/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2011-2018 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM 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.

    OpenFOAM 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 OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "faceCollapser.H"
#include "polyMesh.H"
#include "polyTopoChange.H"
#include "polyModifyPoint.H"
#include "polyModifyFace.H"
#include "polyRemoveFace.H"
#include "SortableList.H"
#include "meshTools.H"
#include "OFstream.H"


// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

// Insert labelList into labelHashSet. Optional excluded element.
void Foam::faceCollapser::insert
(
    const labelList& elems,
    const label excludeElem,
    labelHashSet& set
)
{
    forAll(elems, i)
    {
        if (elems[i] != excludeElem)
        {
            set.insert(elems[i]);
        }
    }
}


// Find edge amongst candidate edges. FatalError if none.
Foam::label Foam::faceCollapser::findEdge
(
    const edgeList& edges,
    const labelList& edgeLabels,
    const label v0,
    const label v1
)
{
    forAll(edgeLabels, i)
    {
        label edgeI = edgeLabels[i];

        const edge& e = edges[edgeI];

        if
        (
            (e[0] == v0 && e[1] == v1)
         || (e[0] == v1 && e[1] == v0)
        )
        {
            return edgeI;
        }
    }

    FatalErrorInFunction
        << " and " << v1 << " in edge labels " << edgeLabels
        << abort(FatalError);

    return -1;
}


// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //

// Replace vertices in face
void Foam::faceCollapser::filterFace
(
    const Map<labelList>& splitEdges,
    const label facei,
    polyTopoChange& meshMod
) const
{
    const face& f = mesh_.faces()[facei];
    const labelList& fEdges = mesh_.faceEdges()[facei];

    // Space for replaced vertices and split edges.
    DynamicList<label> newFace(10 * f.size());

    forAll(f, fp)
    {
        label v0 = f[fp];

        newFace.append(v0);

        // Look ahead one to get edge.
        label fp1 = f.fcIndex(fp);

        label v1 = f[fp1];

        // Get split on edge if any.
        label edgeI = findEdge(mesh_.edges(), fEdges, v0, v1);

        Map<labelList>::const_iterator edgeFnd =
            splitEdges.find(edgeI);

        if (edgeFnd != splitEdges.end())
        {
            // edgeI has been split (by introducing new vertices).
            // Insert new vertices in face in correct order
            // (splitEdges was constructed to be from edge.start() to end())

            const labelList& extraVerts = edgeFnd();

            if (v0 == mesh_.edges()[edgeI].start())
            {
                forAll(extraVerts, i)
                {
                    newFace.append(extraVerts[i]);
                }
            }
            else
            {
                forAllReverse(extraVerts, i)
                {
                    newFace.append(extraVerts[i]);
                }
            }
        }
    }
    face newF(newFace.shrink());

    // Pout<< "Modifying face:" << facei << " from " << f << " to " << newFace
    //    << endl;

    if (newF != f)
    {
        label nei = -1;

        label patchi = -1;

        if (mesh_.isInternalFace(facei))
        {
            nei = mesh_.faceNeighbour()[facei];
        }
        else
        {
            patchi = mesh_.boundaryMesh().whichPatch(facei);
        }

        // Get current zone info
        label zoneID = mesh_.faceZones().whichZone(facei);

        bool zoneFlip = false;

        if (zoneID >= 0)
        {
            const faceZone& fZone = mesh_.faceZones()[zoneID];

            zoneFlip = fZone.flipMap()[fZone.whichFace(facei)];
        }

        meshMod.setAction
        (
            polyModifyFace
            (
                newF,                       // modified face
                facei,                      // label of face being modified
                mesh_.faceOwner()[facei],   // owner
                nei,                        // neighbour
                false,                      // face flip
                patchi,                     // patch for face
                false,                      // remove from zone
                zoneID,                     // zone for face
                zoneFlip                    // face flip in zone
            )
        );
    }
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

// Construct from mesh
Foam::faceCollapser::faceCollapser(const polyMesh& mesh)
:
    mesh_(mesh)
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

void Foam::faceCollapser::setRefinement
(
    const labelList& faceLabels,
    const labelList& fpStart,
    const labelList& fpEnd,
    polyTopoChange& meshMod
) const
{
    const pointField& points = mesh_.points();
    const edgeList& edges = mesh_.edges();
    const faceList& faces = mesh_.faces();
    const labelListList& edgeFaces = mesh_.edgeFaces();


    // From split edge to newly introduced point(s). Can be more than one per
    // edge!
    Map<labelList> splitEdges(faceLabels.size());

    // Mark faces in any way affect by modifying points/edges. Used later on
    // to prevent having to redo all faces.
    labelHashSet affectedFaces(4*faceLabels.size());


    //
    // Add/remove vertices and construct mapping
    //

    forAll(faceLabels, i)
    {
        const label facei = faceLabels[i];

        const face& f = faces[facei];

        const label fpA = fpStart[i];
        const label fpB = fpEnd[i];

        const point& pA = points[f[fpA]];
        const point& pB = points[f[fpB]];

        Pout<< "Face:" << f << " collapsed to fp:" << fpA << ' '  << fpB
            << " with points:" << pA << ' ' << pB
            << endl;

        // Create line from fpA to fpB
        linePointRef lineAB(pA, pB);

        // Get projections of all vertices onto line.

        // Distance(squared) to pA for every point on face.
        SortableList<scalar> dist(f.size());

        dist[fpA] = 0;
        dist[fpB] = magSqr(pB - pA);

        // Step from fpA to fpB
        // ~~~~~~~~~~~~~~~~~~~~
        // (by incrementing)

        label fpMin1 = fpA;
        label fp = f.fcIndex(fpMin1);

        while (fp != fpB)
        {
            // See where fp sorts. Make sure it is above fpMin1!
            pointHit near = lineAB.nearestDist(points[f[fp]]);

            scalar w = magSqr(near.rawPoint() - pA);

            if (w <= dist[fpMin1])
            {
                // Offset.
                w = dist[fpMin1] + 1e-6*(dist[fpB] - dist[fpA]);

                point newPoint
                (
                    pA + Foam::sqrt(w / (dist[fpB] - dist[fpA]))*(pB - pA)
                );

                Pout<< "Adapting position of vertex " << f[fp] << " on face "
                    << f << " from " << near.rawPoint() << " to " << newPoint
                    << endl;

                near.setPoint(newPoint);
            }

            // Responsibility of caller to make sure polyModifyPoint is only
            // called once per point. (so max only one collapse face per
            // edge)
            meshMod.setAction
            (
                polyModifyPoint
                (
                    f[fp],
                    near.rawPoint(),
                    false,
                    -1,
                    true
                )
            );

            dist[fp] = w;

            // Step to next vertex.
            fpMin1 = fp;
            fp = f.fcIndex(fpMin1);
        }

        // Step from fpA to fpB
        // ~~~~~~~~~~~~~~~~~~~~
        // (by decrementing)

        fpMin1 = fpA;
        fp = f.rcIndex(fpMin1);

        while (fp != fpB)
        {
            // See where fp sorts. Make sure it is below fpMin1!
            pointHit near = lineAB.nearestDist(points[f[fp]]);

            scalar w = magSqr(near.rawPoint() - pA);

            if (w <= dist[fpMin1])
            {
                // Offset.
                w = dist[fpMin1] + 1e-6*(dist[fpB] - dist[fpA]);

                point newPoint
                (
                    pA + Foam::sqrt(w / (dist[fpB] - dist[fpA]))*(pB - pA)
                );

                Pout<< "Adapting position of vertex " << f[fp] << " on face "
                    << f << " from " << near.rawPoint() << " to " << newPoint
                    << endl;

                near.setPoint(newPoint);
            }

            // Responsibility of caller to make sure polyModifyPoint is only
            // called once per point. (so max only one collapse face per
            // edge)
            meshMod.setAction
            (
                polyModifyPoint
                (
                    f[fp],
                    near.rawPoint(),
                    false,
                    -1,
                    true
                )
            );

            dist[fp] = w;

            // Step to previous vertex.
            fpMin1 = fp;
            fp = f.rcIndex(fpMin1);
        }

        dist.sort();

        // Check that fpB sorts latest.
        if (dist.indices()[dist.size()-1] != fpB)
        {
            OFstream str("conflictingFace.obj");
            meshTools::writeOBJ(str, faceList(1, f), points);

            FatalErrorInFunction
                << "Trying to collapse face:" << facei << " vertices:" << f
                << " to edges between vertices " << f[fpA] << " and "
                << f[fpB] << " but " << f[fpB] << " does not seem to be the"
                << " vertex furthest away from " << f[fpA] << endl
                << "Dumped conflicting face to obj file conflictingFace.obj"
                << abort(FatalError);
        }


        // From fp to index in sort:
        Pout<< "Face:" << f << " fpA:" << fpA << " fpB:" << fpB << nl;

        labelList sortedFp(f.size());
        forAll(dist.indices(), i)
        {
            label fp = dist.indices()[i];

            Pout<< "   fp:" << fp << " distance:" << dist[i] << nl;

            sortedFp[fp] = i;
        }

        const labelList& fEdges = mesh_.faceEdges()[facei];

        // Now look up all edges in the face and see if they get extra
        // vertices inserted and build an edge-to-intersected-points table.

        // Order of inserted points is in edge order (from e.start to
        // e.end)

        forAll(f, fp)
        {
            label fp1 = f.fcIndex(fp);

            // Get index in sorted list
            label sorted0 = sortedFp[fp];
            label sorted1 = sortedFp[fp1];

            // Get indices in increasing order
            DynamicList<label> edgePoints(f.size());

            // Whether edgePoints are from fp to fp1
            bool fpToFp1;

            if (sorted0 < sorted1)
            {
                fpToFp1 = true;

                for (label j = sorted0+1; j < sorted1; j++)
                {
                    edgePoints.append(f[dist.indices()[j]]);
                }
            }
            else
            {
                fpToFp1 = false;

                for (label j = sorted1+1; j < sorted0; j++)
                {
                    edgePoints.append(f[dist.indices()[j]]);
                }
            }

            if (edgePoints.size())
            {
                edgePoints.shrink();

                label edgeI = findEdge(edges, fEdges, f[fp], f[fp1]);

                const edge& e = edges[edgeI];

                if (fpToFp1 == (f[fp] == e.start()))
                {
                    splitEdges.insert(edgeI, edgePoints);
                }
                else
                {
                    reverse(edgePoints);
                    splitEdges.insert(edgeI, edgePoints);
                }

                // Mark all faces affected
                insert(edgeFaces[edgeI], facei, affectedFaces);
            }
        }
    }

    forAllConstIter(Map<labelList>, splitEdges, iter)
    {
        Pout<< "Split edge:" << iter.key()
            << " verts:" << mesh_.edges()[iter.key()]
            << " in:" << nl;
        const labelList& edgePoints = iter();

        forAll(edgePoints, i)
        {
            Pout<< "    " << edgePoints[i] << nl;
        }
    }


    //
    // Remove faces.
    //

    forAll(faceLabels, i)
    {
        const label facei = faceLabels[i];

        meshMod.setAction(polyRemoveFace(facei));

        // Update list of faces we still have to modify
        affectedFaces.erase(facei);
    }


    //
    // Modify faces affected (but not removed)
    //

    forAllConstIter(labelHashSet, affectedFaces, iter)
    {
        filterFace(splitEdges, iter.key(), meshMod);
    }
}


// ************************************************************************* //
