WIP: OrderWatcher WebSocket

Currently incomplete. Main challenge is to figure out how to test
a client + server setup in the single-threaded javascript environment.

2 files changed, 192 insertions, 0 deletions

diff --git a/packages/order-watcher/src/order_watcher/order_watcher_websocket.ts b/packages/order-watcher/src/order_watcher/order_watcher_websocket.ts
new file mode 100644
index 000000000..84afc4000
--- /dev/null
+++ b/packages/order-watcher/src/order_watcher/order_watcher_websocket.ts
@@ -0,0 +1,184 @@
+import { ContractAddresses } from '@0x/contract-addresses';
+import { SignedOrder } from '@0x/types';
+import { BigNumber, logUtils } from '@0x/utils';
+import { Provider } from 'ethereum-types';
+import * as http from 'http';
+import * as WebSocket from 'websocket';
+
+import { webSocketUtf8MessageSchema } from '../schemas/websocket_utf8_message_schema';
+import { OnOrderStateChangeCallback, OrderWatcherConfig } from '../types';
+import { assert } from '../utils/assert';
+
+import { OrderWatcher } from './order_watcher';
+
+const DEFAULT_HTTP_PORT = 8080;
+
+const enum OrderWatcherAction {
+    // Actions initiated by the user.
+    getStats = 'getStats',
+    addOrderAsync = 'addOrderAsync',
+    removeOrder = 'removeOrder',
+    // These are spontaneous; they are primarily orderstate changes.
+    orderWatcherUpdate = 'orderWatcherUpdate',
+    // `subscribe` and `unsubscribe` are methods of OrderWatcher, but we don't
+    // need to expose them to the WebSocket server user because the user implicitly
+    // subscribes and unsubscribes by connecting and disconnecting from the server.
+}
+
+// Users have to create a json object of this format and attach it to
+// the data field of their WebSocket message to interact with this server.
+interface WebSocketRequestData {
+    action: OrderWatcherAction;
+    params: any;
+}
+
+// Users should expect a json object of this format in the data field
+// of the WebSocket messages that this server sends out.
+interface WebSocketResponseData {
+    action: OrderWatcherAction;
+    success: number;
+    result: any;
+}
+
+// Wraps the OrderWatcher functionality in a WebSocket server. Motivations:
+// 1) Users can watch orders via non-typescript programs.
+// 2) Better encapsulation so that users can work
+export class OrderWatcherWebSocketServer {
+    public httpServer: http.Server;
+    public readonly _orderWatcher: OrderWatcher;
+    private readonly _connectionStore: Set<WebSocket.connection>;
+    private readonly _wsServer: WebSocket.server;
+    /**
+     * Instantiate a new web socket server which provides OrderWatcher functionality
+     *  @param provider Web3 provider to use for JSON RPC calls (for OrderWatcher)
+     *  @param networkId NetworkId to watch orders on (for OrderWatcher)
+     *  @param contractAddresses Optional contract addresses. Defaults to known
+     *  addresses based on networkId (for OrderWatcher)
+     *  @param partialConfig Optional configurations (for OrderWatcher)
+     */
+    constructor(
+        provider: Provider,
+        networkId: number,
+        contractAddresses?: ContractAddresses,
+        partialConfig?: Partial<OrderWatcherConfig>,
+    ) {
+        this._orderWatcher = new OrderWatcher(provider, networkId, contractAddresses, partialConfig);
+        this._connectionStore = new Set();
+        this.httpServer = http.createServer();
+        this._wsServer = new WebSocket.server({
+            httpServer: this.httpServer,
+            autoAcceptConnections: false,
+        });
+
+        this._wsServer.on('request', (request: any) => {
+            // Designed for usage pattern where client and server are run on the same
+            // machine by the same user. As such, no security checks are in place.
+            const connection: WebSocket.connection = request.accept(null, request.origin);
+            logUtils.log(`${new Date()} [Server] Accepted connection from origin ${request.origin}.`);
+            connection.on('message', this._messageCallback.bind(this, connection));
+            connection.on('close', this._closeCallback.bind(this, connection));
+            this._connectionStore.add(connection);
+        });
+
+        // Have the WebSocket server subscribe to the OrderWatcher to receive updates.
+        // These updates are then broadcast to clients in the _connectionStore.
+        this._orderWatcher.subscribe(this._broadcastCallback);
+    }
+
+    /**
+     * Activates the WebSocket server by having its HTTP server start listening.
+     */
+    public listen(): void {
+        this.httpServer.listen(DEFAULT_HTTP_PORT, () => {
+            logUtils.log(`${new Date()} [Server] Listening on port ${DEFAULT_HTTP_PORT}`);
+        });
+    }
+
+    public close(): void {
+        this.httpServer.close();
+    }
+
+    private _messageCallback(connection: WebSocket.connection, message: any): void {
+        assert.doesConformToSchema('message', message, webSocketUtf8MessageSchema);
+        const requestData: WebSocketRequestData = JSON.parse(message.utf8Data);
+        const responseData = this._routeRequest(requestData);
+        logUtils.log(`${new Date()} [Server] OrderWatcher output: ${JSON.stringify(responseData)}`);
+        connection.sendUTF(JSON.stringify(responseData));
+    }
+
+    private _closeCallback(connection: WebSocket.connection): void {
+        this._connectionStore.delete(connection);
+        logUtils.log(`${new Date()} [Server] Client ${connection.remoteAddress} disconnected.`);
+    }
+
+    private _routeRequest(requestData: WebSocketRequestData): WebSocketResponseData {
+        const responseData: WebSocketResponseData = {
+            action: requestData.action,
+            success: 0,
+            result: undefined,
+        };
+
+        try {
+            logUtils.log(`${new Date()} [Server] Request received: ${requestData.action}`);
+            switch (requestData.action) {
+                case 'addOrderAsync': {
+                    const signedOrder: SignedOrder = this._parseSignedOrder(requestData);
+                    // tslint:disable-next-line:no-floating-promises
+                    this._orderWatcher.addOrderAsync(signedOrder); // Ok to fireNforget
+                    break;
+                }
+                case 'removeOrder': {
+                    this._orderWatcher.removeOrder(requestData.params.orderHash);
+                    break;
+                }
+                case 'getStats': {
+                    responseData.result = this._orderWatcher.getStats();
+                    break;
+                }
+                default:
+                    throw new Error(`[Server] Invalid request action: ${requestData.action}`);
+            }
+            responseData.success = 1;
+        } catch (err) {
+            responseData.result = { error: err.toString() };
+        }
+        return responseData;
+    }
+
+    /**
+     * Broadcasts OrderState changes to ALL connected clients. At the moment,
+     * we do not support clients subscribing to only a subset of orders. As such,
+     * Client B will be notified of changes to an order that Client A added.
+     */
+    private readonly _broadcastCallback: OnOrderStateChangeCallback = (err, orderState) => {
+        this._connectionStore.forEach((connection: WebSocket.connection) => {
+            const responseData: WebSocketResponseData = {
+                action: OrderWatcherAction.orderWatcherUpdate,
+                success: 1,
+                result: orderState || err,
+            };
+            connection.sendUTF(JSON.stringify(responseData));
+        });
+        // tslint:disable-next-line:semicolon
+    }; // tslint thinks this is a class method, It's actally a property that holds a function.
+
+    /**
+     * Recover types lost when the payload is stringified.
+     */
+    private readonly _parseSignedOrder = (requestData: WebSocketRequestData) => {
+        const signedOrder = requestData.params.signedOrder;
+        const bigNumberFields = [
+            'salt',
+            'makerFee',
+            'takerFee',
+            'makerAssetAmount',
+            'takerAssetAmount',
+            'expirationTimeSeconds',
+        ];
+        for (const field of bigNumberFields) {
+            signedOrder[field] = new BigNumber(signedOrder[field]);
+        }
+        return signedOrder;
+        // tslint:disable-next-line:semicolon
+    }; // tslint thinks this is a class method, It's actally a property that holds a function.
+}
diff --git a/packages/order-watcher/src/schemas/websocket_utf8_message_schema.ts b/packages/order-watcher/src/schemas/websocket_utf8_message_schema.ts
new file mode 100644
index 000000000..0a0eed407
--- /dev/null
+++ b/packages/order-watcher/src/schemas/websocket_utf8_message_schema.ts
@@ -0,0 +1,8 @@
+export const webSocketUtf8MessageSchema = {
+    id: '/WebSocketUtf8MessageSchema',
+    properties: {
+        utf8Data: { type: 'string' },
+    },
+    type: 'object',
+    required: ['utf8Data'],
+};