package telegram

import (
	"crypto/sha1"
	"encoding/binary"
	"fmt"
	"github.com/pkg/errors"
	"hash/maphash"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	osUser "os/user"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	"dev.narayana.im/narayana/telegabber/telegram/cache"
	"dev.narayana.im/narayana/telegabber/telegram/formatter"
	"dev.narayana.im/narayana/telegabber/xmpp/gateway"

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

type VCardInfo struct {
	Fn       string
	Photo    *client.File
	Nickname string
	Given    string
	Family   string
	Tel      string
	Info     string
}

var errOffline = errors.New("TDlib instance is offline")

var spaceRegex = regexp.MustCompile(`\s+`)
var replyRegex = regexp.MustCompile("\\A>>? ?([0-9]+)\\n")

const newlineChar string = "\n"
const messageHeaderSeparator string = " | "

// GetContactByUsername resolves username to user id retrieves user and chat information
func (c *Client) GetContactByUsername(username string) (*client.Chat, *client.User, error) {
	if !c.Online() {
		return nil, nil, errOffline
	}

	var chat *client.Chat
	var err error
	var userID int64
	if strings.HasPrefix(username, "@") {
		chat, err = c.client.SearchPublicChat(&client.SearchPublicChatRequest{
			Username: username,
		})

		if err != nil {
			return nil, nil, err
		}

		userID = chat.Id
	} else {
		userID, err = strconv.ParseInt(username, 10, 64)
		if err != nil {
			return nil, nil, err
		}
	}

	return c.GetContactByID(userID, chat)
}

// GetContactByID gets user and chat information from cache (or tries to retrieve it, if missing)
func (c *Client) GetContactByID(id int64, chat *client.Chat) (*client.Chat, *client.User, error) {
	if !c.Online() || id == 0 {
		return nil, nil, errOffline
	}

	var user *client.User
	var cacheChat *client.Chat
	var ok bool
	var err error

	user, ok = c.cache.GetUser(id)
	if !ok && id > 0 {
		user, err = c.client.GetUser(&client.GetUserRequest{
			UserId: id,
		})
		if err == nil {
			c.cache.SetUser(id, user)
		}
	}

	cacheChat, ok = c.cache.GetChat(id)
	if !ok {
		if chat == nil {
			cacheChat, err = c.client.GetChat(&client.GetChatRequest{
				ChatId: id,
			})
			if err != nil {
				// error is irrelevant if the user was found successfully
				if user != nil {
					return nil, user, nil
				}

				return nil, nil, err
			}

			c.cache.SetChat(id, cacheChat)
		} else {
			c.cache.SetChat(id, chat)
		}
	}
	if chat == nil {
		chat = cacheChat
	}

	return chat, user, nil
}

// IsPM checks if a chat is PM
func (c *Client) IsPM(id int64) (bool, error) {
	if !c.Online() || id == 0 {
		return false, errOffline
	}

	var err error

	chat, ok := c.cache.GetChat(id)
	if !ok {
		chat, err = c.client.GetChat(&client.GetChatRequest{
			ChatId: id,
		})
		if err != nil {
			return false, err
		}

		c.cache.SetChat(id, chat)
	}

	chatType := chat.Type.ChatTypeType()
	if chatType == client.TypeChatTypePrivate || chatType == client.TypeChatTypeSecret {
		return true, nil
	}
	return false, nil
}

func (c *Client) userStatusToText(status client.UserStatus, chatID int64) (string, string, string) {
	var show, textStatus, presenceType string

	switch status.UserStatusType() {
	case client.TypeUserStatusOnline:
		onlineStatus, _ := status.(*client.UserStatusOnline)

		c.DelayedStatusesLock.Lock()
		c.DelayedStatuses[chatID] = &DelayedStatus{
			TimestampOnline:  time.Now().Unix(),
			TimestampExpired: int64(onlineStatus.Expires),
		}
		c.DelayedStatusesLock.Unlock()

		textStatus = "Online"
	case client.TypeUserStatusRecently:
		show, textStatus = "dnd", "Last seen recently"

		c.DelayedStatusesLock.Lock()
		delete(c.DelayedStatuses, chatID)
		c.DelayedStatusesLock.Unlock()
	case client.TypeUserStatusLastWeek:
		show, textStatus = "xa", "Last seen last week"
	case client.TypeUserStatusLastMonth:
		show, textStatus = "xa", "Last seen last month"
	case client.TypeUserStatusEmpty:
		presenceType, textStatus = "unavailable", "Last seen a long time ago"
	case client.TypeUserStatusOffline:
		offlineStatus, _ := status.(*client.UserStatusOffline)
		// this will stop working in 2038 O\
		wasOnline := int64(offlineStatus.WasOnline)
		elapsed := time.Now().Unix() - wasOnline
		if elapsed < 3600 {
			show = "away"
		} else {
			show = "xa"
		}
		textStatus = c.LastSeenStatus(wasOnline)

		c.DelayedStatusesLock.Lock()
		delete(c.DelayedStatuses, chatID)
		c.DelayedStatusesLock.Unlock()
	}

	return show, textStatus, presenceType
}

// LastSeenStatus formats a timestamp to a "Last seen at" string
func (c *Client) LastSeenStatus(timestamp int64) string {
	return time.Unix(int64(timestamp), 0).
		In(c.Session.TimezoneToLocation()).
		Format("Last seen at 15:04 02/01/2006")
}

// ProcessStatusUpdate sets contact status
func (c *Client) ProcessStatusUpdate(chatID int64, status string, show string, oldArgs ...args.V) error {
	if !c.Online() {
		return nil
	}

	log.WithFields(log.Fields{
		"chat_id": chatID,
	}).Info("Status update for")

	chat, user, err := c.GetContactByID(chatID, nil)
	if err != nil {
		return err
	}

	var photo string
	if chat != nil && chat.Photo != nil {
		file, path, err := c.ForceOpenFile(chat.Photo.Small, 1)
		if err == nil {
			defer file.Close()

			hash := sha1.New()
			_, err = io.Copy(hash, file)
			if err == nil {
				photo = fmt.Sprintf("%x", hash.Sum(nil))
			} else {
				log.Errorf("Error calculating hash: %v", path)
			}
		} else if path != "" {
			log.Errorf("Photo does not exist: %v", path)
		}
	}

	var presenceType string
	if gateway.SPType.IsSet(oldArgs) {
		presenceType = gateway.SPType.Get(oldArgs)
	}

	cachedStatus, ok := c.cache.GetStatus(chatID)
	if status == "" {
		if ok {
			show, status = cachedStatus.XMPP, cachedStatus.Description
		} else if user != nil && user.Status != nil {
			show, status, presenceType = c.userStatusToText(user.Status, chatID)
		} else {
			show, status = "chat", chat.Title
		}
	}

	c.cache.SetStatus(chatID, show, status)

	newArgs := []args.V{
		gateway.SPFrom(strconv.FormatInt(chatID, 10)),
		gateway.SPShow(show),
		gateway.SPStatus(status),
		gateway.SPPhoto(photo),
		gateway.SPResource(gateway.Jid.Resource),
		gateway.SPImmed(gateway.SPImmed.Get(oldArgs)),
	}
	if presenceType != "" {
		newArgs = append(newArgs, gateway.SPType(presenceType))
	}

	return gateway.SendPresence(
		c.xmpp,
		c.jid,
		newArgs...,
	)
}

func (c *Client) formatContact(chatID int64) string {
	if chatID == 0 {
		return ""
	}

	chat, user, err := c.GetContactByID(chatID, nil)
	if err != nil {
		return "unknown contact: " + err.Error()
	}

	var str string
	if chat != nil {
		str = fmt.Sprintf("%s (%v)", chat.Title, chat.Id)
	} else if user != nil {
		username := user.Username
		if username == "" {
			username = strconv.FormatInt(user.Id, 10)
		}

		str = fmt.Sprintf("%s %s (%v)", user.FirstName, user.LastName, username)
	} else {
		str = strconv.FormatInt(chatID, 10)
	}

	str = spaceRegex.ReplaceAllString(str, " ")

	return str
}

func (c *Client) getSenderId(message *client.Message) (senderId int64) {
	if message.SenderId != nil {
		switch message.SenderId.MessageSenderType() {
		case client.TypeMessageSenderUser:
			senderUser, _ := message.SenderId.(*client.MessageSenderUser)
			senderId = senderUser.UserId
		case client.TypeMessageSenderChat:
			senderChat, _ := message.SenderId.(*client.MessageSenderChat)
			senderId = senderChat.ChatId
		}
	}

	return
}

func (c *Client) formatSender(message *client.Message) string {
	return c.formatContact(c.getSenderId(message))
}

func (c *Client) getMessageReply(message *client.Message) (reply *gateway.Reply, replyMsg *client.Message) {
	if message.ReplyToMessageId != 0 {
		var err error
		replyMsg, err = c.client.GetMessage(&client.GetMessageRequest{
			ChatId:    message.ChatId,
			MessageId: message.ReplyToMessageId,
		})
		if err != nil {
			log.Errorf("<error fetching message: %s>", err.Error())
			return
		}

		replyId, err := gateway.IdsDB.GetByTgIds(c.Session.Login, c.jid, message.ChatId, message.ReplyToMessageId)
		if err != nil {
			replyId = strconv.FormatInt(message.ReplyToMessageId, 10)
		}
		reply = &gateway.Reply{
			Author: fmt.Sprintf("%v@%s", c.getSenderId(replyMsg), gateway.Jid.Full()),
			Id:     replyId,
		}
	}

	return
}

func (c *Client) formatMessage(chatID int64, messageID int64, preview bool, message *client.Message) string {
	var err error
	if message == nil {
		message, err = c.client.GetMessage(&client.GetMessageRequest{
			ChatId:    chatID,
			MessageId: messageID,
		})
		if err != nil {
			return fmt.Sprintf("<error fetching message: %s>", err.Error())
		}
	}

	if message == nil {
		return ""
	}

	var str strings.Builder
	// add messageid and sender
	str.WriteString(fmt.Sprintf("%v | %s | ", message.Id, c.formatSender(message)))
	// add date
	if !preview {
		str.WriteString(
			time.Unix(int64(message.Date), 0).
				In(c.Session.TimezoneToLocation()).
				Format("02 Jan 2006 15:04:05 | "),
		)
	}

	// text message
	var text string
	if message.Content != nil {
		text = c.messageToText(message, preview)
	}
	if text != "" {
		if !preview {
			str.WriteString(text)
		} else {
			newlinePos := strings.Index(text, newlineChar)
			if newlinePos == -1 {
				str.WriteString(text)
			} else {
				str.WriteString(text[0:newlinePos])
			}
		}
	}

	return str.String()
}

func (c *Client) formatForward(fwd *client.MessageForwardInfo) string {
	switch fwd.Origin.MessageForwardOriginType() {
	case client.TypeMessageForwardOriginUser:
		originUser := fwd.Origin.(*client.MessageForwardOriginUser)
		return c.formatContact(originUser.SenderUserId)
	case client.TypeMessageForwardOriginChat:
		originChat := fwd.Origin.(*client.MessageForwardOriginChat)
		var signature string
		if originChat.AuthorSignature != "" {
			signature = fmt.Sprintf(" (%s)", originChat.AuthorSignature)
		}
		return c.formatContact(originChat.SenderChatId) + signature
	case client.TypeMessageForwardOriginHiddenUser:
		originUser := fwd.Origin.(*client.MessageForwardOriginHiddenUser)
		return originUser.SenderName
	case client.TypeMessageForwardOriginChannel:
		channel := fwd.Origin.(*client.MessageForwardOriginChannel)
		var signature string
		if channel.AuthorSignature != "" {
			signature = fmt.Sprintf(" (%s)", channel.AuthorSignature)
		}
		return c.formatContact(channel.ChatId) + signature
	case client.TypeMessageForwardOriginMessageImport:
		originImport := fwd.Origin.(*client.MessageForwardOriginMessageImport)
		return originImport.SenderName
	}
	return "Unknown forward type"
}

func (c *Client) formatFile(file *client.File, compact bool) (string, string) {
	if file == nil {
		return "", ""
	}
	src, link := c.PermastoreFile(file, false)

	if compact {
		return link, link
	} else {
		return fmt.Sprintf("%s (%v kbytes) | %s", filepath.Base(src), file.Size/1024, link), link
	}
}

// PermastoreFile steals a file out of TDlib control into an independent shared directory
func (c *Client) PermastoreFile(file *client.File, clone bool) (string, string) {
	log.Debugf("file: %#v", file)
	if file == nil || file.Local == nil || file.Remote == nil {
		return "", ""
	}

	gateway.StorageLock.Lock()
	defer gateway.StorageLock.Unlock()

	var link string
	var src string

	if c.content.Path != "" && c.content.Link != "" {
		src = file.Local.Path // source path
		_, err := os.Stat(src)
		if err != nil {
			log.Errorf("Cannot access source file: %v", err)
			return "", ""
		}

		size64 := uint64(file.Size)
		c.prepareDiskSpace(size64)

		basename := file.Remote.UniqueId + filepath.Ext(src)
		dest := c.content.Path + "/" + basename // destination path
		link = c.content.Link + "/" + basename  // download link

		if clone {
			file, path, err := c.ForceOpenFile(file, 1)
			if err == nil {
				defer file.Close()

				// mode
				mode := os.FileMode(0644)
				fi, err := os.Stat(path)
				if err == nil {
					mode = fi.Mode().Perm()
				}

				// create destination
				tempFile, err := os.OpenFile(dest, os.O_CREATE|os.O_EXCL|os.O_WRONLY, mode)
				if err != nil {
					pathErr := err.(*os.PathError)
					if pathErr.Err.Error() == "file exists" {
						log.Warn(err.Error())
						return src, link
					} else {
						log.Errorf("File creation error: %v", err)
						return "<ERROR>", ""
					}
				}
				defer tempFile.Close()
				// copy
				_, err = io.Copy(tempFile, file)
				if err != nil {
					log.Errorf("File copying error: %v", err)
					return "<ERROR>", ""
				}
			} else if path != "" {
				log.Errorf("Source file does not exist: %v", path)
				return "<ERROR>", ""
			} else {
				log.Errorf("PHOTO: %#v", err.Error())
				return "<ERROR>", ""
			}
		} else {
			// move
			err = os.Rename(src, dest)
			if err != nil {
				linkErr := err.(*os.LinkError)
				if linkErr.Err.Error() == "file exists" {
					log.Warn(err.Error())
				} else {
					log.Errorf("File moving error: %v", err)
					return "<ERROR>", ""
				}
			}
		}

		// chown
		if c.content.User != "" {
			user, err := osUser.Lookup(c.content.User)
			if err == nil {
				uid, err := strconv.ParseInt(user.Uid, 10, 0)
				if err == nil {
					err = os.Chown(dest, int(uid), -1)
					if err != nil {
						log.Errorf("Chown error: %v", err)
					}
				} else {
					log.Errorf("Broken uid: %v", err)
				}
			} else {
				log.Errorf("Wrong user name for chown: %v", err)
			}
		}

		// copy or move should have succeeded at this point
		gateway.CachedStorageSize += size64
	}

	return src, link
}

func (c *Client) formatBantime(hours int64) int32 {
	var until int32
	if hours > 0 {
		until = int32(time.Now().Unix() + hours*3600)
	}

	return until
}

func (c *Client) formatLocation(location *client.Location) string {
	return fmt.Sprintf(
		"coordinates: %v,%v | https://www.google.com/maps/search/%v,%v/",
		location.Latitude,
		location.Longitude,
		location.Latitude,
		location.Longitude,
	)
}

func (c *Client) messageToText(message *client.Message, preview bool) string {
	if message.Content == nil {
		log.Warnf("Unknown message: %#v", message)
		return "<empty message>"
	}

	markupFunction := formatter.EntityToXEP0393
	switch message.Content.MessageContentType() {
	case client.TypeMessageSticker:
		sticker, _ := message.Content.(*client.MessageSticker)
		return sticker.Sticker.Emoji
	case client.TypeMessageAnimatedEmoji:
		animatedEmoji, _ := message.Content.(*client.MessageAnimatedEmoji)
		return animatedEmoji.Emoji
	case client.TypeMessageBasicGroupChatCreate, client.TypeMessageSupergroupChatCreate:
		return "has created chat"
	case client.TypeMessageChatJoinByLink:
		return "joined chat via invite link"
	case client.TypeMessageChatAddMembers:
		addMembers, _ := message.Content.(*client.MessageChatAddMembers)

		text := "invited "
		if len(addMembers.MemberUserIds) > 0 {
			text += c.formatContact(addMembers.MemberUserIds[0])
		}

		return text
	case client.TypeMessageChatDeleteMember:
		deleteMember, _ := message.Content.(*client.MessageChatDeleteMember)
		return "kicked " + c.formatContact(deleteMember.UserId)
	case client.TypeMessagePinMessage:
		pinMessage, _ := message.Content.(*client.MessagePinMessage)
		return "pinned message: " + c.formatMessage(message.ChatId, pinMessage.MessageId, preview, nil)
	case client.TypeMessageChatChangeTitle:
		changeTitle, _ := message.Content.(*client.MessageChatChangeTitle)
		return "chat title set to: " + changeTitle.Title
	case client.TypeMessageLocation:
		location, _ := message.Content.(*client.MessageLocation)
		return c.formatLocation(location.Location)
	case client.TypeMessageVenue:
		venue, _ := message.Content.(*client.MessageVenue)
		if preview {
			return venue.Venue.Title
		} else {
			return fmt.Sprintf(
				"*%s*\n%s\n%s",
				venue.Venue.Title,
				venue.Venue.Address,
				c.formatLocation(venue.Venue.Location),
			)
		}
	case client.TypeMessagePhoto:
		photo, _ := message.Content.(*client.MessagePhoto)
		if preview {
			return photo.Caption.Text
		} else {
			return formatter.Format(
				photo.Caption.Text,
				photo.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageAudio:
		audio, _ := message.Content.(*client.MessageAudio)
		if preview {
			return audio.Caption.Text
		} else {
			return formatter.Format(
				audio.Caption.Text,
				audio.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageVideo:
		video, _ := message.Content.(*client.MessageVideo)
		if preview {
			return video.Caption.Text
		} else {
			return formatter.Format(
				video.Caption.Text,
				video.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageDocument:
		document, _ := message.Content.(*client.MessageDocument)
		if preview {
			return document.Caption.Text
		} else {
			return formatter.Format(
				document.Caption.Text,
				document.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageText:
		text, _ := message.Content.(*client.MessageText)
		if preview {
			return text.Text.Text
		} else {
			return formatter.Format(
				text.Text.Text,
				text.Text.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageVoiceNote:
		voice, _ := message.Content.(*client.MessageVoiceNote)
		if preview {
			return voice.Caption.Text
		} else {
			return formatter.Format(
				voice.Caption.Text,
				voice.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageVideoNote:
		return ""
	case client.TypeMessageAnimation:
		animation, _ := message.Content.(*client.MessageAnimation)
		if preview {
			return animation.Caption.Text
		} else {
			return formatter.Format(
				animation.Caption.Text,
				animation.Caption.Entities,
				markupFunction,
			)
		}
	case client.TypeMessageContact:
		contact, _ := message.Content.(*client.MessageContact)
		if preview {
			return contact.Contact.FirstName + " " + contact.Contact.LastName
		} else {
			var jid string
			if contact.Contact.UserId != 0 {
				jid = fmt.Sprintf("%v@%s", contact.Contact.UserId, gateway.Jid.Bare())
			}
			return fmt.Sprintf(
				"*%s %s*\n%s\n%s\n%s",
				contact.Contact.FirstName,
				contact.Contact.LastName,
				contact.Contact.PhoneNumber,
				contact.Contact.Vcard,
				jid,
			)
		}
	case client.TypeMessageDice:
		dice, _ := message.Content.(*client.MessageDice)
		return fmt.Sprintf("%s 1d6: [%v]", dice.Emoji, dice.Value)
	case client.TypeMessagePoll:
		poll, _ := message.Content.(*client.MessagePoll)

		if preview {
			return poll.Poll.Question
		} else {
			rows := []string{}
			rows = append(rows, fmt.Sprintf("*%s*", poll.Poll.Question))
			for _, option := range poll.Poll.Options {
				var tick string
				if option.IsChosen {
					tick = "x"
				} else {
					tick = " "
				}
				rows = append(rows, fmt.Sprintf(
					"[%s] %s | %v%% | %v vote",
					tick,
					option.Text,
					option.VotePercentage,
					option.VoterCount,
				))
			}

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

	return fmt.Sprintf("unknown message (%s)", message.Content.MessageContentType())
}

func (c *Client) contentToFile(content client.MessageContent) (*client.File, *client.File) {
	if content == nil {
		return nil, nil
	}

	switch content.MessageContentType() {
	case client.TypeMessageSticker:
		sticker, _ := content.(*client.MessageSticker)
		file := sticker.Sticker.Sticker
		if sticker.Sticker.IsAnimated && sticker.Sticker.Thumbnail != nil && sticker.Sticker.Thumbnail.File != nil {
			file = sticker.Sticker.Thumbnail.File
		}
		return file, nil
	case client.TypeMessageVoiceNote:
		voice, _ := content.(*client.MessageVoiceNote)
		return voice.VoiceNote.Voice, nil
	case client.TypeMessageVideoNote:
		video, _ := content.(*client.MessageVideoNote)
		var preview *client.File
		if video.VideoNote.Thumbnail != nil {
			preview = video.VideoNote.Thumbnail.File
		}
		return video.VideoNote.Video, preview
	case client.TypeMessageAnimation:
		animation, _ := content.(*client.MessageAnimation)
		var preview *client.File
		if animation.Animation.Thumbnail != nil {
			preview = animation.Animation.Thumbnail.File
		}
		return animation.Animation.Animation, preview
	case client.TypeMessagePhoto:
		photo, _ := content.(*client.MessagePhoto)
		sizes := photo.Photo.Sizes
		if len(sizes) >= 1 {
			file := sizes[len(sizes)-1].Photo
			return file, nil
		}
		return nil, nil
	case client.TypeMessageAudio:
		audio, _ := content.(*client.MessageAudio)
		var preview *client.File
		if audio.Audio.AlbumCoverThumbnail != nil {
			preview = audio.Audio.AlbumCoverThumbnail.File
		}
		return audio.Audio.Audio, preview
	case client.TypeMessageVideo:
		video, _ := content.(*client.MessageVideo)
		var preview *client.File
		if video.Video.Thumbnail != nil {
			preview = video.Video.Thumbnail.File
		}
		return video.Video.Video, preview
	case client.TypeMessageDocument:
		document, _ := content.(*client.MessageDocument)
		var preview *client.File
		if document.Document.Thumbnail != nil {
			preview = document.Document.Thumbnail.File
		}
		return document.Document.Document, preview
	}

	return nil, nil
}

func (c *Client) countCharsInLines(lines *[]string) (count int) {
	for _, line := range *lines {
		count += len(line)
	}
	return
}

func (c *Client) messageToPrefix(message *client.Message, previewString string, fileString string, replyMsg *client.Message) (string, int, int) {
	isPM, err := c.IsPM(message.ChatId)
	if err != nil {
		log.Errorf("Could not determine if chat is PM: %v", err)
	}

	var replyStart, replyEnd int
	prefix := []string{}
	// message direction
	var directionChar string
	if !isPM || !gateway.MessageOutgoingPermission || !c.Session.Carbons {
		if c.Session.AsciiArrows {
			if message.IsOutgoing {
				directionChar = "> "
			} else {
				directionChar = "< "
			}
		} else {
			if message.IsOutgoing {
				directionChar = "➡ "
			} else {
				directionChar = "⬅ "
			}
		}
	}
	if !isPM || !c.Session.HideIds {
		prefix = append(prefix, directionChar+strconv.FormatInt(message.Id, 10))
	}
	// show sender in group chats
	if !isPM {
		sender := c.formatSender(message)
		if sender != "" {
			prefix = append(prefix, sender)
		}
	}
	// reply to
	if message.ReplyToMessageId != 0 {
		if len(prefix) > 0 {
			replyStart = c.countCharsInLines(&prefix) + (len(prefix)-1)*len(messageHeaderSeparator)
		}
		replyLine := "reply: " + c.formatMessage(message.ChatId, message.ReplyToMessageId, true, replyMsg)
		prefix = append(prefix, replyLine)
		replyEnd = replyStart + len(replyLine)
		if len(prefix) > 0 {
			replyEnd += len(messageHeaderSeparator)
		}
	}
	if message.ForwardInfo != nil {
		prefix = append(prefix, "fwd: "+c.formatForward(message.ForwardInfo))
	}
	// preview
	if previewString != "" {
		prefix = append(prefix, "preview: "+previewString)
	}
	// file
	if fileString != "" {
		prefix = append(prefix, "file: "+fileString)
	}

	return strings.Join(prefix, messageHeaderSeparator), replyStart, replyEnd
}

func (c *Client) ensureDownloadFile(file *client.File) *client.File {
	gateway.StorageLock.Lock()
	defer gateway.StorageLock.Unlock()

	if file != nil {
		c.prepareDiskSpace(uint64(file.Size))

		newFile, err := c.DownloadFile(file.Id, 1, true)
		if err == nil {
			return newFile
		}
	}

	return file
}

// ProcessIncomingMessage transfers a message to XMPP side and marks it as read on Telegram side
func (c *Client) ProcessIncomingMessage(chatId int64, message *client.Message, ignoredResource string) {
	var isPM bool
	var err error
	if gateway.MessageOutgoingPermission && c.Session.Carbons {
		isPM, err = c.IsPM(chatId)
		if err != nil {
			log.Errorf("Could not determine if chat is PM: %v", err)
		}
	}

	isOutgoing := message.IsOutgoing
	isCarbon := isPM && isOutgoing
	jids := c.getCarbonFullJids(isOutgoing, ignoredResource)
	if len(jids) == 0 {
		log.Info("The only resource is ignored, aborting")
		return
	}

	var text, oob, auxText string

	reply, replyMsg := c.getMessageReply(message)

	content := message.Content
	if content != nil && content.MessageContentType() == client.TypeMessageChatChangePhoto {
		chat, err := c.client.GetChat(&client.GetChatRequest{
			ChatId: chatId,
		})
		if err == nil {
			c.cache.SetChat(chatId, chat)
			go c.ProcessStatusUpdate(chatId, "", "", gateway.SPImmed(true))
			text = "<Chat photo has changed>"
		}
	} else {
		text = c.messageToText(message, false)

		// OTR support (I do not know why would you need it, seriously)
		if !(strings.HasPrefix(text, "?OTR") || (c.Session.RawMessages && !c.Session.OOBMode)) {
			file, preview := c.contentToFile(content)

			// download file and preview (if present)
			file = c.ensureDownloadFile(file)
			preview = c.ensureDownloadFile(preview)

			previewName, _ := c.formatFile(preview, true)
			fileName, link := c.formatFile(file, false)

			oob = link
			if c.Session.OOBMode && oob != "" {
				typ := message.Content.MessageContentType()
				if typ != client.TypeMessageSticker {
					auxText = text
				}
				text = oob
			} else if !c.Session.RawMessages {
				var newText strings.Builder

				prefix, replyStart, replyEnd := c.messageToPrefix(message, previewName, fileName, replyMsg)
				newText.WriteString(prefix)
				if reply != nil {
					reply.Start = uint64(replyStart)
					reply.End = uint64(replyEnd)
				}

				if text != "" {
					// \n if it is groupchat and message is not empty
					if prefix != "" {
						if chatId < 0 {
							newText.WriteString("\n")
						} else if chatId > 0 {
							newText.WriteString(" | ")
						}
					}

					newText.WriteString(text)
				}
				text = newText.String()
			}
		}
	}

	// mark message as read
	c.client.ViewMessages(&client.ViewMessagesRequest{
		ChatId:     chatId,
		MessageIds: []int64{message.Id},
		ForceRead:  true,
	})

	// forward message to XMPP
	sId := strconv.FormatInt(message.Id, 10)
	sChatId := strconv.FormatInt(chatId, 10)

	for _, jid := range jids {
		gateway.SendMessageWithOOB(jid, sChatId, text, sId, c.xmpp, reply, oob, isCarbon)
		if auxText != "" {
			gateway.SendMessage(jid, sChatId, auxText, sId, c.xmpp, reply, isCarbon)
		}
	}
}

// PrepareMessageContent creates a simple text message
func (c *Client) PrepareOutgoingMessageContent(text string) client.InputMessageContent {
	return c.prepareOutgoingMessageContent(text, nil)
}

// ProcessOutgoingMessage executes commands or sends messages to mapped chats, returns message id
func (c *Client) ProcessOutgoingMessage(chatID int64, text string, returnJid string, replyId int64, replaceId int64) int64 {
	if !c.Online() {
		// we're offline
		return 0
	}

	if replaceId == 0 && (strings.HasPrefix(text, "/") || strings.HasPrefix(text, "!")) {
		// try to execute commands
		response, isCommand := c.ProcessChatCommand(chatID, text)
		if response != "" {
			c.returnMessage(returnJid, chatID, response)
		}
		// do not send on success
		if isCommand {
			return 0
		}
	}

	log.Warnf("Sending message to chat %v", chatID)

	// quotations
	var reply int64
	if replaceId == 0 && replyId == 0 {
		replySlice := replyRegex.FindStringSubmatch(text)
		if len(replySlice) > 1 {
			reply, _ = strconv.ParseInt(replySlice[1], 10, 64)
		}
	} else {
		reply = replyId
	}

	// attach a file
	var file *client.InputFileLocal
	if c.content.Upload != "" && strings.HasPrefix(text, c.content.Upload) {
		response, err := http.Get(text)
		if err != nil {
			c.returnError(returnJid, chatID, "Failed to fetch the uploaded file", err)
		}
		if response != nil && response.Body != nil {
			defer response.Body.Close()

			if response.StatusCode != 200 {
				c.returnMessage(returnJid, chatID, fmt.Sprintf("Received status code %v", response.StatusCode))
			}

			tempDir, err := ioutil.TempDir("", "telegabber-*")
			if err != nil {
				c.returnError(returnJid, chatID, "Failed to create a temporary directory", err)
			}
			tempFile, err := os.Create(filepath.Join(tempDir, filepath.Base(text)))
			if err != nil {
				c.returnError(returnJid, chatID, "Failed to create a temporary file", err)
			}

			_, err = io.Copy(tempFile, response.Body)
			if err != nil {
				c.returnError(returnJid, chatID, "Failed to write a temporary file", err)
			}

			file = &client.InputFileLocal{
				Path: tempFile.Name(),
			}
		}
	}

	// remove first line from text
	if file != nil || (reply != 0 && replyId == 0) {
		newlinePos := strings.Index(text, newlineChar)
		if newlinePos != -1 {
			text = text[newlinePos+1:]
		} else {
			text = ""
		}
	}

	content := c.prepareOutgoingMessageContent(text, file)

	if replaceId != 0 {
		tgMessage, err := c.client.EditMessageText(&client.EditMessageTextRequest{
			ChatId:              chatID,
			MessageId:           replaceId,
			InputMessageContent: content,
		})
		if err != nil {
			c.returnError(returnJid, chatID, "Not edited", err)
			return 0
		}
		return tgMessage.Id
	}

	tgMessage, err := c.client.SendMessage(&client.SendMessageRequest{
		ChatId:              chatID,
		ReplyToMessageId:    reply,
		InputMessageContent: content,
	})
	if err != nil {
		c.returnError(returnJid, chatID, "Not sent", err)
		return 0
	}
	return tgMessage.Id
}

func (c *Client) returnMessage(returnJid string, chatID int64, text string) {
	gateway.SendTextMessage(returnJid, strconv.FormatInt(chatID, 10), text, c.xmpp)
}

func (c *Client) returnError(returnJid string, chatID int64, msg string, err error) {
	c.returnMessage(returnJid, chatID, fmt.Sprintf("%s: %s", msg, err.Error()))
}

func (c *Client) prepareOutgoingMessageContent(text string, file *client.InputFileLocal) client.InputMessageContent {
	formattedText := &client.FormattedText{
		Text: text,
	}

	var content client.InputMessageContent
	if file != nil {
		// we can try to send a document
		content = &client.InputMessageDocument{
			Document: file,
			Caption:  formattedText,
		}
	} else {
		// compile our message
		content = &client.InputMessageText{
			Text: formattedText,
		}
	}
	return content
}

// StatusesRange proxies the following function from unexported cache
func (c *Client) StatusesRange() chan *cache.Status {
	return c.cache.StatusesRange()
}

func (c *Client) addResource(resource string) {
	if resource == "" {
		return
	}
	c.locks.resourcesLock.Lock()
	defer c.locks.resourcesLock.Unlock()

	c.resources[resource] = true
}

func (c *Client) deleteResource(resource string) {
	c.locks.resourcesLock.Lock()
	defer c.locks.resourcesLock.Unlock()

	if _, ok := c.resources[resource]; ok {
		delete(c.resources, resource)
	}
}

func (c *Client) resourcesRange() chan string {
	c.locks.resourcesLock.Lock()

	resourceChan := make(chan string, 1)

	go func() {
		defer func() {
			c.locks.resourcesLock.Unlock()
			close(resourceChan)
		}()

		for resource := range c.resources {
			resourceChan <- resource
		}
	}()

	return resourceChan
}

// resend statuses to (to another resource, for example)
func (c *Client) roster(resource string) {
	c.locks.resourcesLock.Lock()
	if _, ok := c.resources[resource]; ok {
		c.locks.resourcesLock.Unlock()
		return // we know it
	}
	c.locks.resourcesLock.Unlock()

	log.Warnf("Sending roster for %v", resource)

	for _, chat := range c.cache.ChatsKeys() {
		c.ProcessStatusUpdate(chat, "", "")
	}

	gateway.SendPresence(c.xmpp, c.jid, gateway.SPStatus("Logged in as: "+c.Session.Login))

	c.addResource(resource)
}

// get last messages from specified chat
func (c *Client) getLastMessages(id int64, query string, from int64, count int32) (*client.Messages, error) {
	return c.client.SearchChatMessages(&client.SearchChatMessagesRequest{
		ChatId:   id,
		Query:    query,
		SenderId: &client.MessageSenderUser{UserId: from},
		Filter:   &client.SearchMessagesFilterEmpty{},
		Limit:    count,
	})
}

// DownloadFile actually obtains a file by id given by TDlib
func (c *Client) DownloadFile(id int32, priority int32, synchronous bool) (*client.File, error) {
	return c.client.DownloadFile(&client.DownloadFileRequest{
		FileId:      id,
		Priority:    priority,
		Synchronous: synchronous,
	})
}

// ForceOpenFile reliably obtains a file if possible
func (c *Client) ForceOpenFile(tgFile *client.File, priority int32) (*os.File, string, error) {
	if tgFile == nil {
		return nil, "", errors.New("File not found")
	}

	path := tgFile.Local.Path
	file, err := os.Open(path)
	if err == nil {
		return file, path, nil
	} else
	// obtain the photo right now if still not downloaded
	if !tgFile.Local.IsDownloadingCompleted {
		tdFile, tdErr := c.DownloadFile(tgFile.Id, priority, true)
		if tdErr == nil {
			path = tdFile.Local.Path
			file, err = os.Open(path)
			return file, path, err
		}
	}

	// give up
	return nil, path, err
}

// GetChatDescription obtains bio or description according to the chat type
func (c *Client) GetChatDescription(chat *client.Chat) string {
	chatType := chat.Type.ChatTypeType()
	if chatType == client.TypeChatTypePrivate {
		privateType, _ := chat.Type.(*client.ChatTypePrivate)
		fullInfo, err := c.client.GetUserFullInfo(&client.GetUserFullInfoRequest{
			UserId: privateType.UserId,
		})
		if err == nil {
			if fullInfo.Bio != "" {
				return fullInfo.Bio
			} else if fullInfo.Description != "" {
				return fullInfo.Description
			}
		} else {
			log.Warnf("Coudln't retrieve private chat info: %v", err.Error())
		}
	} else if chatType == client.TypeChatTypeBasicGroup {
		basicGroupType, _ := chat.Type.(*client.ChatTypeBasicGroup)
		fullInfo, err := c.client.GetBasicGroupFullInfo(&client.GetBasicGroupFullInfoRequest{
			BasicGroupId: basicGroupType.BasicGroupId,
		})
		if err == nil {
			return fullInfo.Description
		} else {
			log.Warnf("Coudln't retrieve basic group info: %v", err.Error())
		}
	} else if chatType == client.TypeChatTypeSupergroup {
		supergroupType, _ := chat.Type.(*client.ChatTypeSupergroup)
		fullInfo, err := c.client.GetSupergroupFullInfo(&client.GetSupergroupFullInfoRequest{
			SupergroupId: supergroupType.SupergroupId,
		})
		if err == nil {
			return fullInfo.Description
		} else {
			log.Warnf("Coudln't retrieve supergroup info: %v", err.Error())
		}
	}
	return ""
}

// subscribe to a Telegram ID
func (c *Client) subscribeToID(id int64, chat *client.Chat) {
	var args []args.V
	args = append(args, gateway.SPFrom(strconv.FormatInt(id, 10)))
	args = append(args, gateway.SPType("subscribe"))

	if chat == nil {
		chat, _, _ = c.GetContactByID(id, nil)
	}
	if chat != nil {
		args = append(args, gateway.SPNickname(chat.Title))

		gateway.SetNickname(c.jid, strconv.FormatInt(id, 10), chat.Title, c.xmpp)
	}

	gateway.SendPresence(
		c.xmpp,
		c.jid,
		args...,
	)
}

func (c *Client) prepareDiskSpace(size uint64) {
	if gateway.StorageQuota > 0 && c.content.Path != "" {
		var loweredQuota uint64
		if gateway.StorageQuota >= size {
			loweredQuota = gateway.StorageQuota - size
		}
		if gateway.CachedStorageSize >= loweredQuota {
			log.Warn("Storage is rapidly clogged")
			gateway.CleanOldFiles(c.content.Path, loweredQuota)
		}
	}
}

func (c *Client) GetVcardInfo(toID int64) (VCardInfo, error) {
	var info VCardInfo
	chat, user, err := c.GetContactByID(toID, nil)
	if err != nil {
		return info, err
	}

	if chat != nil {
		info.Fn = chat.Title

		if chat.Photo != nil {
			info.Photo = chat.Photo.Small
		}
		info.Info = c.GetChatDescription(chat)
	}
	if user != nil {
		info.Nickname = user.Username
		info.Given = user.FirstName
		info.Family = user.LastName
		info.Tel = user.PhoneNumber
	}

	return info, nil
}

func (c *Client) UpdateChatNicknames() {
	for _, id := range c.cache.ChatsKeys() {
		chat, ok := c.cache.GetChat(id)
		if ok {
			gateway.SendPresence(
				c.xmpp,
				c.jid,
				gateway.SPFrom(strconv.FormatInt(id, 10)),
				gateway.SPNickname(chat.Title),
			)
			gateway.SetNickname(c.jid, strconv.FormatInt(id, 10), chat.Title, c.xmpp)
		}
	}
}

// AddToOutbox remembers the resource from which a message with given ID was sent
func (c *Client) AddToOutbox(xmppId, resource string) {
	c.locks.outboxLock.Lock()
	defer c.locks.outboxLock.Unlock()

	c.outbox[xmppId] = resource
}

func (c *Client) popFromOutbox(xmppId string) string {
	c.locks.outboxLock.Lock()
	defer c.locks.outboxLock.Unlock()

	resource, ok := c.outbox[xmppId]
	if ok {
		delete(c.outbox, xmppId)
	} else {
		log.Warnf("No %v xmppId in outbox", xmppId)
	}
	return resource
}

func (c *Client) getCarbonFullJids(isOutgoing bool, ignoredResource string) []string {
	var jids []string
	if isOutgoing {
		for resource := range c.resourcesRange() {
			if ignoredResource == "" || resource != ignoredResource {
				jids = append(jids, c.jid+"/"+resource)
			}
		}
	} else {
		jids = []string{c.jid}
	}
	return jids
}

func (c *Client) calculateMessageHash(messageId int64, content client.MessageContent) uint64 {
	var h maphash.Hash
	h.SetSeed(c.msgHashSeed)

	buf8 := make([]byte, 8)
	binary.BigEndian.PutUint64(buf8, uint64(messageId))
	h.Write(buf8)

	if content != nil && content.MessageContentType() == client.TypeMessageText {
		textContent, ok := content.(*client.MessageText)
		if !ok {
			uhOh()
		}

		if textContent.Text != nil {
			h.WriteString(textContent.Text.Text)
			for _, entity := range textContent.Text.Entities {
				buf4 := make([]byte, 4)
				binary.BigEndian.PutUint32(buf4, uint32(entity.Offset))
				h.Write(buf4)
				binary.BigEndian.PutUint32(buf4, uint32(entity.Length))
				h.Write(buf4)
				h.WriteString(entity.Type.TextEntityTypeType())
			}
		}
	}

	return h.Sum64()
}

func (c *Client) updateLastMessageHash(chatId, messageId int64, content client.MessageContent) {
	c.locks.lastMsgHashesLock.Lock()
	defer c.locks.lastMsgHashesLock.Unlock()

	c.lastMsgHashes[chatId] = c.calculateMessageHash(messageId, content)
}

func (c *Client) hasLastMessageHashChanged(chatId, messageId int64, content client.MessageContent) bool {
	c.locks.lastMsgHashesLock.Lock()
	defer c.locks.lastMsgHashesLock.Unlock()

	oldHash, ok := c.lastMsgHashes[chatId]
	newHash := c.calculateMessageHash(messageId, content)

	if !ok {
		log.Warnf("Last message hash for chat %v does not exist", chatId)
	}
	log.WithFields(log.Fields{
		"old hash": oldHash,
		"new hash": newHash,
	}).Info("Message hashes")

	return !ok || oldHash != newHash
}