/*
 * XMSS Index Registry
 * A registry for XMSS private keys, keeps track of the leaf index for
 * independend copies of the same key.
 * (C) 2016 Matthias Gierlings
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 **/

#include <botan/xmss_index_registry.h>
#include <limits>

namespace Botan {

const std::string XMSS_Index_Registry::m_index_hash_function = "SHA-256";

uint64_t XMSS_Index_Registry::make_key_id(
   const secure_vector<uint8_t>& private_seed,
   const secure_vector<uint8_t>& prf) const
   {
   std::unique_ptr<HashFunction> hash =
      HashFunction::create(m_index_hash_function);
   BOTAN_ASSERT(hash != nullptr, "XMSS_Index_Registry requires SHA-256");
   hash->update(private_seed);
   hash->update(prf);
   secure_vector<uint8_t> result = hash->final();
   uint64_t key_id = 0;
   for(size_t i = 0; i < sizeof(key_id); i++)
      {
      key_id = ((key_id << 8) | result[i]);
      }

   return key_id;
   }

std::shared_ptr<Atomic<size_t>>
XMSS_Index_Registry::get(const secure_vector<uint8_t>& private_seed,
                         const secure_vector<uint8_t>& prf)
   {
   size_t pos = get(make_key_id(private_seed, prf));

   if(pos < std::numeric_limits<size_t>::max())
      {
      return m_leaf_indices[pos];
      }
   else
      {
      return m_leaf_indices[add(make_key_id(private_seed, prf))];
      }
   }

size_t XMSS_Index_Registry::get(uint64_t id) const
   {
   for(size_t i = 0; i < m_key_ids.size(); i++)
      {
      if(m_key_ids[i] == id)
         {
         return i;
         }
      }

   return std::numeric_limits<size_t>::max();
   }

size_t XMSS_Index_Registry::add(uint64_t id, size_t last_unused)
   {
   lock_guard_type<mutex_type> lock(m_mutex);
   size_t pos = get(id);
   if(pos < m_key_ids.size())
      {
      if(last_unused > *(m_leaf_indices[pos]))
         {
         m_leaf_indices[pos] = std::make_shared<Atomic<size_t>>(last_unused);
         }
      return pos;
      }

   m_key_ids.push_back(id);
   m_leaf_indices.push_back(std::make_shared<Atomic<size_t>>(last_unused));
   return m_key_ids.size() - 1;
   }

}