Implement the speedbump

d2m/actions/delete-message.js

@@ -4,21 +4,25 @@ const passthrough = require("../../passthrough")
 const {sync, db, select, from} = passthrough
 /** @type {import("../../matrix/api")} */
 const api = sync.require("../../matrix/api")
+/** @type {import("./speedbump")} */
+const speedbump = sync.require("./speedbump")
 
 /**
  * @param {import("discord-api-types/v10").GatewayMessageDeleteDispatchData} data
  */
 async function deleteMessage(data) {
-	const roomID = select("channel_room", "room_id", {channel_id: data.channel_id}).pluck().get()
-	if (!roomID) return
+	const row = select("channel_room", ["room_id", "speedbump_id", "speedbump_checked"], {channel_id: data.channel_id}).get()
+	if (!row) return
 
 	const eventsToRedact = select("event_message", "event_id", {message_id: data.id}).pluck().all()
 	db.prepare("DELETE FROM message_channel WHERE message_id = ?").run(data.id)
 	db.prepare("DELETE FROM event_message WHERE message_id = ?").run(data.id)
 	for (const eventID of eventsToRedact) {
 		// Unfortunately, we can't specify a sender to do the redaction as, unless we find out that info via the audit logs
-		await api.redactEvent(roomID, eventID)
+		await api.redactEvent(row.room_id, eventID)
 	}
+
+	speedbump.updateCache(data.channel_id, row.speedbump_id, row.speedbump_checked)
 }
 
 /**

d2m/actions/speedbump.js

@@ -0,0 +1,51 @@
+// @ts-check
+
+const DiscordTypes = require("discord-api-types/v10")
+const passthrough = require("../../passthrough")
+const {discord, db} = passthrough
+
+const SPEEDBUMP_SPEED = 4000 // 4 seconds delay
+const SPEEDBUMP_UPDATE_FREQUENCY = 2 * 60 * 60 // 2 hours
+
+/** @type {Set<any>} */
+const KNOWN_BOTS = new Set([
+	"466378653216014359" // PluralKit
+])
+
+/**
+ * Fetch new speedbump data for the channel and put it in the database as cache
+ * @param {string} channelID
+ * @param {string?} speedbumpID
+ * @param {number?} speedbumpChecked
+ */
+async function updateCache(channelID, speedbumpID, speedbumpChecked) {
+	const now = Math.floor(Date.now() / 1000)
+	if (speedbumpChecked && now - speedbumpChecked < SPEEDBUMP_UPDATE_FREQUENCY) return
+	const webhooks = await discord.snow.webhook.getChannelWebhooks(channelID)
+	const found = webhooks.find(b => KNOWN_BOTS.has(b.application_id))?.application_id || null
+	db.prepare("UPDATE channel_room SET speedbump_id = ?, speedbump_checked = ? WHERE channel_id = ?").run(found, now, channelID)
+}
+
+/** @type {Set<string>} set of messageID */
+const bumping = new Set()
+
+/**
+ * Slow down a message. After it passes the speedbump, return whether it's okay or if it's been deleted.
+ * @param {string} messageID
+ */
+async function doSpeedbump(messageID) {
+	bumping.add(messageID)
+	await new Promise(resolve => setTimeout(resolve, SPEEDBUMP_SPEED))
+	return !bumping.delete(messageID)
+}
+
+/**
+ * @param {string} messageID
+ */
+function onMessageDelete(messageID) {
+	bumping.delete(messageID)
+}
+
+module.exports.updateCache = updateCache
+module.exports.doSpeedbump = doSpeedbump
+module.exports.onMessageDelete = onMessageDelete