feat(matrix): introduce Gitter and Matrix member count badges (#500)

* feat: add Gitter members badge

* feat: add Matrix members badge with Gitter fallback

* docs(matrix): update examples

* perf(matrix): fail fast if room does NOT exist

* style(gitter): tweak scrapping pattern

api/gitter.ts

@@ -0,0 +1,39 @@
+import got from '../libs/got'
+import { millify } from '../libs/utils'
+import { createBadgenHandler, PathArgs } from '../libs/create-badgen-handler'
+
+const BRAND_COLOR = 'ED1965'
+
+export default createBadgenHandler({
+  title: 'Gitter',
+  examples: {
+    '/gitter/members/redom/lobby': 'members',
+    '/gitter/members/redom/redom': 'members'
+  },
+  handlers: {
+    '/gitter/members/:org/:room': handler
+  }
+})
+
+async function handler ({ org, room }: PathArgs) {
+  const membersCount = await fetchMembersCount(org, room)
+  if (Number.isNaN(membersCount)) {
+    return {
+      subject: 'gitter',
+      status: 'unknown',
+      color: 'grey'
+    }
+  }
+
+  const suffix = membersCount === 1 ? 'member' : 'members'
+  return {
+    subject: 'gitter',
+    status: `${millify(membersCount)} ${suffix}`,
+    color: BRAND_COLOR
+  }
+}
+
+export async function fetchMembersCount(org: string, room: string) {
+  const html = await got(`https://gitter.im/${org}/${room}`).text()
+  return Number(html.match(/"userCount"\s*:\s*(\d+)/)?.[1])
+}

api/matrix.ts

@@ -0,0 +1,84 @@
+import { Got } from 'got'
+import got from '../libs/got'
+import { millify } from '../libs/utils'
+import { fetchMembersCount as fetchGitterMembersCount } from './gitter'
+import { createBadgenHandler, PathArgs } from '../libs/create-badgen-handler'
+
+const BRAND_COLOR = 'black'
+
+export default createBadgenHandler({
+  title: 'Matrix',
+  examples: {
+    '/matrix/members/rust/matrix.org': 'members',
+    '/matrix/members/thisweekinmatrix': 'members',
+    '/matrix/members/archlinux/archlinux.org': 'members',
+    '/matrix/members/redom_redom/gitter.im': 'members'
+  },
+  handlers: {
+    '/matrix/members/:room/:server?': handler
+  }
+})
+
+async function handler ({ room, server = 'matrix.org' }: PathArgs) {
+  const roomName = room.replace(/^#/, '')
+  const membersCount = await fetchMembersCount(roomName, server)
+  if (Number.isNaN(membersCount)) {
+    return {
+      subject: 'matrix',
+      status: 'unknown',
+      color: 'grey'
+    }
+  }
+
+  const status = [
+    millify(membersCount),
+    server === 'gitter.im' ? 'gitter' : '',
+    membersCount === 1 ? 'member' : 'members'
+  ].join(' ')
+
+  return {
+    subject: `#${roomName}:${server}`,
+    status,
+    color: BRAND_COLOR
+  }
+}
+
+async function fetchMembersCount(roomName: string, server: string) {
+  if (server === 'gitter.im') {
+    const [gitterOrg, gitterRoom] = roomName.split('_')
+    return fetchGitterMembersCount(gitterOrg, gitterRoom)
+  }
+  const homeserver = await getHomeserver(server)
+  const client = got.extend({ prefixUrl: `${homeserver}/_matrix/client/r0` })
+  const roomAlias = `#${roomName}:${server}`
+  const room = await findPublicRoom(client, roomAlias)
+  return room?.num_joined_members
+}
+
+// https://matrix.org/docs/spec/client_server/latest#get-well-known-matrix-client
+async function getHomeserver(server: string) {
+  const endpoint = `https://${server}/.well-known/matrix/client`
+  const { 'm.homeserver': homeserver } = await got(endpoint).json<any>()
+  return homeserver?.base_url
+}
+
+// https://matrix.org/docs/spec/client_server/latest#get-matrix-client-r0-publicrooms
+async function findPublicRoom(client: Got, roomAlias: string) {
+  const roomId = await getRoomId(client, roomAlias)
+  const searchParams = new URLSearchParams({ limit: '500' })
+  // eslint-disable-next-line no-constant-condition
+  while (true) {
+    const { chunk, next_batch } = await client.get('publicRooms', { searchParams }).json<any>()
+    const room = chunk.find(it => it.room_id === roomId)
+    if (room) return room
+    if (!next_batch) return
+    searchParams.set('since', next_batch)
+  }
+}
+
+// https://matrix.org/docs/spec/client_server/latest#get-matrix-client-r0-directory-room-roomalias
+async function getRoomId(client: Got, roomAlias: string) {
+  const endpoint = `directory/room/${encodeURIComponent(roomAlias)}`
+  const { room_id } = await client.get(endpoint).json<any>()
+  return room_id
+}

libs/badge-list.ts

@@ -61,6 +61,9 @@ export const liveBadgeList = [
   // social
   'devrant',
   'peertube',
+  // chat
+  'gitter',
+  'matrix',
   // utilities
   'opencollective',
   'keybase',