strong-arc/devtools/server/backend.js

A visual suite for the StrongLoop API Platform

var extend = require('util')._extend;
var debug = require('debug')('studio:devtools');

module.exports = DevToolsBackend;

function DevToolsBackend() {
}

var sampleCpuProfile = loadExampleJsonSync('sample.cpuprofile');
var sampleHeapSnapshot = loadExampleJsonSync('sample.heapsnapshot');

var COMMANDS = {
  'Worker.canInspectWorkers': { result: false },

  'Page.getScriptExecutionStatus': { result: 'enabled' },
  'Page.getResourceTree': {
    frameTree: {
      frame: {
        id: 'dummy-toplevel-frame',
        url: 'app.js',
        securityOrigin: 'localhost'
      },
      resources: []
    }
  },

  'IndexedDB.requestDatabaseNames': {
    databaseNames: []
  },

  // Temporary implementation returning sample data
  'Profiler.stop': { profile: sampleCpuProfile },

  'HeapProfiler.takeHeapSnapshot': function(params, done) {
    this._sendSampleHeapSnapshot();
    done();
  },

  'HeapProfiler.startTrackingHeapObjects': function(params, done) {
    done(new Error('Heap Timeline is not implemented yet.'));
    // Now we are supposed to periodically send back heap changes
    // Sample transcript from Chrome Canary
    //   {"method":"HeapProfiler.heapStatsUpdate",
    //     "params":{"statsUpdate":[0,40196,3597832]}}
    //   {"method":"HeapProfiler.lastSeenObjectId",
    //     "params":{"lastSeenObjectId":80511,"timestamp":1409762645308.25}}
    // See also documentation in protocol.json
  },

  'HeapProfiler.stopTrackingHeapObjects': function(params, done) {
    // This prevents errors in the frontend
    // The timeline is still not displayed correctly though
    // (or perhaps our sample data is not good for the timeline view)
    this._sendSampleHeapSnapshot();
    done();
  }
};

extend(DevToolsBackend.prototype, {
  serve: function(client) {
    this.client = client;
    this.client.on('message', this._onRequest.bind(this));
    this.client.on('error', this._onError.bind(this));
  },

  _onRequest: function(data) {
    var request;
    try {
      request = JSON.parse(data);
    } catch(err) {
      console.warn('**warn** malformed JSON request %j', data);
    }
    debug('request #%s %s', request.id, request.method, request.params);
    this._handle(request);
  },

  _handle: function(request) {
    var self = this;
    var resultOrHandler = COMMANDS[request.method];
    var fn = typeof resultOrHandler === 'function' ?
      resultOrHandler :
      function(params, callback) {
        callback(null, resultOrHandler);
      };

    fn.call(this, request.params, function handleResult(err, result) {
      debug('response #%s %s', request.id, request.method, result);
      var response = { id: request.id };
      if (err) {
        response.error = err.toString();
      } else {
        response.result = result;
      }
      self._sendMessage(response);
    });
  },

  _onError: function(err) {
    console.warn('**warn** websocket error', err);
  },

  _sendMessage: function(message) {
    this.client.send(JSON.stringify(message));
  },

  _sendSampleHeapSnapshot: function() {
    /*jshint -W106*/
    this._sendMessage({
      method: 'HeapProfiler.reportHeapSnapshotProgress',
      params: {
        done: sampleHeapSnapshot.snapshot.node_count,
        total: sampleHeapSnapshot.snapshot.node_count,
        finished: true
      }
    });

    this._sendMessage({
      'method': 'HeapProfiler.addHeapSnapshotChunk',
      'params': {
        'chunk': JSON.stringify(sampleHeapSnapshot)
      }
    });
  }
});

function loadExampleJsonSync(name) {
  var fs = require('fs');
  var path = require('path');
  return JSON.parse(
    fs.readFileSync(
      path.resolve(__dirname, '..', 'examples', name),
      'utf8'));
}