Clean up and simplify WebSocket implementation on the JS side

Summary:- Get rid of no longer necessary WebSocket.js v WebSocketBase.js split
- Use `EventTarget(list, of, events)` as base class to auto-generate `oneventname` getters/setters that get invoked along with other event handlers
- Type annotation `any` considered harmful, especially when we can easily spell out the actual type
- Throw in some `const` goodness for free

**Test Plan:** Launch UIExplorer example app, supplied `websocket_test_server` script, and try different combinations of sending and receiving text and binary data on both iOS and Android.
Closes facebook#6889

Differential Revision: D3184835

Pulled By: mkonicek

fb-gh-sync-id: f21707f4e97aa5a79847f5157e0a9f132a1a01cd
fbshipit-source-id: f21707f4e97aa5a79847f5157e0a9f132a1a01cd

Author: philikon

Examples/UIExplorer/UIExplorerList.android.js

@@ -174,6 +174,10 @@ const APIExamples = [
     key: 'VibrationExample',
     module: require('./VibrationExample'),
   },
+  {
+    key: 'WebSocketExample',
+    module: require('./WebSocketExample'),
+  },
   {
     key: 'XHRExample',
     module: require('./XHRExample'),

Examples/UIExplorer/UIExplorerList.ios.js

@@ -248,6 +248,10 @@ var APIExamples: Array<UIExplorerExample> = [
     key: 'VibrationExample',
     module: require('./VibrationExample'),
   },
+  {
+    key: 'WebSocketExample',
+    module: require('./WebSocketExample'),
+  },
   {
     key: 'XHRExample',
     module: require('./XHRExample.ios'),

Examples/UIExplorer/WebSocketExample.js

@@ -0,0 +1,286 @@
+/**
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @flow
+ */
+'use strict';
+
+/* eslint-env browser */
+
+const React = require('react');
+const ReactNative = require('react-native');
+const {
+  PixelRatio,
+  StyleSheet,
+  Text,
+  TextInput,
+  TouchableOpacity,
+  View,
+} = ReactNative;
+
+const DEFAULT_WS_URL = 'ws://localhost:5555/';
+const WS_EVENTS = [
+  'close',
+  'error',
+  'message',
+  'open',
+];
+const WS_STATES = [
+  /* 0 */ 'CONNECTING',
+  /* 1 */ 'OPEN',
+  /* 2 */ 'CLOSING',
+  /* 3 */ 'CLOSED',
+];
+
+class Button extends React.Component {
+  render(): ReactElement {
+    const label = <Text style={styles.buttonLabel}>{this.props.label}</Text>;
+    if (this.props.disabled) {
+      return (
+        <View style={[styles.button, styles.disabledButton]}>
+          {label}
+        </View>
+      );
+    }
+    return (
+      <TouchableOpacity
+        onPress={this.props.onPress}
+        style={styles.button}>
+        {label}
+      </TouchableOpacity>
+    );
+  }
+}
+
+class Row extends React.Component {
+  render(): ReactElement {
+    return (
+      <View style={styles.row}>
+        <Text>{this.props.label}</Text>
+        <Text>{this.props.value}</Text>
+      </View>
+    );
+  }
+}
+
+function showValue(value) {
+  if (value === undefined || value === null) {
+    return '(no value)';
+  }
+  console.log('typeof Uint8Array', typeof Uint8Array);
+  if (typeof ArrayBuffer !== 'undefined' &&
+      typeof Uint8Array !== 'undefined' &&
+      value instanceof ArrayBuffer) {
+    return `ArrayBuffer {${Array.from(new Uint8Array(value))}}`;
+  }
+  return value;
+}
+
+type State = {
+  url: string;
+  socket: ?WebSocket;
+  socketState: ?number;
+  lastSocketEvent: ?string;
+  lastMessage: ?string | ?ArrayBuffer;
+  outgoingMessage: string;
+};
+
+class WebSocketExample extends React.Component<any, any, State> {
+
+  static title = 'WebSocket';
+  static description = 'WebSocket API';
+
+  state: State = {
+    url: DEFAULT_WS_URL,
+    socket: null,
+    socketState: null,
+    lastSocketEvent: null,
+    lastMessage: null,
+    outgoingMessage: '',
+  };
+
+  _connect = () => {
+    const socket = new WebSocket(this.state.url);
+    WS_EVENTS.forEach(ev => socket.addEventListener(ev, this._onSocketEvent));
+    this.setState({
+      socket,
+      socketState: socket.readyState,
+    });
+  };
+
+  _disconnect = () => {
+    if (!this.state.socket) {
+      return;
+    }
+    this.state.socket.close();
+  };
+
+  // Ideally this would be a MessageEvent, but Flow's definition
+  // doesn't inherit from Event, so it's 'any' for now.
+  // See https://github.com/facebook/flow/issues/1654.
+  _onSocketEvent = (event: any) => {
+    const state: any = {
+      socketState: event.target.readyState,
+      lastSocketEvent: event.type,
+    };
+    if (event.type === 'message') {
+      state.lastMessage = event.data;
+    }
+    this.setState(state);
+  };
+
+  _sendText = () => {
+    if (!this.state.socket) {
+      return;
+    }
+    this.state.socket.send(this.state.outgoingMessage);
+    this.setState({outgoingMessage: ''});
+  };
+
+  _sendBinary = () => {
+    if (!this.state.socket ||
+        typeof ArrayBuffer === 'undefined' ||
+        typeof Uint8Array === 'undefined') {
+      return;
+    }
+    const {outgoingMessage} = this.state;
+    const buffer = new Uint8Array(outgoingMessage.length);
+    for (let i = 0; i < outgoingMessage.length; i++) {
+      buffer[i] = outgoingMessage.charCodeAt(i);
+    }
+    this.state.socket.send(buffer);
+    this.setState({outgoingMessage: ''});
+  };
+
+  render(): ReactElement {
+    const socketState = WS_STATES[this.state.socketState || -1];
+    const canConnect =
+      !this.state.socket ||
+      this.state.socket.readyState >= WebSocket.CLOSING;
+    const canSend = !!this.state.socket;
+    return (
+      <View style={styles.container}>
+        <View style={styles.note}>
+          <Text>Pro tip:</Text>
+          <Text style={styles.monospace}>
+            node Examples/UIExplorer/websocket_test_server.js
+          </Text>
+          <Text>
+            {' in the '}
+            <Text style={styles.monospace}>react-native</Text>
+            {' directory starts a test server.'}
+          </Text>
+        </View>
+        <Row
+          label="Current WebSocket state"
+          value={showValue(socketState)}
+        />
+        <Row
+          label="Last WebSocket event"
+          value={showValue(this.state.lastSocketEvent)}
+        />
+        <Row
+          label="Last message received"
+          value={showValue(this.state.lastMessage)}
+        />
+        <TextInput
+          style={styles.textInput}
+          autoCorrect={false}
+          placeholder="Server URL..."
+          onChangeText={(url) => this.setState({url})}
+          value={this.state.url}
+        />
+        <Button
+          onPress={this._connect}
+          label="Connect"
+          disabled={!canConnect}
+        />
+        <Button
+          onPress={this._disconnect}
+          label="Disconnect"
+          disabled={canConnect}
+        />
+        <TextInput
+          style={styles.textInput}
+          autoCorrect={false}
+          placeholder="Type message here..."
+          onChangeText={(outgoingMessage) => this.setState({outgoingMessage})}
+          value={this.state.outgoingMessage}
+        />
+        <View style={styles.buttonRow}>
+          <Button
+            onPress={this._sendText}
+            label="Send as text"
+            disabled={!canSend}
+          />
+          <Button
+            onPress={this._sendBinary}
+            label="Send as binary"
+            disabled={!canSend}
+          />
+        </View>
+      </View>
+    );
+  }
+
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+  },
+  note: {
+    padding: 8,
+    margin: 4,
+    backgroundColor: 'white',
+  },
+  monospace: {
+    fontFamily: 'courier',
+    fontSize: 11,
+  },
+  row: {
+    height: 40,
+    padding: 4,
+    backgroundColor: 'white',
+    flexDirection: 'row',
+    justifyContent: 'space-between',
+    alignItems: 'center',
+    borderBottomWidth: 1 / PixelRatio.get(),
+    borderColor: 'grey',
+  },
+  button: {
+    margin: 8,
+    padding: 8,
+    borderRadius: 4,
+    backgroundColor: 'blue',
+    alignSelf: 'center',
+  },
+  disabledButton: {
+    opacity: 0.5,
+  },
+  buttonLabel: {
+    color: 'white',
+  },
+  buttonRow: {
+    flexDirection: 'row',
+    justifyContent: 'center',
+  },
+  textInput: {
+    height: 40,
+    backgroundColor: 'white',
+    margin: 8,
+    padding: 8,
+  },
+});
+
+module.exports = WebSocketExample;

Examples/UIExplorer/websocket_test_server.js

@@ -0,0 +1,43 @@
+/**
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @flow
+ */
+'use strict';
+
+/* eslint-env node */
+
+const WebSocket = require('ws');
+
+console.log(`\
+Test server for WebSocketExample
+
+This will send each incoming message right back to the other side.a
+Restart with the '--binary' command line flag to have it respond with an
+ArrayBuffer instead of a string.
+`);
+
+const respondWithBinary = process.argv.indexOf('--binary') !== -1;
+const server = new WebSocket.Server({port: 5555});
+server.on('connection', (ws) => {
+  ws.on('message', (message) => {
+    console.log('Received message: %s', message);
+    if (respondWithBinary) {
+      message = new Buffer(message);
+    }
+    ws.send(message);
+  });
+
+  console.log('Incoming connection!');
+  ws.send('Why hello there!');
+});