add js client lib (#2)

Author: asurkov

js/src/LogEvent.js

@@ -0,0 +1,129 @@
+// Copyright 2018 Sourcerer Inc. All Rights Reserved.
+// Author: Alexander Surkov ([email protected])
+
+(function(exports) {
+
+/**
+ * Elastic LogStash logging.
+ */
+class LogEvent
+{
+  constructor(url, { headers })
+  {
+    console.assert(url);
+    console.assert(headers);
+
+    this.url = url;
+    if (headers['set-cookie']) {
+      let value = headers['set-cookie'];
+      let parts = value.split(';').filter((v) => !!v.trim());
+      let cookiePart = parts[0].split('=');
+      this.session = cookiePart[1];
+    }
+  }
+
+  /**
+   * Logs an error.
+   */
+  error(message)
+  {
+    this.event('error', { message });
+  }
+
+  /**
+   * Logs an event of the given type.
+   */
+  event(type, fields)
+  {
+    let data = Object.assign({
+      session: this.session,
+      type,
+      timestamp: Date.now()
+    }, fields);
+
+    let thisobj = this;
+    return new Promise((resolve, reject) => {
+      ('XMLHttpRequest' in exports) ?
+        thisobj.browserRequest(data, resolve, reject) :
+        thisobj.nodeRequest(data, resolve, reject);
+    });
+  }
+
+  nodeRequest(data, resolve, reject)
+  {
+    let params = encodeURIComponent(JSON.stringify(data));
+
+    let url = new URL(this.url);
+    let protocol = url.protocol.replace(':', '');
+    if (protocol != 'http' && protocol != 'https') {
+      reject({ error: 'Unsupported protocol' });
+      return;
+    }
+
+    const options = {
+      hostname: url.hostname,
+      port: url.port,
+      path: url.pathname,
+      method,
+      headers: {
+        'Content-Type': 'application/x-www-form-urlencoded'
+      },
+      agent: keepAliveAgent,
+      timeout: 1000,
+      checkServerIdentity: function (host, cert) {
+        return undefined;
+      }
+    };
+
+    const req = require(protocol).request(options, (res) => {
+      if (res.statusCode != 200) {
+        reject({
+          error: `HTTP error`,
+          status: res.statusCode
+        });
+        return;
+      }
+
+      let stream = new require('stream').Transform();
+      res.on('data', (chunk) => {
+        stream.push(chunk);
+      });
+      res.on('end', () => {
+        resolve(new Buffer(stream.read()));
+      });
+    });
+    req.on('error', (e) => {
+      reject({
+       error: `HTTP error`,
+       status: e
+     });
+    });
+    req.end();
+  }
+
+  browserRequest(data, resolve, reject)
+  {
+    const req = new XMLHttpRequest();
+    req.open('POST', this.url, true);
+
+    // Send the proper header information along with the request.
+    req.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
+    req.withCredentials = true;
+    req.onreadystatechange = () => {
+      if (req.readyState == 4 && req.status == 200) {
+        resolve(req.responseText);
+      }
+      else {
+        reject({
+          error: `HTTP error`,
+          status: req.status
+        });
+      }
+    }
+    req.send(encodeURIComponent(JSON.stringify(data)));
+  }
+};
+
+exports.LogEvent = LogEvent;
+
+})(typeof exports === 'undefined'? this : exports);