text: // Copyright (c) 2014-2016, The Monero 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,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  // FIXME: move this into a full wallet2 unit test suite, if possible
  
  #include "gtest/gtest.h"
  
  #include "wallet/wallet2.h"
  #include <string>
  
  static tools::wallet2::transfer_container make_transfers_container(size_t N)
  {
    tools::wallet2::transfer_container transfers;
    for (size_t n = 0; n < N; ++n)
    {
      transfers.push_back(AUTO_VAL_INIT(tools::wallet2::transfer_details()));
      tools::wallet2::transfer_details &td = transfers.back();
      td.m_block_height = 1000;
      td.m_spent = false;
      td.m_txid = cryptonote::null_hash;
      td.m_txid.data[0] = n & 0xff;
      td.m_txid.data[1] = (n >> 8) & 0xff;
      td.m_txid.data[2] = (n >> 16) & 0xff;
      td.m_txid.data[3] = (n >> 24) & 0xff;
    }
    return transfers;
  }
  
  #define SELECT(idx) \
    do { \
      auto i = std::find(unused_indices.begin(), unused_indices.end(), idx); \
      ASSERT_TRUE(i != unused_indices.end()); \
      unused_indices.erase(i); \
      selected.push_back(idx); \
    } while(0)
  
  #define PICK(expected) \
    do { \
      size_t idx = w.pop_best_value_from(transfers, unused_indices, selected); \
      ASSERT_EQ(expected, idx); \
      selected.push_back(idx); \
    } while(0)
  
  TEST(select_outputs, one_out_of_N)
  {
    tools::wallet2 w;
  
    // check that if there are N-1 outputs of the same height, one of them
    // already selected, the next one selected is the one that's from a
    // different height
    tools::wallet2::transfer_container transfers = make_transfers_container(10);
    transfers[6].m_block_height = 700;
    std::vector<size_t> unused_indices({0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
    std::list<size_t> selected;
    SELECT(2);
    PICK(6);
  }
  
  TEST(select_outputs, order)
  {
    tools::wallet2 w;
  
    // check that most unrelated heights are picked in order
    tools::wallet2::transfer_container transfers = make_transfers_container(5);
    transfers[0].m_block_height = 700;
    transfers[1].m_block_height = 700;
    transfers[2].m_block_height = 704;
    transfers[3].m_block_height = 716;
    transfers[4].m_block_height = 701;
    std::vector<size_t> unused_indices({0, 1, 2, 3, 4});
    std::list<size_t> selected;
    SELECT(0);
    PICK(3); // first the one that's far away
    PICK(2); // then the one that's close
    PICK(4); // then the one that's adjacent
    PICK(1); // then the one that's on the same height
  }
  
  