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	/**
	* \authors The HEJ collaboration (see AUTHORS for details)
	* \date 2019-2020
	* \copyright GPLv2 or later
	*/
	#include "HEJ/PDF.hh"

	#include <cmath>
	#include <cstdlib>
	#include <iostream>
	#include <stdexcept>
	#include <string>

	#include "LHAPDF/LHAPDF.h"

	namespace HEJ {

	namespace {

	int to_beam(ParticleID id){
	if(std::abs(id) == pid::proton){
	return (id > 0)?1:-1;
	}
	throw std::invalid_argument(
	"unknown beam type: " + std::to_string(id)
	);
	}

	} // namespace

	PDF::PDF(int id, ParticleID beam1, ParticleID beam2):
	pdf_{LHAPDF::mkPDF(id)},
	beamtype_{{to_beam(beam1), to_beam(beam2)}}
	{}

	double PDF::pdfpt(size_t beam_idx, double x, double q, ParticleID id) const{
	if(!(inRangeQ(q) && inRangeX(x))) return 0.;

	if(id == pid::gluon){
	return pdf_->xfxQ(pid::gluon,x,q);
	}
	if(std::abs(id) <= pid::top){
	return pdf_->xfxQ(id*beamtype_[beam_idx],x,q);
	}
	std::cerr << "particle type unknown: "<< id << std::endl;
	return 0.0;

	}

	double PDF::Halphas(double q) const{
	double as = pdf_->alphasQ(q);
	if (std::isnan(as) \|\| as > 0.5) {
	as = 0.5;
	}
	return as;
	}

	int PDF::id() const{
	return pdf_->lhapdfID();
	}

	bool PDF::inRangeQ(double q) const{
	return pdf_->inRangeQ(q);
	}

	bool PDF::inRangeX(double x) const{
	return pdf_->inRangeX(x);
	}

	// can't be in header since we forward declare LHAPDF::PDF
	PDF::~PDF() = default;
	PDF::PDF(PDF && other) noexcept = default;
	PDF & PDF::operator=(PDF && other) noexcept = default;


	} // namespace HEJ