out-of-your-element/m2d/actions/add-reaction.js

// @ts-check

const assert = require("assert").strict
const Ty = require("../../types")

const passthrough = require("../../passthrough")
const {discord, sync, db, select} = passthrough

/**
 * @param {Ty.Event.Outer<Ty.Event.M_Reaction>} event
 */
async function addReaction(event) {
	const channelID = select("channel_room", "channel_id", "WHERE room_id = ?").pluck().get(event.room_id)
	if (!channelID) return // We just assume the bridge has already been created
	const messageID = select("event_message", "message_id", "WHERE event_id = ? AND part = 0").pluck().get(event.content["m.relates_to"].event_id) // 0 = primary
	if (!messageID) return // Nothing can be done if the parent message was never bridged.

	// no need to sync the matrix member to the other side. but if I did need to, this is where I'd do it

	let emoji = event.content["m.relates_to"].key // TODO: handle custom text or emoji reactions
	let encoded = encodeURIComponent(emoji)
	let encodedTrimmed = encoded.replace(/%EF%B8%8F/g, "")

	// https://github.com/discord/discord-api-docs/issues/2723#issuecomment-807022205 ????????????

	const forceTrimmedList = [
		"%F0%9F%91%8D", // 👍
		"%E2%AD%90" // ⭐
	]

	let discordPreferredEncoding =
		( forceTrimmedList.includes(encodedTrimmed) ? encodedTrimmed
		: encodedTrimmed !== encoded && [...emoji].length === 2 ? encoded
		: encodedTrimmed)

	console.log("add reaction from matrix:", emoji, encoded, encodedTrimmed, "chosen:", discordPreferredEncoding)

	return discord.snow.channel.createReaction(channelID, messageID, discordPreferredEncoding)
}

module.exports.addReaction = addReaction