Slack to discord message migration tool

go.mod

module github.com/Code-Hex/slack2discord

go 1.18

require (
	github.com/Code-Hex/dd v1.1.0 // indirect
	github.com/bwmarrin/discordgo v0.25.0 // indirect
	github.com/gorilla/websocket v1.4.2 // indirect
	github.com/slack-go/slack v0.11.2 // indirect
	golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b // indirect
	golang.org/x/sys v0.0.0-20210927094055-39ccf1dd6fa6 // indirect
)

main.go

package main

import (
	"context"
	"fmt"
	"html"
	"os"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/bwmarrin/discordgo"
	"github.com/slack-go/slack"
)

func main() {
	if err := run(context.Background()); err != nil {
		fmt.Fprintf(os.Stderr, "failed to run: %q", err)
		os.Exit(1)
	}
}

const slackChannel = "C..." // slack channel ID
const discordChannel = "..." // discord channel ID

// <              # opening angle bracket
// ([^>\|]+)      # link
// (?:\|([^>]+))? # label
// >              # closing angle bracket
var re = regexp.MustCompile(`<([^>\|]+)(?:\|([^>]+))?>`)

func run(ctx context.Context) error {
	slackClient := slack.New("xoxp-...")
	session, err := discordgo.New("...")
	if err != nil {
		return err
	}

	messages, err := history(ctx, slackClient)
	if err != nil {
		return err
	}
	for _, m := range messages {
		fmt.Println("-------", m.Timestamp)
		fmt.Println(m.Text)
		_, err = session.ChannelMessageSend(discordChannel, m.Text)
		if err != nil {
			return fmt.Errorf("failed to send message: %w", err)
		}
		time.Sleep(time.Millisecond * 500)
	}
	// fmt.Println(dd.Dump(messages))
	return nil
}

type Message struct {
	Text      string
	Timestamp string // to use save point
}

func history(ctx context.Context, slackClient *slack.Client) ([]*Message, error) {
	var (
		cursor   string
		messages []*Message
	)
	for i := 0; ; i++ {
		resp, err := slackClient.GetConversationHistoryContext(ctx, &slack.GetConversationHistoryParameters{
			ChannelID: slackChannel,
			Cursor:    cursor,
		})
		if err != nil {
			return nil, err
		}
		for _, message := range resp.Messages {
			// If failed, you can continue to specify the timestamp here!
			// if message.Timestamp <= "1648392833.619319" {
			// 	continue
			// }
			text := strings.TrimSpace(message.Text)
			if text == "" {
				continue
			}
			if strings.Contains(text, "さんがチャンネルに参加しました") {
				continue
			}
			if strings.Contains(text, "がこのチャンネルの説明を") {
				continue
			}
			replacedText := re.ReplaceAllStringFunc(text, func(s string) string {
				parts := re.FindStringSubmatch(s)
				link := parts[1]
				return link
			})

			t, err := ts2time(message.Timestamp)
			if err != nil {
				return nil, err
			}

			content := fmt.Sprintf("(%s)\n\n%s", t.Format("2006-01-02 15:04:05"), html.UnescapeString(replacedText))
			messages = append(messages, &Message{
				Text:      content,
				Timestamp: message.Timestamp,
			})
		}
		if !resp.HasMore {
			break
		}
		cursor = resp.ResponseMetaData.NextCursor
		time.Sleep(time.Millisecond * 500)
		fmt.Println(i, len(messages), cursor)
	}
	return reverse(messages), nil
}

var jst *time.Location
var once sync.Once

func getJST() *time.Location {
	once.Do(func() {
		jst, _ = time.LoadLocation("Asia/Tokyo")
	})
	return jst
}

func ts2time(ts string) (time.Time, error) {
	sep := strings.Split(ts, ".")
	if len(sep) != 2 {
		return time.Time{}, fmt.Errorf("unexpected ts: %s", ts)
	}
	sec, ms := sep[0], sep[1]
	seci, err := strconv.Atoi(sec)
	if err != nil {
		return time.Time{}, fmt.Errorf("seci: %w", err)
	}
	msi, err := strconv.Atoi(ms)
	if err != nil {
		return time.Time{}, fmt.Errorf("msi: %w", err)
	}
	return time.Unix(int64(seci), int64(msi)).In(getJST()), nil
}

func reverse(s []*Message) []*Message {
	for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
		s[i], s[j] = s[j], s[i]
	}
	return s
}

Get Discord API Token for yours!

Discord の自分のアカウントの Token を取得しよう！

Get Slack API for yours!

You need to get user (xoxp-) token.

• https://stackoverflow.com/a/67795540
• Your Apps > OAuth & Permissions > User Token Scopes

User Token Scopes

Scopes that access user data and act on behalf of users that authorize them.

OAuth Scope	Description
channels:history	View messages and other content in a user’s public channels
im:history	View messages and other content in a user’s direct messages