, because WhatsApp is disconnected.")
        }

        return strings.Join(lines, "\n")
}

// whatsappSendCheck returns the JID of chat, and an error when id, chat, or
// text cannot go to a send. The chat is a private chat or a group, and not the
// chat of the user with itself.
func whatsappSendCheck(id, chat, text string, own []string) (types.JID, error) {
        jid, err := types.ParseJID(chat)
        switch {
        case strings.TrimSpace(id) == "" || len(id) > whatsappSendIDBytes:
                return types.EmptyJID, fmt.Errorf("the id must have 1 to %d bytes", whatsappSendIDBytes)
        case strings.TrimSpace(text) == "" || len(text) > whatsappSendBytes:
                return types.EmptyJID, fmt.Errorf("the text must have 1 to %d bytes", whatsappSendBytes)
        case err != nil || jid.User == "" || jid != jid.ToNonAD() || jid.String() != chat:
                return types.EmptyJID, fmt.Errorf("%q is not the ID of a WhatsApp chat: find the ID with whatsapp_find", chat)
        case jid.Server != types.DefaultUserServer && jid.Server != types.HiddenUserServer && jid.Server != types.GroupServer:
                return types.EmptyJID, fmt.Errorf("%q is not a private chat or a group", chat)
        case slices.Contains(own, jid.User):
                return types.EmptyJID, errors.New("this is the chat of the user with itself: send to another chat")
        }

        return jid, nil
}

// 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
}

// 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
}