/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2024 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.
 */

#ifndef NDN_CXX_SECURITY_TRANSFORM_PRIVATE_KEY_HPP
#define NDN_CXX_SECURITY_TRANSFORM_PRIVATE_KEY_HPP

#include "ndn-cxx/detail/common.hpp"
#include "ndn-cxx/encoding/buffer.hpp"
#include "ndn-cxx/security/security-common.hpp"

namespace ndn {

class KeyParams;

namespace security::transform {

/**
 * @brief Abstraction of a private key in crypto transformations.
 */
class PrivateKey : noncopyable
{
public:
  class Error : public std::runtime_error
  {
  public:
    using std::runtime_error::runtime_error;
  };

  /**
   * @brief Callback for application to handle password input.
   *
   * The password must be written to @p buf and must not be longer than @p bufSize chars.
   * It is recommended to ask the user to verify the password if @p shouldConfirm is true,
   * e.g., by prompting for it twice. The callback must return the number of characters
   * in the password or 0 if an error occurred.
   */
  using PasswordCallback = std::function<int(char* buf, size_t bufSize, bool shouldConfirm)>;

public:
  /**
   * @brief Creates an empty private key instance.
   *
   * One must call `loadXXXX(...)` to load a private key.
   */
  PrivateKey();

  ~PrivateKey();

  /**
   * @brief Returns the type of the private key.
   */
  KeyType
  getKeyType() const;

  /**
   * @brief Returns the size of the private key in bits.
   */
  size_t
  getKeySize() const;

  /**
   * @brief Returns a digest of the private key.
   *
   * @note Currently supports only HMAC keys.
   */
  ConstBufferPtr
  getKeyDigest(DigestAlgorithm algo) const;

  /**
   * @brief Load a raw private key from a buffer @p buf
   *
   * @note Currently supports only HMAC keys.
   */
  void
  loadRaw(KeyType type, span<const uint8_t> buf);

  /**
   * @brief Load the private key in PKCS#1 format from a buffer @p buf
   */
  void
  loadPkcs1(span<const uint8_t> buf);

  /**
   * @brief Load the private key in PKCS#1 format from a stream @p is
   */
  void
  loadPkcs1(std::istream& is);

  /**
   * @brief Load the private key in base64-encoded PKCS#1 format from a buffer @p buf
   */
  void
  loadPkcs1Base64(span<const uint8_t> buf);

  /**
   * @brief Load the private key in base64-encoded PKCS#1 format from a stream @p is
   */
  void
  loadPkcs1Base64(std::istream& is);

  /**
   * @brief Load the private key in encrypted PKCS#8 format from a buffer @p buf with passphrase @p pw
   * @pre strlen(pw) == pwLen
   */
  void
  loadPkcs8(span<const uint8_t> buf, const char* pw, size_t pwLen);

  /**
   * @brief Load the private key in encrypted PKCS#8 format from a buffer @p buf with
   *        passphrase obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  loadPkcs8(span<const uint8_t> buf, PasswordCallback pwCallback = nullptr);

  /**
   * @brief Load the private key in encrypted PKCS#8 format from a stream @p is with passphrase @p pw
   * @pre strlen(pw) == pwLen
   */
  void
  loadPkcs8(std::istream& is, const char* pw, size_t pwLen);

  /**
   * @brief Load the private key in encrypted PKCS#8 format from a stream @p is with passphrase
   *        obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  loadPkcs8(std::istream& is, PasswordCallback pwCallback = nullptr);

  /**
   * @brief Load the private key in base64-encoded encrypted PKCS#8 format from a buffer @p buf
   *        with passphrase @p pw
   * @pre strlen(pw) == pwLen
   */
  void
  loadPkcs8Base64(span<const uint8_t> buf, const char* pw, size_t pwLen);

  /**
   * @brief Load the private key in encrypted PKCS#8 format from a buffer @p buf with
   *        passphrase obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  loadPkcs8Base64(span<const uint8_t> buf, PasswordCallback pwCallback = nullptr);

  /**
   * @brief Load the private key in base64-encoded encrypted PKCS#8 format from a stream @p is
   *        with passphrase @p pw
   * @pre strlen(pw) == pwLen
   */
  void
  loadPkcs8Base64(std::istream& is, const char* pw, size_t pwLen);

  /**
   * @brief Load the private key in base64-encoded encrypted PKCS#8 format from a stream @p is
   *        with passphrase obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  loadPkcs8Base64(std::istream& is, PasswordCallback pwCallback = nullptr);

  /**
   * @brief Save the private key in PKCS#1 format into a stream @p os
   */
  void
  savePkcs1(std::ostream& os) const;

  /**
   * @brief Save the private key in base64-encoded PKCS#1 format into a stream @p os
   */
  void
  savePkcs1Base64(std::ostream& os) const;

  /**
   * @brief Save the private key in encrypted PKCS#8 format into a stream @p os
   */
  void
  savePkcs8(std::ostream& os, const char* pw, size_t pwLen) const;

  /**
   * @brief Save the private key in encrypted PKCS#8 format into a stream @p os with passphrase
   *        obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  savePkcs8(std::ostream& os, PasswordCallback pwCallback = nullptr) const;

  /**
   * @brief Save the private key in base64-encoded encrypted PKCS#8 format into a stream @p os
   */
  void
  savePkcs8Base64(std::ostream& os, const char* pw, size_t pwLen) const;

  /**
   * @brief Save the private key in base64-encoded encrypted PKCS#8 format into a stream @p os
   *        with passphrase obtained from @p pwCallback
   *
   * The default password callback is provided by OpenSSL
   */
  void
  savePkcs8Base64(std::ostream& os, PasswordCallback pwCallback = nullptr) const;

  /**
   * @return Public key bits in PKCS#8 format
   */
  ConstBufferPtr
  derivePublicKey() const;

  /**
   * @return Plain text of @p cipherText decrypted using this private key.
   *
   * Only RSA encryption is supported for now.
   */
  ConstBufferPtr
  decrypt(span<const uint8_t> cipherText) const;

private:
  friend class SignerFilter;
  friend class VerifierFilter;

  /**
   * @return A pointer to an OpenSSL EVP_PKEY instance.
   *
   * The caller needs to explicitly cast the return value to `EVP_PKEY*`.
   */
  void*
  getEvpPkey() const;

  ConstBufferPtr
  toPkcs1() const;

  ConstBufferPtr
  toPkcs8(const char* pw, size_t pwLen) const;

  ConstBufferPtr
  toPkcs8(PasswordCallback pwCallback = nullptr) const;

  ConstBufferPtr
  rsaDecrypt(span<const uint8_t> cipherText) const;

private:
  friend unique_ptr<PrivateKey> generatePrivateKey(const KeyParams&);

  static unique_ptr<PrivateKey>
  generateRsaKey(uint32_t keySize);

  static unique_ptr<PrivateKey>
  generateEcKey(uint32_t keySize);

  static unique_ptr<PrivateKey>
  generateHmacKey(uint32_t keySize);

private:
  class Impl;
  const unique_ptr<Impl> m_impl;
};

/**
 * @brief Generate a private key according to @p keyParams
 *
 * @note The corresponding public key can be derived from the private key.
 *
 * @throw std::invalid_argument the specified key type is not supported
 * @throw PrivateKey::Error     key generation failed
 */
unique_ptr<PrivateKey>
generatePrivateKey(const KeyParams& keyParams);

} // namespace security::transform
} // namespace ndn

#endif // NDN_CXX_SECURITY_TRANSFORM_PRIVATE_KEY_HPP