implement room preview

src/Link.js

@@ -23,7 +23,7 @@ const EVENT_WITH_ROOMALIAS_PATTERN = /^[#]([^:]*):(.+)\/\$([^:]+):(.+)$/;
 const USERID_PATTERN = /^@([^:]+):(.+)$/;
 const GROUPID_PATTERN = /^\+([^:]+):(.+)$/;
 
-const IdentifierKind = createEnum(
+export const IdentifierKind = createEnum(
 	"RoomId",
 	"RoomAlias",
 	"UserId",

src/preview/HomeServer.js

@@ -43,7 +43,7 @@ export class HomeServer {
 	}
 
 	async getUserProfile(userId) {
-		const {body} = await this._request(`${this.baseURL}/_matrix/client/r0/profile/${userId}`, {method: "GET"}).response();
+		const {body} = await this._request(`${this.baseURL}/_matrix/client/r0/profile/${encodeURIComponent(userId)}`).response();
 		return body;
 	}
 
@@ -51,8 +51,28 @@ export class HomeServer {
 		//`/_matrix/client/r0/groups/${groupId}/profile`
 	}
 
-	getPublicRooms() {
+	async findPublicRoomById(roomId) {
+		const {body, status} = await this._request(`${this.baseURL}/_matrix/client/r0/directory/list/room/${encodeURIComponent(roomId)}`).response();
+		if (status !== 200 || body.visibility !== "public") {
+			return;
+		}
+		let nextBatch;
+		do {
+			const queryParams = encodeQueryParams({limit: 10000, since: nextBatch});
+			const {body, status} = await this._request(`${this.baseURL}/_matrix/client/r0/publicRooms?${queryParams}`).response();
+			nextBatch = body.next_batch;
+			const publicRoom = body.chunk.find(c => c.room_id === roomId);
+			if (publicRoom) {
+				return publicRoom;
+			}
+		} while (nextBatch);
+	}
 
+	async getRoomIdFromAlias(alias) {
+		const {status, body}  = await this._request(`${this.baseURL}/_matrix/client/r0/directory/room/${encodeURIComponent(alias)}`).response();
+		if (status === 200) {
+			return body.room_id;
+		}
 	}
 
 	mxcUrlThumbnail(url, width, height, method) {
@@ -74,3 +94,15 @@ function parseMxcUrl(url) {
         return null;
     }
 }
+
+function encodeQueryParams(queryParams) {
+    return Object.entries(queryParams || {})
+        .filter(([, value]) => value !== undefined)
+        .map(([name, value]) => {
+            if (typeof value === "object") {
+                value = JSON.stringify(value);
+            }
+            return `${encodeURIComponent(name)}=${encodeURIComponent(value)}`;
+        })
+        .join("&");
+}

src/preview/PreviewViewModel.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {LinkKind, getLabelForLinkKind} from "../Link.js";
+import {LinkKind, IdentifierKind, getLabelForLinkKind} from "../Link.js";
 import {ViewModel} from "../utils/ViewModel.js";
 import {resolveServer} from "./HomeServer.js";
 import {ClientListViewModel} from "../client/ClientListViewModel.js";
@@ -32,6 +32,7 @@ export class PreviewViewModel extends ViewModel {
 		this.loading = false;
 		this.name = null;
 		this.avatarUrl = null;
+		this.identifier = null;
 		this.previewDomain = null;
 		this.clientsViewModel = null;
 		this.acceptInstructions = null;
@@ -51,6 +52,10 @@ export class PreviewViewModel extends ViewModel {
 				switch (this._link.kind) {
 					case LinkKind.User:
 						await this._loadUserPreview(homeserver, this._link.identifier);
+						break;
+					case LinkKind.Room:
+						await this._loadRoomPreview(homeserver, this._link);
+						break;
 				}
 				// assume we're done if nothing threw
 				this.previewDomain = server;
@@ -69,10 +74,24 @@ export class PreviewViewModel extends ViewModel {
 		this.avatarUrl = profile.avatar_url ?
 			homeserver.mxcUrlThumbnail(profile.avatar_url, 64, 64, "crop") :
 			null;
+		this.identifier = userId;
 	}
 
-	get identifier() {
-		return this._link.identifier;
+	async _loadRoomPreview(homeserver, link) {
+		let publicRoom;
+		if (link.identifierKind === IdentifierKind.RoomId) {
+			publicRoom = await homeserver.findPublicRoomById(link.identifier);
+		} else if (link.identifierKind === IdentifierKind.RoomAlias) {
+			const roomId = await homeserver.getRoomIdFromAlias(link.identifier);
+			if (roomId) {
+				publicRoom = await homeserver.findPublicRoomById(roomId);
+			}
+		}
+		this.name = publicRoom?.name || publicRoom?.canonical_alias || link.identifier;
+		this.avatarUrl = publicRoom?.avatar_url ? 
+			homeserver.mxcUrlThumbnail(publicRoom.avatar_url, 64, 64, "crop") :
+			null;
+		this.identifier = `${publicRoom?.canonical_alias || link.identifier} | ${publicRoom?.num_joined_members} members`;
 	}
 
 	get showClientsLabel() {

src/utils/xhr.js

@@ -79,7 +79,10 @@ function xhrAsPromise(xhr, method, url) {
     });
 }
 
-export function xhrRequest(url, options) {
+export function xhrRequest(url, options = {}) {
+    if (!options.method) {
+        options.method = "GET";
+    }
     let {cache, body, method} = options;
     if (!cache) {
         url = addCacheBuster(url);