Make two WhatsApp tests independent of the load

[onechat] / whatsapp.go

package main

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

        "go.mau.fi/whatsmeow"
        "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."

        // 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)
}

// 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.batches, err = openWhatsAppBatches(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 WhatsAppBatches
// 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
        batches      *WhatsAppBatches

        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.batches.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, 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.batches.CloseAll()
        case catchingUp:
                return nil
        default:
                _, err = w.batches.CloseDue(time.Now())
        }

        if err != nil {
                return err
        }

        var turns []Message
        for _, batch := range w.batches.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.batches.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.
func (w *WhatsApp) pair(ctx 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(ctx)
        }

        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()

        chat, message, found := w.message(ctx, event)
        if !found {
                return true
        }

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

                return false
        }

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

        return true
}

// message returns the chat and the batch message of event, or false when the
// batches do not take it. They 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 (w *WhatsApp) message(ctx context.Context, event *events.Message) (WhatsAppChat, WhatsAppMessage, bool) {
        w.mutex.Lock()
        device := w.device
        own := slices.Clone(w.own)
        w.mutex.Unlock()

        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 w.text(ctx, device, own, event)
        }

        return WhatsAppChat{}, WhatsAppMessage{}, false
}

// text returns the chat and the batch message of event, a message that the
// batches take when it has text.
func (w *WhatsApp) text(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)

        for _, id := range own {
                text = strings.ReplaceAll(text, id, "OWN")
        }

        message.Text = 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
}

// 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()

        for _, id := range w.own {
                text = strings.ReplaceAll(text, id, "OWN")
        }

        return text
}

// 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
}

// 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")
}

// 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
}

// 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
}