/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the OpenMM molecular simulation toolkit.                   *
 * See https://openmm.org/development.                                        *
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 * Portions copyright (c) 2025 Stanford University and the Authors.           *
 * Authors: Peter Eastman                                                     *
 * Contributors:                                                              *
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#include "openmm/DPDIntegrator.h"
#include "openmm/Context.h"
#include "openmm/OpenMMException.h"
#include "openmm/internal/ContextImpl.h"
#include "openmm/kernels.h"
#include <string>

using namespace OpenMM;
using namespace std;

DPDIntegrator::DPDIntegrator(double temperature, double defaultFriction, double defaultCutoff, double stepSize) {
    setTemperature(temperature);
    setDefaultFriction(defaultFriction);
    setDefaultCutoff(defaultCutoff);
    setStepSize(stepSize);
    setConstraintTolerance(1e-5);
    setRandomNumberSeed(0);
}

void DPDIntegrator::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(IntegrateDPDStepKernel::Name(), contextRef);
    kernel.getAs<IntegrateDPDStepKernel>().initialize(contextRef.getSystem(), *this);
}

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

void DPDIntegrator::setDefaultFriction(double friction) {
    if (friction < 0)
        throw OpenMMException("Friction cannot be negative");
    defaultFriction = friction;
}

void DPDIntegrator::setDefaultCutoff(double cutoff) {
    if (cutoff <= 0)
        throw OpenMMException("Cutoff must be positive");
    defaultCutoff = cutoff;
}

int DPDIntegrator::getParticleType(int index) const {
    if (particleType.find(index) == particleType.end())
        return 0;
    return particleType.at(index);
    
}

void DPDIntegrator::setParticleType(int index, int type) {
    particleType[index] = type;
}

const map<int, int>& DPDIntegrator::getParticleTypes() const {
    return particleType;
}

int DPDIntegrator::addTypePair(int type1, int type2, double friction, double cutoff) {
    pairs.push_back(TypePairInfo(type1, type2, friction, cutoff));
    return pairs.size()-1;
}

void DPDIntegrator::getTypePairParameters(int pairIndex, int& type1, int& type2, double& friction, double& cutoff) const {
    ASSERT_VALID_INDEX(pairIndex, pairs);
    type1 = pairs[pairIndex].type1;
    type2 = pairs[pairIndex].type2;
    friction = pairs[pairIndex].friction;
    cutoff = pairs[pairIndex].cutoff;
}

void DPDIntegrator::setTypePairParameters(int pairIndex, int type1, int type2, double friction, double cutoff) {
    ASSERT_VALID_INDEX(pairIndex, pairs);
    pairs[pairIndex].type1 = type1;
    pairs[pairIndex].type2 = type2;
    pairs[pairIndex].friction = friction;
    pairs[pairIndex].cutoff = cutoff;
}

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

vector<string> DPDIntegrator::getKernelNames() {
    return {IntegrateDPDStepKernel::Name()};
}

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

bool DPDIntegrator::kineticEnergyRequiresForce() const {
    return false;
}

void DPDIntegrator::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<IntegrateDPDStepKernel>().execute(*context, *this);
    }
}

int DPDIntegrator::getNumTypePairs() const {
    return pairs.size();
}
