telegabber/telegram/commands.go

package telegram

import (
	"fmt"
	"github.com/pkg/errors"
	"strconv"
	"strings"
	"time"
	"unicode"

	"dev.narayana.im/narayana/telegabber/xmpp/gateway"

	log "github.com/sirupsen/logrus"
	"github.com/zelenin/go-tdlib/client"
)

const notEnoughArguments string = "Not enough arguments"
const telegramNotInitialized string = "Telegram connection is not initialized yet"
const notOnline string = "Not online"

var permissionsAdmin = client.ChatMemberStatusAdministrator{
	CanBeEdited:        true,
	CanChangeInfo:      true,
	CanPostMessages:    true,
	CanEditMessages:    true,
	CanDeleteMessages:  true,
	CanInviteUsers:     true,
	CanRestrictMembers: true,
	CanPinMessages:     true,
	CanPromoteMembers:  false,
}
var permissionsMember = client.ChatPermissions{
	CanSendMessages:       true,
	CanSendMediaMessages:  true,
	CanSendPolls:          true,
	CanSendOtherMessages:  true,
	CanAddWebPagePreviews: true,
	CanChangeInfo:         true,
	CanInviteUsers:        true,
	CanPinMessages:        true,
}
var permissionsReadonly = client.ChatPermissions{}

var transportCommands = map[string]command{
	"login":       command{"phone", "sign in"},
	"logout":      command{"", "sign out"},
	"code":        command{"", "check one-time code"},
	"password":    command{"", "check 2fa password"},
	"setusername": command{"", "update @username"},
	"setname":     command{"first last", "update name"},
	"setbio":      command{"", "update about"},
	"setpassword": command{"[old] [new]", "set or remove password"},
	"config":      command{"[param] [value]", "view or update configuration options"},
}

var chatCommands = map[string]command{
	"d":          command{"[n]", "delete your last message(s)"},
	"s":          command{"edited message", "edit your last message"},
	"silent":     command{"message", "send a message without sound"},
	"schedule":   command{"{online | 2006-01-02T15:04:05 | 15:04:05} message", "schedules a message either to timestamp or to whenever the user goes online"},
	"add":        command{"@username", "add @username to your chat list"},
	"join":       command{"https://t.me/invite_link", "join to chat via invite link"},
	"group":      command{"title", "create groupchat «title» with current user"},
	"supergroup": command{"title description", "create new supergroup «title» with «description»"},
	"channel":    command{"title description", "create new channel «title» with «description»"},
	"secret":     command{"", "create secretchat with current user"},
	"search":     command{"string [limit]", "search <string> in current chat"},
	"history":    command{"[limit]", "get last [limit] messages from current chat"},
	"block":      command{"", "blacklist current user"},
	"unblock":    command{"", "unblacklist current user"},
	"invite":     command{"id or @username", "add user to current chat"},
	"link":       command{"", "get invite link for current chat"},
	"kick":       command{"id or @username", "remove user to current chat"},
	"mute":       command{"id or @username [hours]", "mute user in current chat"},
	"unmute":     command{"id or @username", "unrestrict user from current chat"},
	"ban":        command{"id or @username [hours]", "restrict @username from current chat for [hours] or forever"},
	"unban":      command{"id or @username", "unbans @username in current chat (and devotes from admins)"},
	"promote":    command{"id or @username [title]", "promote user to admin in current chat"},
	"leave":      command{"", "leave current chat"},
	"leave!":     command{"", "leave current chat (for owners)"},
	"ttl":        command{"", "set secret chat messages TTL before self-destroying (in seconds)"},
	"close":      command{"", "close current secret chat"},
	"delete":     command{"", "delete current chat from chat list"},
	"members":    command{"[query]", "search members [by optional query] in current chat (requires admin rights)"},
}

var transportConfigurationOptions = map[string]configurationOption{
	"timezone":    configurationOption{"<timezone>", "adjust timezone for Telegram user statuses (example: +02:00)"},
	"keeponline":  configurationOption{"<bool>", "always keep telegram session online and rely on jabber offline messages (example: true)"},
	"rawmessages": configurationOption{"<bool>", "do not add additional info (message id, origin etc.) to incoming messages (example: true)"},
}

type command struct {
	arguments   string
	description string
}
type configurationOption command

type helpType int

const (
	helpTypeTransport helpType = iota
	helpTypeChat
)

func helpString(ht helpType) string {
	var str strings.Builder
	var commandMap map[string]command

	switch ht {
	case helpTypeTransport:
		commandMap = transportCommands
	case helpTypeChat:
		commandMap = chatCommands
	}

	str.WriteString("Available commands:\n")
	for name, command := range commandMap {
		str.WriteString("/")
		str.WriteString(name)
		if command.arguments != "" {
			str.WriteString(" ")
			str.WriteString(command.arguments)
		}
		str.WriteString(" — ")
		str.WriteString(command.description)
		str.WriteString("\n")
	}

	if ht == helpTypeTransport {
		str.WriteString("Configuration options\n")
		for name, option := range transportConfigurationOptions {
			str.WriteString(name)
			str.WriteString(" ")
			str.WriteString(option.arguments)
			str.WriteString(" — ")
			str.WriteString(option.description)
			str.WriteString("\n")
		}
	}

	return str.String()
}

func parseCommand(cmdline string) (string, []string) {
	bodyFields := strings.Fields(cmdline)
	return bodyFields[0][1:], bodyFields[1:]
}

func rawCmdArguments(cmdline string, start uint8) string {
	var state uint
	//  /cmd   ababa galamaga
	// 01   2  3    45
	startState := uint(3 + 2*start)
	for i, r := range cmdline {
		isOdd := state%2 == 1
		isSpace := unicode.IsSpace(r)
		if (!isOdd && !isSpace) || (isOdd && isSpace) {
			state += 1
		}
		if state == startState {
			return cmdline[i:]
		}
	}
	return ""
}

func (c *Client) unsubscribe(chatID int64) error {
	return gateway.SendPresence(
		c.xmpp,
		c.jid,
		gateway.SPFrom(strconv.FormatInt(chatID, 10)),
		gateway.SPType("unsubscribed"),
	)
}

func (c *Client) sendMessagesReverse(chatID int64, messages []*client.Message) {
	for i := len(messages) - 1; i >= 0; i-- {
		gateway.SendMessage(
			c.jid,
			strconv.FormatInt(chatID, 10),
			c.formatMessage(0, 0, false, messages[i]),
			c.xmpp,
		)
	}
}

func (c *Client) usernameOrIDToID(username string) (int64, error) {
	userID, err := strconv.ParseInt(username, 10, 64)
	// couldn't parse the id, try to lookup as a username
	if err != nil {
		chat, err := c.client.SearchPublicChat(&client.SearchPublicChatRequest{
			Username: username,
		})
		if err != nil {
			return 0, err
		}

		userID = chat.Id
		if userID <= 0 {
			return 0, errors.New("Not a user")
		}
	}

	return userID, nil
}

// ProcessTransportCommand executes a command sent directly to the component
// and returns a response
func (c *Client) ProcessTransportCommand(cmdline string, resource string) string {
	cmd, args := parseCommand(cmdline)
	switch cmd {
	case "login", "code", "password":
		if cmd == "login" && c.Session.Login != "" {
			return ""
		}

		if len(args) < 1 {
			return notEnoughArguments
		}

		if cmd == "login" {
			wasSessionLoginEmpty := c.Session.Login == ""
			c.Session.Login = args[0]

			if wasSessionLoginEmpty && c.authorizer == nil {
				go func() {
					err := c.Connect(resource)
					if err != nil {
						log.Error(errors.Wrap(err, "TDlib connection failure"))
					}
				}()
				// a quirk for authorizer to become ready. If it's still not,
				// nothing bad: the command just needs to be resent again
				time.Sleep(1e5)
			}
		}

		if c.authorizer == nil {
			return telegramNotInitialized
		}

		switch cmd {
		// sign in
		case "login":
			c.authorizer.PhoneNumber <- args[0]
		// check auth code
		case "code":
			c.authorizer.Code <- args[0]
		// check auth password
		case "password":
			c.authorizer.Password <- args[0]
		}
	// sign out
	case "logout":
		if !c.Online() {
			return notOnline
		}

		for _, id := range c.cache.ChatsKeys() {
			c.unsubscribe(id)
		}

		_, err := c.client.LogOut()
		if err != nil {
			c.forceClose()
			return errors.Wrap(err, "Logout error").Error()
		}

		c.Session.Login = ""
	// set @username
	case "setusername":
		if !c.Online() {
			return notOnline
		}

		var username string
		if len(args) > 0 {
			username = args[0]
		}

		_, err := c.client.SetUsername(&client.SetUsernameRequest{
			Username: username,
		})
		if err != nil {
			return errors.Wrap(err, "Couldn't set username").Error()
		}
	// set My Name
	case "setname":
		if !c.Online() {
			return notOnline
		}

		var firstname string
		var lastname string
		if len(args) > 0 {
			firstname = args[0]
		}
		if len(args) > 1 {
			lastname = args[1]
		}

		_, err := c.client.SetName(&client.SetNameRequest{
			FirstName: firstname,
			LastName:  lastname,
		})
		if err != nil {
			return errors.Wrap(err, "Couldn't set name").Error()
		}
	// set About
	case "setbio":
		if !c.Online() {
			return notOnline
		}

		_, err := c.client.SetBio(&client.SetBioRequest{
			Bio: rawCmdArguments(cmdline, 0),
		})
		if err != nil {
			return errors.Wrap(err, "Couldn't set bio").Error()
		}
	// set password
	case "setpassword":
		if !c.Online() {
			return notOnline
		}

		var oldPassword string
		var newPassword string
		// 0 or 1 argument is ignored and the password is reset
		if len(args) > 1 {
			oldPassword = args[0]
			newPassword = args[1]
		}
		_, err := c.client.SetPassword(&client.SetPasswordRequest{
			OldPassword: oldPassword,
			NewPassword: newPassword,
		})
		if err != nil {
			return errors.Wrap(err, "Couldn't set password").Error()
		}
	case "config":
		if len(args) > 1 {
			value, err := c.Session.Set(args[0], args[1])
			if err != nil {
				return err.Error()
			}
			gateway.DirtySessions = true

			return fmt.Sprintf("%s set to %s", args[0], value)
		} else if len(args) > 0 {
			value, err := c.Session.Get(args[0])
			if err != nil {
				return err.Error()
			}

			return fmt.Sprintf("%s is set to %s", args[0], value)
		}

		var entries []string
		for key, value := range c.Session.ToMap() {
			entries = append(entries, fmt.Sprintf("%s is set to %s", key, value))
		}

		return strings.Join(entries, "\n")
	case "help":
		return helpString(helpTypeTransport)
	}

	return ""
}

// ProcessChatCommand executes a command sent in a mapped chat
// and returns a response and the status of command support
func (c *Client) ProcessChatCommand(chatID int64, cmdline string) (string, bool) {
	if !c.Online() {
		return notOnline, true
	}

	cmd, args := parseCommand(cmdline)
	switch cmd {
	// delete message
	case "d":
		if c.me == nil {
			return "@me is not initialized", true
		}

		var limit int32
		if len(args) > 0 {
			limit64, err := strconv.ParseInt(args[0], 10, 32)
			if err != nil {
				return err.Error(), true
			}
			limit = int32(limit64)
		} else {
			limit = 1
		}

		messages, err := c.getLastMessages(chatID, "", c.me.Id, limit)
		if err != nil {
			return err.Error(), true
		}
		log.Debugf("pre-deletion query: %#v %#v", messages, messages.Messages)

		var messageIds []int64
		for _, message := range messages.Messages {
			if message != nil {
				messageIds = append(messageIds, message.Id)
			}
		}

		_, err = c.client.DeleteMessages(&client.DeleteMessagesRequest{
			ChatId:     chatID,
			MessageIds: messageIds,
			Revoke:     true,
		})
		if err != nil {
			return err.Error(), true
		}
	// edit message
	case "s":
		if c.me == nil {
			return "@me is not initialized", true
		}
		if len(args) < 1 {
			return "Not enough arguments", true
		}

		messages, err := c.getLastMessages(chatID, "", c.me.Id, 1)
		if err != nil {
			return err.Error(), true
		}
		if len(messages.Messages) == 0 {
			return "No last message", true
		}

		message := messages.Messages[0]
		if message == nil {
			return "Last message is empty", true
		}

		content := c.ProcessOutgoingMessage(0, rawCmdArguments(cmdline, 0), "")

		if content != nil {
			c.client.EditMessageText(&client.EditMessageTextRequest{
				ChatId:              chatID,
				MessageId:           message.Id,
				InputMessageContent: content,
			})
		} else {
			return "Message processing error", true
		}
	// send without sound
	case "silent":
		if len(args) < 1 {
			return "Not enough arguments", true
		}

		content := c.ProcessOutgoingMessage(0, rawCmdArguments(cmdline, 0), "")

		if content != nil {
			_, err := c.client.SendMessage(&client.SendMessageRequest{
				ChatId:              chatID,
				InputMessageContent: content,
				Options: &client.MessageSendOptions{
					DisableNotification: true,
				},
			})
			if err != nil {
				return err.Error(), true
			}
		} else {
			return "Message processing error", true
		}
	// schedule a message to timestamp or to going online
	case "schedule":
		if len(args) < 2 {
			return "Not enough arguments", true
		}

		var state client.MessageSchedulingState
		var result string
		due := args[0]
		if due == "online" {
			state = &client.MessageSchedulingStateSendWhenOnline{}
			result = due
		} else {
			if c.Session.Timezone == "" {
				due += "Z"
			} else {
				due += c.Session.Timezone
			}

			switch 0 {
			default:
				// try bare time first
				timestamp, err := time.Parse("15:04:05Z07:00", due)
				if err == nil {
					now := time.Now().In(c.Session.TimezoneToLocation())
					// combine timestamp's time with today's date
					timestamp = time.Date(
						now.Year(),
						now.Month(),
						now.Day(),
						timestamp.Hour(),
						timestamp.Minute(),
						timestamp.Second(),
						0,
						timestamp.Location(),
					)
					diff := timestamp.Sub(now)
					if diff < 0 { // set to tomorrow
						timestamp = timestamp.AddDate(0, 0, 1)
					}
					state = &client.MessageSchedulingStateSendAtDate{
						SendDate: int32(timestamp.Unix()),
					}
					result = timestamp.Format(time.RFC3339)

					break
				}

				timestamp, err = time.Parse(time.RFC3339, due)
				if err == nil {
					// 2038 doomsday again
					state = &client.MessageSchedulingStateSendAtDate{
						SendDate: int32(timestamp.Unix()),
					}
					result = timestamp.Format(time.RFC3339)

					break
				}

				return "Invalid schedule time specifier", true
			}
		}

		content := c.ProcessOutgoingMessage(0, rawCmdArguments(cmdline, 1), "")

		if content != nil {
			_, err := c.client.SendMessage(&client.SendMessageRequest{
				ChatId:              chatID,
				InputMessageContent: content,
				Options: &client.MessageSendOptions{
					SchedulingState: state,
				},
			})
			if err != nil {
				return err.Error(), true
			}
			return "Scheduled to " + result, true
		} else {
			return "Message processing error", true
		}
	// add @contact
	case "add":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		chat, err := c.client.SearchPublicChat(&client.SearchPublicChatRequest{
			Username: args[0],
		})
		if err != nil {
			return err.Error(), true
		}
		if chat == nil {
			return "No error, but chat is nil", true
		}

		c.subscribeToID(chat.Id, chat)
	// join https://t.me/publichat
	case "join":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		_, err := c.client.JoinChatByInviteLink(&client.JoinChatByInviteLinkRequest{
			InviteLink: args[0],
		})
		if err != nil {
			return err.Error(), true
		}
	// create new supergroup
	case "supergroup":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		_, err := c.client.CreateNewSupergroupChat(&client.CreateNewSupergroupChatRequest{
			Title:       args[0],
			Description: rawCmdArguments(cmdline, 1),
		})
		if err != nil {
			return err.Error(), true
		}
	// create new channel
	case "channel":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		_, err := c.client.CreateNewSupergroupChat(&client.CreateNewSupergroupChatRequest{
			Title:       args[0],
			Description: rawCmdArguments(cmdline, 1),
			IsChannel:   true,
		})
		if err != nil {
			return err.Error(), true
		}
	// create new secret chat with current user
	case "secret":
		_, err := c.client.CreateNewSecretChat(&client.CreateNewSecretChatRequest{
			UserId: chatID,
		})
		if err != nil {
			return err.Error(), true
		}
	// create group chat with current user
	case "group":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		_, err := c.client.CreateNewBasicGroupChat(&client.CreateNewBasicGroupChatRequest{
			UserIds: []int64{chatID},
			Title:   args[0],
		})
		if err != nil {
			return err.Error(), true
		}
	// blacklists current user
	case "block":
		_, err := c.client.ToggleMessageSenderIsBlocked(&client.ToggleMessageSenderIsBlockedRequest{
			SenderId:  &client.MessageSenderUser{UserId: chatID},
			IsBlocked: true,
		})
		if err != nil {
			return err.Error(), true
		}
	// unblacklists current user
	case "unblock":
		_, err := c.client.ToggleMessageSenderIsBlocked(&client.ToggleMessageSenderIsBlockedRequest{
			SenderId:  &client.MessageSenderUser{UserId: chatID},
			IsBlocked: false,
		})
		if err != nil {
			return err.Error(), true
		}
	// invite @username to current groupchat
	case "invite":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		_, err = c.client.AddChatMember(&client.AddChatMemberRequest{
			ChatId:       chatID,
			UserId:       contact.Id,
			ForwardLimit: 100,
		})
		if err != nil {
			return err.Error(), true
		}
	// get link to current chat
	case "link":
		link, err := c.client.CreateChatInviteLink(&client.CreateChatInviteLinkRequest{
			ChatId: chatID,
		})
		if err != nil {
			return err.Error(), true
		}
		return link.InviteLink, true
	// kick @username from current group chat
	case "kick":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status:   &client.ChatMemberStatusLeft{},
		})
		if err != nil {
			return err.Error(), true
		}
	// mute @username [n hours]
	case "mute":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		var hours int64
		if len(args) > 1 {
			hours, err = strconv.ParseInt(args[1], 10, 32)
			if err != nil {
				return "Invalid number of hours", true
			}
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status: &client.ChatMemberStatusRestricted{
				IsMember:            true,
				RestrictedUntilDate: c.formatBantime(hours),
				Permissions:         &permissionsReadonly,
			},
		})
		if err != nil {
			return err.Error(), true
		}
	// unmute @username
	case "unmute":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status: &client.ChatMemberStatusRestricted{
				IsMember:            true,
				RestrictedUntilDate: 0,
				Permissions:         &permissionsMember,
			},
		})
		if err != nil {
			return err.Error(), true
		}
	// ban @username from current chat [for N hours]
	case "ban":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		var hours int64
		if len(args) > 1 {
			hours, err = strconv.ParseInt(args[1], 10, 32)
			if err != nil {
				return "Invalid number of hours", true
			}
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status: &client.ChatMemberStatusBanned{
				BannedUntilDate: c.formatBantime(hours),
			},
		})
		if err != nil {
			return err.Error(), true
		}
	// unban @username
	case "unban":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status:   &client.ChatMemberStatusMember{},
		})
		if err != nil {
			return err.Error(), true
		}
	// promote @username to admin
	case "promote":
		if len(args) < 1 {
			return notEnoughArguments, true
		}

		contact, _, err := c.GetContactByUsername(args[0])
		if err != nil {
			return err.Error(), true
		}

		// clone the permissions
		status := permissionsAdmin

		if len(args) > 1 {
			status.CustomTitle = args[1]
		}

		_, err = c.client.SetChatMemberStatus(&client.SetChatMemberStatusRequest{
			ChatId:   chatID,
			MemberId: &client.MessageSenderUser{UserId: contact.Id},
			Status:   &status,
		})
		if err != nil {
			return err.Error(), true
		}
	// leave current chat
	case "leave":
		_, err := c.client.LeaveChat(&client.LeaveChatRequest{
			ChatId: chatID,
		})
		if err != nil {
			return err.Error(), true
		}

		err = c.unsubscribe(chatID)
		if err != nil {
			return err.Error(), true
		}
	// leave current chat (for owners)
	case "leave!":
		_, err := c.client.DeleteChat(&client.DeleteChatRequest{
			ChatId: chatID,
		})
		if err != nil {
			return err.Error(), true
		}

		err = c.unsubscribe(chatID)
		if err != nil {
			return err.Error(), true
		}
	// set TTL
	case "ttl":
		var ttl int64
		var err error
		if len(args) > 0 {
			ttl, err = strconv.ParseInt(args[0], 10, 32)
			if err != nil {
				return "Invalid TTL", true
			}
		}
		_, err = c.client.SetChatMessageTtl(&client.SetChatMessageTtlRequest{
			ChatId: chatID,
			Ttl:    int32(ttl),
		})

		if err != nil {
			return err.Error(), true
		}
	// close secret chat
	case "close":
		chat, _, err := c.GetContactByID(chatID, nil)
		if err != nil {
			return err.Error(), true
		}

		chatType := chat.Type.ChatTypeType()
		if chatType == client.TypeChatTypeSecret {
			chatTypeSecret, _ := chat.Type.(*client.ChatTypeSecret)
			_, err = c.client.CloseSecretChat(&client.CloseSecretChatRequest{
				SecretChatId: chatTypeSecret.SecretChatId,
			})
			if err != nil {
				return err.Error(), true
			}

			err = c.unsubscribe(chatID)
			if err != nil {
				return err.Error(), true
			}
		}
	// delete current chat
	case "delete":
		_, err := c.client.DeleteChatHistory(&client.DeleteChatHistoryRequest{
			ChatId:             chatID,
			RemoveFromChatList: true,
			Revoke:             true,
		})
		if err != nil {
			return err.Error(), true
		}

		err = c.unsubscribe(chatID)
		if err != nil {
			return err.Error(), true
		}
	// message search
	case "search":
		var limit int32 = 100
		if len(args) > 1 {
			newLimit, err := strconv.ParseInt(args[1], 10, 32)
			if err == nil {
				limit = int32(newLimit)
			}
		}

		var query string
		if len(args) > 0 {
			query = args[0]
		}

		messages, err := c.getLastMessages(chatID, query, 0, limit)
		if err != nil {
			return err.Error(), true
		}

		c.sendMessagesReverse(chatID, messages.Messages)
	// get latest entries from history
	case "history":
		var limit int32 = 10
		if len(args) > 0 {
			newLimit, err := strconv.ParseInt(args[0], 10, 32)
			if err == nil {
				limit = int32(newLimit)
			}
		}

		var messages *client.Messages
		var err error
		for _ = range make([]struct{}, 2) {
			messages, err = c.client.GetChatHistory(&client.GetChatHistoryRequest{
				ChatId: chatID,
				Limit:  limit,
			})
			if err != nil {
				return err.Error(), true
			}

			// TDlib yields only the latest message on the first request
			if !(len(messages.Messages) == 1 && limit > 1) {
				break
			}
		}

		c.sendMessagesReverse(chatID, messages.Messages)
	// chat members
	case "members":
		var query string
		if len(args) > 0 {
			query = args[0]
		}

		members, err := c.client.SearchChatMembers(&client.SearchChatMembersRequest{
			ChatId: chatID,
			Limit:  9999,
			Query:  query,
			Filter: &client.ChatMembersFilterMembers{},
		})
		if err != nil {
			return err.Error(), true
		}

		var entries []string
		for _, member := range members.Members {
			var senderId int64
			switch member.MemberId.MessageSenderType() {
			case client.TypeMessageSenderUser:
				memberUser, _ := member.MemberId.(*client.MessageSenderUser)
				senderId = memberUser.UserId
			case client.TypeMessageSenderChat:
				memberChat, _ := member.MemberId.(*client.MessageSenderChat)
				senderId = memberChat.ChatId
			}
			entries = append(entries, fmt.Sprintf(
				"%v | role: %v",
				c.formatContact(senderId),
				member.Status.ChatMemberStatusType(),
			))
		}

		return strings.Join(entries, "\n"), true
	case "help":
		return helpString(helpTypeChat), true
	default:
		return "", false
	}

	return "", true
}