Attempt to re-register for a scalar token if ours is invalid

This mostly helps with people migrating between integration managers where their old scalar token may no longer be valid. This also solves the problem of people switching between scalar and scalar-staging in the wild.

Signed-off-by: Travis Ralston <travpc@gmail.com>

src/ScalarAuthClient.js

@@ -38,11 +38,53 @@ class ScalarAuthClient {
 
     // Returns a scalar_token string
     getScalarToken() {
-        const tok = window.localStorage.getItem("mx_scalar_token");
-        if (tok) return Promise.resolve(tok);
+        const token = window.localStorage.getItem("mx_scalar_token");
 
-        // No saved token, so do the dance to get one. First, we
-        // need an openid bearer token from the HS.
+        if (!token) {
+            return this.registerForToken();
+        } else {
+            return this.validateToken(token).then(userId => {
+                const me = MatrixClientPeg.get().getUserId();
+                if (userId !== me) {
+                    throw new Error("Scalar token is owned by someone else: " + me);
+                }
+                return token;
+            }).catch(err => {
+                console.error(err);
+
+                // Something went wrong - try to get a new token.
+                console.warn("Registering for new scalar token");
+                return this.registerForToken();
+            })
+        }
+    }
+
+    validateToken(token) {
+        let url = SdkConfig.get().integrations_rest_url + "/account";
+
+        const defer = Promise.defer();
+        request({
+            method: "GET",
+            uri: url,
+            qs: {scalar_token: token},
+            json: true,
+        }, (err, response, body) => {
+            if (err) {
+                defer.reject(err);
+            } else if (response.statusCode / 100 !== 2) {
+                defer.reject({statusCode: response.statusCode});
+            } else if (!body || !body.user_id) {
+                defer.reject(new Error("Missing user_id in response"));
+            } else {
+                defer.resolve(body.user_id);
+            }
+        });
+
+        return defer.promise;
+    }
+
+    registerForToken() {
+        // Get openid bearer token from the HS as the first part of our dance
         return MatrixClientPeg.get().getOpenIdToken().then((token_object) => {
             // Now we can send that to scalar and exchange it for a scalar token
             return this.exchangeForScalarToken(token_object);