/////////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2021 - Equinor ASA
//
//  ResInsight is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
//  FITNESS FOR A PARTICULAR PURPOSE.
//
//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
//  for more details.
//
/////////////////////////////////////////////////////////////////////////////////

#pragma once

#include <array>
#include <cstddef>

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
class RivIntersectionVertexWeights
{
public:
    explicit RivIntersectionVertexWeights()
        : m_count( 0 )
    {
    }

    /*
    v111 k11 v11   v112  v211 k21  v21    v212
      +------+-----+      +--------+------+
             |                     |
             |k1                   |k2
             |   k                 |
           v1+--------+------------+v2
             |                     |
             |                     |
             |                     |
      +------+----+       +--------+-------+
    v121 k12 v12  v122   v221 k22  v22   v222

    Where the k's are normalized distances along the edge, from the edge start vertex .

    This is the interpolation scheme:

    v   = (1 - k  )* v1   + k *v2;

    v1  = (1 - k1 )* v11  + k1*v12;
    v2  = (1 - k2 )* v21  + k2*v22;

    v11 = (1 - k11)* v111 + k11*v112;
    v12 = (1 - k12)* v121 + k12*v122;
    v21 = (1 - k21)* v211 + k21*v212;
    v22 = (1 - k22)* v221 + k22*v222;

    Substitution and reorganizing gives the expressions seen below.

    */

    explicit RivIntersectionVertexWeights( size_t edgeVx111,
                                           size_t edgeVx112,
                                           double k11,
                                           size_t edgeVx121,
                                           size_t edgeVx122,
                                           double k12,
                                           size_t edgeVx211,
                                           size_t edgeVx212,
                                           double k21,
                                           size_t edgeVx221,
                                           size_t edgeVx222,
                                           double k22,
                                           double k1,
                                           double k2,
                                           double k )
        : m_count( 8 )
    {
        m_vxIds[0] = ( edgeVx111 );
        m_vxIds[1] = ( edgeVx112 );
        m_vxIds[2] = ( edgeVx121 );
        m_vxIds[3] = ( edgeVx122 );
        m_vxIds[4] = ( edgeVx211 );
        m_vxIds[5] = ( edgeVx212 );
        m_vxIds[6] = ( edgeVx221 );
        m_vxIds[7] = ( edgeVx222 );

        m_weights[7] = ( (float)( k * k2 * k22 ) );
        m_weights[6] = ( (float)( k * k2 - k * k2 * k22 ) );
        m_weights[5] = ( (float)( ( k - k * k2 ) * k21 ) );
        m_weights[4] = ( (float)( ( k * k2 - k ) * k21 - k * k2 + k ) );
        m_weights[3] = ( (float)( ( 1 - k ) * k1 * k12 ) );
        m_weights[2] = ( (float)( ( k - 1 ) * k1 * k12 + ( 1 - k ) * k1 ) );
        m_weights[1] = ( (float)( ( ( k - 1 ) * k1 - k + 1 ) * k11 ) );
        m_weights[0] = ( (float)( ( ( 1 - k ) * k1 + k - 1 ) * k11 + ( k - 1 ) * k1 - k + 1 ) );
    }

    explicit RivIntersectionVertexWeights( size_t edge1Vx1,
                                           size_t edge1Vx2,
                                           double normDistFromE1V1,
                                           size_t edge2Vx1,
                                           size_t edge2Vx2,
                                           double normDistFromE2V1,
                                           double normDistFromE1Cut )
        : m_count( 4 )
    {
        m_vxIds[0] = ( edge1Vx1 );
        m_vxIds[1] = ( edge1Vx2 );
        m_vxIds[2] = ( edge2Vx1 );
        m_vxIds[3] = ( edge2Vx2 );

        m_weights[0] = ( (float)( 1.0 - normDistFromE1V1 - normDistFromE1Cut + normDistFromE1V1 * normDistFromE1Cut ) );
        m_weights[1] = ( (float)( normDistFromE1V1 - normDistFromE1V1 * normDistFromE1Cut ) );
        m_weights[2] = ( (float)( normDistFromE1Cut - normDistFromE2V1 * normDistFromE1Cut ) );
        m_weights[3] = ( (float)( normDistFromE2V1 * normDistFromE1Cut ) );
    }

    explicit RivIntersectionVertexWeights( size_t edge1Vx1, size_t edge1Vx2, double normDistFromE1V1 )
        : m_count( 2 )
    {
        m_vxIds[0] = ( edge1Vx1 );
        m_vxIds[1] = ( edge1Vx2 );

        m_weights[0] = ( (float)( 1.0 - normDistFromE1V1 ) );
        m_weights[1] = ( (float)( normDistFromE1V1 ) );
    }

    explicit RivIntersectionVertexWeights( const std::array<size_t, 8>& vxIds, const std::array<double, 8>& explicitWeights )
        : m_count( 8 )
        , m_vxIds( vxIds )
    {
        for ( size_t i = 0; i < 8; ++i )
        {
            m_weights[i] = static_cast<float>( explicitWeights[i] );
        }
    }

    int    size() const { return m_count; }
    size_t vxId( int idx ) const { return m_vxIds[idx]; }
    float  weight( int idx ) const { return m_weights[idx]; }

private:
    std::array<size_t, 8> m_vxIds;
    std::array<float, 8>  m_weights;
    int                   m_count;
};