Add GatewayServer and GatewayClient(frontend)

This commit adds a websocket server that clients
can connect and authenticate to. Once they're
authenticated, they will start to receive
relevant events. One issue is that the server
does not ping for dead connections yet
and the fact that new listeners for the guild
are added for each connection. There is also
the bug in WatchedGuild that prevents other
bridge users from seeing eachother's
messages.

GatewayServer.js

@@ -0,0 +1,192 @@
+import { WebSocketServer } from "ws";
+import { guildMap } from "./common.js";
+import { decodeToken } from "./tokens.js";
+
+const messageSchema = { t: "number", d: "object" };
+const authenticationTimeoutMs = 15000;
+const messageTypes = {
+    HELLO: 0,
+    YOO: 1,
+    READY: 2,
+    EVENT: 3
+};
+
+class GatewayServer {
+    constructor(server, extraWebsocketServerConfig={}) {
+        this.wss = new WebSocketServer({
+            server,
+            ...extraWebsocketServerConfig
+        });
+
+        this.wss.on("connection", (ws) => {
+            this.onConnection(ws);
+            ws.on("message", (data, isBinary) => {
+                this.onMessage(ws, data, isBinary);
+            });
+            ws.on("close", (code, reason) => {
+                this.onDisconnect(code, reason.toString());
+            })
+        });
+    }
+
+    _clientDispatch(ws, e) {
+        switch (e.type) {
+            case "INIT": {
+                ws.state = ws.state || {
+                    authenticated: false,
+                    user: null,
+                    token: null,
+                    alive: true,
+                    handlers: new Map()
+                };
+                break;
+            }
+            case "AUTHENTICATE_AS": {
+                ws.state.user = e.user;
+                ws.state.authenticated = true;
+                break;
+            }
+            case "SET_ALIVE": {
+                ws.state.alive = e.alive;
+                break;
+            }
+            case "SET_TOKEN": {
+                ws.state.token = e.token;
+                break;
+            }
+            case "ADD_HANDLER": {
+                ws.state.handlers.set(e.guildId, e.handler);
+                break;
+            }
+        }
+    }
+
+    _checkMessageSchema(message) {
+        for (const [key, value] of Object.entries(message)) {
+            if (!messageSchema[key])
+                return false;
+
+            if (typeof value !== messageSchema[key])
+                return false;
+        }
+        return true;
+    }
+
+    onConnection(ws) {
+        this._clientDispatch(ws, { type: "INIT" });
+
+        setTimeout(() => {
+            if (!ws.state.authenticated) {
+                ws.close(4001, "Authentication timeout.");
+            }
+        }, authenticationTimeoutMs);
+
+        ws.send(JSON.stringify({
+            t: messageTypes.HELLO,
+            d: null
+        }));
+    }
+
+    async onMessage(ws, message, isBinary) {
+        if (isBinary)
+            return ws.close(4000, "Binary payload not supported.");
+
+        try {
+            message = JSON.parse(message.toString());
+        } catch (e) {
+            console.error("GatewayServer: payload decode error", e);
+            return ws.close(4000, "Payload error.");
+        }
+        
+        if (!this._checkMessageSchema(message))
+            return ws.close(4000, "JSON payload does not match schema.");
+
+        switch (message.t) {
+            case messageTypes.YOO: {
+                if (message.d.token) {
+                    let user;
+                    try {
+                        user = await decodeToken(message.d.token);
+                    } catch(e) {
+                        console.error(e);
+                        ws.close(4001, "Bad token.");
+                        break;
+                    }
+                    if (user && user.username) {
+                        if (!user.guildAccess || user.guildAccess.length < 1) {
+                            ws.close(4002, "No possible events: no guilds.");
+                            break;
+                        }
+
+                        this._clientDispatch(ws, {
+                            type: "SET_TOKEN",
+                            token: message.token
+                        });
+                        this._clientDispatch(ws, {
+                            type: "AUTHENTICATE_AS",
+                            user
+                        });
+
+                        // TODO: it might actually be more efficient to have a single listener
+                        // for each guild and broadcast the relevant events that way
+                        user.guildAccess.forEach((guildId) => {
+                            const guild = guildMap.get(guildId);
+                            if (!guild) {
+                                ws.close(4003, "User is in a guild that does not exist.");
+                                return;
+                            }
+                            const handle = (ev) => {
+                                ws.send(JSON.stringify({
+                                    t: messageTypes.EVENT,
+                                    d: ev
+                                }));
+                            };
+                            guild.on("pushed", handle);
+                            this._clientDispatch(ws, {
+                                type: "ADD_HANDLER",
+                                handler: handle,
+                                guildId
+                            })
+                        });
+
+                        ws.send(JSON.stringify({
+                            t: messageTypes.READY,
+                            d: {
+                                user: {
+                                    username: user.username,
+                                    guildAccess: user.guildAccess,
+                                    discordID: user.discordID,
+                                    avatarURL: user.avatarURL
+                                }
+                            }
+                        }));
+                    } else {
+                        ws.close(4001, "Bad token.");
+                        break;
+                    }
+                } else {
+                    ws.close(4001, "No token.");
+                    break;
+                }        
+                break;
+            }
+
+            default: {
+                return ws.close(4000, "Invalid payload type.");
+            }
+        }
+    }
+
+    onDisconnect(ws) {
+        if (ws.state && ws.state.handlers && ws.state.handlers.length > 0) {
+            for (const [guildId, handler] of ws.state.handlers.entries()) {
+                const guild = guildMap.get(guildId);
+                if (guild) {
+                    guild.removeListener("pushed", handler);
+                }
+            }
+        }
+    }
+}
+
+export default GatewayServer;

WatchedGuild.js

@@ -59,6 +59,7 @@ class WatchedGuild extends EventEmitter {
             if (message.guild_id !== this.upstreamGuildId)
                 return;
 
+            // TODOOOOOO: bridge user's wont get message events from other bridge users in the same channel
             const maybeKnownWebhook = this.knownWebhooks.get(message.channel_id);
             if (maybeKnownWebhook && maybeKnownWebhook.id === message.webhook_id)
                 return; // ignore messages coming from our webhook

frontend/src/api/GatewayClient.js

@@ -0,0 +1,93 @@
+const messageSchema = { t: "number", d: "object" };
+const messageTypes = {
+    HELLO: 0,
+    YOO: 1,
+    READY: 2,
+    EVENT: 3
+};
+
+export default class GatewayClient {
+    constructor(gatewayPath) {
+        this.gatewayPath = gatewayPath;
+        this.ws = null;
+        this.token = null;
+        this.user = null;
+        this.onEvent = (e) => {};
+    }
+
+    connect(token) {
+        if (!token)
+            token = this.token;
+
+        console.log("gateway: connecting");
+
+        this.ws = new WebSocket(this.gatewayPath);
+
+        this.ws.addEventListener("message", ({ data }) => {
+            if (typeof data !== "string") {
+                console.warn("gateway: got non-string data from server, ignoring...");
+                return;
+            }
+
+            let message;
+            try {
+                message = JSON.parse(data);
+            } catch(e) {
+                console.warn("gateway: got invalid JSON from server (failed to parse), ignoring...");
+                return;
+            }
+
+            if (!this._checkMessageSchema(message)) {
+                console.warn("gateway: got invalid JSON from server (does not match schema), ignoring...");
+                return;
+            }
+
+            switch (message.t) {
+                case messageTypes.HELLO: {
+                    console.log("gateway: HELLO");
+                    this.ws.send(JSON.stringify({
+                        t: messageTypes.YOO,
+                        d: {
+                            token
+                        }
+                    }));
+                    break;
+                }
+                case messageTypes.READY: {
+                    console.log("gateway: READY");
+                    this.user = message.d.user;
+                    break;
+                }
+                case messageTypes.EVENT: {
+                    this.onEvent(message.d);
+                    break;
+                }
+                default: {
+                    console.warn("gateway: got invalid JSON from server (invalid type), ignoring...");
+                    return;
+                }
+            }
+        });
+        this.ws.addEventListener("open", () => {
+            console.log("gateway: open");
+        });
+        this.ws.addEventListener("close", () => {
+            console.log("gateway: closed");
+            setTimeout(() => {
+                console.log("gateway: reconnecting");
+                this.connect();
+            }, 4000);
+        });
+    }
+
+    _checkMessageSchema(message) {
+        for (const [key, value] of Object.entries(message)) {
+            if (!messageSchema[key])
+                return false;
+
+            if (typeof value !== messageSchema[key])
+                return false;
+        }
+        return true;
+    }
+}

frontend/src/components/App.svelte

@@ -1,5 +1,7 @@
 <script>
 	import { apiClient } from "../api/common";
+	import GatewayClient from "../api/GatewayClient";
+	import { supportsWebsockets } from "../util/browser";
 	import ChatView from "./ChatView.svelte";
 	import FuzzyView from "./FuzzyView.svelte";
 	import MessageDisplay from "./MessageDisplay.svelte";
@@ -11,6 +13,21 @@ import MessageDisplay from "./MessageDisplay.svelte";
 	let user = null;
 	let view = { type: "CHAT" };
 
+	function handleEvent(event) {
+		if (event.eventType === "MESSAGE_CREATE") {
+			const guildId = event.message.guild_id;
+			const channelId = event.message.channel_id;
+
+			if (!messageStore[guildId]) {
+				messageStore[guildId] = {};
+			}
+			if (!messageStore[guildId][channelId]) {
+				messageStore[guildId][channelId] = [];
+			}
+			messageStore[guildId][channelId] = [...messageStore[guildId][channelId], event.message];
+		}
+	}
+
 	apiClient.getRequest("/users/@self", false)
 		.then((res) => {
 			let userErrorMessage = "";
@@ -52,21 +69,18 @@ import MessageDisplay from "./MessageDisplay.svelte";
 					selectedChannel = guilds[0].channels[0];
 			}
 
+			if (supportsWebsockets()) {
+				console.log("App: browser supports WebSocket, using gateway");
+				const gatewayConnection = new GatewayClient(`${ location.protocol === "https:" ? "wss://" : "ws://" }${location.host}/gateway`);
+				gatewayConnection.onEvent = handleEvent;
+				gatewayConnection.connect(apiClient.token);
+			} else {
+				console.warn("App: browser does not WebSocket, using polling");
 				const { poll } = apiClient.createPollingListener(null, ({ event }) => {
-				if (event.eventType === "MESSAGE_CREATE") {
+					handleEvent(event);
-					const guildId = event.message.guild_id;
-					const channelId = event.message.channel_id;
-
-					if (!messageStore[guildId]) {
-						messageStore[guildId] = {};
-					}
-					if (!messageStore[guildId][channelId]) {
-						messageStore[guildId][channelId] = [];
-					}
-					messageStore[guildId][channelId] = [...messageStore[guildId][channelId], event.message];
-				}
 				});
 				poll();
+			}
 		});
 
 

frontend/src/util/browser.js

@@ -0,0 +1,3 @@
+export function supportsWebsockets() {
+    return !!window.WebSocket;
+};

index.js

@@ -1,7 +1,9 @@
+import http from "node:http";
 import express from "express";
 import apiRoute from "./routes/api.js";
 import { mainHttpListenPort } from "./config.js";
 import { bot } from "./common.js";
+import GatewayServer from "./GatewayServer.js";
 
 // might introduce bugs and probably a bad idea
 Object.freeze(Object.prototype);
@@ -9,12 +11,16 @@ Object.freeze(Object);
 
 
 const app = express();
+const httpServer = http.createServer(app);
+const gatewayServer = new GatewayServer(httpServer, {
+    path: "/gateway"
+});
 
 app.use(express.json());
 app.use("/", express.static("frontend/public/"));
 app.use("/api/v1", apiRoute);
 
-app.listen(mainHttpListenPort, () => {
+httpServer.listen(mainHttpListenPort, () => {
     console.log(`server main: listen on ${mainHttpListenPort}`);
     bot.connect();
 });