/* Copyright (c) 2017 Pieter Wuille
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <graphene/peerplays_sidechain/bitcoin/bech32.hpp>
#include <graphene/peerplays_sidechain/bitcoin/segwit_addr.hpp>

namespace {

typedef std::vector<uint8_t> data;

/** Convert from one power-of-2 number base to another. */
template <int frombits, int tobits, bool pad>
bool convertbits(data &out, const data &in) {
   int acc = 0;
   int bits = 0;
   const int maxv = (1 << tobits) - 1;
   const int max_acc = (1 << (frombits + tobits - 1)) - 1;
   for (size_t i = 0; i < in.size(); ++i) {
      int value = in[i];
      acc = ((acc << frombits) | value) & max_acc;
      bits += frombits;
      while (bits >= tobits) {
         bits -= tobits;
         out.push_back((acc >> bits) & maxv);
      }
   }
   if (pad) {
      if (bits)
         out.push_back((acc << (tobits - bits)) & maxv);
   } else if (bits >= frombits || ((acc << (tobits - bits)) & maxv)) {
      return false;
   }
   return true;
}

} // namespace

namespace graphene { namespace peerplays_sidechain { namespace bitcoin { namespace segwit_addr {

/** Decode a SegWit address. */
std::pair<int, data> decode(const std::string &hrp, const std::string &addr) {
   std::pair<std::string, data> dec = bech32::Decode(addr);
   if (dec.first != hrp || dec.second.size() < 1)
      return std::make_pair(-1, data());
   data conv;
   if (!convertbits<5, 8, false>(conv, data(dec.second.begin() + 1, dec.second.end())) ||
       conv.size() < 2 || conv.size() > 40 || dec.second[0] > 16 || (dec.second[0] == 0 && conv.size() != 20 && conv.size() != 32)) {
      return std::make_pair(-1, data());
   }
   return std::make_pair(dec.second[0], conv);
}

/** Encode a SegWit address. */
std::string encode(const std::string &hrp, int witver, const data &witprog) {
   data enc;
   enc.push_back(witver);
   convertbits<8, 5, true>(enc, witprog);
   std::string ret = bech32::Encode(hrp, enc);
   if (decode(hrp, ret).first == -1)
      return "";
   return ret;
}

}}}} // namespace graphene::peerplays_sidechain::bitcoin::segwit_addr