/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the OpenMM molecular simulation toolkit originating from   *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org.               *
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 * Portions copyright (c) 2025 Stanford University and the Authors.           *
 * Authors: Peter Eastman                                                     *
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#include "openmm/internal/CustomVolumeForceImpl.h"
#include "openmm/internal/ContextImpl.h"
#include "lepton/ParsedExpression.h"
#include "lepton/Parser.h"

using namespace OpenMM;
using namespace std;

CustomVolumeForceImpl::CustomVolumeForceImpl(const CustomVolumeForce& owner) : CustomCPPForceImpl(owner), owner(owner) {
    Lepton::ParsedExpression expression = Lepton::Parser::parse(owner.getEnergyFunction());
    energyExpression = expression.createCompiledExpression();
    map<string, double*> variableLocations;
    globalParameterNames.resize(owner.getNumGlobalParameters());
    globalValues.resize(owner.getNumGlobalParameters());
    for (int i = 0; i < owner.getNumGlobalParameters(); i++) {
        string name = owner.getGlobalParameterName(i);
        defaultParameters[name] = owner.getGlobalParameterDefaultValue(i);
        globalParameterNames[i] = name;
        variableLocations[name] = &globalValues[i];
    }
    variableLocations["v"] = &volume;
    variableLocations["ax"] = &a[0];
    variableLocations["bx"] = &b[0];
    variableLocations["by"] = &b[1];
    variableLocations["cx"] = &c[0];
    variableLocations["cy"] = &c[1];
    variableLocations["cz"] = &c[2];
    energyExpression.setVariableLocations(variableLocations);
}

void CustomVolumeForceImpl::initialize(ContextImpl& context) {
    CustomCPPForceImpl::initialize(context);
}

double CustomVolumeForceImpl::computeForce(ContextImpl& context, const vector<Vec3>& positions, vector<Vec3>& forces) {
    for (int i = 0; i < globalParameterNames.size(); i++)
        globalValues[i] = context.getParameter(globalParameterNames[i]);
    context.getPeriodicBoxVectors(a, b, c);
    volume = a[0]*b[1]*c[2];
    return energyExpression.evaluate();
}

map<string, double> CustomVolumeForceImpl::getDefaultParameters() {
    return defaultParameters;
}