private Map<String, String> findRootDefinition(Collection<MethodReference> methodReferences) {

    Map<String, String> roots = new HashMap<String, String>();

    if (methodReferences.size() == 0) {
      return roots;
    }

    String rootAlias = null;
    String repository = null;

    for (MethodReference methodReference : methodReferences) {
      String methodReferenceName = methodReference.getName();

      // get alias
      // ->createQueryBuilder('test');
      if ("createQueryBuilder".equals(methodReferenceName)) {
        String possibleAlias =
            PhpElementsUtil.getStringValue(
                PsiElementUtils.getMethodParameterPsiElementAt(methodReference, 0));
        if (possibleAlias != null) {
          rootAlias = possibleAlias;
        }
      }

      // find repository class
      // getRepository('Foo')->createQueryBuilder('test');
      if ("getRepository".equals(methodReferenceName)) {
        String possibleRepository =
            PhpElementsUtil.getStringValue(
                PsiElementUtils.getMethodParameterPsiElementAt(methodReference, 0));
        if (possibleRepository != null) {
          repository = possibleRepository;
          PhpClass phpClass = EntityHelper.resolveShortcutName(project, repository);
          if (phpClass != null) {
            repository = phpClass.getPresentableFQN();
          }
        }
      }

      // $qb->from('Foo\Class', 'article')
      if ("from".equals(methodReferenceName)) {
        String table =
            PhpElementsUtil.getStringValue(
                PsiElementUtils.getMethodParameterPsiElementAt(methodReference, 0));
        String alias =
            PhpElementsUtil.getStringValue(
                PsiElementUtils.getMethodParameterPsiElementAt(methodReference, 1));
        if (table != null && alias != null) {
          PhpClass phpClass = EntityHelper.resolveShortcutName(project, table);
          if (phpClass != null) {
            table = phpClass.getPresentableFQN();
          }

          roots.put(table, alias);
        }
      }
    }

    // we have a valid root so add it
    if (rootAlias != null && repository != null) {
      roots.put(repository, rootAlias);
    }

    // we found a alias but not a repository name, so try a scope search if we are inside repository
    // class
    // class implements \Doctrine\Common\Persistence\ObjectRepository, so search for model name of
    // "repositoryClass"
    if (rootAlias != null && repository == null) {
      MethodReference methodReference = methodReferences.iterator().next();
      PhpClass phpClass = PsiTreeUtil.getParentOfType(methodReference, PhpClass.class);
      if (new Symfony2InterfacesUtil()
          .isInstanceOf(phpClass, "\\Doctrine\\Common\\Persistence\\ObjectRepository")) {
        for (DoctrineModel model : EntityHelper.getModelClasses(project)) {
          String className = model.getPhpClass().getPresentableFQN();
          if (className != null) {
            PhpClass resolvedRepoName = EntityHelper.getEntityRepositoryClass(project, className);
            if (PhpElementsUtil.isEqualClassName(resolvedRepoName, phpClass.getPresentableFQN())) {
              roots.put(className, rootAlias);
              return roots;
            }
          }
        }
      }
    }

    // search on PhpTypeProvider
    // $er->createQueryBuilder()
    if (rootAlias != null && repository == null) {
      for (MethodReference methodReference : methodReferences) {
        if ("createQueryBuilder".equals(methodReference.getName())) {
          String signature = methodReference.getSignature();
          int endIndex = signature.lastIndexOf(ObjectRepositoryTypeProvider.TRIM_KEY);
          if (endIndex != -1) {
            String parameter = signature.substring(endIndex + 1);
            int point = parameter.indexOf(".");
            if (point > -1) {
              parameter = parameter.substring(0, point);
              parameter =
                  PhpTypeProviderUtil.getResolvedParameter(
                      PhpIndex.getInstance(project), parameter);
              if (parameter != null) {
                PhpClass phpClass = EntityHelper.resolveShortcutName(project, parameter);
                if (phpClass != null && phpClass.getPresentableFQN() != null) {
                  roots.put(phpClass.getPresentableFQN(), rootAlias);
                  return roots;
                }
              }
            }
          }
        }
      }
    }

    return roots;
  }