function receiveMessage()

in salesforce/canvas/public/javascripts/canvas-all.js [886:938]
11 lines of code
4 McCabe index (conditional complexity)

    function receiveMessage(callback, source_origin) {
      if (window.postMessage) {
        if (callback) {
          internalCallback = function (e) {
            var data, r;
            var sfdcJson = Sfdc.JSON || JSON;
            $$.console.log('Post Message Got callback', e);
            if (!$$.isNil(e)) {
              if (
                typeof source_origin === 'string' &&
                e.origin !== source_origin
              ) {
                $$.console.log(
                  "source origin's don't match",
                  e.origin,
                  source_origin
                );
                return false;
              }
              if ($$.isFunction(source_origin)) {
                r = source_origin(e.origin, e.data);
                if (r === false) {
                  $$.console.log(
                    "source origin's function returning false",
                    e.origin,
                    e.data
                  );
                  return false;
                }
              }
              if ($$.appearsJson(e.data)) {
                try {
                  data = sfdcJson.parse(e.data);
                } catch (ignore) {}
                if (
                  !$$.isNil(data) &&
                  ($$.isNil(data.targetModule) ||
                    data.targetModule === 'Canvas')
                ) {
                  $$.console.log('Invoking callback');
                  callback(data, r);
                }
              }
            }
          };
        }
        if (window.addEventListener) {
          window.addEventListener('message', internalCallback, false);
        } else {
          window.attachEvent('onmessage', internalCallback);
        }
      }
    }