From 3a5b7c1d0ed4939e9e6b23b621da7c83a3140f6d Mon Sep 17 00:00:00 2001
From: Bruno Windels <bruno@windels.cloud>
Date: Mon, 23 Aug 2021 18:47:36 +0200
Subject: [PATCH] support well-known lookup

---
 src/matrix/SessionContainer.js | 22 +++++++++---
 src/matrix/well-known.js       | 64 ++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+), 4 deletions(-)
 create mode 100644 src/matrix/well-known.js

diff --git a/src/matrix/SessionContainer.js b/src/matrix/SessionContainer.js
index ab20a4eb..7233eeb0 100644
--- a/src/matrix/SessionContainer.js
+++ b/src/matrix/SessionContainer.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2020, 2021 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,6 +16,7 @@ limitations under the License.
 */
 
 import {createEnum} from "../utils/enum.js";
+import {lookupHomeServer} from "./well-known.js";
 import {AbortableOperation} from "../utils/AbortableOperation";
 import {ObservableValue} from "../observable/ObservableValue.js";
 import {HomeServerApi} from "./net/HomeServerApi.js";
@@ -36,6 +38,16 @@ function normalizeHomeserver(homeServer) {
     }
 }
 
+function getRetryHomeServer(homeServer) {
+    const url = new URL(homeServer);
+    const {host} = url;
+    const dotCount = host.split(".").length - 1;
+    if (dotCount === 1) {
+        url.host = `www.${host}`;
+        return url.origin;
+    }
+}
+
 export const LoadStatus = createEnum(
     "NotLoading",
     "Login",
@@ -108,7 +120,7 @@ export class SessionContainer {
         implements LoginMethod
         */
         const flows = options.flows;
-        const result = {};
+        const result = {homeServer};
         for (const flow of flows) {
             if (flow.type === "m.login.password") {
                 result.password = (username, password) => new PasswordLoginMethod({homeServer, username, password});
@@ -124,11 +136,13 @@ export class SessionContainer {
     }
 
     queryLogin(homeServer) {
-        const normalizedHS = normalizeHomeserver(homeServer);
-        const hsApi = new HomeServerApi({homeServer: normalizedHS, request: this._platform.request});
         return new AbortableOperation(async setAbortable => {
+            homeServer = await lookupHomeServer(homeServer, (url, options) => {
+                return setAbortable(this._platform.request(url, options));
+            });
+            const hsApi = new HomeServerApi({homeServer, request: this._platform.request});
             const response = await setAbortable(hsApi.getLoginFlows()).response();
-            return this._parseLoginOptions(response, normalizedHS);
+            return this._parseLoginOptions(response, homeServer);
         });
     }
 
diff --git a/src/matrix/well-known.js b/src/matrix/well-known.js
new file mode 100644
index 00000000..a33a734a
--- /dev/null
+++ b/src/matrix/well-known.js
@@ -0,0 +1,64 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+function normalizeHomeserver(homeServer) {
+    try {
+        return new URL(homeServer).origin;
+    } catch (err) {
+        return new URL(`https://${homeServer}`).origin;
+    }
+}
+
+function getRetryHomeServer(homeServer) {
+    const url = new URL(homeServer);
+    const {host} = url;
+    const dotCount = host.split(".").length - 1;
+    if (dotCount === 1) {
+        url.host = `www.${host}`;
+        return url.origin;
+    }
+}
+
+export async function lookupHomeServer(homeServer, request) {
+        homeServer = normalizeHomeserver(homeServer);
+        const requestOptions = {format: "json", timeout: 30000, method: "GET"};
+        let wellKnownResponse = null;
+        while (!wellKnownResponse) {
+            try {
+                const wellKnownUrl = `${homeServer}/.well-known/matrix/client`;
+                wellKnownResponse = await request(wellKnownUrl, requestOptions).response();
+            } catch (err) {
+                if (err.name === "ConnectionError") {
+                    const retryHS = getRetryHomeServer(homeServer);
+                    if (retryHS) {
+                        homeServer = retryHS;
+                    } else {
+                        throw err;
+                    }
+                } else {
+                    throw err;
+                }
+            }
+        }
+        if (wellKnownResponse.status === 200) {
+            const {body} = wellKnownResponse;
+            const wellKnownHomeServer = body["m.homeserver"]?.["base_url"];
+            if (typeof wellKnownHomeServer === "string") {
+                homeServer = normalizeHomeserver(wellKnownHomeServer);
+            }
+        }
+        return homeServer
+}