text: // Copyright (c) 2014-2017, The Ferro Project
  // 
  // All rights reserved.
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  // 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.
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  // 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
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  // 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 <algorithm>
  #include <cstdio>
  
  #include "cryptonote_basic/cryptonote_basic.h"
  #include "blockchain_db/blockchain_db.h"
  #include "hardfork.h"
  
  #undef FERRO_DEFAULT_LOG_CATEGORY
  #define FERRO_DEFAULT_LOG_CATEGORY "hardfork"
  
  using namespace cryptonote;
  
  static uint8_t get_block_vote(const cryptonote::block &b)
  {
    // Pre-hardfork blocks have a minor version hardcoded to 0.
    // For the purposes of voting, we consider 0 to refer to
    // version number 1, which is what all blocks from the genesis
    // block are. It makes things simpler.
    if (b.minor_version == 0)
      return 1;
    return b.minor_version;
  }
  
  static uint8_t get_block_version(const cryptonote::block &b)
  {
    return b.major_version;
  }
  
  HardFork::HardFork(cryptonote::BlockchainDB &db, uint8_t original_version, uint64_t original_version_till_height, time_t forked_time, time_t update_time, uint64_t window_size, uint8_t default_threshold_percent):
    db(db),
    original_version(original_version),
    original_version_till_height(original_version_till_height),
    forked_time(forked_time),
    update_time(update_time),
    window_size(window_size),
    default_threshold_percent(default_threshold_percent)
  {
    if (window_size == 0)
      throw "window_size needs to be strictly positive";
    if (default_threshold_percent > 100)
      throw "default_threshold_percent needs to be between 0 and 100";
  }
  
  bool HardFork::add_fork(uint8_t version, uint64_t height, uint8_t threshold, time_t time)
  {
    CRITICAL_REGION_LOCAL(lock);
  
    // add in order
    if (version == 0)
      return false;
    if (!heights.empty()) {
      if (version <= heights.back().version)
        return false;
      if (height <= heights.back().height)
        return false;
      if (time <= heights.back().time)
        return false;
    }
    if (threshold > 100)
      return false;
    heights.push_back(Params(version, height, threshold, time));
    return true;
  }
  
  bool HardFork::add_fork(uint8_t version, uint64_t height, time_t time)
  {
    return add_fork(version, height, default_threshold_percent, time);
  }
  
  uint8_t HardFork::get_effective_version(uint8_t voting_version) const
  {
    if (!heights.empty()) {
      uint8_t max_version = heights.back().version;
      if (voting_version > max_version)
        voting_version = max_version;
    }
    return voting_version;
  }
  
  bool HardFork::do_check(uint8_t block_version, uint8_t voting_version) const
  {
    return block_version == heights[current_fork_index].version
        && voting_version >= heights[current_fork_index].version;
  }
  
  bool HardFork::check(const cryptonote::block &block) const
  {
    CRITICAL_REGION_LOCAL(lock);
    return do_check(::get_block_version(block), ::get_block_vote(block));
  }
  
  bool HardFork::do_check_for_height(uint8_t block_version, uint8_t voting_version, uint64_t height) const
  {
    int fork_index = get_voted_fork_index(height);
    return block_version == heights[fork_index].version
        && voting_version >= heights[fork_index].version;
  }
  
  bool HardFork::check_for_height(const cryptonote::block &block, uint64_t height) const
  {
    CRITICAL_REGION_LOCAL(lock);
    return do_check_for_height(::get_block_version(block), ::get_block_vote(block), height);
  }
  
  bool HardFork::add(uint8_t block_version, uint8_t voting_version, uint64_t height)
  {
    CRITICAL_REGION_LOCAL(lock);
  
    if (!do_check(block_version, voting_version))
      return false;
  
    db.set_hard_fork_version(height, heights[current_fork_index].version);
  
    voting_version = get_effective_version(voting_version);
  
    while (versions.size() >= window_size) {
      const uint8_t old_version = versions.front();
      assert(last_versions[old_version] >= 1);
      last_versions[old_version]--;
      versions.pop_front();
    }
  
    last_versions[voting_version]++;
    versions.push_back(voting_version);
  
    uint8_t voted = get_voted_fork_index(height + 1);
    if (voted > current_fork_index) {
      current_fork_index = voted;
    }
  
    return true;
  }
  
  bool HardFork::add(const cryptonote::block &block, uint64_t height)
  {
    return add(::get_block_version(block), ::get_block_vote(block), height);
  }
  
  void HardFork::init()
  {
    CRITICAL_REGION_LOCAL(lock);
  
    // add a placeholder for the default version, to avoid special cases
    if (heights.empty())
      heights.push_back(Params(original_version, 0, 0, 0));
  
    versions.clear();
    for (size_t n = 0; n < 256; ++n)
      last_versions[n] = 0;
    current_fork_index = 0;
  
    // restore state from DB
    uint64_t height = db.height();
    if (height > window_size)
      height -= window_size - 1;
    else
      height = 1;
  
    bool populate = false;
    try
    {
      db.get_hard_fork_version(0);
    }
    catch (...) { populate = true; }
    if (populate) {
      MINFO("The DB has no hard fork info, reparsing from start");
      height = 1;
    }
    MDEBUG("reorganizing from " << height);
    if (populate) {
      reorganize_from_chain_height(height);
      // reorg will not touch the genesis block, use this as a flag for populating done
      db.set_hard_fork_version(0, original_version);
    }
    else {
      rescan_from_chain_height(height);
    }
    MDEBUG("reorganization done");
  }
  
  uint8_t HardFork::get_block_version(uint64_t height) const
  {
    if (height <= original_version_till_height)
      return original_version;
  
    const cryptonote::block &block = db.get_block_from_height(height);
    return ::get_block_version(block);
  }
  
  bool HardFork::reorganize_from_block_height(uint64_t height)
  {
    CRITICAL_REGION_LOCAL(lock);
    if (height >= db.height())
      return false;
  
    db.set_batch_transactions(true);
    bool stop_batch = db.batch_start();
  
    versions.clear();
  
    for (size_t n = 0; n < 256; ++n)
      last_versions[n] = 0;
    const uint64_t rescan_height = height >= (window_size - 1) ? height - (window_size  -1) : 0;
    const uint8_t start_version = height == 0 ? original_version : db.get_hard_fork_version(height);
    while (current_fork_index > 0 && heights[current_fork_index].version > start_version) {
      --current_fork_index;
    }
    for (uint64_t h = rescan_height; h <= height; ++h) {
      cryptonote::block b = db.get_block_from_height(h);
      const uint8_t v = get_effective_version(get_block_vote(b));
      last_versions[v]++;
      versions.push_back(v);
    }
  
    uint8_t voted = get_voted_fork_index(height + 1);
    if (voted > current_fork_index) {
      current_fork_index = voted;
    }
  
    const uint64_t bc_height = db.height();
    for (uint64_t h = height + 1; h < bc_height; ++h) {
      add(db.get_block_from_height(h), h);
    }
  
    if (stop_batch)
      db.batch_stop();
  
    return true;
  }
  
  bool HardFork::reorganize_from_chain_height(uint64_t height)
  {
    if (height == 0)
      return false;
    return reorganize_from_block_height(height - 1);
  }
  
  bool HardFork::rescan_from_block_height(uint64_t height)
  {
    CRITICAL_REGION_LOCAL(lock);
    db.block_txn_start(true);
    if (height >= db.height()) {
      db.block_txn_stop();
      return false;
    }
  
    versions.clear();
  
    for (size_t n = 0; n < 256; ++n)
      last_versions[n] = 0;
    for (uint64_t h = height; h < db.height(); ++h) {
      cryptonote::block b = db.get_block_from_height(h);
      const uint8_t v = get_effective_version(get_block_vote(b));
      last_versions[v]++;
      versions.push_back(v);
    }
  
    uint8_t lastv = db.get_hard_fork_version(db.height() - 1);
    current_fork_index = 0;
    while (current_fork_index + 1 < heights.size() && heights[current_fork_index].version != lastv)
      ++current_fork_index;
  
    uint8_t voted = get_voted_fork_index(db.height());
    if (voted > current_fork_index) {
      current_fork_index = voted;
    }
  
    db.block_txn_stop();
  
    return true;
  }
  
  bool HardFork::rescan_from_chain_height(uint64_t height)
  {
    if (height == 0)
      return false;
    return rescan_from_block_height(height - 1);
  }
  
  int HardFork::get_voted_fork_index(uint64_t height) const
  {
    CRITICAL_REGION_LOCAL(lock);
    uint32_t accumulated_votes = 0;
    for (unsigned int n = heights.size() - 1; n > current_fork_index; --n) {
      uint8_t v = heights[n].version;
      accumulated_votes += last_versions[v];
      uint32_t threshold = (window_size * heights[n].threshold + 99) / 100;
      if (height >= heights[n].height && accumulated_votes >= threshold) {
        return n;
      }
    }
    return current_fork_index;
  }
  
  HardFork::State HardFork::get_state(time_t t) const
  {
    CRITICAL_REGION_LOCAL(lock);
  
    // no hard forks setup yet
    if (heights.size() <= 1)
      return Ready;
  
    time_t t_last_fork = heights.back().time;
    if (t >= t_last_fork + forked_time)
      return LikelyForked;
    if (t >= t_last_fork + update_time)
      return UpdateNeeded;
    return Ready;
  }
  
  HardFork::State HardFork::get_state() const
  {
    return get_state(time(NULL));
  }
  
  uint8_t HardFork::get(uint64_t height) const
  {
    CRITICAL_REGION_LOCAL(lock);
    if (height > db.height()) {
      assert(false);
      return 255;
    }
    if (height == db.height()) {
      return get_current_version();
    }
    return db.get_hard_fork_version(height);
  }
  
  uint8_t HardFork::get_current_version() const
  {
    CRITICAL_REGION_LOCAL(lock);
    return heights[current_fork_index].version;
  }
  
  uint8_t HardFork::get_ideal_version() const
  {
    CRITICAL_REGION_LOCAL(lock);
    return heights.back().version;
  }
  
  uint8_t HardFork::get_ideal_version(uint64_t height) const
  {
    CRITICAL_REGION_LOCAL(lock);
    for (unsigned int n = heights.size() - 1; n > 0; --n) {
      if (height >= heights[n].height) {
        return heights[n].version;
      }
    }
    return original_version;
  }
  
  uint64_t HardFork::get_earliest_ideal_height_for_version(uint8_t version) const
  {
    for (unsigned int n = heights.size() - 1; n > 0; --n) {
      if (heights[n].version <= version)
        return heights[n].height;
    }
    return 0;
  }
  
  uint8_t HardFork::get_next_version() const
  {
    CRITICAL_REGION_LOCAL(lock);
    uint64_t height = db.height();
    for (unsigned int n = heights.size() - 1; n > 0; --n) {
      if (height >= heights[n].height) {
        return heights[n < heights.size() - 1 ? n + 1 : n].version;
      }
    }
    return original_version;
  }
  
  bool HardFork::get_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint64_t &earliest_height, uint8_t &voting) const
  {
    CRITICAL_REGION_LOCAL(lock);
  
    const uint8_t current_version = heights[current_fork_index].version;
    const bool enabled = current_version >= version;
    window = versions.size();
    votes = 0;
    for (size_t n = version; n < 256; ++n)
        votes += last_versions[n];
    threshold = (window * heights[current_fork_index].threshold + 99) / 100;
    //assert((votes >= threshold) == enabled);
    earliest_height = get_earliest_ideal_height_for_version(version);
    voting = heights.back().version;
    return enabled;
  }
  
  