/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the OpenMM molecular simulation toolkit.                   *
 * See https://openmm.org/development.                                        *
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 * Portions copyright (c) 2008-2020 Stanford University and the Authors.      *
 * Authors: Peter Eastman                                                     *
 * Contributors:                                                              *
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#include "openmm/VerletIntegrator.h"
#include "openmm/Context.h"
#include "openmm/OpenMMException.h"
#include "openmm/internal/ContextImpl.h"
#include "openmm/kernels.h"
#include <string>

using namespace OpenMM;
using std::string;
using std::vector;

VerletIntegrator::VerletIntegrator(double stepSize) {
    setStepSize(stepSize);
    setConstraintTolerance(1e-5);
}

void VerletIntegrator::initialize(ContextImpl& contextRef) {
    if (owner != NULL && &contextRef.getOwner() != owner)
        throw OpenMMException("This Integrator is already bound to a context");
    context = &contextRef;
    owner = &contextRef.getOwner();
    kernel = context->getPlatform().createKernel(IntegrateVerletStepKernel::Name(), contextRef);
    kernel.getAs<IntegrateVerletStepKernel>().initialize(contextRef.getSystem(), *this);
}

void VerletIntegrator::cleanup() {
    kernel = Kernel();
}

vector<string> VerletIntegrator::getKernelNames() {
    return {IntegrateVerletStepKernel::Name()};
}

double VerletIntegrator::computeKineticEnergy() {
    return kernel.getAs<IntegrateVerletStepKernel>().computeKineticEnergy(*context, *this);
}

void VerletIntegrator::step(int steps) {
    if (context == NULL)
        throw OpenMMException("This Integrator is not bound to a context!");
    for (int i = 0; i < steps; ++i) {
        context->updateContextState();
        context->calcForcesAndEnergy(true, false, getIntegrationForceGroups());
        kernel.getAs<IntegrateVerletStepKernel>().execute(*context, *this);
    }
}
