Separate websocket internals for RPC (#1893)

* websocket centralization

* more centralization

* whoops

* Update WebSocket.js

src/WebSocket.js

@@ -0,0 +1,40 @@
+const browser = typeof window !== 'undefined';
+const zlib = require('zlib');
+const querystring = require('querystring');
+
+if (browser) {
+  exports.WebSocket = window.WebSocket; // eslint-disable-line no-undef
+} else {
+  try {
+    exports.WebSocket = require('uws');
+  } catch (err) {
+    exports.WebSocket = require('ws');
+  }
+}
+
+try {
+  var erlpack = require('erlpack');
+  if (!erlpack.pack) erlpack = null;
+} catch (err) {} // eslint-disable-line no-empty
+
+exports.encoding = erlpack ? 'etf' : 'json';
+
+exports.pack = erlpack ? erlpack.pack : JSON.stringify;
+
+exports.unpack = data => {
+  if (Array.isArray(data)) data = Buffer.concat(data);
+  if (data instanceof ArrayBuffer) data = Buffer.from(new Uint8Array(data));
+
+  if (erlpack && typeof data !== 'string') return erlpack.unpack(data);
+  else if (data instanceof Buffer) data = zlib.inflateSync(data).toString();
+  return JSON.parse(data);
+};
+
+exports.create = (gateway, query = {}, ...args) => {
+  query.encoding = exports.encoding;
+  const ws = new exports.WebSocket(`${gateway}?${querystring.stringify(query)}`, ...args);
+  if (browser) ws.binaryType = 'arraybuffer';
+  return ws;
+};
+
+for (const state of ['CONNECTING', 'OPEN', 'CLOSING', 'CLOSED']) exports[state] = exports.WebSocket[state];