//
// Copyright (C) 2013 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#ifndef SHILL_CRYPTO_UTIL_PROXY_H_
#define SHILL_CRYPTO_UTIL_PROXY_H_

#include <memory>
#include <string>
#include <vector>

#include <base/cancelable_callback.h>
#include <base/macros.h>
#include <base/memory/weak_ptr.h>
#include <gtest/gtest_prod.h>  // for FRIEND_TEST

#include "shill/callbacks.h"
#include "shill/error.h"
#include "shill/net/io_handler.h"
#include "shill/shims/protos/crypto_util.pb.h"

namespace shill {

class EventDispatcher;
class FileIO;
class ProcessManager;

class CryptoUtilProxy : public base::SupportsWeakPtr<CryptoUtilProxy> {
 public:
  static const char kCommandVerify[];
  static const char kCommandEncrypt[];
  static const char kCryptoUtilShimPath[];

  explicit CryptoUtilProxy(EventDispatcher* dispatcher);
  virtual ~CryptoUtilProxy();

  // Verify credentials for the currently connected endpoint of
  // |connected_service|.  This is a fairly expensive/time consuming operation.
  // Returns true if we've succeeded in kicking off a job to an external shim
  // to verify credentials.  |result_callback| will be called with the actual
  // result of the job, either true, or false with a descriptive error.
  //
  // |certificate| should be a device certificate in PEM format.
  // |public_key| is a base64 encoded DER RSAPublicKey format public key.
  // |nonce| has no particular format requirements.
  // |signed_data| is the base64 encoded signed string given by the device.
  // |destination_udn| has no format requirements.
  // |ssid| has no constraints.
  // |bssid| should be in the human readable format: 00:11:22:33:44:55.
  virtual bool VerifyDestination(const std::string& certificate,
                                 const std::string& public_key,
                                 const std::string& nonce,
                                 const std::string& signed_data,
                                 const std::string& destination_udn,
                                 const std::vector<uint8_t>& ssid,
                                 const std::string& bssid,
                                 const ResultBoolCallback& result_callback,
                                 Error* error);

  // Encrypt |data| under |public_key|.  This is a fairly time consuming
  // process.  Returns true if we've succeeded in kicking off a job to an
  // external shim to sign the data.  |result_callback| will be called with the
  // results of the operation: an empty string and a descriptive error or the
  // base64 encoded bytes of the encrypted data.
  //
  // |public_key| is a base64 encoded DER RSAPublicKey format public key.
  // |data| has no particular format requirements.
  virtual bool EncryptData(const std::string& public_key,
                           const std::string& data,
                           const ResultStringCallback& result_callback,
                           Error* error);

 private:
  friend class CryptoUtilProxyTest;
  friend class MockCryptoUtilProxy;
  FRIEND_TEST(CryptoUtilProxyTest, BasicAPIUsage);
  FRIEND_TEST(CryptoUtilProxyTest, FailuresReturnValues);
  FRIEND_TEST(CryptoUtilProxyTest, OnlyOneInstanceInFlightAtATime);
  FRIEND_TEST(CryptoUtilProxyTest, ShimLifeTime);
  FRIEND_TEST(CryptoUtilProxyTest, TimeoutsTriggerFailure);
  FRIEND_TEST(CryptoUtilProxyTest, ShimCleanedBeforeCallback);

  // Helper method for parsing the proto buffer return codes sent back by the
  // shim.
  static bool ParseResponseReturnCode(int proto_return_code, Error* e);

  // Kick off a run of the shim to verify credentials or sign data.  Callers
  // pass in the command they want to run on the shim (literally a command line
  // argument to the shim), and a handler to handle the result.  The handler is
  // called both on errors, timeouts, and success.  Behind the scenes, we first
  // send |input| down to the shim through a pipe to its stdin, then wait for
  // bytes to comes back over a pipe connected to the shim's stdout.
  virtual bool StartShimForCommand(const std::string& command,
                                   const std::string& input,
                                   const StringCallback& result_handler);
  // This is the big hammer we use to clean up past shim state.
  virtual void CleanupShim(const Error& shim_result);
  virtual void OnShimDeath(int exit_status);

  // Callbacks that handle IO operations between shill and the shim.
  // Called on changes in file descriptor state.
  void HandleShimStdinReady(int fd);
  void HandleShimOutput(InputData* data);
  void HandleShimReadError(const std::string& error_msg);
  void HandleShimError(const Error& error);
  void HandleShimTimeout();
  // Used to handle the final result of both operations.  |result| is a
  // seriallized protocol buffer or an empty string on error.  On error,
  // |error| is filled in with an appropriate error condition.
  // |result_callback| is a callback from the original caller (the manager).
  void HandleVerifyResult(const ResultBoolCallback& result_handler,
                          const std::string& result,
                          const Error& error);
  void HandleEncryptResult(const ResultStringCallback& result_handler,
                           const std::string& result,
                           const Error& error);

  EventDispatcher* dispatcher_;
  ProcessManager* process_manager_;
  FileIO* file_io_;
  std::string input_buffer_;
  std::string::const_iterator next_input_byte_;
  std::string output_buffer_;
  int shim_stdin_;
  int shim_stdout_;
  pid_t shim_pid_;
  std::unique_ptr<IOHandler> shim_stdin_handler_;
  std::unique_ptr<IOHandler> shim_stdout_handler_;
  Error shim_result_;
  StringCallback result_handler_;
  base::CancelableClosure shim_job_timeout_callback_;

  DISALLOW_COPY_AND_ASSIGN(CryptoUtilProxy);
};

}  // namespace shill

#endif  // SHILL_CRYPTO_UTIL_PROXY_H_