m->d: Users who aren't joined can be mentioned

This works by writing @name in the message, where `name` is the username
or displayname of the person in the guild you want to mention. If it
matched, the person will be joined and mentioned on their side.

Unfortunately this requires you to guess the person's name, and may lead
to embarrassment if it doesn't activate as you intended. Good luck!

m2d/actions/send-event.js

@@ -73,7 +73,7 @@ async function sendEvent(event) {
 
 	// 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 {messagesToEdit, messagesToSend, messagesToDelete} = await eventToMessage.eventToMessage(event, guild, {api})
+	let {messagesToEdit, messagesToSend, messagesToDelete} = await eventToMessage.eventToMessage(event, guild, {api, snow: discord.snow})
 
 	messagesToEdit = await Promise.all(messagesToEdit.map(async e => {
 		e.message = await resolvePendingFiles(e.message)

m2d/converters/event-to-message.js

@@ -259,7 +259,7 @@ async function uploadEndOfMessageSpriteSheet(content, attachments, pendingFiles)
 /**
  * @param {Ty.Event.Outer_M_Room_Message | Ty.Event.Outer_M_Room_Message_File | Ty.Event.Outer_M_Sticker | Ty.Event.Outer_M_Room_Message_Encrypted_File} event
  * @param {import("discord-api-types/v10").APIGuild} guild
- * @param {{api: import("../../matrix/api")}} di simple-as-nails dependency injection for the matrix API
+ * @param {{api: import("../../matrix/api"), snow: import("snowtransfer").SnowTransfer}} di simple-as-nails dependency injection for the matrix API
  */
 async function eventToMessage(event, guild, di) {
 	/** @type {(DiscordTypes.RESTPostAPIWebhookWithTokenJSONBody & {files?: {name: string, file: Buffer | Readable}[]})[]} */
@@ -289,6 +289,8 @@ async function eventToMessage(event, guild, di) {
 	const attachments = []
 	/** @type {({name: string, url: string} | {name: string, url: string, key: string, iv: string} | {name: string, buffer: Buffer})[]} */
 	const pendingFiles = []
+	/** @type {DiscordTypes.APIUser[]} */
+	const ensureJoined = []
 
 	// Convert content depending on what the message is
 	if (event.type === "m.room.message" && (event.content.msgtype === "m.text" || event.content.msgtype === "m.emote")) {
@@ -502,6 +504,17 @@ async function eventToMessage(event, guild, di) {
 
 	content = displayNameRunoff + replyLine + content
 
+	// Handling written @mentions: we need to look for candidate Discord members to join to the room
+	let writtenMentionMatch = content.match(/(?:^|[^"<>/A-Za-z0-9])@([A-Za-z][A-Za-z0-9._\[\]\(\)-]+):?/d) // d flag requires Node 16+
+	if (writtenMentionMatch) {
+		const results = await di.snow.guild.searchGuildMembers(guild.id, {query: writtenMentionMatch[1]})
+		if (results[0]) {
+			assert(results[0].user)
+			content = content.slice(0, writtenMentionMatch.index) + `<@${results[0].user.id}>` + content.slice(writtenMentionMatch.index + writtenMentionMatch[0].length)
+			ensureJoined.push(results[0].user)
+		}
+	}
+
 	// Split into 2000 character chunks
 	const chunks = chunk(content, 2000)
 	messages = messages.concat(chunks.map(content => ({
@@ -543,7 +556,8 @@ async function eventToMessage(event, guild, di) {
 	return {
 		messagesToEdit,
 		messagesToSend,
-		messagesToDelete: messageIDsToEdit
+		messagesToDelete: messageIDsToEdit,
+		ensureJoined
 	}
 }
 

m2d/converters/event-to-message.test.js

@@ -63,6 +63,7 @@ test("event2message: body is used when there is no formatted_body", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -89,8 +90,15 @@ test("event2message: any markdown in body is escaped, except strikethrough", asy
 			unsigned: {
 				age: 405299
 			}
+		}, {}, {
+			snow: {
+				guild: {
+					searchGuildMembers: () => []
+				}
+			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -122,6 +130,7 @@ test("event2message: links in formatted body are not broken", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -151,6 +160,7 @@ test("event2message: links in plaintext body are not broken", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -181,6 +191,7 @@ test("event2message: basic html is converted to markdown", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -211,6 +222,7 @@ test("event2message: spoilers work", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -241,6 +253,7 @@ test("event2message: markdown syntax is escaped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -271,6 +284,7 @@ test("event2message: html lines are bridged correctly", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -301,6 +315,7 @@ test("event2message: html lines are bridged correctly", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -332,6 +347,7 @@ test("event2message: whitespace is collapsed", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -364,6 +380,7 @@ test("event2message: lists are bridged correctly", async t => {
 			"room_id": "!BpMdOUkWWhFxmTrENV:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -392,6 +409,7 @@ test("event2message: long messages are split", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -426,6 +444,7 @@ test("event2message: code blocks work", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -457,6 +476,7 @@ test("event2message: code block contents are formatted correctly and not escaped
 			"room_id": "!BpMdOUkWWhFxmTrENV:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -487,6 +507,7 @@ test("event2message: quotes have an appropriate amount of whitespace", async t =
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -528,6 +549,7 @@ test("event2message: lists have appropriate line breaks", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -556,6 +578,7 @@ test("event2message: m.emote plaintext works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -586,6 +609,7 @@ test("event2message: m.emote markdown syntax is escaped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -633,6 +657,7 @@ test("event2message: rich reply to a sim user", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -709,6 +734,7 @@ test("event2message: rich reply to an already-edited message will quote the new
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -756,6 +782,7 @@ test("event2message: should avoid using blockquote contents as reply preview in
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -841,6 +868,7 @@ test("event2message: should include a reply preview when message ends with a blo
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -921,6 +949,7 @@ test("event2message: should include a reply preview when replying to a descripti
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -970,6 +999,7 @@ test("event2message: entities are not escaped in main message or reply preview",
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1048,6 +1078,7 @@ test("event2message: editing a rich reply to a sim user", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1144874214311067708",
@@ -1102,6 +1133,7 @@ test("event2message: editing a plaintext body message", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1153,6 +1185,7 @@ test("event2message: editing a plaintext message to be longer", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1208,6 +1241,7 @@ test("event2message: editing a plaintext message to be shorter", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: ["1145688633186193481"],
 			messagesToEdit: [{
 				id: "1145688633186193480",
@@ -1265,6 +1299,7 @@ test("event2message: editing a formatted body message", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1317,6 +1352,7 @@ test("event2message: rich reply to a matrix user's long message with formatting"
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1376,6 +1412,7 @@ test("event2message: rich reply to an image", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1427,6 +1464,7 @@ test("event2message: rich reply to a spoiler should ensure the spoiler is hidden
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1478,6 +1516,7 @@ test("event2message: with layered rich replies, the preview should only be the r
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1508,6 +1547,7 @@ test("event2message: raw mentioning discord users in plaintext body works", asyn
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1538,6 +1578,7 @@ test("event2message: raw mentioning discord users in formatted body works", asyn
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1568,6 +1609,7 @@ test("event2message: mentioning discord users works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1598,6 +1640,7 @@ test("event2message: mentioning matrix users works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1628,6 +1671,7 @@ test("event2message: mentioning bridged rooms works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1658,6 +1702,7 @@ test("event2message: colon after mentions is stripped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1699,6 +1744,7 @@ test("event2message: caches the member if the member is not known", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1743,6 +1789,7 @@ test("event2message: skips caching the member if the member does not exist, some
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1786,6 +1833,7 @@ test("event2message: overly long usernames are shifted into the message content"
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1818,6 +1866,7 @@ test("event2message: overly long usernames are not treated specially when the ms
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1847,6 +1896,7 @@ test("event2message: text attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1881,6 +1931,7 @@ test("event2message: image attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1930,6 +1981,7 @@ test("event2message: encrypted image attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1974,6 +2026,7 @@ test("event2message: stickers work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2002,6 +2055,7 @@ test("event2message: static emojis work", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2028,6 +2082,7 @@ test("event2message: animated emojis work", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2054,6 +2109,7 @@ test("event2message: unknown emojis in the middle are linked", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2065,6 +2121,53 @@ test("event2message: unknown emojis in the middle are linked", async t => {
 	)
 })
 
+test("event2message: guessed @mentions may join members to mention", async t => {
+	let called = 0
+	const subtext = {
+		user: {
+			id: "321876634777218072",
+			username: "subtext",
+			discriminator: "0"
+		}
+	}
+	t.deepEqual(
+		await eventToMessage({
+			type: "m.room.message",
+			sender: "@cadence:cadence.moe",
+			content: {
+				msgtype: "m.text",
+				body: "@subtext: what food would you like to order?"
+			},
+			event_id: "$u5gSwSzv_ZQS3eM00mnTBCor8nx_A_AwuQz7e59PZk8",
+			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
+		}, {
+			id: "112760669178241024"
+		}, {
+			snow: {
+				guild: {
+					async searchGuildMembers(guildID, options) {
+						called++
+						t.equal(guildID, "112760669178241024")
+						t.deepEqual(options, {query: "subtext"})
+						return [subtext]
+					}
+				}
+			}
+		}),
+		{
+			messagesToDelete: [],
+			messagesToEdit: [],
+			messagesToSend: [{
+				username: "cadence [they]",
+				content: "<@321876634777218072> what food would you like to order?",
+				avatar_url: undefined
+			}],
+			ensureJoined: [subtext.user]
+		}
+	)
+	t.equal(called, 1, "searchGuildMembers should be called once")
+})
+
 slow()("event2message: unknown emoji in the end is reuploaded as a sprite sheet", async t => {
 	const messages = await eventToMessage({
 		type: "m.room.message",