#ifndef XGBOOST_REGRANK_OBJ_HPP
#define XGBOOST_REGRANK_OBJ_HPP
/*!
 * \file xgboost_regrank_obj.h
 * \brief implementation of objective functions
 * \author Tianqi Chen, Kailong Chen
 */
namespace xgboost{
    namespace regrank{        
        class RegressionObj : public IObjFunction{
        public:
            RegressionObj(void){
                loss.loss_type = LossType::kLinearSquare;
            }
            virtual ~RegressionObj(){}
            virtual void SetParam(const char *name, const char *val){
                if( !strcmp( "loss_type", name ) ) loss.loss_type = atoi( val );
            }
            virtual void GetGradient(const std::vector<float>& preds,  
                                     const DMatrix::Info &info,
                                     std::vector<float> &grad, 
                                     std::vector<float> &hess ) {
                grad.resize(preds.size()); hess.resize(preds.size());

                const unsigned ndata = static_cast<unsigned>(preds.size());
                #pragma omp parallel for schedule( static )
                for (unsigned j = 0; j < ndata; ++j){
                    grad[j] = loss.FirstOrderGradient(preds[j], info.labels[j]) * info.GetWeight(j);
                    hess[j] = loss.SecondOrderGradient(preds[j], info.labels[j]) * info.GetWeight(j);
                }
            }
            virtual const char* DefaultEvalMetric(void) {
                if( loss.loss_type == LossType::kLogisticClassify ) return "error";
                else return "rmse";
            }
            virtual void PredTransform(std::vector<float> &preds){
                const unsigned ndata = static_cast<unsigned>(preds.size());
                #pragma omp parallel for schedule( static )
                for (unsigned j = 0; j < ndata; ++j){
                    preds[j] = loss.PredTransform( preds[j] );
                }
            }
        private:
            LossType loss;
        };
    };

    namespace regrank{
        // TODO rank objective
    };
};
#endif