Experimental support for URL preview handling (MSC4417)

src/Bridge.ts

@@ -15,6 +15,7 @@
   MatrixError,
   RoomEvent,
   PLManager,
+  UserID,
 } from "matrix-bot-sdk";
 import BotUsersManager from "./managers/BotUsersManager";
 import { BridgeConfig, BridgePermissionLevel } from "./config/Config";
@@ -109,6 +110,7 @@
 import { OAuthRequest, OAuthRequestResult } from "./tokens/Oauth";
 import { IJsonType } from "matrix-bot-sdk/lib/helpers/Types";
 import { GitLabInstance } from "./config/sections";
+import { ApiError, ErrCode } from "./api";
 
 const log = new Logger("Bridge");
 
@@ -188,6 +190,7 @@
         this.config.github.auth.id,
         await fs.readFile(this.config.github.auth.privateKeyFile, "utf-8"),
         this.config.github.baseUrl,
+        this.tokenStore,
       );
       await this.github.start();
     }
@@ -245,6 +248,58 @@
       Metrics.matrixAppserviceDecryptionFailed.inc();
     });
 
+    this.as.on(
+      "previewUrl.query",
+      (
+        { url, userId }: { url: string; userId?: string },
+        callback: (statusCode: number, data: any) => void,
+      ) => {
+        log.debug(`Got request to preview ${url} (for ${userId}`);
+        if (!userId) {
+          return callback(
+            400,
+            new ApiError(
+              "user_id value must be provided",
+              ErrCode.ForbiddenUser,
+            ).jsonBody,
+          );
+        }
+
+        if (url.startsWith("https://github.com")) {
+          if (!this.github) {
+            return callback(
+              400,
+              new ApiError(
+                "Service is not configured with GitHub",
+                ErrCode.DisabledFeature,
+              ).jsonBody,
+            );
+          }
+          return this.github
+            .handleURLPreview(new URL(url), new UserID(userId))
+            .then((response) => {
+              callback(200, response);
+            })
+            .catch((ex) => {
+              log.warn(`Failed to preview ${url} (for ${userId})`, ex);
+              if (ex instanceof ApiError) {
+                callback(ex.statusCode, ex.jsonBody);
+              } else {
+                return callback(
+                  500,
+                  new ApiError("Unknown error", ErrCode.Unknown).jsonBody,
+                );
+              }
+            });
+        } else {
+          return callback(
+            404,
+            new ApiError("Unsupported URL", ErrCode.NotFound).jsonBody,
+          );
+        }
+      },
+    );
+
     this.queue.subscribe("response.matrix.message");
     this.queue.subscribe("notifications.user.events");
     this.queue.subscribe("github.*");
@@ -1484,7 +1539,7 @@
       );
       // This might be a reply to a notification
       try {
         const evContent = replyEvent.content as any;
         const splitParts: string[] =
           evContent["uk.half-shot.matrix-hookshot.github.repo"]?.name.split(
             "/",

src/github/GithubInstance.ts

@@ -11,6 +11,9 @@ import {
 } from "./Types";
 import axios from "axios";
 import UserAgent from "../UserAgent";
+import { UserID } from "matrix-bot-sdk";
+import { UserTokenStore } from "../tokens/UserTokenStore";
+import { ApiError, ErrCode } from "../api";
 
 const log = new Logger("GithubInstance");
 
@@ -66,6 +69,7 @@ export class GithubInstance {
     private readonly appId: number | string,
     private readonly privateKey: string,
     private readonly baseUrl: URL,
+    private readonly tokenStore: UserTokenStore,
   ) {
     this.appId = parseInt(appId as string, 10);
   }
@@ -283,6 +287,55 @@ export class GithubInstance {
       `login/oauth/${action}?${q}`
     );
   }
+
+  public async handleURLPreview(url: URL, userId: UserID): Promise<any> {
+    // Try to get some info for the user.
+    // TODO: Fallback to public access?
+    const octokit = await this.tokenStore.getOctokitForUser(userId.toString());
+    if (!octokit) {
+      throw new ApiError(
+        "User is not authenticated with GitHub",
+        ErrCode.ForbiddenUser,
+      );
+    }
+    // Attempt to parse what the URL is about..
+    const [_, owner, repo, type, number] = url.pathname.split("/");
+    if (owner && repo) {
+      if (type === "pull") {
+        const pull = await octokit.pulls.get({
+          owner,
+          repo,
+          pull_number: parseInt(number, 10),
+        });
+        if (pull.status === 200) {
+          return {
+            "og:title": `${pull.data.base.repo.name} | ${pull.data.title} by @${pull.data.user.login}`,
+            "og:description": pull.data.body,
+          };
+        } else {
+          throw new ApiError(
+            `Could not access pull request, status ${pull.status}`,
+            ErrCode.NotFound,
+          );
+        }
+      } else if (type === "issues") {
+        throw new ApiError(
+          `Could not access issue request, not implemented`,
+          ErrCode.NotFound,
+        );
+      } else {
+        throw new ApiError(
+          `URL not processable, unknown type ${type}`,
+          ErrCode.NotFound,
+        );
+      }
+    } else {
+      throw new ApiError(
+        `URL not processable, must be in the format of org/repo`,
+        ErrCode.NotFound,
+      );
+    }
+  }
 }
 
 export class GithubGraphQLClient {