/*
 * This program source code file is part of KICAD, a free EDA CAD application.
 *
 * Copyright (C) 2013-2017 CERN
 * Copyright (C) 2019-2021 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * @author Maciej Suminski <maciej.suminski@cern.ch>
 * @author Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
 *
 * This program 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 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

/**
 * @file ratsnest_data.cpp
 * @brief Class that computes missing connections on a PCB.
 */

#ifdef PROFILE
#include <profile.h>
#endif

#include <ratsnest/ratsnest_data.h>
#include <functional>
using namespace std::placeholders;

#include <algorithm>
#include <cassert>
#include <limits>

#include <delaunator.hpp>

class disjoint_set
{

public:
    disjoint_set( size_t size )
    {
        m_data.resize( size );
        m_depth.resize( size, 0 );

        for( size_t i = 0; i < size; i++ )
            m_data[i]  = i;
    }

    int find( int aVal )
    {
        int root = aVal;

        while( m_data[root] != root )
            root = m_data[root];

        // Compress the path
        while( m_data[aVal] != aVal )
        {
            auto& tmp = m_data[aVal];
            aVal      = tmp;
            tmp       = root;
        }

        return root;
    }


    bool unite( int aVal1, int aVal2 )
    {
        aVal1 = find( aVal1 );
        aVal2 = find( aVal2 );

        if( aVal1 != aVal2 )
        {
            if( m_depth[aVal1] < m_depth[aVal2] )
            {
                m_data[aVal1] = aVal2;
            }
            else
            {
                m_data[aVal2] = aVal1;

                if( m_depth[aVal1] == m_depth[aVal2] )
                    m_depth[aVal1]++;
            }

            return true;
        }

        return false;
    }

private:
    std::vector<int> m_data;
    std::vector<int> m_depth;
};


void RN_NET::kruskalMST( std::vector<CN_EDGE>& aEdges,
                         const std::set< std::pair<KIID, KIID> >& aExclusions )
{
    disjoint_set dset( m_nodes.size() );

    m_rnEdges.clear();

    int i = 0;

    for( const CN_ANCHOR_PTR& node : m_nodes )
        node->SetTag( i++ );

    for( CN_EDGE& tmp : aEdges )
    {
        const CN_ANCHOR_PTR&  source = tmp.GetSourceNode();
        const CN_ANCHOR_PTR&  target = tmp.GetTargetNode();

        if( dset.unite( source->GetTag(), target->GetTag() ) )
        {
            if( tmp.GetWeight() > 0 )
            {
                std::pair<KIID, KIID> ids = { source->Parent()->m_Uuid, target->Parent()->m_Uuid };
                tmp.SetVisible( aExclusions.count( ids ) == 0 );

                m_rnEdges.push_back( tmp );
            }
        }
    }
}


class RN_NET::TRIANGULATOR_STATE
{
private:
    std::multiset<CN_ANCHOR_PTR, CN_PTR_CMP> m_allNodes;


    // Checks if all nodes in aNodes lie on a single line. Requires the nodes to
    // have unique coordinates!
    bool areNodesColinear( const std::vector<CN_ANCHOR_PTR>& aNodes ) const
    {
        if ( aNodes.size() <= 2 )
            return true;

        const VECTOR2I p0( aNodes[0]->Pos() );
        const VECTOR2I v0( aNodes[1]->Pos() - p0 );

        for( unsigned i = 2; i < aNodes.size(); i++ )
        {
            const VECTOR2I v1 = aNodes[i]->Pos() - p0;

            if( v0.Cross( v1 ) != 0 )
                return false;
        }

        return true;
    }

public:

    void Clear()
    {
        m_allNodes.clear();
    }

    void AddNode( CN_ANCHOR_PTR aNode )
    {
        m_allNodes.insert( aNode );
    }

    void Triangulate( std::vector<CN_EDGE>& mstEdges )
    {
        std::vector<double>                       node_pts;
        std::vector<CN_ANCHOR_PTR>                anchors;
        std::vector< std::vector<CN_ANCHOR_PTR> > anchorChains( m_allNodes.size() );

        node_pts.reserve( 2 * m_allNodes.size() );
        anchors.reserve( m_allNodes.size() );

        CN_ANCHOR_PTR prev = nullptr;

        for( const CN_ANCHOR_PTR& n : m_allNodes )
        {
            if( !prev || prev->Pos() != n->Pos() )
            {
                node_pts.push_back( n->Pos().x );
                node_pts.push_back( n->Pos().y );
                anchors.push_back( n );
                prev = n;
            }

            anchorChains[anchors.size() - 1].push_back( n );
        }

        if( anchors.size() < 2 )
        {
            return;
        }
        else if( areNodesColinear( anchors ) )
        {
            // special case: all nodes are on the same line - there's no
            // triangulation for such set. In this case, we sort along any coordinate
            // and chain the nodes together.
            for( size_t i = 0; i < anchors.size() - 1; i++ )
            {
                const CN_ANCHOR_PTR& src = anchors[i];
                const CN_ANCHOR_PTR& dst = anchors[i + 1];
                mstEdges.emplace_back( src, dst, src->Dist( *dst ) );
            }
        }
        else
        {
            delaunator::Delaunator delaunator( node_pts );
            auto& triangles = delaunator.triangles;

            for( size_t i = 0; i < triangles.size(); i += 3 )
            {
                CN_ANCHOR_PTR src = anchors[triangles[i]];
                CN_ANCHOR_PTR dst = anchors[triangles[i + 1]];
                mstEdges.emplace_back( src, dst, src->Dist( *dst ) );

                src = anchors[triangles[i + 1]];
                dst = anchors[triangles[i + 2]];
                mstEdges.emplace_back( src, dst, src->Dist( *dst ) );

                src = anchors[triangles[i + 2]];
                dst = anchors[triangles[i]];
                mstEdges.emplace_back( src, dst, src->Dist( *dst ) );
            }

            for( size_t i = 0; i < delaunator.halfedges.size(); i++ )
            {
                if( delaunator.halfedges[i] == delaunator::INVALID_INDEX )
                    continue;

                const CN_ANCHOR_PTR& src = anchors[triangles[i]];
                const CN_ANCHOR_PTR& dst = anchors[triangles[delaunator.halfedges[i]]];
                mstEdges.emplace_back( src, dst, src->Dist( *dst ) );
            }
        }

        for( size_t i = 0; i < anchorChains.size(); i++ )
        {
            std::vector<CN_ANCHOR_PTR>& chain = anchorChains[i];

            if( chain.size() < 2 )
                continue;

            std::sort( chain.begin(), chain.end(),
                    [] ( const CN_ANCHOR_PTR& a, const CN_ANCHOR_PTR& b )
                    {
                        return a->GetCluster().get() < b->GetCluster().get();
                    } );

            for( unsigned int j = 1; j < chain.size(); j++ )
            {
                const CN_ANCHOR_PTR& prevNode = chain[j - 1];
                const CN_ANCHOR_PTR& curNode  = chain[j];
                int weight = prevNode->GetCluster() != curNode->GetCluster() ? 1 : 0;
                mstEdges.emplace_back( prevNode, curNode, weight );
            }
        }
    }
};


RN_NET::RN_NET() : m_dirty( true )
{
    m_triangulator.reset( new TRIANGULATOR_STATE );
}


void RN_NET::compute( const std::set< std::pair<KIID, KIID> >& aExclusions )
{
    // Special cases do not need complicated algorithms (actually, it does not work well with
    // the Delaunay triangulator)
    if( m_nodes.size() <= 2 )
    {
        m_rnEdges.clear();

        // Check if the only possible connection exists
        if( m_boardEdges.size() == 0 && m_nodes.size() == 2 )
        {
            auto last = ++m_nodes.begin();

            // There can be only one possible connection, but it is missing
            CN_EDGE               edge( *m_nodes.begin(), *last );
            const CN_ANCHOR_PTR&  source = edge.GetSourceNode();
            const CN_ANCHOR_PTR&  target = edge.GetTargetNode();
            std::pair<KIID, KIID> ids = { source->Parent()->m_Uuid, target->Parent()->m_Uuid };

            source->SetTag( 0 );
            target->SetTag( 1 );
            edge.SetVisible( aExclusions.count( ids ) == 0 );

            m_rnEdges.push_back( edge );
        }
        else
        {
            // Set tags to m_nodes as connected
            for( const CN_ANCHOR_PTR& node : m_nodes )
                node->SetTag( 0 );
        }

        return;
    }


    m_triangulator->Clear();

    for( const CN_ANCHOR_PTR& n : m_nodes )
        m_triangulator->AddNode( n );

    std::vector<CN_EDGE> triangEdges;
    triangEdges.reserve( m_nodes.size() + m_boardEdges.size() );

#ifdef PROFILE
    PROF_COUNTER cnt("triangulate");
#endif
    m_triangulator->Triangulate( triangEdges );
#ifdef PROFILE
    cnt.Show();
#endif

    for( const CN_EDGE& e : m_boardEdges )
        triangEdges.emplace_back( e );

    std::sort( triangEdges.begin(), triangEdges.end() );

// Get the minimal spanning tree
#ifdef PROFILE
    PROF_COUNTER cnt2("mst");
#endif
    kruskalMST( triangEdges, aExclusions );
#ifdef PROFILE
    cnt2.Show();
#endif
}



void RN_NET::Update( const std::set< std::pair<KIID, KIID> >& aExclusions )
{
    compute( aExclusions );

    m_dirty = false;
}


void RN_NET::Clear()
{
    m_rnEdges.clear();
    m_boardEdges.clear();
    m_nodes.clear();

    m_dirty = true;
}


void RN_NET::AddCluster( CN_CLUSTER_PTR aCluster )
{
    CN_ANCHOR_PTR firstAnchor;

    for( CN_ITEM* item : *aCluster )
    {
        bool                        isZone = dynamic_cast<CN_ZONE_LAYER*>( item );
        std::vector<CN_ANCHOR_PTR>& anchors = item->Anchors();
        unsigned int                nAnchors = isZone ? 1 : anchors.size();

        if( nAnchors > anchors.size() )
            nAnchors = anchors.size();

        for( unsigned int i = 0; i < nAnchors; i++ )
        {
            anchors[i]->SetCluster( aCluster );
            m_nodes.insert( anchors[i] );

            if( firstAnchor )
            {
                if( firstAnchor != anchors[i] )
                    m_boardEdges.emplace_back( firstAnchor, anchors[i], 0 );
            }
            else
            {
                firstAnchor = anchors[i];
            }
        }
    }
}


bool RN_NET::NearestBicoloredPair( const RN_NET& aOtherNet, CN_ANCHOR_PTR& aNode1,
                                   CN_ANCHOR_PTR& aNode2 ) const
{
    bool rv = false;

    SEG::ecoord distMax_sq = VECTOR2I::ECOORD_MAX;

    auto verify =
            [&]( const std::shared_ptr<CN_ANCHOR>& aTestNode1,
                 const std::shared_ptr<CN_ANCHOR>& aTestNode2 )
            {
                VECTOR2I    diff = aTestNode1->Pos() - aTestNode2->Pos();
                SEG::ecoord dist_sq = diff.SquaredEuclideanNorm();

                if( dist_sq < distMax_sq )
                {
                    rv      = true;
                    distMax_sq = dist_sq;
                    aNode1  = aTestNode1;
                    aNode2  = aTestNode2;
                }
            };

    /// Sweep-line algorithm to cut the number of comparisons to find the closest point
    ///
    /// Step 1: The outer loop needs to be the subset (selected nodes) as it is a linear search
    for( const std::shared_ptr<CN_ANCHOR>& nodeA : aOtherNet.m_nodes )
    {
        if( nodeA->GetNoLine() )
            continue;

        /// Step 2: O( log n ) search to identify a close element ordered by x
        /// The fwd_it iterator will move forward through the elements while
        /// the rev_it iterator will move backward through the same set
        auto fwd_it = m_nodes.lower_bound( nodeA );
        auto rev_it = std::make_reverse_iterator( fwd_it );

        for( ; fwd_it != m_nodes.end(); ++fwd_it )
        {
            const std::shared_ptr<CN_ANCHOR>& nodeB = *fwd_it;

            if( nodeB->GetNoLine() )
                continue;

            SEG::ecoord distX_sq = SEG::Square( nodeA->Pos().x - nodeB->Pos().x );

            /// As soon as the x distance (primary sort) is larger than the smallest distance,
            /// stop checking further elements
            if( distX_sq > distMax_sq )
                break;

            verify( nodeA, nodeB );
        }

        /// Step 3: using the same starting point, check points backwards for closer points
        for( ; rev_it != m_nodes.rend(); ++rev_it )
        {
            const std::shared_ptr<CN_ANCHOR>& nodeB = *rev_it;

            if( nodeB->GetNoLine() )
                continue;

            SEG::ecoord distX_sq = SEG::Square( nodeA->Pos().x - nodeB->Pos().x );

            if( distX_sq > distMax_sq )
                break;

            verify( nodeA, nodeB );
        }
    }

    return rv;
}