Link WhatsApp with a pairing code

[onechat] / whatsapp.go

package main

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

        "go.mau.fi/whatsmeow"
        "go.mau.fi/whatsmeow/store"
        "go.mau.fi/whatsmeow/store/sqlstore"
        "go.mau.fi/whatsmeow/types/events"
        waLog "go.mau.fi/whatsmeow/util/log"

        // The session store of the library opens SQLite with this pure Go
        // driver.
        _ "modernc.org/sqlite"
)

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

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

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

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

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

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

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

        // 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
)

// 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
}

// 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,
                requests:    make(chan WhatsAppRequest, whatsappRequests),
                logouts:     make(chan struct{}, 1),
        }

        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.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 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.
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
        requests    chan WhatsAppRequest
        logouts     chan struct{}

        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
}

// Run connects a linked device, 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.
func (w *WhatsApp) Run(ctx context.Context, l *TurnLoop, notify func(Event)) {
        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 {
                select {
                case <-ctx.Done():
                        return
                case <-w.logouts:
                        w.loggedOut(l)
                case request := <-w.requests:
                        cancel()
                        pairing.Wait()
                        cancel = func() {}

                        switch {
                        case request.unlink:
                                w.unlink(ctx, l, request.answer)
                        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()
        }

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

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

// loggedOut 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(l *TurnLoop) {
        if !w.isLinked() {
                return
        }

        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.")
}

// unlink 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.
func (w *WhatsApp) unlink(ctx context.Context, l *TurnLoop, answer func(text string)) {
        w.mutex.Lock()
        linked := w.linked
        client := w.client
        w.mutex.Unlock()

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

        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
        }

        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
        }

        answer("WhatsApp is unlinked.")
}

// 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
        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
// 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 {
        var notice string
        w.mutex.Lock()
        switch event := event.(type) {
        case *events.PairSuccess:
                w.own = whatsappOwnIDs(event.ID.User, event.LID.User)
        case *events.Connected:
                w.connected = true
                w.connectedAt = w.clock()
                if w.timer != nil {
                        w.timer.Stop()
                }

                if w.noticed {
                        w.noticed = false
                        notice = "WhatsApp is connected again."
                }
        case *events.Disconnected:
                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.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
}

// 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
}

// 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
}

// 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
}