security: Abstract certificate fetching from v2::Validator

Change-Id: Ia98d11ac67b0095f632818ac37a19a1e5a7656a8
Refs: #3921
diff --git a/src/security/v2/certificate-fetcher.cpp b/src/security/v2/certificate-fetcher.cpp
new file mode 100644
index 0000000..ffb4416
--- /dev/null
+++ b/src/security/v2/certificate-fetcher.cpp
@@ -0,0 +1,67 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2017 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#include "certificate-fetcher.hpp"
+#include "util/logger.hpp"
+
+namespace ndn {
+namespace security {
+namespace v2 {
+
+NDN_LOG_INIT(ndn.security.v2.CertificateFetcher);
+
+#define NDN_LOG_DEBUG_DEPTH(x) NDN_LOG_DEBUG(std::string(state->getDepth() + 1, '>') << " " << x)
+
+CertificateFetcher::CertificateFetcher()
+  : m_certStorage(nullptr)
+{
+}
+
+CertificateFetcher::~CertificateFetcher() = default;
+
+void
+CertificateFetcher::setCertificateStorage(CertificateStorage& certStorage)
+{
+  m_certStorage = &certStorage;
+}
+
+void
+CertificateFetcher::fetch(const shared_ptr<CertificateRequest>& certRequest,
+                          const shared_ptr<ValidationState>& state,
+                          const ValidationContinuation& continueValidation)
+{
+  BOOST_ASSERT(m_certStorage != nullptr);
+  auto cert = m_certStorage->getUnverifiedCertCache().find(certRequest->m_interest);
+  if (cert != nullptr) {
+    NDN_LOG_DEBUG_DEPTH("Found certificate in **un**verified key cache " << cert->getName());
+    continueValidation(*cert, state);
+    return;
+  }
+  doFetch(certRequest, state,
+          [continueValidation, this] (const Certificate& cert, const shared_ptr<ValidationState>& state) {
+            m_certStorage->cacheUnverifiedCert(Certificate(cert));
+            continueValidation(cert, state);
+          });
+}
+
+} // namespace v2
+} // namespace security
+} // namespace ndn