/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2016 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 "linearSpring.H"
#include "rigidBodyModel.H"
#include "addToRunTimeSelectionTable.H"

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

namespace Foam
{
namespace RBD
{
namespace restraints
{
    defineTypeNameAndDebug(linearSpring, 0);

    addToRunTimeSelectionTable
    (
        restraint,
        linearSpring,
        dictionary
    );
}
}
}


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

Foam::RBD::restraints::linearSpring::linearSpring
(
    const word& name,
    const dictionary& dict,
    const rigidBodyModel& model
)
:
    restraint(name, dict, model),
    anchor_(),
    refAttachmentPt_(),
    stiffness_(),
    damping_(),
    restLength_()
{
    read(dict);
}


// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //

Foam::RBD::restraints::linearSpring::~linearSpring()
{}


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

Foam::spatialVector Foam::RBD::restraints::linearSpring::restrain() const
{
    spatialVector attachmentPt
    (
        model_.X0(bodyIndex_).inv() && spatialVector(Zero, refAttachmentPt_)
    );

    // Current axis of the spring
    vector r = attachmentPt.l() - anchor_;
    scalar magR = mag(r);
    r /= (magR + VSMALL);

    // Velocity of the end of the spring
    vector v = model_.v(bodyIndex_, refAttachmentPt_).l();

    // Force and moment including optional damping
    vector force = (-stiffness_*(magR - restLength_) - damping_*(r & v))*r;
    vector moment = (attachmentPt.l() - model_.X0(bodyIndex_).r()) ^ force;

    if (model_.debug)
    {
        Info<< " attachmentPt - anchor " << r*magR
            << " spring length " << magR
            << " force " << force
            << " moment " << moment
            << endl;
    }

    return spatialVector(moment, force);
}


bool Foam::RBD::restraints::linearSpring::read
(
    const dictionary& dict
)
{
    restraint::read(dict);

    coeffs_.lookup("anchor") >> anchor_;
    coeffs_.lookup("refAttachmentPt") >> refAttachmentPt_;
    coeffs_.lookup("stiffness") >> stiffness_;
    coeffs_.lookup("damping") >> damping_;
    coeffs_.lookup("restLength") >> restLength_;

    return true;
}


void Foam::RBD::restraints::linearSpring::write
(
    Ostream& os
) const
{
    restraint::write(os);

    os.writeKeyword("anchor")
        << anchor_ << token::END_STATEMENT << nl;

    os.writeKeyword("refAttachmentPt")
        << refAttachmentPt_ << token::END_STATEMENT << nl;

    os.writeKeyword("stiffness")
        << stiffness_ << token::END_STATEMENT << nl;

    os.writeKeyword("damping")
        << damping_ << token::END_STATEMENT << nl;

    os.writeKeyword("restLength")
        << restLength_ << token::END_STATEMENT << nl;
}


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