// Copyright (c)      2018, The Loki Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
//    conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
//    of conditions and the following disclaimer in the documentation and/or other
//    materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
//    used to endorse or promote products derived from this software without specific
//    prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "service_node_voting.h"
#include "service_node_list.h"
#include "cryptonote_basic/tx_extra.h"
#include "cryptonote_basic/cryptonote_format_utils.h"
#include "cryptonote_basic/verification_context.h"
#include "cryptonote_basic/connection_context.h"
#include "cryptonote_protocol/cryptonote_protocol_defs.h"
#include "checkpoints/checkpoints.h"

#include "misc_log_ex.h"
#include "string_tools.h"

#include <random>
#include <string>
#include <vector>

#include <boost/endian/conversion.hpp>

#undef LOKI_DEFAULT_LOG_CATEGORY
#define LOKI_DEFAULT_LOG_CATEGORY "service_nodes"

namespace service_nodes
{
  bool convert_deregister_vote_to_legacy(quorum_vote_t const &vote, legacy_deregister_vote &legacy_vote)
  {
    if (vote.type != quorum_type::obligations || vote.state_change.state != new_state::deregister)
      return false;

    legacy_vote.block_height           = vote.block_height;
    legacy_vote.service_node_index     = vote.state_change.worker_index;
    legacy_vote.voters_quorum_index    = vote.index_in_group;
    legacy_vote.signature              = vote.signature;
    return true;
  }

  // TODO(loki): Post HF12 remove legacy votes, no longer should be propagated
  quorum_vote_t convert_legacy_deregister_vote(legacy_deregister_vote const &vote)
  {
    quorum_vote_t result             = {};
    result.type                      = quorum_type::obligations;
    result.block_height              = vote.block_height;
    result.signature                 = vote.signature;
    result.group                     = quorum_group::validator;
    result.index_in_group            = vote.voters_quorum_index;
    result.state_change.worker_index = vote.service_node_index;
    result.state_change.state        = new_state::deregister;
    return result;
  }

  static crypto::hash make_state_change_vote_hash(uint64_t block_height, uint32_t service_node_index, new_state state)
  {
    uint16_t state_int = static_cast<uint16_t>(state);

    char buf[sizeof(block_height) + sizeof(service_node_index) + sizeof(state_int)];

    boost::endian::native_to_little_inplace(block_height);
    boost::endian::native_to_little_inplace(service_node_index);
    boost::endian::native_to_little_inplace(state_int);
    memcpy(buf,                                                     &block_height,       sizeof(block_height));
    memcpy(buf + sizeof(block_height),                              &service_node_index, sizeof(service_node_index));
    memcpy(buf + sizeof(block_height) + sizeof(service_node_index), &state_int,          sizeof(state_int));

    auto size = sizeof(buf);
    if (state == new_state::deregister)
        size -= sizeof(uint16_t); // Don't include state value for deregs (to be backwards compatible with pre-v12 dereg votes)

    crypto::hash result;
    crypto::cn_fast_hash(buf, size, result);
    return result;
  }

  crypto::signature make_signature_from_vote(quorum_vote_t const &vote, const crypto::public_key& pub, const crypto::secret_key& sec)
  {
    crypto::signature result = {};
    switch(vote.type)
    {
      default:
      {
        LOG_PRINT_L1("Unhandled vote type with value: " << (int)vote.type);
        assert("Unhandled vote type" == 0);
        return result;
      };

      case quorum_type::obligations:
      {
        crypto::hash hash = make_state_change_vote_hash(vote.block_height, vote.state_change.worker_index, vote.state_change.state);
        crypto::generate_signature(hash, pub, sec, result);
      }
      break;

      case quorum_type::checkpointing:
      {
        crypto::hash hash = vote.checkpoint.block_hash;
        crypto::generate_signature(hash, pub, sec, result);
      }
      break;
    }

    return result;
  }

  crypto::signature make_signature_from_tx_state_change(cryptonote::tx_extra_service_node_state_change const &state_change, crypto::public_key const &pub, crypto::secret_key const &sec)
  {
    crypto::signature result;
    crypto::hash hash = make_state_change_vote_hash(state_change.block_height, state_change.service_node_index, state_change.state);
    crypto::generate_signature(hash, pub, sec, result);
    return result;
  }

  static bool bounds_check_worker_index(service_nodes::testing_quorum const &quorum, uint32_t worker_index, cryptonote::vote_verification_context *vvc)
  {
    if (worker_index >= quorum.workers.size())
    {
      if (vvc) vvc->m_worker_index_out_of_bounds = true;
      LOG_PRINT_L1("Quorum worker index in was out of bounds: " << worker_index << ", expected to be in range of: [0, " << quorum.workers.size() << ")");
      return false;
    }
    return true;
  }

  static bool bounds_check_validator_index(service_nodes::testing_quorum const &quorum, uint32_t validator_index, cryptonote::vote_verification_context *vvc)
  {
    if (validator_index >= quorum.validators.size())
    {
      if (vvc) vvc->m_validator_index_out_of_bounds = true;
      LOG_PRINT_L1("Validator's index was out of bounds: " << validator_index << ", expected to be in range of: [0, " << quorum.validators.size() << ")");
      return false;
    }
    return true;
  }

  // If we get an incoming vote of state change tx that is outside the acceptable range by this many
  // blocks then ignore it but don't trigger a connection drop; the sending side could be a couple
  // blocks out of sync and sending something that it thinks is legit.
  constexpr uint64_t VERIFY_HEIGHT_BUFFER = 5;

  static bool bad_tx(cryptonote::tx_verification_context &tvc) {
    tvc.m_verifivation_failed = true;
    return false;
  }

  bool verify_tx_state_change(const cryptonote::tx_extra_service_node_state_change &state_change,
                              uint64_t latest_height,
                              cryptonote::tx_verification_context &tvc,
                              const service_nodes::testing_quorum &quorum,
                              const uint8_t hf_version)
  {
    auto &vvc = tvc.m_vote_ctx;
    if (state_change.state != new_state::deregister && hf_version < cryptonote::network_version_12_checkpointing)
    {
      LOG_PRINT_L1("Non-deregister state changes are invalid before v12");
      return bad_tx(tvc);
    }

    if (state_change.state >= new_state::_count)
    {
      LOG_PRINT_L1("Unknown state change to new state: " << static_cast<uint16_t>(state_change.state));
      return bad_tx(tvc);
    }

    if (state_change.votes.size() < service_nodes::STATE_CHANGE_MIN_VOTES_TO_CHANGE_STATE)
    {
      LOG_PRINT_L1("Not enough votes");
      vvc.m_not_enough_votes = true;
      return bad_tx(tvc);
    }

    if (state_change.votes.size() > service_nodes::STATE_CHANGE_QUORUM_SIZE)
    {
      LOG_PRINT_L1("Too many votes");
      return bad_tx(tvc);
    }

    if (!bounds_check_worker_index(quorum, state_change.service_node_index, &vvc))
      return bad_tx(tvc);

    // Check if state_change is too old or too new to hold onto
    {
      if (state_change.block_height >= latest_height)
      {
        LOG_PRINT_L1("Received state change tx for height: " << state_change.block_height
                     << " and service node: "              << state_change.service_node_index
                     << ", is newer than current height: " << latest_height
                     << " blocks and has been rejected.");
        vvc.m_invalid_block_height = true;
        if (state_change.block_height >= latest_height + VERIFY_HEIGHT_BUFFER)
          tvc.m_verifivation_failed = true;
        return false;
      }

      if (latest_height >= state_change.block_height + service_nodes::STATE_CHANGE_TX_LIFETIME_IN_BLOCKS)
      {
        LOG_PRINT_L1("Received state change tx for height: "
                     << state_change.block_height << " and service node: " << state_change.service_node_index
                     << ", is older than: " << service_nodes::STATE_CHANGE_TX_LIFETIME_IN_BLOCKS
                     << " (current height: " << latest_height << ") "
                     << "blocks and has been rejected.");
        vvc.m_invalid_block_height = true;
        if (latest_height >= state_change.block_height + (service_nodes::STATE_CHANGE_TX_LIFETIME_IN_BLOCKS + VERIFY_HEIGHT_BUFFER))
          tvc.m_verifivation_failed = true;
        return false;
      }
    }

    crypto::hash const hash = make_state_change_vote_hash(state_change.block_height, state_change.service_node_index, state_change.state);
    std::array<int, service_nodes::STATE_CHANGE_QUORUM_SIZE> validator_set = {};
    for (const auto &vote : state_change.votes)
    {
      if (!bounds_check_validator_index(quorum, vote.validator_index, &vvc))
        return bad_tx(tvc);

      if (++validator_set[vote.validator_index] > 1)
      {
        vvc.m_duplicate_voters = true;
        LOG_PRINT_L1("Voter quorum index is duplicated: " << vote.validator_index);
        return bad_tx(tvc);
      }

      crypto::public_key const &key = quorum.validators[vote.validator_index];
      if (!crypto::check_signature(hash, key, vote.signature))
      {
        LOG_PRINT_L1("Invalid signatures for votes");
        vvc.m_signature_not_valid = true;
        return bad_tx(tvc);
      }
    }

    return true;
  }

  bool verify_checkpoint(cryptonote::checkpoint_t const &checkpoint, service_nodes::testing_quorum const &quorum)
  {
    if (checkpoint.type == cryptonote::checkpoint_type::service_node)
    {
      if (checkpoint.signatures.size() < service_nodes::CHECKPOINT_MIN_VOTES)
      {
        LOG_PRINT_L1("Checkpoint has insufficient signatures to be considered");
        return false;
      }

      if (checkpoint.signatures.size() > service_nodes::CHECKPOINT_QUORUM_SIZE)
      {
        LOG_PRINT_L1("Checkpoint has too many signatures to be considered");
        return false;
      }

      std::array<size_t, service_nodes::CHECKPOINT_QUORUM_SIZE> unique_vote_set = {};
      for (service_nodes::voter_to_signature const &voter_to_signature : checkpoint.signatures)
      {
        if (!bounds_check_worker_index(quorum, voter_to_signature.voter_index, nullptr)) return false;

        if (unique_vote_set[voter_to_signature.voter_index]++)
        {
          LOG_PRINT_L1("Voter quorum index is duplicated: " << voter_to_signature.voter_index);
          return false;
        }

        crypto::public_key const &key = quorum.workers[voter_to_signature.voter_index];
        if (!crypto::check_signature(checkpoint.block_hash, key, voter_to_signature.signature))
        {
          LOG_PRINT_L1("Invalid signatures for votes");
          return false;
        }
      }
    }
    else
    {
      if (checkpoint.signatures.size() != 0)
      {
        LOG_PRINT_L1("Non service-node checkpoints should have no signatures");
        return false;
      }
    }

    return true;
  }

  quorum_vote_t make_state_change_vote(uint64_t block_height, uint16_t validator_index, uint16_t worker_index, new_state state, crypto::public_key const &pub_key, crypto::secret_key const &sec_key)
  {
    quorum_vote_t result             = {};
    result.type                      = quorum_type::obligations;
    result.block_height              = block_height;
    result.group                     = quorum_group::validator;
    result.index_in_group            = validator_index;
    result.state_change.worker_index = worker_index;
    result.state_change.state        = state;
    result.signature                 = make_signature_from_vote(result, pub_key, sec_key);
    return result;
  }

  bool verify_vote(const quorum_vote_t& vote, uint64_t latest_height, cryptonote::vote_verification_context &vvc, const service_nodes::testing_quorum &quorum)
  {
    bool result = true;
    if (vote.group == quorum_group::invalid)
      result = false;
    else if (vote.group == quorum_group::validator)
      result = bounds_check_validator_index(quorum, vote.index_in_group, &vvc);
    else
      result = bounds_check_worker_index(quorum, vote.index_in_group, &vvc);

    if (!result)
      return result;

    //
    // NOTE: Validate vote age
    //
    {
      bool height_in_buffer = false;
      if (latest_height > vote.block_height + VOTE_LIFETIME)
      {
        height_in_buffer = latest_height <= vote.block_height + (VOTE_LIFETIME + VERIFY_HEIGHT_BUFFER);
        LOG_PRINT_L1("Received vote for height: " << vote.block_height << ", is older than: " << VOTE_LIFETIME
                                                  << " blocks and has been rejected.");
        vvc.m_invalid_block_height = true;
      }
      else if (vote.block_height > latest_height)
      {
        height_in_buffer = vote.block_height <= latest_height + VERIFY_HEIGHT_BUFFER;
        LOG_PRINT_L1("Received vote for height: " << vote.block_height << ", is newer than: " << latest_height
                                                  << " (latest block height) and has been rejected.");
        vvc.m_invalid_block_height = true;
      }

      if (vvc.m_invalid_block_height)
      {
        result                    = false;
        vvc.m_verification_failed = !height_in_buffer;
        return result;
      }
    }

    {
      crypto::public_key key = crypto::null_pkey;
      crypto::hash hash      = crypto::null_hash;

      switch(vote.type)
      {
        default:
        {
          LOG_PRINT_L1("Unhandled vote type with value: " << (int)vote.type);
          assert("Unhandled vote type" == 0);
          return false;
        };

        case quorum_type::obligations:
        {
          if (vote.group != quorum_group::validator)
          {
            LOG_PRINT_L1("Vote received specifies incorrect voting group, expected vote from validator");
            vvc.m_incorrect_voting_group = true;
            return false;
          }

          key = quorum.validators[vote.index_in_group];
          hash = make_state_change_vote_hash(vote.block_height, vote.state_change.worker_index, vote.state_change.state);

          bool result = bounds_check_worker_index(quorum, vote.state_change.worker_index, &vvc);
          if (!result)
            return result;
        }
        break;

        case quorum_type::checkpointing:
        {
          if (vote.group != quorum_group::worker)
          {
            LOG_PRINT_L1("Vote received specifies incorrect voting group, expected vote from worker");
            vvc.m_incorrect_voting_group = true;
            return false;
          }

          key  = quorum.workers[vote.index_in_group];
          hash = vote.checkpoint.block_hash;
        }
        break;
      }

      //
      // NOTE: Validate vote signature
      //
      result = crypto::check_signature(hash, key, vote.signature);
      if (!result)
      {
        vvc.m_signature_not_valid = true;
        return result;
      }
    }

    result = true;
    return result;
  }

  template <typename T>
  static std::vector<pool_vote_entry> *find_vote_in_pool(std::vector<T> &pool, const quorum_vote_t &vote, bool create) {
    T typed_vote{vote};
    auto it = std::find(pool.begin(), pool.end(), typed_vote);
    if (it != pool.end())
      return &it->votes;
    if (!create)
      return nullptr;
    pool.push_back(std::move(typed_vote));
    return &pool.back().votes;
  }

  std::vector<pool_vote_entry> *voting_pool::find_vote_pool(const quorum_vote_t &find_vote, bool create_if_not_found) {
    switch(find_vote.type)
    {
      default:
        LOG_PRINT_L1("Unhandled find_vote type with value: " << (int)find_vote.type);
        assert("Unhandled find_vote type" == 0);
        return nullptr;

      case quorum_type::obligations:
        return find_vote_in_pool(m_obligations_pool, find_vote, create_if_not_found);

      case quorum_type::checkpointing:
        return find_vote_in_pool(m_checkpoint_pool, find_vote, create_if_not_found);
    }
  }

  void voting_pool::set_relayed(const std::vector<quorum_vote_t>& votes)
  {
    CRITICAL_REGION_LOCAL(m_lock);
    const time_t now = time(NULL);

    for (const quorum_vote_t &find_vote : votes)
    {
      std::vector<pool_vote_entry> *vote_pool = find_vote_pool(find_vote);

      if (vote_pool) // We found the group that this vote belongs to
      {
        auto vote = std::find_if(vote_pool->begin(), vote_pool->end(), [&find_vote](pool_vote_entry const &entry) {
            return (find_vote.index_in_group == entry.vote.index_in_group);
        });

        if (vote != vote_pool->end())
        {
          vote->time_last_sent_p2p = now;
        }
      }
    }
  }

  template <typename T>
  static void append_relayable_votes(std::vector<quorum_vote_t> &result, const T &pool, const uint64_t max_last_sent, uint64_t min_height) {
    for (const auto &pool_entry : pool)
      for (const auto &vote_entry : pool_entry.votes)
        if (vote_entry.vote.block_height >= min_height && vote_entry.time_last_sent_p2p <= max_last_sent)
          result.push_back(vote_entry.vote);
  }

  std::vector<quorum_vote_t> voting_pool::get_relayable_votes(uint64_t height) const
  {
    CRITICAL_REGION_LOCAL(m_lock);

    // TODO(doyle): Rate-limiting: A better threshold value that follows suite with transaction relay time back-off
#if defined(LOKI_ENABLE_INTEGRATION_TEST_HOOKS)
    constexpr uint64_t TIME_BETWEEN_RELAY = 0;
#else
    constexpr uint64_t TIME_BETWEEN_RELAY = 60 * 2;
#endif

    const uint64_t max_last_sent = static_cast<uint64_t>(time(nullptr)) - TIME_BETWEEN_RELAY;
    const uint64_t min_height = height > VOTE_LIFETIME ? height - VOTE_LIFETIME : 0;

    std::vector<quorum_vote_t> result;
    append_relayable_votes(result, m_obligations_pool, max_last_sent, min_height);
    append_relayable_votes(result, m_checkpoint_pool,  max_last_sent, min_height);
    return result;
  }

  // return: True if the vote was unique
  static bool add_vote_to_pool_if_unique(std::vector<pool_vote_entry> &votes, quorum_vote_t const &vote)
  {
    auto vote_it = std::find_if(votes.begin(), votes.end(), [&vote](pool_vote_entry const &pool_entry) {
        assert(pool_entry.vote.group == vote.group);
        return (pool_entry.vote.index_in_group == vote.index_in_group);
    });

    if (vote_it == votes.end())
    {
      votes.push_back({vote});
      return true;
    }

    return false;
  }

  std::vector<pool_vote_entry> voting_pool::add_pool_vote_if_unique(uint64_t latest_height,
                                                                    const quorum_vote_t& vote,
                                                                    cryptonote::vote_verification_context& vvc,
                                                                    const service_nodes::testing_quorum &quorum)
  {
    if (!verify_vote(vote, latest_height, vvc, quorum))
    {
      LOG_PRINT_L1("Signature verification failed for deregister vote");
      return {};
    }

    CRITICAL_REGION_LOCAL(m_lock);
    auto *votes = find_vote_pool(vote, /*create_if_not_found=*/ true);
    if (!votes)
      return {};

    vvc.m_added_to_pool = add_vote_to_pool_if_unique(*votes, vote);
    return *votes;
  }

  void voting_pool::remove_used_votes(std::vector<cryptonote::transaction> const &txs, uint8_t hard_fork_version)
  {
    // TODO(doyle): Cull checkpoint votes
    CRITICAL_REGION_LOCAL(m_lock);
    if (m_obligations_pool.empty())
      return;

    for (const auto &tx : txs)
    {
      if (tx.type != cryptonote::txtype::state_change)
        continue;

      cryptonote::tx_extra_service_node_state_change state_change;
      if (!get_service_node_state_change_from_tx_extra(tx.extra, state_change, hard_fork_version))
      {
        LOG_ERROR("Could not get state change from tx, possibly corrupt tx");
        continue;
      }

      auto it = std::find(m_obligations_pool.begin(), m_obligations_pool.end(), state_change);

      if (it != m_obligations_pool.end())
        m_obligations_pool.erase(it);
    }
  }

  template <typename T>
  static void cull_votes(std::vector<T> &vote_pool, uint64_t min_height, uint64_t max_height)
  {
    for (auto it = vote_pool.begin(); it != vote_pool.end(); )
    {
      const T &pool_entry = *it;
      if (pool_entry.height < min_height || pool_entry.height > max_height)
        it = vote_pool.erase(it);
      else
        ++it;
    }
  }

  void voting_pool::remove_expired_votes(uint64_t height)
  {
    CRITICAL_REGION_LOCAL(m_lock);
    uint64_t min_height = (height < VOTE_LIFETIME) ? 0 : height - VOTE_LIFETIME;
    cull_votes(m_obligations_pool, min_height, height);
    cull_votes(m_checkpoint_pool, min_height, height);
  }
}; // namespace service_nodes