Support m->d redacting messages and reactions

m2d/actions/add-reaction.js

@@ -5,6 +5,8 @@ const Ty = require("../../types")
 
 const passthrough = require("../../passthrough")
 const {discord, sync, db, select} = passthrough
+/** @type {import("../converters/utils")} */
+const utils = sync.require("../converters/utils")
 
 /**
  * @param {Ty.Event.Outer<Ty.Event.M_Reaction>} event
@@ -48,7 +50,9 @@ async function addReaction(event) {
 		console.log("add reaction from matrix:", emoji, encoded, encodedTrimmed, "chosen:", discordPreferredEncoding)
 	}
 
-	return discord.snow.channel.createReaction(channelID, messageID, discordPreferredEncoding) // acting as the discord bot itself
+	await discord.snow.channel.createReaction(channelID, messageID, discordPreferredEncoding) // acting as the discord bot itself
+
+	db.prepare("REPLACE INTO reaction (hashed_event_id, message_id, encoded_emoji) VALUES (?, ?, ?)").run(utils.getEventIDHash(event.event_id), messageID, discordPreferredEncoding)
 }
 
 module.exports.addReaction = addReaction

m2d/actions/redact.js

@@ -0,0 +1,39 @@
+// @ts-check
+
+const assert = require("assert").strict
+const Ty = require("../../types")
+
+const passthrough = require("../../passthrough")
+const {discord, sync, db, select, from} = passthrough
+/** @type {import("../converters/utils")} */
+const utils = sync.require("../converters/utils")
+
+/**
+ * @param {Ty.Event.Outer_M_Room_Redaction} event
+ */
+async function deleteMessage(event) {
+	const row = from("event_message").join("message_channel", "message_id").select("channel_id", "message_id").and("WHERE event_id = ?").get(event.event_id)
+	if (!row) return
+	return discord.snow.channel.deleteMessage(row.channel_id, row.message_id, event.content.reason)
+}
+
+/**
+ * @param {Ty.Event.Outer_M_Room_Redaction} event
+ */
+async function removeReaction(event) {
+	const hash = utils.getEventIDHash(event.redacts)
+	const row = from("reaction").join("message_channel", "message_id").select("channel_id", "message_id", "encoded_emoji").and("WHERE hashed_event_id = ?").get(hash)
+	if (!row) return
+	return discord.snow.channel.deleteReactionSelf(row.channel_id, row.message_id, row.encoded_emoji)
+}
+
+/**
+ * Try everything that could possibly be redacted.
+ * @param {Ty.Event.Outer_M_Room_Redaction} event
+ */
+async function handle(event) {
+	await deleteMessage(event)
+	await removeReaction(event)
+}
+
+module.exports.handle = handle

m2d/converters/utils.js

@@ -38,7 +38,7 @@ function getPublicUrlForMxc(mxc) {
 /**
  * Event IDs are really big and have more entropy than we need.
  * If we want to store the event ID in the database, we can store a more compact version by hashing it with this.
- * Choosing a 64-bit non-cryptographic hash as only a 32-bit hash will see birthday collisions unreasonably frequently: https://en.wikipedia.org/wiki/Birthday_attack#Mathematics
+ * I choose a 64-bit non-cryptographic hash as only a 32-bit hash will see birthday collisions unreasonably frequently: https://en.wikipedia.org/wiki/Birthday_attack#Mathematics
  * xxhash outputs an unsigned 64-bit integer.
  * Converting to a signed 64-bit integer with no bit loss so that it can be stored in an SQLite integer field as-is: https://www.sqlite.org/fileformat2.html#record_format
  * This should give very efficient storage with sufficient entropy.

m2d/event-dispatcher.js

@@ -12,6 +12,8 @@ const {discord, db, sync, as} = require("../passthrough")
 const sendEvent = sync.require("./actions/send-event")
 /** @type {import("./actions/add-reaction")} */
 const addReaction = sync.require("./actions/add-reaction")
+/** @type {import("./actions/redact")} */
+const redact = sync.require("./actions/redact")
 /** @type {import("./converters/utils")} */
 const utils = sync.require("./converters/utils")
 /** @type {import("../matrix/api")}) */
@@ -101,6 +103,15 @@ async event => {
 	}
 }))
 
+sync.addTemporaryListener(as, "type:m.room.redaction", guard("m.room.redaction",
+/**
+ * @param {Ty.Event.Outer_M_Room_Redaction} event it is a m.room.redaction because that's what this listener is filtering for
+ */
+async event => {
+	if (utils.eventSenderIsFromDiscord(event.sender)) return
+	await redact.handle(event)
+}))
+
 sync.addTemporaryListener(as, "type:m.room.avatar", guard("m.room.avatar",
 /**
  * @param {Ty.Event.StateOuter<Ty.Event.M_Room_Avatar>} event