/*
* Auto Seeded RNG
* (C) 2008,2016 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_AUTO_SEEDING_RNG_H_
#define BOTAN_AUTO_SEEDING_RNG_H_

#include <botan/rng.h>
#include <memory>

namespace Botan {

class Stateful_RNG;

/**
* A userspace PRNG
*/
class BOTAN_PUBLIC_API(2, 0) AutoSeeded_RNG final : public RandomNumberGenerator {
   public:
      /**
      * Test whether this RNG has been seeded
      * @return true if this RNG is seeded and ready for use
      */
      bool is_seeded() const override;

      /**
      * Test whether this RNG accepts externally provided input
      * @return false if this RNG is known to ignore provided inputs
      */
      bool accepts_input() const override { return true; }

      /**
      * Mark state as requiring a reseed on next use
      */
      void force_reseed();

      /**
      * Poll the provided sources for entropy and reseed from them
      * @param srcs the entropy sources to poll
      * @param poll_bits the number of bits to collect
      * @return estimate of the number of bits collected
      */
      size_t reseed_from_sources(Entropy_Sources& srcs,
                                 size_t poll_bits = RandomNumberGenerator::DefaultPollBits) override;

      /**
      * Return the name of this RNG type
      * @return the name of this RNG type
      */
      std::string name() const override;

      /**
      * Clear all internally held values of this RNG
      */
      void clear() override;

      /**
      * Uses the system RNG (if available) or else a default group of
      * entropy sources (all other systems) to gather seed material.
      *
      * @param reseed_interval specifies a limit of how many times
      * the RNG will be called before automatic reseeding is performed
      */
      BOTAN_FUTURE_EXPLICIT AutoSeeded_RNG(size_t reseed_interval = RandomNumberGenerator::DefaultReseedInterval);

      /**
      * Create an AutoSeeded_RNG which will get seed material from some other
      * RNG instance. For example you could provide a reference to the system
      * RNG or a hardware RNG.
      *
      * @param underlying_rng is a reference to some RNG which will be used
      * to perform the periodic reseeding
      * @param reseed_interval specifies a limit of how many times
      * the RNG will be called before automatic reseeding is performed
      */
      BOTAN_FUTURE_EXPLICIT AutoSeeded_RNG(RandomNumberGenerator& underlying_rng,
                                           size_t reseed_interval = RandomNumberGenerator::DefaultReseedInterval);

      /**
      * Create an AutoSeeded_RNG which will get seed material from a set of
      * entropy sources.
      *
      * @param entropy_sources will be polled to perform reseeding periodically
      * @param reseed_interval specifies a limit of how many times
      * the RNG will be called before automatic reseeding is performed
      */
      BOTAN_FUTURE_EXPLICIT AutoSeeded_RNG(Entropy_Sources& entropy_sources,
                                           size_t reseed_interval = RandomNumberGenerator::DefaultReseedInterval);

      /**
      * Create an AutoSeeded_RNG which will get seed material from both an
      * underlying RNG and a set of entropy sources.
      *
      * @param underlying_rng is a reference to some RNG which will be used
      * to perform the periodic reseeding
      * @param entropy_sources will be polled to perform reseeding periodically
      * @param reseed_interval specifies a limit of how many times
      * the RNG will be called before automatic reseeding is performed
      */
      AutoSeeded_RNG(RandomNumberGenerator& underlying_rng,
                     Entropy_Sources& entropy_sources,
                     size_t reseed_interval = RandomNumberGenerator::DefaultReseedInterval);

      AutoSeeded_RNG(const AutoSeeded_RNG& other) = delete;
      /**
      * Move constructor
      */
      AutoSeeded_RNG(AutoSeeded_RNG&& other) noexcept;
      AutoSeeded_RNG& operator=(const AutoSeeded_RNG& other) = delete;
      AutoSeeded_RNG& operator=(AutoSeeded_RNG&& other) = delete;

      ~AutoSeeded_RNG() override;

   private:
      void fill_bytes_with_input(std::span<uint8_t> out, std::span<const uint8_t> in) override;

   private:
      std::unique_ptr<Stateful_RNG> m_rng;
};

}  // namespace Botan

#endif
