matterbridge/bridge/discord/webhook.go

package bdiscord

import (
	"bytes"
	"strings"

	"github.com/42wim/matterbridge/bridge/config"
	"github.com/42wim/matterbridge/bridge/helper"
	"github.com/bwmarrin/discordgo"
)

// shouldMessageUseWebhooks checks if have a channel specific webhook, if we're not using auto webhooks
func (b *Bdiscord) shouldMessageUseWebhooks(msg *config.Message) bool {
	if b.useAutoWebhooks {
		return true
	}

	b.channelsMutex.RLock()
	defer b.channelsMutex.RUnlock()
	if ci, ok := b.channelInfoMap[msg.Channel+b.Account]; ok {
		if ci.Options.WebhookURL != "" {
			return true
		}
	}
	return false
}

// maybeGetLocalAvatar checks if UseLocalAvatar contains the message's
// account or protocol, and if so, returns the Discord avatar (if exists)
func (b *Bdiscord) maybeGetLocalAvatar(msg *config.Message) string {
	for _, val := range b.GetStringSlice("UseLocalAvatar") {
		if msg.Protocol != val && msg.Account != val {
			continue
		}

		member, err := b.getGuildMemberByNick(msg.Username)
		if err != nil {
			return ""
		}

		return member.User.AvatarURL("")
	}
	return ""
}

func (b *Bdiscord) webhookSendTextOnly(msg *config.Message, channelID string) (string, error) {
	msgParts := helper.ClipOrSplitMessage(msg.Text, MessageLength, b.GetString("MessageClipped"), b.GetInt("MessageSplitMaxCount"))
	msgIds := []string{}
	for _, msgPart := range msgParts {
		res, err := b.transmitter.Send(
			channelID,
			&discordgo.WebhookParams{
				Content:         msgPart,
				Username:        msg.Username,
				AvatarURL:       msg.Avatar,
				AllowedMentions: b.getAllowedMentions(),
			},
		)
		if err != nil {
			return "", err
		} else {
			msgIds = append(msgIds, res.ID)
		}
	}
	// Exploit that a discord message ID is actually just a large number, so we encode a list of IDs by separating them with ";".
	return strings.Join(msgIds, ";"), nil
}

func (b *Bdiscord) webhookSendFilesOnly(msg *config.Message, channelID string) error {
	for _, f := range msg.Extra["file"] {
		fi := f.(config.FileInfo) //nolint:forcetypeassert
		var err error

		if fi.URL != "" {
			err = b.webhookSendFileFromURL(msg, channelID, &fi)
		} else if fi.Data != nil {
			err = b.webhookSendFileFromData(msg, channelID, &fi)
		} else {
			b.Log.Errorf("Attachment %#v for message %#v had neither Data nor URL", fi, msg)
		}

		if err != nil {
			b.Log.Errorf("Could not send attachment %#v for message %#v: %s", fi, msg, err)
			return err
		}
	}

	return nil
}

func (b *Bdiscord) webhookSendFileFromData(msg *config.Message, channelID string, fi *config.FileInfo) error {
	file := discordgo.File{
		Name:        fi.Name,
		ContentType: "",
		Reader:      bytes.NewReader(*fi.Data),
	}
	content := fi.Comment

	// Cannot use the resulting ID for any edits anyway, so throw it away.
	// This has to be re-enabled when we implement message deletion.
	_, err := b.transmitter.Send(
		channelID,
		&discordgo.WebhookParams{
			Username:        msg.Username,
			AvatarURL:       msg.Avatar,
			Files:           []*discordgo.File{&file},
			Content:         content,
			AllowedMentions: b.getAllowedMentions(),
		},
	)
	return err
}

func (b *Bdiscord) webhookSendFileFromURL(msg *config.Message, channelID string, fi *config.FileInfo) error {
	// discord client will display any file url as an inline embed,
	// without us having to do anything special.
	_, err := b.transmitter.Send(
		channelID,
		&discordgo.WebhookParams{
			Content:             fi.URL,
			Username:            msg.Username,
			AvatarURL:           msg.Avatar,
			AllowedMentions:     b.getAllowedMentions(),
		},
	)
	return err
}

// webhookSend send one or more message via webhook, taking care of file
// uploads (from slack, telegram or mattermost).
// Returns messageID and error.
func (b *Bdiscord) webhookSend(msg *config.Message, channelID string) (string, error) {
	var (
		res string
		err error
	)

	// If avatar is unset, mutate the message to include the local avatar (but only if settings say we should do this)
	if msg.Avatar == "" {
		msg.Avatar = b.maybeGetLocalAvatar(msg)
	}

	// WebhookParams can have either `Content` or `File`.

	// We can't send empty messages.
	if msg.Text != "" {
		res, err = b.webhookSendTextOnly(msg, channelID)
	}

	if err == nil && msg.Extra != nil {
		err = b.webhookSendFilesOnly(msg, channelID)
	}

	return res, err
}

func (b *Bdiscord) handleEventWebhook(msg *config.Message, channelID string) (string, error) {
	// skip events
	if msg.Event != "" && msg.Event != config.EventUserAction && msg.Event != config.EventJoinLeave && msg.Event != config.EventTopicChange {
		return "", nil
	}

	// skip empty messages
	if msg.Text == "" && (msg.Extra == nil || len(msg.Extra["file"]) == 0) {
		b.Log.Debugf("Skipping empty message %#v", msg)
		return "", nil
	}

	// discord username must be [0..32] max
	if len(msg.Username) > 32 {
		msg.Username = msg.Username[0:32]
	}

	if msg.ID != "" {
		// Exploit that a discord message ID is actually just a large number, and we encode a list of IDs by separating them with ";".
		msgIds := strings.Split(msg.ID, ";")
		msgParts := helper.ClipOrSplitMessage(b.replaceUserMentions(msg.Text), MessageLength, b.GetString("MessageClipped"), len(msgIds))
		for len(msgParts) < len(msgIds) {
			msgParts = append(msgParts, "((obsoleted by edit))")
		}
		b.Log.Debugf("Editing webhook message")
		var editErr error = nil
		for i := range msgParts {
			// In case of split-messages where some parts remain the same (i.e. only a typo-fix in a huge message), this causes some noop-updates.
			// TODO: Optimize away noop-updates of un-edited messages
			editErr = b.transmitter.Edit(channelID, msgIds[i], &discordgo.WebhookParams{
				Content:         msgParts[i],
				Username:        msg.Username,
				AllowedMentions: b.getAllowedMentions(),
			})
			if editErr != nil {
				break
			}
		}
		if editErr == nil {
			return msg.ID, nil
		}
		b.Log.Errorf("Could not edit webhook message(s): %s; sending as new message(s) instead", editErr)
	}

	b.Log.Debugf("Processing webhook sending for message %#v", msg)
	msg.Text = b.replaceUserMentions(msg.Text)
	msgID, err := b.webhookSend(msg, channelID)
	if err != nil {
		b.Log.Errorf("Could not broadcast via webhook for message %#v: %s", msgID, err)
		return "", err
	}
	return msgID, nil
}