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#include <sal/config.h>

#undef LANGUAGE_NONE
#if defined _WIN32
#define WINAPI __stdcall
#endif
#define LoadInverseLib FALSE
#define LoadLanguageLib FALSE
#ifdef SYSTEM_LPSOLVE
#include <lpsolve/lp_lib.h>
#else
#include <lp_lib.h>
#endif
#undef LANGUAGE_NONE

#include "SolverComponent.hxx"
#include <strings.hrc>

#include <com/sun/star/frame/XModel.hpp>
#include <com/sun/star/table/CellAddress.hpp>
#include <rtl/math.hxx>
#include <algorithm>
#include <memory>
#include <vector>

namespace com::sun::star::uno { class XComponentContext; }

using namespace com::sun::star;

namespace {

class LpsolveSolver : public SolverComponent
{
public:
    LpsolveSolver() {}

private:
    virtual void SAL_CALL solve() override;
    virtual OUString SAL_CALL getImplementationName() override
    {
        return u"com.sun.star.comp.Calc.LpsolveSolver"_ustr;
    }
    virtual OUString SAL_CALL getComponentDescription() override
    {
        return SolverComponent::GetResourceString( RID_SOLVER_COMPONENT );
    }
};

}

void SAL_CALL LpsolveSolver::solve()
{
    uno::Reference<frame::XModel> xModel( mxDoc, uno::UNO_QUERY_THROW );

    maStatus.clear();
    mbSuccess = false;

    if ( mnEpsilonLevel < EPS_TIGHT || mnEpsilonLevel > EPS_BAGGY )
    {
        maStatus = SolverComponent::GetResourceString( RID_ERROR_EPSILONLEVEL );
        return;
    }

    xModel->lockControllers();

    // collect variables in vector (?)

    const auto & aVariableCells = maVariables;
    size_t nVariables = aVariableCells.size();
    size_t nVar = 0;

    // collect all dependent cells

    ScSolverCellHashMap aCellsHash;
    aCellsHash[maObjective].reserve( nVariables + 1 );                  // objective function

    for (const auto& rConstr : maConstraints)
    {
        table::CellAddress aCellAddr = rConstr.Left;
        aCellsHash[aCellAddr].reserve( nVariables + 1 );                // constraints: left hand side

        if ( rConstr.Right >>= aCellAddr )
            aCellsHash[aCellAddr].reserve( nVariables + 1 );            // constraints: right hand side
    }

    // set all variables to zero
    //! store old values?
    //! use old values as initial values?
    for ( const auto& rVarCell : aVariableCells )
    {
        SolverComponent::SetValue( mxDoc, rVarCell, 0.0 );
    }

    // read initial values from all dependent cells
    for ( auto& rEntry : aCellsHash )
    {
        double fValue = SolverComponent::GetValue( mxDoc, rEntry.first );
        rEntry.second.push_back( fValue );                         // store as first element, as-is
    }

    // loop through variables
    for ( const auto& rVarCell : aVariableCells )
    {
        SolverComponent::SetValue( mxDoc, rVarCell, 1.0 );      // set to 1 to examine influence

        // read value change from all dependent cells
        for ( auto& rEntry : aCellsHash )
        {
            double fChanged = SolverComponent::GetValue( mxDoc, rEntry.first );
            double fInitial = rEntry.second.front();
            rEntry.second.push_back( fChanged - fInitial );
        }

        SolverComponent::SetValue( mxDoc, rVarCell, 2.0 );      // minimal test for linearity

        for ( const auto& rEntry : aCellsHash )
        {
            double fInitial = rEntry.second.front();
            double fCoeff   = rEntry.second.back();       // last appended: coefficient for this variable
            double fTwo     = SolverComponent::GetValue( mxDoc, rEntry.first );

            bool bLinear = rtl::math::approxEqual( fTwo, fInitial + 2.0 * fCoeff ) ||
                           rtl::math::approxEqual( fInitial, fTwo - 2.0 * fCoeff );
            // second comparison is needed in case fTwo is zero
            if ( !bLinear )
                maStatus = SolverComponent::GetResourceString( RID_ERROR_NONLINEAR );
        }

        SolverComponent::SetValue( mxDoc, rVarCell, 0.0 );      // set back to zero for examining next variable
    }

    xModel->unlockControllers();

    if ( !maStatus.isEmpty() )
        return;


    // build lp_solve model


    lprec* lp = make_lp( 0, nVariables );
    if ( !lp )
        return;

    set_outputfile( lp, const_cast<char*>( "" ) );  // no output

    // set objective function

    const std::vector<double>& rObjCoeff = aCellsHash[maObjective];
    std::unique_ptr<REAL[]> pObjVal(new REAL[nVariables+1]);
    pObjVal[0] = 0.0;                           // ignored
    for (nVar=0; nVar<nVariables; nVar++)
        pObjVal[nVar+1] = rObjCoeff[nVar+1];
    set_obj_fn( lp, pObjVal.get() );
    pObjVal.reset();
    set_rh( lp, 0, rObjCoeff[0] );              // constant term of objective

    // add rows

    set_add_rowmode(lp, TRUE);

    for (const auto& rConstr : maConstraints)
    {
        // integer constraints are set later
        sheet::SolverConstraintOperator eOp = rConstr.Operator;
        if ( eOp == sheet::SolverConstraintOperator_LESS_EQUAL ||
             eOp == sheet::SolverConstraintOperator_GREATER_EQUAL ||
             eOp == sheet::SolverConstraintOperator_EQUAL )
        {
            double fDirectValue = 0.0;
            bool bRightCell = false;
            table::CellAddress aRightAddr;
            const uno::Any& rRightAny = rConstr.Right;
            if ( rRightAny >>= aRightAddr )
                bRightCell = true;                  // cell specified as right-hand side
            else
                rRightAny >>= fDirectValue;         // constant value

            table::CellAddress aLeftAddr = rConstr.Left;

            const std::vector<double>& rLeftCoeff = aCellsHash[aLeftAddr];
            std::unique_ptr<REAL[]> pValues(new REAL[nVariables+1] );
            pValues[0] = 0.0;                               // ignored?
            for (nVar=0; nVar<nVariables; nVar++)
                pValues[nVar+1] = rLeftCoeff[nVar+1];

            // if left hand cell has a constant term, put into rhs value
            double fRightValue = -rLeftCoeff[0];

            if ( bRightCell )
            {
                const std::vector<double>& rRightCoeff = aCellsHash[aRightAddr];
                // modify pValues with rhs coefficients
                for (nVar=0; nVar<nVariables; nVar++)
                    pValues[nVar+1] -= rRightCoeff[nVar+1];

                fRightValue += rRightCoeff[0];      // constant term
            }
            else
                fRightValue += fDirectValue;

            int nConstrType = LE;
            switch ( eOp )
            {
                case sheet::SolverConstraintOperator_LESS_EQUAL:    nConstrType = LE; break;
                case sheet::SolverConstraintOperator_GREATER_EQUAL: nConstrType = GE; break;
                case sheet::SolverConstraintOperator_EQUAL:         nConstrType = EQ; break;
                default:
                    OSL_FAIL( "unexpected enum type" );
            }
            add_constraint( lp, pValues.get(), nConstrType, fRightValue );
        }
    }

    set_add_rowmode(lp, FALSE);

    // apply settings to all variables

    for (nVar=0; nVar<nVariables; nVar++)
    {
        if ( !mbNonNegative )
            set_unbounded(lp, nVar+1);          // allow negative (default is non-negative)
                                                //! collect bounds from constraints?
        if ( mbInteger )
            set_int(lp, nVar+1, TRUE);
    }

    // apply single-var integer constraints

    for (const auto& rConstr : maConstraints)
    {
        sheet::SolverConstraintOperator eOp = rConstr.Operator;
        if ( eOp == sheet::SolverConstraintOperator_INTEGER ||
             eOp == sheet::SolverConstraintOperator_BINARY )
        {
            table::CellAddress aLeftAddr = rConstr.Left;
            // find variable index for cell
            for (nVar=0; nVar<nVariables; nVar++)
                if ( AddressEqual( aVariableCells[nVar], aLeftAddr ) )
                {
                    if ( eOp == sheet::SolverConstraintOperator_INTEGER )
                        set_int(lp, nVar+1, TRUE);
                    else
                        set_binary(lp, nVar+1, TRUE);
                }
        }
    }

    if ( mbMaximize )
        set_maxim(lp);
    else
        set_minim(lp);

    if ( !mbLimitBBDepth )
        set_bb_depthlimit( lp, 0 );

    set_epslevel( lp, mnEpsilonLevel );
    set_timeout( lp, mnTimeout );

    // solve model

    int nResult = ::solve( lp );

    mbSuccess = ( nResult == OPTIMAL );
    if ( mbSuccess )
    {
        // get solution

        maSolution.realloc( nVariables );

        REAL* pResultVar = nullptr;
        get_ptr_variables( lp, &pResultVar );
        std::copy_n(pResultVar, nVariables, maSolution.getArray());

        mfResultValue = get_objective( lp );
    }
    else if ( nResult == INFEASIBLE )
        maStatus = SolverComponent::GetResourceString( RID_ERROR_INFEASIBLE );
    else if ( nResult == UNBOUNDED )
        maStatus = SolverComponent::GetResourceString( RID_ERROR_UNBOUNDED );
    else if ( nResult == TIMEOUT || nResult == SUBOPTIMAL )
        maStatus = SolverComponent::GetResourceString( RID_ERROR_TIMEOUT );
    // SUBOPTIMAL is assumed to be caused by a timeout, and reported as an error

    delete_lp( lp );
}

extern "C" SAL_DLLPUBLIC_EXPORT css::uno::XInterface *
com_sun_star_comp_Calc_LpsolveSolver_get_implementation(
    css::uno::XComponentContext *,
    css::uno::Sequence<css::uno::Any> const &)
{
    return cppu::acquire(new LpsolveSolver());
}

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