// This file is part of the AliceVision project.
// Copyright (c) 2016 AliceVision contributors.
// Copyright (c) 2012 openMVG contributors.
// This Source Code Form is subject to the terms of the Mozilla Public License,
// v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.

#pragma once

namespace aliceVision {
namespace sfm {

/// association of Ids to a contiguous set of Ids
template<typename IterablePairs, typename PairValueType>
void reindex(const IterablePairs& pairs,
             HashMap<PairValueType, PairValueType>& _reindexForward,
             HashMap<PairValueType, PairValueType>& _reindexBackward)
{
    typedef std::pair<PairValueType, PairValueType> PairT;

    // get an unique set of Ids
    std::set<std::size_t> _uniqueId;

    for (typename IterablePairs::const_iterator iter = pairs.begin(); iter != pairs.end(); ++iter)
    {
        _uniqueId.insert(iter->first);
        _uniqueId.insert(iter->second);
    }

    // build the Forward and Backward mapping
    for (typename IterablePairs::const_iterator iter = pairs.begin(); iter != pairs.end(); ++iter)
    {
        if (_reindexForward.find(iter->first) == _reindexForward.end())
        {
            const size_t dist = std::distance(_uniqueId.begin(), _uniqueId.find(iter->first));
            _reindexForward[iter->first] = dist;
            _reindexBackward[dist] = iter->first;
        }

        if (_reindexForward.find(iter->second) == _reindexForward.end())
        {
            const size_t dist = std::distance(_uniqueId.begin(), _uniqueId.find(iter->second));
            _reindexForward[iter->second] = dist;
            _reindexBackward[dist] = iter->second;
        }
    }
}

}  // namespace sfm
}  // namespace aliceVision
