/*
* Stream Cipher
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_STREAM_CIPHER_H_
#define BOTAN_STREAM_CIPHER_H_

#include <botan/sym_algo.h>
#include <string>
#include <memory>

namespace Botan {

/**
* Base class for all stream ciphers
*/
class BOTAN_PUBLIC_API(2,0) StreamCipher : public SymmetricAlgorithm
   {
   public:
      virtual ~StreamCipher() = default;

      /**
      * Create an instance based on a name
      * If provider is empty then best available is chosen.
      * @param algo_spec algorithm name
      * @param provider provider implementation to use
      * @return a null pointer if the algo/provider combination cannot be found
      */
      static std::unique_ptr<StreamCipher>
         create(const std::string& algo_spec,
                const std::string& provider = "");

      /**
      * Create an instance based on a name
      * If provider is empty then best available is chosen.
      * @param algo_spec algorithm name
      * @param provider provider implementation to use
      * Throws a Lookup_Error if the algo/provider combination cannot be found
      */
      static std::unique_ptr<StreamCipher>
         create_or_throw(const std::string& algo_spec,
                         const std::string& provider = "");

      /**
      * @return list of available providers for this algorithm, empty if not available
      */
      static std::vector<std::string> providers(const std::string& algo_spec);

      /**
      * Encrypt or decrypt a message
      * @param in the plaintext
      * @param out the byte array to hold the output, i.e. the ciphertext
      * @param len the length of both in and out in bytes
      */
      virtual void cipher(const uint8_t in[], uint8_t out[], size_t len) = 0;

      /**
      * Write keystream bytes to a buffer
      * @param out the byte array to hold the keystream
      * @param len the length of out in bytes
      */
      virtual void write_keystream(uint8_t out[], size_t len)
         {
         clear_mem(out, len);
         cipher1(out, len);
         }

      /**
      * Encrypt or decrypt a message
      * The message is encrypted/decrypted in place.
      * @param buf the plaintext / ciphertext
      * @param len the length of buf in bytes
      */
      void cipher1(uint8_t buf[], size_t len)
         { cipher(buf, buf, len); }

      /**
      * Encrypt a message
      * The message is encrypted/decrypted in place.
      * @param inout the plaintext / ciphertext
      */
      template<typename Alloc>
         void encipher(std::vector<uint8_t, Alloc>& inout)
         { cipher(inout.data(), inout.data(), inout.size()); }

      /**
      * Encrypt a message
      * The message is encrypted in place.
      * @param inout the plaintext / ciphertext
      */
      template<typename Alloc>
         void encrypt(std::vector<uint8_t, Alloc>& inout)
         { cipher(inout.data(), inout.data(), inout.size()); }

      /**
      * Decrypt a message in place
      * The message is decrypted in place.
      * @param inout the plaintext / ciphertext
      */
      template<typename Alloc>
         void decrypt(std::vector<uint8_t, Alloc>& inout)
         { cipher(inout.data(), inout.data(), inout.size()); }

      /**
      * Resync the cipher using the IV
      * @param iv the initialization vector
      * @param iv_len the length of the IV in bytes
      */
      virtual void set_iv(const uint8_t iv[], size_t iv_len) = 0;

      /**
      * Return the default (preferred) nonce length
      * If this function returns 0, then this cipher does not support nonces
      */
      virtual size_t default_iv_length() const { return 0; }

      /**
      * @param iv_len the length of the IV in bytes
      * @return if the length is valid for this algorithm
      */
      virtual bool valid_iv_length(size_t iv_len) const { return (iv_len == 0); }

      /**
      * @return a new object representing the same algorithm as *this
      */
      virtual StreamCipher* clone() const = 0;

      /**
      * Set the offset and the state used later to generate the keystream
      * @param offset the offset where we begin to generate the keystream
      */
      virtual void seek(uint64_t offset) = 0;

      /**
      * @return provider information about this implementation. Default is "base",
      * might also return "sse2", "avx2", "openssl", or some other arbitrary string.
      */
      virtual std::string provider() const { return "base"; }
   };

}

#endif