1 files changed, 127 insertions, 0 deletions
diff --git a/packages/connect/src/ws_orderbook_channel.ts b/packages/connect/src/ws_orderbook_channel.ts
new file mode 100644
index 000000000..78b823dbe
--- /dev/null
+++ b/packages/connect/src/ws_orderbook_channel.ts
@@ -0,0 +1,127 @@
+import * as _ from 'lodash';
+import * as WebSocket from 'websocket';
+import {assert} from '@0xproject/assert';
+import {schemas} from '@0xproject/json-schemas';
+import {SignedOrder} from '0x.js';
+import {
+    OrderbookChannel,
+    OrderbookChannelHandler,
+    OrderbookChannelMessageTypes,
+    OrderbookChannelSubscriptionOpts,
+} from './types';
+import {orderbookChannelMessageParsers} from './utils/orderbook_channel_message_parsers';
+
+enum ConnectionEventType {
+    Close = 'close',
+    Error = 'error',
+    Message = 'message',
+}
+
+enum ClientEventType {
+    Connect = 'connect',
+    ConnectFailed = 'connectFailed',
+}
+
+/**
+ * This class includes all the functionality related to interacting with a websocket endpoint
+ * that implements the standard relayer API v0
+ */
+export class WebSocketOrderbookChannel implements OrderbookChannel {
+    private apiEndpointUrl: string;
+    private client: WebSocket.client;
+    private connectionIfExists?: WebSocket.connection;
+    /**
+     * Instantiates a new WebSocketOrderbookChannel instance
+     * @param   url                 The base url for making API calls
+     * @return  An instance of WebSocketOrderbookChannel
+     */
+    constructor(url: string) {
+        assert.isUri('url', url);
+        this.apiEndpointUrl = url;
+        this.client = new WebSocket.client();
+    }
+    /**
+     * Subscribe to orderbook snapshots and updates from the websocket
+     * @param   subscriptionOpts     An OrderbookChannelSubscriptionOpts instance describing which
+     *                               token pair to subscribe to
+     * @param   handler              An OrderbookChannelHandler instance that responds to various
+     *                               channel updates
+     */
+    public subscribe(subscriptionOpts: OrderbookChannelSubscriptionOpts, handler: OrderbookChannelHandler): void {
+        assert.doesConformToSchema(
+            'subscriptionOpts', subscriptionOpts, schemas.relayerApiOrderbookChannelSubscribePayload);
+        assert.isFunction('handler.onSnapshot', _.get(handler, 'onSnapshot'));
+        assert.isFunction('handler.onUpdate', _.get(handler, 'onUpdate'));
+        assert.isFunction('handler.onError', _.get(handler, 'onError'));
+        assert.isFunction('handler.onClose', _.get(handler, 'onClose'));
+        const subscribeMessage = {
+            type: 'subscribe',
+            channel: 'orderbook',
+            payload: subscriptionOpts,
+        };
+        this._getConnection((error, connection) => {
+            if (!_.isUndefined(error)) {
+                handler.onError(this, error);
+            } else if (!_.isUndefined(connection) && connection.connected) {
+                connection.on(ConnectionEventType.Error, wsError => {
+                    handler.onError(this, wsError);
+                });
+                connection.on(ConnectionEventType.Close, () => {
+                    handler.onClose(this);
+                });
+                connection.on(ConnectionEventType.Message, message => {
+                    this._handleWebSocketMessage(message, handler);
+                });
+                connection.sendUTF(JSON.stringify(subscribeMessage));
+            }
+        });
+    }
+    /**
+     * Close the websocket and stop receiving updates
+     */
+    public close() {
+        if (!_.isUndefined(this.connectionIfExists)) {
+            this.connectionIfExists.close();
+        }
+    }
+    private _getConnection(callback: (error?: Error, connection?: WebSocket.connection) => void) {
+        if (!_.isUndefined(this.connectionIfExists) && this.connectionIfExists.connected) {
+            callback(undefined, this.connectionIfExists);
+        } else {
+            this.client.on(ClientEventType.Connect, connection => {
+                this.connectionIfExists = connection;
+                callback(undefined, this.connectionIfExists);
+            });
+            this.client.on(ClientEventType.ConnectFailed, error => {
+                callback(error, undefined);
+            });
+            this.client.connect(this.apiEndpointUrl);
+        }
+    }
+    private _handleWebSocketMessage(message: WebSocket.IMessage, handler: OrderbookChannelHandler): void {
+        if (!_.isUndefined(message.utf8Data)) {
+            try {
+                const utf8Data = message.utf8Data;
+                const parserResult = orderbookChannelMessageParsers.parser(utf8Data);
+                const type = parserResult.type;
+                switch (parserResult.type) {
+                    case (OrderbookChannelMessageTypes.Snapshot): {
+                        handler.onSnapshot(this, parserResult.payload);
+                        break;
+                    }
+                    case (OrderbookChannelMessageTypes.Update): {
+                        handler.onUpdate(this, parserResult.payload);
+                        break;
+                    }
+                    default: {
+                        handler.onError(this, new Error(`Message has missing a type parameter: ${utf8Data}`));
+                    }
+                }
+            } catch (error) {
+                handler.onError(this, error);
+            }
+        } else {
+            handler.onError(this, new Error(`Message does not contain utf8Data`));
+        }
+    }
+}