/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
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 * This is part of the OpenMM molecular simulation toolkit.                   *
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 * Authors: Peter Eastman                                                     *
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#include "openmm/DrudeLangevinIntegrator.h"
#include "openmm/Context.h"
#include "openmm/OpenMMException.h"
#include "openmm/DrudeKernels.h"
#include "openmm/internal/ContextImpl.h"
#include "openmm/internal/DrudeHelpers.h"
#include <cmath>
#include <ctime>
#include <set>
#include <string>

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

DrudeLangevinIntegrator::DrudeLangevinIntegrator(double temperature, double frictionCoeff, double drudeTemperature, double drudeFrictionCoeff, double stepSize) : DrudeIntegrator(stepSize) {
    setTemperature(temperature);
    setFriction(frictionCoeff);
    setDrudeTemperature(drudeTemperature);
    setDrudeFriction(drudeFrictionCoeff);
    setMaxDrudeDistance(0.02);
    setStepSize(stepSize);
    setConstraintTolerance(1e-5);
    setRandomNumberSeed(0);
}

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

void DrudeLangevinIntegrator::setTemperature(double temp) {
    if (temp < 0)
        throw OpenMMException("Temperature cannot be negative");
    temperature = temp;
}

void DrudeLangevinIntegrator::setFriction(double coeff) {
    if (coeff < 0)
        throw OpenMMException("Friction cannot be negative");
    friction = coeff;
}

void DrudeLangevinIntegrator::setDrudeFriction(double coeff) {
    if (coeff < 0)
        throw OpenMMException("Friction cannot be negative");
    drudeFriction = coeff;
}

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

vector<string> DrudeLangevinIntegrator::getKernelNames() {
    return {IntegrateDrudeLangevinStepKernel::Name()};
}

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

void DrudeLangevinIntegrator::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);
        kernel.getAs<IntegrateDrudeLangevinStepKernel>().execute(*context, *this);
    }
}

double DrudeLangevinIntegrator::computeSystemTemperature() {
    if (context == NULL)
        throw OpenMMException("This Integrator is not bound to a context!");  
    context->calcForcesAndEnergy(true, false, getIntegrationForceGroups());
    vector<Vec3> velocities;
    context->computeShiftedVelocities(getVelocityTimeOffset(), velocities);
    return computeTemperaturesFromVelocities(*context, velocities).first;
}

double DrudeLangevinIntegrator::computeDrudeTemperature() {
    if (context == NULL)
        throw OpenMMException("This Integrator is not bound to a context!");  
    context->calcForcesAndEnergy(true, false, getIntegrationForceGroups());
    vector<Vec3> velocities;
    context->computeShiftedVelocities(getVelocityTimeOffset(), velocities);
    return computeTemperaturesFromVelocities(*context, velocities).second;
} 

