/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | www.openfoam.com
     \\/     M anipulation  |
-------------------------------------------------------------------------------
    Copyright (C) 2011-2016 OpenFOAM Foundation
    Copyright (C) 2020 OpenCFD Ltd.
-------------------------------------------------------------------------------
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/>.

Class
    Foam::faceCollapser

Description
    Collapses faces into edges. Used to remove sliver faces (faces with small
    area but non-zero span).

    Passed in as
    - face label
    - the two indices in the face (fpA, fpB) which delimit the vertices to be
      kept.

    Takes the vertices outside the range fpA..fpB and projects them onto the
    kept edges (edges using kept vertices only).

    Note:
    - Use in combination with edge collapse to cleanup meshes.
    - Can not remove cells so will mess up trying to remove a face on a tet.
    - WIP. Should be combined with edge collapsing and cell collapsing into
      proper 'collapser'.
    - Caller is responsible for making sure kept vertices (fpA..fpB) for one
      face are not the vertices to be removed for another face.

SourceFiles
    faceCollapser.C

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

#ifndef faceCollapser_H
#define faceCollapser_H

#include "labelList.H"
#include "point.H"
#include "Map.H"
#include "HashSet.H"
#include "typeInfo.H"
#include "edgeList.H"

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

namespace Foam
{

// Forward Declarations
class polyMesh;
class polyTopoChange;
class mapPolyMesh;

/*---------------------------------------------------------------------------*\
                           Class faceCollapser Declaration
\*---------------------------------------------------------------------------*/

class faceCollapser
{
    // Private Data

        //- Reference to mesh
        const polyMesh& mesh_;


    // Static Functions

        //- Insert labelList into labelHashSet. Optional excluded element.
        static void insert
        (
            const labelList& elems,
            const label excludeElem,
            labelHashSet& set
        );

        //- Find edge amongst candidate edges.
        static label findEdge
        (
            const edgeList& edges,
            const labelList& edgeLabels,
            const label v0,
            const label v1
        );


    // Private Member Functions

        //- Replace vertices in face
        void filterFace
        (
            const Map<labelList>& splitEdges,
            const label facei,
            polyTopoChange& meshMod
        ) const;


        //- No copy construct
        faceCollapser(const faceCollapser&) = delete;

        //- No copy assignment
        void operator=(const faceCollapser&) = delete;


public:

    //- Runtime type information
    ClassName("faceCollapser");


    // Constructors

        //- Construct from mesh.
        explicit faceCollapser(const polyMesh& mesh);


    // Member Functions

        // Edit

            //- Collapse faces along endpoints. Play commands into
            //  polyTopoChange to create mesh.
            void setRefinement
            (
                const labelList& faceLabels,
                const labelList& fpA,
                const labelList& fpB,
                polyTopoChange&
            ) const;

            //- Update stored quantities for new mesh labels.
            void updateMesh(const mapPolyMesh&)
            {}
};


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

} // End namespace Foam

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

#endif

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