feat: format message from telegram and upload attachments (#1924)

* feat: format message from telegram and download documents

* fix: remove bool in expression

* refactor: convert to markdown

* refactor: resolve remarks and add support new message types

* refactor: resolve remarks

* feat: add test for mime type

---------

Co-authored-by: Александр Тумайкин <AATumaykin@tsum.ru>

plugin/telegram/animation.go

@@ -0,0 +1,14 @@
+package telegram
+
+// Animation represents an animation file.
+type Animation struct {
+	FileID       string     `json:"file_id"`        // FileID is the identifier for this file, which can be used to download or reuse the file
+	FileUniqueID string     `json:"file_unique_id"` // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Width        int        `json:"width"`          // Width video width as defined by sender
+	Height       int        `json:"height"`         // Height video height as defined by sender
+	Duration     int        `json:"duration"`       // Duration of the video in seconds as defined by sender
+	Thumbnail    *PhotoSize `json:"thumb"`          // Thumbnail animation thumbnail as defined by sender
+	FileName     string     `json:"file_name"`      // FileName original animation filename as defined by sender
+	MimeType     string     `json:"mime_type"`      // MimeType of the file as defined by sender
+	FileSize     int        `json:"file_size"`
+}

plugin/telegram/attachment.go

@@ -0,0 +1,38 @@
+package telegram
+
+import (
+	"path"
+
+	"github.com/usememos/memos/common/log"
+	"go.uber.org/zap"
+)
+
+type Attachment struct {
+	FileName string
+	MimeType string
+	FileSize int64
+	Data     []byte
+}
+
+var mimeTypes = map[string]string{
+	".jpg": "image/jpeg",
+	".png": "image/png",
+	".mp4": "video/mp4", // for video note
+	".oga": "audio/ogg", // for voice
+}
+
+func (b Attachment) GetMimeType() string {
+	if b.MimeType != "" {
+		return b.MimeType
+	}
+
+	mime, ok := mimeTypes[path.Ext(b.FileName)]
+	if !ok {
+		// Handle unknown file extension
+		log.Warn("Unknown file type for ", zap.String("filename", b.FileName))
+
+		return "application/octet-stream"
+	}
+
+	return mime
+}

plugin/telegram/attachment_test.go

@@ -0,0 +1,83 @@
+package telegram
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetMimeType(t *testing.T) {
+	tests := []struct {
+		mimeType string
+		fileName string
+		expected string
+	}{
+		{
+			fileName: "file.jpg",
+			mimeType: "image/jpeg",
+			expected: "image/jpeg",
+		},
+		{
+			fileName: "file.png",
+			mimeType: "image/png",
+			expected: "image/png",
+		},
+		{
+			fileName: "file.pdf",
+			mimeType: "application/pdf",
+			expected: "application/pdf",
+		},
+		{
+			fileName: "file.php",
+			mimeType: "application/x-php",
+			expected: "application/x-php",
+		},
+		{
+			fileName: "file.xlsx",
+			mimeType: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+			expected: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+		},
+		{
+			fileName: "file.oga",
+			mimeType: "audio/ogg",
+			expected: "audio/ogg",
+		},
+		{
+			fileName: "file.jpg",
+			expected: "image/jpeg",
+		},
+		{
+			fileName: "file.png",
+			expected: "image/png",
+		},
+		{
+			fileName: "file.mp4",
+			expected: "video/mp4",
+		},
+		{
+			fileName: "file.pdf",
+			expected: "application/octet-stream",
+		},
+		{
+			fileName: "file.oga",
+			expected: "audio/ogg",
+		},
+		{
+			fileName: "file.xlsx",
+			expected: "application/octet-stream",
+		},
+		{
+			fileName: "file.txt",
+			expected: "application/octet-stream",
+		},
+	}
+
+	for _, test := range tests {
+		attachment := Attachment{
+			FileName: test.fileName,
+			MimeType: test.mimeType,
+		}
+
+		require.Equal(t, test.expected, attachment.GetMimeType())
+	}
+}

plugin/telegram/audio.go

@@ -0,0 +1,14 @@
+package telegram
+
+// Audio represents an audio file to be treated as music by the Telegram clients.
+type Audio struct {
+	FileID       string     `json:"file_id"`        // FileID is an identifier for this file, which can be used to download or reuse the file
+	FileUniqueID string     `json:"file_unique_id"` // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Duration     int        `json:"duration"`       // Duration of the audio in seconds as defined by sender
+	Performer    string     `json:"performer"`      // Performer of the audio as defined by sender or by audio tags
+	Title        string     `json:"title"`          // Title of the audio as defined by sender or by audio tags
+	FileName     string     `json:"file_name"`      // FileName is the original filename as defined by sender
+	MimeType     string     `json:"mime_type"`      // MimeType of the file as defined by sender
+	FileSize     int        `json:"file_size"`      // FileSize file size
+	Thumbnail    *PhotoSize `json:"thumb"`          // Thumbnail is the album cover to which the music file belongs
+}

plugin/telegram/bot.go

@@ -13,7 +13,7 @@ import (
 
 type Handler interface {
 	BotToken(ctx context.Context) string
-	MessageHandle(ctx context.Context, bot *Bot, message Message, blobs map[string][]byte) error
+	MessageHandle(ctx context.Context, bot *Bot, message Message, attachments []Attachment) error
 	CallbackQueryHandle(ctx context.Context, bot *Bot, callbackQuery CallbackQuery) error
 }
 
@@ -65,9 +65,9 @@ func (b *Bot) Start(ctx context.Context) {
 			if update.Message != nil {
 				message := *update.Message
 
-				// skip message other than text or photo
-				if message.Text == nil && message.Photo == nil {
-					_, err := b.SendReplyMessage(ctx, message.Chat.ID, message.MessageID, "Only text or photo message be supported")
+				// skip unsupported message
+				if !message.IsSupported() {
+					_, err := b.SendReplyMessage(ctx, message.Chat.ID, message.MessageID, "Supported messages: animation, audio, text, document, photo, video, video note, voice, other messages with caption")
 					if err != nil {
 						log.Error(fmt.Sprintf("fail to telegram.SendReplyMessage for messageID=%d", message.MessageID), zap.Error(err))
 					}

plugin/telegram/chat.go

@@ -1,9 +1,19 @@
 package telegram
 
+type ChatType string
+
+const (
+	Private    = "private"
+	Group      = "group"
+	SuperGroup = "supergroup"
+	Channel    = "channel"
+)
+
 type Chat struct {
-	ID        int    `json:"id"`
-	Title     string `json:"title"`
-	Type      string `json:"type"`
-	FirstName string `json:"first_name"`
-	LastName  string `json:"last_name"`
+	ID        int      `json:"id"`
+	Title     string   `json:"title"`      // Title for supergroups, channels and group chats
+	Type      ChatType `json:"type"`       // Type of chat, can be either “private”, “group”, “supergroup” or “channel”
+	FirstName string   `json:"first_name"` // FirstName of the other party in a private chat
+	LastName  string   `json:"last_name"`  // LastName of the other party in a private chat
+	UserName  string   `json:"username"`   // UserName for private chats, supergroups and channels if available
 }

plugin/telegram/document.go

@@ -0,0 +1,11 @@
+package telegram
+
+// Document represents a general file.
+type Document struct {
+	FileID       string     `json:"file_id"`        // FileID is an identifier for this file, which can be used to download or reuse the file
+	FileUniqueID string     `json:"file_unique_id"` // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Thumbnail    *PhotoSize `json:"thumb"`          // Thumbnail document thumbnail as defined by sender
+	FileName     string     `json:"file_name"`      // FileName original filename as defined by sender
+	MimeType     string     `json:"mime_type"`      // MimeType  of the file as defined by sender
+	FileSize     int        `json:"file_size"`
+}

plugin/telegram/download.go

@@ -8,18 +8,72 @@ import (
 	"strings"
 )
 
-// downloadFileId download file with fileID, return the filepath and blob.
-func (b *Bot) downloadFileID(ctx context.Context, fileID string) (string, []byte, error) {
-	file, err := b.GetFile(ctx, fileID)
-	if err != nil {
-		return "", nil, err
-	}
-	blob, err := b.downloadFilepath(ctx, file.FilePath)
-	if err != nil {
-		return "", nil, err
+func (b *Bot) downloadAttachment(ctx context.Context, message *Message) (*Attachment, error) {
+	var fileID, fileName, mimeType string
+	switch {
+	case len(message.Photo) > 0:
+		fileID = message.GetMaxPhotoFileID()
+	case message.Animation != nil:
+		fileID = message.Animation.FileID
+		fileName = message.Animation.FileName
+		mimeType = message.Animation.MimeType
+	case message.Audio != nil:
+		fileID = message.Audio.FileID
+		fileName = message.Audio.FileName
+		mimeType = message.Audio.MimeType
+	case message.Document != nil:
+		fileID = message.Document.FileID
+		fileName = message.Document.FileName
+		mimeType = message.Document.MimeType
+	case message.Video != nil:
+		fileID = message.Video.FileID
+		fileName = message.Video.FileName
+		mimeType = message.Video.MimeType
+	case message.VideoNote != nil:
+		fileID = message.VideoNote.FileID
+	case message.Voice != nil:
+		fileID = message.Voice.FileID
+		mimeType = message.Voice.MimeType
 	}
 
-	return file.FilePath, blob, nil
+	if fileID == "" {
+		return nil, nil
+	}
+
+	attachment, err := b.downloadFileID(ctx, fileID)
+	if err != nil {
+		return nil, err
+	}
+
+	if fileName != "" {
+		attachment.FileName = fileName
+	}
+
+	if mimeType != "" {
+		attachment.MimeType = mimeType
+	}
+
+	return attachment, nil
+}
+
+// downloadFileId download file with fileID, return Blob struct.
+func (b *Bot) downloadFileID(ctx context.Context, fileID string) (*Attachment, error) {
+	file, err := b.GetFile(ctx, fileID)
+	if err != nil {
+		return nil, err
+	}
+	data, err := b.downloadFilepath(ctx, file.FilePath)
+	if err != nil {
+		return nil, err
+	}
+
+	blob := &Attachment{
+		FileName: file.FilePath,
+		Data:     data,
+		FileSize: file.FileSize,
+	}
+
+	return blob, nil
 }
 
 // downloadFilepath download file with filepath, you can get filepath by calling GetFile.

plugin/telegram/handle.go

@@ -2,24 +2,23 @@ package telegram
 
 import (
 	"context"
-	"fmt"
 )
 
 // handleSingleMessages handle single messages not belongs to group.
 func (b *Bot) handleSingleMessages(ctx context.Context, messages []Message) error {
-	for _, message := range messages {
-		var blobs map[string][]byte
+	var attachments []Attachment
 
-		// download blob if provided
-		if len(message.Photo) > 0 {
-			filepath, blob, err := b.downloadFileID(ctx, message.GetMaxPhotoFileID())
-			if err != nil {
-				return err
-			}
-			blobs = map[string][]byte{filepath: blob}
+	for _, message := range messages {
+		attachment, err := b.downloadAttachment(ctx, &message)
+		if err != nil {
+			return err
 		}
 
-		err := b.handler.MessageHandle(ctx, b, message, blobs)
+		if attachment != nil {
+			attachments = append(attachments, *attachment)
+		}
+
+		err = b.handler.MessageHandle(ctx, b, message, attachments)
 		if err != nil {
 			return err
 		}
@@ -32,7 +31,7 @@ func (b *Bot) handleSingleMessages(ctx context.Context, messages []Message) erro
 func (b *Bot) handleGroupMessages(ctx context.Context, groupMessages []Message) error {
 	captions := make(map[string]string, len(groupMessages))
 	messages := make(map[string]Message, len(groupMessages))
-	blobs := make(map[string]map[string][]byte, len(groupMessages))
+	attachments := make(map[string][]Attachment, len(groupMessages))
 
 	// Group all captions, blobs and messages
 	for _, message := range groupMessages {
@@ -44,14 +43,14 @@ func (b *Bot) handleGroupMessages(ctx context.Context, groupMessages []Message)
 			captions[groupID] += *message.Caption
 		}
 
-		filepath, blob, err := b.downloadFileID(ctx, message.GetMaxPhotoFileID())
+		attachment, err := b.downloadAttachment(ctx, &message)
 		if err != nil {
-			return fmt.Errorf("fail to downloadFileID")
+			return err
 		}
-		if _, found := blobs[groupID]; !found {
-			blobs[groupID] = make(map[string][]byte)
+
+		if attachment != nil {
+			attachments[groupID] = append(attachments[groupID], *attachment)
 		}
-		blobs[groupID][filepath] = blob
 	}
 
 	// Handle each group message
@@ -59,7 +58,7 @@ func (b *Bot) handleGroupMessages(ctx context.Context, groupMessages []Message)
 		// replace Caption with all Caption in the group
 		caption := captions[groupID]
 		message.Caption = &caption
-		err := b.handler.MessageHandle(ctx, b, message, blobs[groupID])
+		err := b.handler.MessageHandle(ctx, b, message, attachments[groupID])
 		if err != nil {
 			return err
 		}

plugin/telegram/message.go

@@ -1,14 +1,26 @@
 package telegram
 
+import "fmt"
+
 type Message struct {
-	MessageID    int         `json:"message_id"`
-	From         User        `json:"from"`
-	Date         int         `json:"date"`
-	Text         *string     `json:"text"`
-	Chat         *Chat       `json:"chat"`
-	MediaGroupID *string     `json:"media_group_id"`
-	Photo        []PhotoSize `json:"photo"`
-	Caption      *string     `json:"caption"`
+	MessageID            int             `json:"message_id"`              // MessageID is a unique message identifier inside this chat
+	From                 User            `json:"from"`                    // From is a sender, empty for messages sent to channels;
+	Date                 int             `json:"date"`                    // Date of the message was sent in Unix time
+	Text                 *string         `json:"text"`                    // Text is for text messages, the actual UTF-8 text of the message, 0-4096 characters;
+	Chat                 *Chat           `json:"chat"`                    // Chat is the conversation the message belongs to
+	ForwardFromChat      *Chat           `json:"forward_from_chat"`       // ForwardFromChat for messages forwarded from channels, information about the original channel;
+	ForwardFromMessageID int             `json:"forward_from_message_id"` // ForwardFromMessageID for messages forwarded from channels, identifier of the original message in the channel;
+	MediaGroupID         *string         `json:"media_group_id"`          // MediaGroupID is the unique identifier of a media message group this message belongs to;
+	Photo                []PhotoSize     `json:"photo"`                   // Photo message is a photo, available sizes of the photo;
+	Caption              *string         `json:"caption"`                 // Caption for the animation, audio, document, photo, video or voice, 0-1024 characters;
+	Entities             []MessageEntity `json:"entities"`                // Entities are for text messages, special entities like usernames, URLs, bot commands, etc. that appear in the text;
+	CaptionEntities      []MessageEntity `json:"caption_entities"`
+	Document             *Document       `json:"document"`   // Document message is a general file, information about the file;
+	Video                *Video          `json:"video"`      // Video message is a video, information about the video;
+	VideoNote            *VideoNote      `json:"video_note"` // VideoNote message is a video note, information about the video message;
+	Voice                *Voice          `json:"voice"`      // Voice message is a voice message, information about the file;
+	Audio                *Audio          `json:"audio"`      // Audio message is an audio file, information about the file;
+	Animation            *Animation      `json:"animation"`  // Animation message is an animation, information about the animation. For backward compatibility, when this field is set, the document field will also be set;
 }
 
 func (m Message) GetMaxPhotoFileID() string {
@@ -22,3 +34,16 @@ func (m Message) GetMaxPhotoFileID() string {
 
 	return photoSize.FileID
 }
+
+func (m Message) GetMessageLink() string {
+	if m.ForwardFromChat != nil && m.ForwardFromChat.Type == Channel {
+		return fmt.Sprintf("https://t.me/%s/%d", m.ForwardFromChat.UserName, m.ForwardFromMessageID)
+	}
+
+	return ""
+}
+
+func (m Message) IsSupported() bool {
+	return m.Text != nil || m.Caption != nil || m.Document != nil || m.Photo != nil || m.Video != nil ||
+		m.Voice != nil || m.VideoNote != nil || m.Audio != nil || m.Animation != nil
+}

plugin/telegram/message_entity.go

@@ -0,0 +1,31 @@
+package telegram
+
+type MessageEntityType string
+
+const (
+	Mention       = "mention"       //  “mention” (@username)
+	Hashtag       = "hashtag"       //  “hashtag” (#hashtag)
+	CashTag       = "cashtag"       //  “cashtag” ($USD)
+	BotCommand    = "bot_command"   //  “bot_command” (/start@jobs_bot)
+	URL           = "url"           //  “url” (https://telegram.org)
+	Email         = "email"         //  “email” (do-not-reply@telegram.org)
+	PhoneNumber   = "phone_number"  //  “phone_number” (+1-212-555-0123)
+	Bold          = "bold"          //  “bold” (bold text)
+	Italic        = "italic"        //  “italic” (italic text)
+	Underline     = "underline"     //  “underline” (underlined text)
+	Strikethrough = "strikethrough" //  “strikethrough” (strikethrough text)
+	Code          = "code"          //  “code” (monowidth string)
+	Pre           = "pre"           //  “pre” (monowidth block)
+	TextLink      = "text_link"     //  “text_link” (for clickable text URLs)
+	TextMention   = "text_mention"  //  “text_mention” (for users without usernames)
+)
+
+// MessageEntity represents one special entity in a text message.
+type MessageEntity struct {
+	Type     MessageEntityType `json:"type"`   // Type of the entity.
+	Offset   int               `json:"offset"` // Offset in UTF-16 code units to the start of the entity
+	Length   int               `json:"length"`
+	URL      string            `json:"url"`      // URL for “text_link” only, url that will be opened after user taps on the text
+	User     *User             `json:"user"`     // User for “text_mention” only, the mentioned user
+	Language string            `json:"language"` // Language for “pre” only, the programming language of the entity text
+}

plugin/telegram/video.go

@@ -0,0 +1,14 @@
+package telegram
+
+// Video represents a video file.
+type Video struct {
+	FileID       string     `json:"file_id"`        // FileID identifier for this file, which can be used to download or reuse
+	FileUniqueID string     `json:"file_unique_id"` // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Width        int        `json:"width"`          // Width video width as defined by sender
+	Height       int        `json:"height"`         // Height video height as defined by sender
+	Duration     int        `json:"duration"`       // Duration of the video in seconds as defined by sender
+	Thumbnail    *PhotoSize `json:"thumb"`          // Thumbnail video thumbnail
+	FileName     string     `json:"file_name"`      // FileName is the original filename as defined by sender
+	MimeType     string     `json:"mime_type"`      // MimeType of a file as defined by sender
+	FileSize     int        `json:"file_size"`
+}

plugin/telegram/video_note.go

@@ -0,0 +1,11 @@
+package telegram
+
+// VideoNote object represents a video message.
+type VideoNote struct {
+	FileID       string     `json:"file_id"`         // FileID identifier for this file, which can be used to download or reuse the file
+	FileUniqueID string     `json:"file_unique_id"`  // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Length       int        `json:"length"`          // Length video width and height (diameter of the video message) as defined by sender
+	Duration     int        `json:"duration"`        // Duration of the video in seconds as defined by sender
+	Thumbnail    *PhotoSize `json:"thumb,omitempty"` // Thumbnail video thumbnail
+	FileSize     int        `json:"file_size"`
+}

plugin/telegram/voice.go

@@ -0,0 +1,10 @@
+package telegram
+
+// Voice represents a voice note.
+type Voice struct {
+	FileID       string `json:"file_id"`        // FileID identifier for this file, which can be used to download or reuse the file
+	FileUniqueID string `json:"file_unique_id"` // FileUniqueID is the unique identifier for this file, which is supposed to be the same over time and for different bots. Can't be used to download or reuse the file.
+	Duration     int    `json:"duration"`       // Duration of the audio in seconds as defined by sender
+	MimeType     string `json:"mime_type"`      // MimeType of the file as defined by sender
+	FileSize     int    `json:"file_size"`
+}

server/telegram.go

@@ -4,8 +4,8 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"path"
 	"strconv"
+	"unicode/utf16"
 
 	"github.com/pkg/errors"
 	apiv1 "github.com/usememos/memos/api/v1"
@@ -30,7 +30,7 @@ const (
 	successMessage = "Success"
 )
 
-func (t *telegramHandler) MessageHandle(ctx context.Context, bot *telegram.Bot, message telegram.Message, blobs map[string][]byte) error {
+func (t *telegramHandler) MessageHandle(ctx context.Context, bot *telegram.Bot, message telegram.Message, attachments []telegram.Attachment) error {
 	reply, err := bot.SendReplyMessage(ctx, message.Chat.ID, message.MessageID, workingMessage)
 	if err != nil {
 		return fmt.Errorf("fail to SendReplyMessage: %s", err)
@@ -65,10 +65,15 @@ func (t *telegramHandler) MessageHandle(ctx context.Context, bot *telegram.Bot,
 	}
 
 	if message.Text != nil {
-		create.Content = *message.Text
+		create.Content = convertToMarkdown(*message.Text, message.Entities)
 	}
-	if blobs != nil && message.Caption != nil {
-		create.Content = *message.Caption
+
+	if message.Caption != nil {
+		create.Content = convertToMarkdown(*message.Caption, message.CaptionEntities)
+	}
+
+	if message.ForwardFromChat != nil {
+		create.Content += fmt.Sprintf("\n\n[Message link](%s)", message.GetMessageLink())
 	}
 
 	memoMessage, err := t.store.CreateMemo(ctx, create)
@@ -78,21 +83,13 @@ func (t *telegramHandler) MessageHandle(ctx context.Context, bot *telegram.Bot,
 	}
 
 	// create resources
-	for filename, blob := range blobs {
-		// TODO support more
-		mime := "application/octet-stream"
-		switch path.Ext(filename) {
-		case ".jpg":
-			mime = "image/jpeg"
-		case ".png":
-			mime = "image/png"
-		}
+	for _, attachment := range attachments {
 		resource, err := t.store.CreateResource(ctx, &store.Resource{
 			CreatorID: creatorID,
-			Filename:  filename,
-			Type:      mime,
-			Size:      int64(len(blob)),
-			Blob:      blob,
+			Filename:  attachment.FileName,
+			Type:      attachment.GetMimeType(),
+			Size:      attachment.FileSize,
+			Blob:      attachment.Data,
 		})
 		if err != nil {
 			_, err := bot.EditMessage(ctx, message.Chat.ID, reply.MessageID, fmt.Sprintf("failed to CreateResource: %s", err), nil)
@@ -158,3 +155,51 @@ func generateKeyboardForMemoID(id int) [][]telegram.InlineKeyboardButton {
 
 	return [][]telegram.InlineKeyboardButton{buttons}
 }
+
+func convertToMarkdown(text string, messageEntities []telegram.MessageEntity) string {
+	insertions := make(map[int]string)
+
+	for _, e := range messageEntities {
+		var before, after string
+
+		// this is supported by the current markdown
+		switch e.Type {
+		case telegram.Bold:
+			before = "**"
+			after = "**"
+		case telegram.Italic:
+			before = "*"
+			after = "*"
+		case telegram.Strikethrough:
+			before = "~~"
+			after = "~~"
+		case telegram.Code:
+			before = "`"
+			after = "`"
+		case telegram.Pre:
+			before = "```" + e.Language
+			after = "```"
+		case telegram.TextLink:
+			before = "["
+			after = fmt.Sprintf(`](%s)`, e.URL)
+		}
+
+		if before != "" {
+			insertions[e.Offset] += before
+			insertions[e.Offset+e.Length] = after + insertions[e.Offset+e.Length]
+		}
+	}
+
+	input := []rune(text)
+	var output []rune
+	utf16pos := 0
+
+	for i := 0; i < len(input); i++ {
+		output = append(output, []rune(insertions[utf16pos])...)
+		output = append(output, input[i])
+		utf16pos += len(utf16.Encode([]rune{input[i]}))
+	}
+	output = append(output, []rune(insertions[utf16pos])...)
+
+	return string(output)
+}