/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
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 * 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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 * Authors: Peter Eastman                                                     *
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/**
 * This tests the reference implementation of CustomCompoundBondForce.
 */

#ifdef WIN32
  #define _USE_MATH_DEFINES // Needed to get M_PI
#endif
#include "openmm/internal/AssertionUtilities.h"
#include "openmm/Context.h"
#include "ReferencePlatform.h"
#include "openmm/CustomCompoundBondForce.h"
#include "openmm/HarmonicAngleForce.h"
#include "openmm/HarmonicBondForce.h"
#include "openmm/PeriodicTorsionForce.h"
#include "openmm/System.h"
#include "openmm/VerletIntegrator.h"
#include "sfmt/SFMT.h"
#include <iostream>
#include <vector>

using namespace OpenMM;
using namespace std;

ReferencePlatform platform;

const double TOL = 1e-5;

void testBond() {
    // Create a system using a CustomCompoundBondForce.

    System customSystem;
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    CustomCompoundBondForce* custom = new CustomCompoundBondForce(4, "0.5*kb*((distance(p1,p2)-b0)^2+(distance(p2,p3)-b0)^2)+0.5*ka*(angle(p2,p3,p4)-a0)^2+kt*(1+cos(dihedral(p1,p2,p3,p4)-t0))");
    custom->addPerBondParameter("kb");
    custom->addPerBondParameter("ka");
    custom->addPerBondParameter("kt");
    custom->addPerBondParameter("b0");
    custom->addPerBondParameter("a0");
    custom->addPerBondParameter("t0");
    vector<int> particles(4);
    particles[0] = 0;
    particles[1] = 1;
    particles[2] = 3;
    particles[3] = 2;
    vector<double> parameters(6);
    parameters[0] = 1.5;
    parameters[1] = 0.8;
    parameters[2] = 0.6;
    parameters[3] = 1.1;
    parameters[4] = 2.9;
    parameters[5] = 1.3;
    custom->addBond(particles, parameters);
    customSystem.addForce(custom);
    ASSERT(!custom->usesPeriodicBoundaryConditions());
    ASSERT(!customSystem.usesPeriodicBoundaryConditions());

    // Create an identical system using standard forces.

    System standardSystem;
    standardSystem.addParticle(1.0);
    standardSystem.addParticle(1.0);
    standardSystem.addParticle(1.0);
    standardSystem.addParticle(1.0);
    HarmonicBondForce* bonds = new HarmonicBondForce();
    bonds->addBond(0, 1, 1.1, 1.5);
    bonds->addBond(1, 3, 1.1, 1.5);
    standardSystem.addForce(bonds);
    HarmonicAngleForce* angles = new HarmonicAngleForce();
    angles->addAngle(1, 3, 2, 2.9, 0.8);
    standardSystem.addForce(angles);
    PeriodicTorsionForce* torsions = new PeriodicTorsionForce();
    torsions->addTorsion(0, 1, 3, 2, 1, 1.3, 0.6);
    standardSystem.addForce(torsions);

    // Set the atoms in various positions, and verify that both systems give identical forces and energy.

    OpenMM_SFMT::SFMT sfmt;
    init_gen_rand(0, sfmt);
    VerletIntegrator integrator1(0.01);
    VerletIntegrator integrator2(0.01);
    Context c1(customSystem, integrator1, platform);
    Context c2(standardSystem, integrator2, platform);
    vector<Vec3> positions(4);
    for (int i = 0; i < 10; i++) {
        for (int j = 0; j < (int) positions.size(); j++)
            positions[j] = Vec3(5.0*genrand_real2(sfmt), 5.0*genrand_real2(sfmt), 5.0*genrand_real2(sfmt));
        c1.setPositions(positions);
        c2.setPositions(positions);
        State s1 = c1.getState(State::Forces | State::Energy);
        State s2 = c2.getState(State::Forces | State::Energy);
        for (int i = 0; i < customSystem.getNumParticles(); i++)
            ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], TOL);
        ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), TOL);
    }
    
    // Try changing the bond parameters and make sure it's still correct.
    
    parameters[0] = 1.6;
    parameters[3] = 1.3;
    custom->setBondParameters(0, particles, parameters);
    custom->updateParametersInContext(c1);
    bonds->setBondParameters(0, 0, 1, 1.3, 1.6);
    bonds->setBondParameters(1, 1, 3, 1.3, 1.6);
    bonds->updateParametersInContext(c2);
    {
        State s1 = c1.getState(State::Forces | State::Energy);
        State s2 = c2.getState(State::Forces | State::Energy);
        const vector<Vec3>& forces = s1.getForces();
        for (int i = 0; i < customSystem.getNumParticles(); i++)
            ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], TOL);
        ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), TOL);
    }
}

void testPositionDependence() {
    System customSystem;
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    CustomCompoundBondForce* custom = new CustomCompoundBondForce(2, "scale1*distance(p1,p2)+scale2*x1+2*y2");
    custom->addGlobalParameter("scale1", 0.3);
    custom->addGlobalParameter("scale2", 0.2);
    vector<int> particles(2);
    particles[0] = 1;
    particles[1] = 0;
    vector<double> parameters;
    custom->addBond(particles, parameters);
    customSystem.addForce(custom);
    vector<Vec3> positions(2);
    positions[0] = Vec3(1.5, 1, 0);
    positions[1] = Vec3(0.5, 1, 0);
    VerletIntegrator integrator(0.01);
    Context context(customSystem, integrator, platform);
    context.setPositions(positions);
    State state = context.getState(State::Forces | State::Energy);
    ASSERT_EQUAL_TOL(0.3*1.0+0.2*0.5+2*1, state.getPotentialEnergy(), 1e-5);
    ASSERT_EQUAL_VEC(Vec3(-0.3, -2, 0), state.getForces()[0], 1e-5);
    ASSERT_EQUAL_VEC(Vec3(0.3-0.2, 0, 0), state.getForces()[1], 1e-5);
}

void testContinuous2DFunction() {
    const int xsize = 10;
    const int ysize = 11;
    const double xmin = 0.4;
    const double xmax = 1.1;
    const double ymin = 0.0;
    const double ymax = 0.9;
    System system;
    system.addParticle(1.0);
    VerletIntegrator integrator(0.01);
    CustomCompoundBondForce* forceField = new CustomCompoundBondForce(1, "fn(x1,y1)+1");
    vector<int> particles(1, 0);
    forceField->addBond(particles, vector<double>());
    vector<double> table(xsize*ysize);
    for (int i = 0; i < xsize; i++) {
        for (int j = 0; j < ysize; j++) {
            double x = xmin + i*(xmax-xmin)/xsize;
            double y = ymin + j*(ymax-ymin)/ysize;
            table[i+xsize*j] = sin(0.25*x)*cos(0.33*y);
        }
    }
    forceField->addTabulatedFunction("fn", new Continuous2DFunction(xsize, ysize, table, xmin, xmax, ymin, ymax));
    system.addForce(forceField);
    Context context(system, integrator, platform);
    vector<Vec3> positions(1);
    for (double x = xmin-0.15; x < xmax+0.2; x += 0.1) {
        for (double y = ymin-0.15; y < ymax+0.2; y += 0.1) {
            positions[0] = Vec3(x, y, 1.5);
            context.setPositions(positions);
            State state = context.getState(State::Forces | State::Energy);
            const vector<Vec3>& forces = state.getForces();
            double energy = 1;
            Vec3 force(0, 0, 0);
            if (x >= xmin && x <= xmax && y >= ymin && y <= ymax) {
                energy = sin(0.25*x)*cos(0.33*y)+1;
                force[0] = -0.25*cos(0.25*x)*cos(0.33*y);
                force[1] = 0.3*sin(0.25*x)*sin(0.33*y);
            }
            ASSERT_EQUAL_VEC(force, forces[0], 0.1);
            ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 0.05);
        }
    }
}

void testContinuous3DFunction() {
    const int xsize = 10;
    const int ysize = 11;
    const int zsize = 12;
    const double xmin = 0.4;
    const double xmax = 1.1;
    const double ymin = 0.0;
    const double ymax = 0.9;
    const double zmin = 0.2;
    const double zmax = 1.3;
    System system;
    system.addParticle(1.0);
    VerletIntegrator integrator(0.01);
    CustomCompoundBondForce* forceField = new CustomCompoundBondForce(1, "fn(x1,y1,z1)+1");
    vector<int> particles(1, 0);
    forceField->addBond(particles, vector<double>());
    vector<double> table(xsize*ysize*zsize);
    for (int i = 0; i < xsize; i++) {
        for (int j = 0; j < ysize; j++) {
            for (int k = 0; k < zsize; k++) {
                double x = xmin + i*(xmax-xmin)/xsize;
                double y = ymin + j*(ymax-ymin)/ysize;
                double z = zmin + k*(zmax-zmin)/zsize;
                table[i+xsize*j+xsize*ysize*k] = sin(0.25*x)*cos(0.33*y)*(1+z);
            }
        }
    }
    forceField->addTabulatedFunction("fn", new Continuous3DFunction(xsize, ysize, zsize, table, xmin, xmax, ymin, ymax, zmin, zmax));
    system.addForce(forceField);
    Context context(system, integrator, platform);
    vector<Vec3> positions(1);
    for (double x = xmin-0.15; x < xmax+0.2; x += 0.1) {
        for (double y = ymin-0.15; y < ymax+0.2; y += 0.1) {
            for (double z = zmin-0.15; z < zmax+0.2; z += 0.1) {
                positions[0] = Vec3(x, y, z);
                context.setPositions(positions);
                State state = context.getState(State::Forces | State::Energy);
                const vector<Vec3>& forces = state.getForces();
                double energy = 1;
                Vec3 force(0, 0, 0);
                if (x >= xmin && x <= xmax && y >= ymin && y <= ymax && z >= zmin && z <= zmax) {
                    energy = sin(0.25*x)*cos(0.33*y)*(1.0+z)+1;
                    force[0] = -0.25*cos(0.25*x)*cos(0.33*y)*(1.0+z);
                    force[1] = 0.3*sin(0.25*x)*sin(0.33*y)*(1.0+z);
                    force[2] = -sin(0.25*x)*cos(0.33*y);
                }
                ASSERT_EQUAL_VEC(force, forces[0], 0.1);
                ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 0.05);
            }
        }
    }
}

void testMultipleBonds() {
    // Two compound bonds using Urey-Bradley example from API doc
    System customSystem;
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    CustomCompoundBondForce* custom = new CustomCompoundBondForce(3,
            "0.5*(kangle*(angle(p1,p2,p3)-theta0)^2+kbond*(distance(p1,p3)-r0)^2)");
    custom->addPerBondParameter("kangle");
    custom->addPerBondParameter("kbond");
    custom->addPerBondParameter("theta0");
    custom->addPerBondParameter("r0");
    vector<double> parameters(4);
    parameters[0] = 1.0;
    parameters[1] = 1.0;
    parameters[2] = 2 * M_PI / 3;
    parameters[3] = sqrt(3.0) / 2;
    vector<int> particles0(3);
    particles0[0] = 0;
    particles0[1] = 1;
    particles0[2] = 2;
    vector<int> particles1(3);
    particles1[0] = 1;
    particles1[1] = 2;
    particles1[2] = 3;
    custom->addBond(particles0, parameters);
    custom->addBond(particles1, parameters);
    customSystem.addForce(custom);

    vector<Vec3> positions(4);
    positions[0] = Vec3(0, 0.5, 0);
    positions[1] = Vec3(0, 0, 0);
    positions[2] = Vec3(0.5, 0, 0);
    positions[3] = Vec3(0.6, 0, 0.4);
    VerletIntegrator integrator(0.01);
    Context context(customSystem, integrator, platform);
    context.setPositions(positions);
    State state = context.getState(State::Forces | State::Energy);
    ASSERT_EQUAL_TOL(0.199, state.getPotentialEnergy(), 1e-3);
    vector<Vec3> forces(state.getForces());
    ASSERT_EQUAL_VEC(Vec3(-1.160, 0.112, 0.0), forces[0], 1e-3);
    ASSERT_EQUAL_VEC(Vec3(0.927, 1.047, -0.638), forces[1], 1e-3);
    ASSERT_EQUAL_VEC(Vec3(-0.543, -1.160, 0.721), forces[2], 1e-3);
    ASSERT_EQUAL_VEC(Vec3(0.776, 0.0, -0.084), forces[3], 1e-3);
}

int main() {
    try {
        testBond();
        testPositionDependence();
        testContinuous2DFunction();
        testContinuous3DFunction();
        testMultipleBonds();
    }
    catch(const exception& e) {
        cout << "exception: " << e.what() << endl;
        return 1;
    }
    cout << "Done" << endl;
    return 0;
}


