/*
Copyright (c) 2009-2015, UT-Battelle, LLC
All rights reserved

[DMRG++, Version 5.]
[by G.A., Oak Ridge National Laboratory]

UT Battelle Open Source Software License 11242008

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*/

/** \ingroup DMRG */
/*@{*/

/*! \file FermionSpinless.h
 *
 *  TBW
 *
 */
#ifndef DMRG_FERMION_SPINLESS
#define DMRG_FERMION_SPINLESS
#include <cassert>
#include "Sort.h" // in PsimagLite
#include "ParametersFermionSpinless.h"
#include "HilbertSpaceFermionSpinless.h"
#include "CrsMatrix.h"
#include "SpinSquaredHelper.h"
#include "SpinSquared.h"
#include "VerySparseMatrix.h"
#include "ProgramGlobals.h"

namespace Dmrg {
//! Model Hubbard for DMRG solver, inherits from ModelBase and implements its interface:
template<typename ModelBaseType>
class FermionSpinless : public ModelBaseType {

	static const int FERMION_SIGN = -1;
	static const int DEGREES_OF_FREEDOM=1;
	static const int NUMBER_OF_ORBITALS=1;

public:

	typedef typename ModelBaseType::ModelHelperType ModelHelperType;
	typedef typename ModelBaseType::SuperGeometryType SuperGeometryType;
	typedef typename ModelBaseType::LeftRightSuperType LeftRightSuperType;
	typedef typename ModelBaseType::LinkType LinkType;
	typedef typename ModelHelperType::OperatorsType OperatorsType;
	typedef typename OperatorsType::OperatorType OperatorType;
	typedef typename ModelHelperType::RealType RealType;
	typedef typename ModelBaseType::QnType QnType;
	typedef typename QnType::VectorQnType VectorQnType;
	typedef typename ModelBaseType::SparseMatrixType SparseMatrixType;
	typedef typename SparseMatrixType::value_type ComplexOrRealType;
	typedef unsigned int long WordType;
	typedef  HilbertSpaceFermionSpinless<WordType> HilbertSpaceType;
	typedef typename ModelBaseType::VectorOperatorType VectorOperatorType;
	typedef typename ModelBaseType::VectorSizeType VectorSizeType;
	typedef typename ModelBaseType::OpsLabelType OpsLabelType;
	typedef typename ModelBaseType::BlockType BlockType;
	typedef typename ModelBaseType::SolverParamsType SolverParamsType;
	typedef typename ModelBaseType::VectorType VectorType;
	typedef typename HilbertSpaceType::HilbertState HilbertState;
	typedef typename PsimagLite::Vector<HilbertState>::Type VectorHilbertStateType;
	typedef typename ModelBaseType::InputValidatorType InputValidatorType;
	typedef	typename ModelBaseType::MyBasis BasisType;
	typedef	typename ModelBaseType::BasisWithOperatorsType MyBasisWithOperators;
	typedef typename PsimagLite::Vector<HilbertState>::Type HilbertBasisType;
	typedef typename ModelBaseType::OpForLinkType OpForLinkType;
	typedef typename ModelBaseType::ModelTermType ModelTermType;

	FermionSpinless(const SolverParamsType& solverParams,
	                InputValidatorType& io,
	                const SuperGeometryType& geometry,
	                SizeType offset = DEGREES_OF_FREEDOM)
	    : ModelBaseType(solverParams, geometry, io),
	      modelParameters_(io),
	      offset_(offset),
	      spinSquared_(spinSquaredHelper_,NUMBER_OF_ORBITALS,DEGREES_OF_FREEDOM)
	{
		SizeType expected = geometry.numberOfSites();
		SizeType found = modelParameters_.potentialV.size();
		if (expected == found) return;
		PsimagLite::String str("FermionSpinless: potentialV: expected ");
		str += ttos(expected) + " values, but found " + ttos(found) + "\n";
		throw PsimagLite::RuntimeError(str);
	}

	void write(PsimagLite::String label1, PsimagLite::IoNg::Out::Serializer& io) const
	{
		if (!io.doesGroupExist(label1))
			io.createGroup(label1);

		PsimagLite::String label = label1 + "/" + this->params().model;
		io.createGroup(label);
		modelParameters_.write(label, io);
		io.write(label + "/offset_", offset_);
		spinSquaredHelper_.write(label, io);
		spinSquared_.write(label, io);
	}

	void addDiagonalsInNaturalBasis(SparseMatrixType &hmatrix,
	                                const BlockType& block,
	                                RealType time)  const
	{
		SizeType n=block.size();

		for (SizeType i = 0; i < n; ++i) {
			SizeType site = block[i];
			const OperatorType& niupop = ModelBaseType::naturalOperator("n", site, 0);
			const SparseMatrixType& niup = niupop.getCRS();

			// V_iup term
			RealType tmp = modelParameters_.potentialV[block[i]];
			hmatrix += tmp*niup;

			if (modelParameters_.potentialT.size()==0) continue;
			RealType cosarg = cos(time*modelParameters_.omega +
			                      modelParameters_.phase);
			// VT_iup term
			tmp = modelParameters_.potentialT[block[i]];
			tmp *= cosarg;
			hmatrix += tmp*niup;
		}
	}

protected:

	void fillLabeledOperators(VectorQnType& qns)
	{
		SizeType site = 0;
		BlockType block(1, site);
		HilbertBasisType natBasis;
		SparseMatrixType tmpMatrix;
		setBasis(natBasis, block);
		setSymmetryRelated(qns, natBasis);

		//! Set the operators c^\daggger_{i\sigma} in the natural basis
		for (SizeType i=0;i<block.size();i++) {
			for (int sigma=0;sigma<DEGREES_OF_FREEDOM;sigma++) {
				tmpMatrix = findOperatorMatrices(i,sigma,natBasis);
				int asign= 1;
				if (sigma>0) asign= 1;
				typename OperatorType::Su2RelatedType su2related;
				if (sigma==0) {
					su2related.source.push_back(i*offset_);
					su2related.source.push_back(i*offset_+1);
					su2related.transpose.push_back(-1);
					su2related.transpose.push_back(-1);
					su2related.offset = NUMBER_OF_ORBITALS;
				}

				OperatorType myOp(tmpMatrix,
				                  ProgramGlobals::FermionOrBosonEnum::FERMION,
				                  typename OperatorType::PairType(1,1-sigma),
				                  asign,
				                  su2related);

				this->createOpsLabel("c").push(myOp);
			}

			tmpMatrix = findOperatorMatrices(i,natBasis);
			RealType angularFactor= 1;
			typename OperatorType::Su2RelatedType su2related;
			su2related.offset = 1; //check FIXME
			OperatorType myOp(tmpMatrix,
			                  ProgramGlobals::FermionOrBosonEnum::BOSON,
			                  typename OperatorType::PairType(0,0),
			                  angularFactor,
			                  su2related);

			this->createOpsLabel("n").push(myOp);
		}

		this->makeTrackable("c");
		this->makeTrackable("n");
	}

	void fillModelLinks()
	{
		ModelTermType& hop = ModelBaseType::createTerm("hopping");
		ModelTermType& ninj = ModelBaseType::createTerm("ninj");

		OpForLinkType cup("c", 0);
		hop.push(cup, 'N', cup, 'C', typename ModelTermType::Su2Properties(1, 1, 0));

		OpForLinkType cdown("c", 1);
		hop.push(cdown, 'N', cdown, 'C', typename ModelTermType::Su2Properties(1, -1, 1));

		OpForLinkType n("n");
		ninj.push(n, 'N', n, 'N');
	}

	void setBasis(HilbertBasisType& basis,
	              const VectorSizeType& block) const
	{
		int sitesTimesDof=DEGREES_OF_FREEDOM*block.size();
		HilbertState total = (1<<sitesTimesDof);

		basis.resize(total);
		for (HilbertState a = 0; a < total; ++a)
			basis[a] = a;
	}

	// Calculate fermionic sign when applying operator
	// c^\dagger_{i\sigma} to basis state ket
	RealType sign(typename HilbertSpaceType::HilbertState const &ket,
	              int i,
	              int sigma) const
	{
		int value=0;
		value += HilbertSpaceType::calcNofElectrons(ket,0,i,0);
		int tmp1 = HilbertSpaceType::get(ket,0) &1;
		if (i>0 && tmp1>0) value++;

		return (value%2==0) ? 1.0 : FERMION_SIGN;
	}

	//! Find c^\dagger_isigma in the natural basis natBasis
	SparseMatrixType findOperatorMatrices(int i,
	                                      int sigma,
	                                      const HilbertBasisType& natBasis) const
	{
		typename HilbertSpaceType::HilbertState bra,ket;
		int n = natBasis.size();
		PsimagLite::Matrix<typename SparseMatrixType::value_type> cm(n,n);

		for (SizeType ii=0;ii<natBasis.size();ii++) {
			bra=ket=natBasis[ii];
			if (HilbertSpaceType::isNonZero(ket,i,sigma)) {

			} else {
				HilbertSpaceType::create(bra,i,sigma);
				int jj = PsimagLite::indexOrMinusOne(natBasis,bra);
				assert(jj >= 0);
				cm(ii,jj) =sign(ket,i,sigma);
			}
		}

		SparseMatrixType creationMatrix(cm);
		return creationMatrix;
	}

	void setSymmetryRelated(VectorQnType& qns,
	                        const HilbertBasisType& basis) const
	{
		// find j,m and flavors (do it by hand since we assume n==1)
		// note: we use 2j instead of j
		// note: we use m+j instead of m
		// This assures us that both j and m are SizeType
		typedef std::pair<SizeType,SizeType> PairType;
		qns.resize(basis.size(), QnType::zero());
		for (SizeType i = 0; i < basis.size(); ++i) {
			PairType jmpair = calcJmValue<PairType>(basis[i]);
			SizeType electrons = HilbertSpaceType::getNofDigits(basis[i],0);
			SizeType flavor = electrons;

			bool sign = electrons & 1;
			qns[i] = QnType(sign, VectorSizeType(1, electrons), jmpair, flavor);
		}
	}

	//! Find n_i in the natural basis natBasis
	SparseMatrixType findOperatorMatrices(int i,
	                                      const VectorHilbertStateType& natBasis) const
	{

		SizeType n = natBasis.size();
		PsimagLite::Matrix<typename SparseMatrixType::value_type> cm(n,n);

		for (SizeType ii=0;ii<natBasis.size();ii++) {
			HilbertState ket=natBasis[ii];
			cm(ii,ii) = 0.0;
			for (int sigma=0;sigma<DEGREES_OF_FREEDOM;sigma++)
				if (HilbertSpaceType::isNonZero(ket,i,sigma))
					cm(ii,ii) += 1.0;
		}

		SparseMatrixType creationMatrix(cm);
		return creationMatrix;
	}

	// note: we use 2j instead of j
	// note: we use m+j instead of m
	// This assures us that both j and m are SizeType
	// does not work for 6 or 9
	template<typename PairType>
	PairType calcJmValue(const HilbertState& ket) const
	{
		SizeType site0=0;
		SizeType site1=0;

		spinSquared_.doOnePairOfSitesA(ket,site0,site1);
		spinSquared_.doOnePairOfSitesB(ket,site0,site1);
		spinSquared_.doDiagonal(ket,site0,site1);

		RealType sz = spinSquared_.spinZ(ket,site0);
		PairType jm= spinSquaredHelper_.getJmPair(sz);

		return jm;
	}

	ParametersFermionSpinless<RealType, QnType>  modelParameters_;
	SizeType offset_;
	SpinSquaredHelper<RealType,WordType> spinSquaredHelper_;
	SpinSquared<SpinSquaredHelper<RealType,WordType> > spinSquared_;
};	//class FermionSpinless

} // namespace Dmrg
/*@}*/
#endif

