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

[DMRG++, Version 2.0.0]
[by G.A., Oak Ridge National Laboratory]

UT Battelle Open Source Software License 11242008

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*/

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

/*! \file ReflectionColor
 *
 *  Critical problems:
 *
 *  - getting a l.i. set in an efficient way
 *  - support for fermionic reflections
 *
 *  Low priority work that needs to be done:
 *
 *  - support for bases that change from site to site
 *
 */
#ifndef REFLECTION_COLOR_H
#define REFLECTION_COLOR_H

#include "LAPACK.h"
#include "Matrix.h"
#include "PackIndices.h" // in PsimagLite
#include "ProgressIndicator.h"
#include "Sort.h"
#include "SparseVector.h"

namespace Dmrg
{

// FIXME: MOVE ELSEWHERE:
template <typename RealType>
bool isAlmostZero(const RealType& x, RealType eps = 1e-20)
{
	return (fabs(x) < eps);
}

// FIXME: MOVE ELSEWHERE:
template <typename RealType>
bool isAlmostZero(const std::complex<RealType>& x, RealType eps = 1e-20)
{
	return (fabs(real(x) * real(x) + imag(x) * imag(x)) < eps);
}

template <typename RealType, typename SparseMatrixType>
class ReflectionColor
{

	typedef PsimagLite::PackIndices PackIndicesType;
	typedef typename SparseMatrixType::value_type ComplexOrRealType;
	typedef typename PsimagLite::Vector<ComplexOrRealType>::Type VectorType;
	typedef SparseVector<typename VectorType::value_type> SparseVectorType;

	enum { AVAILABLE,
		NOT_AVAILABLE,
		COLOR };

public:

	ReflectionColor(const SparseMatrixType& reflection, bool idebug)
	    : reflection_(reflection)
	    , idebug_(idebug)
	{
		//		printFullMatrix(reflection,"reflection");
		findIsolated();

		printInfo();
		//		std::cerr<<"Isolated nodes="<<ipIsolated_.size()<<"\n";
		//		std::cerr<<"Connected nodes="<<ipConnected_.size()<<"\n";

		SizeType firstColor = 2;
		// SparseMatrixType A;
		// generateAmatrix(A,ipConnected_);
		SizeType ncolor = gencolorLabel(reflection, firstColor);

		//		for (SizeType i=0ilabel(ip_isolated) = 0;

		//		% print statistics
		//		% ----------------
		printInfo2(ncolor, firstColor);

		// gencolorCheck(ilabel_,ncolor);

		// gencolorPerm(ilabel_,firstColor,ncolor);

		for (SizeType i = 0; i < ipIsolated_.size(); i++)
			ilabel_[ipIsolated_[i]] = AVAILABLE;

		for (SizeType i = 0; i < ilabel_.size(); i++)
			if (ilabel_[i] == firstColor)
				ipcolor_.push_back(i);
	}

	const typename PsimagLite::Vector<SizeType>::Type& ipcolor() const { return ipcolor_; }

	const typename PsimagLite::Vector<SizeType>::Type& isolated() const { return ipIsolated_; }

private:

	void printInfo() const
	{
		if (!idebug_)
			return;
		std::cout << "ipIsolated ";
		for (SizeType i = 0; i < ipIsolated_.size(); i++)
			std::cout << ipIsolated_[i] << " ";
		std::cout << "\n";
		for (SizeType i = 0; i < ipConnected_.size(); i++)
			std::cout << ipConnected_[i] << " ";
		std::cout << "\n";
	}

	void printInfo2(SizeType ncolor, SizeType firstColor) const
	{
		if (!idebug_)
			return;
		std::cout << "ncolor=" << ncolor << "\n";
		for (SizeType icolor = firstColor; icolor <= ncolor; icolor++) {
			typename PsimagLite::Vector<SizeType>::Type ilist;
			findWithLabel(ilist, ilabel_, icolor);
			std::cout << "color=" << icolor << " size=" << ilist.size() << "\n";
		}
	}

	void generateAmatrix(SparseMatrixType& A, const typename PsimagLite::Vector<SizeType>::Type& ipConnected) const
	{
		A.resize(ipConnected.size());
		SizeType counter = 0;
		typename PsimagLite::Vector<int>::Type ipConnectedInverse(reflection_.rank(), -1);
		for (SizeType i = 0; i < ipConnected.size(); i++)
			ipConnectedInverse[ipConnected[i]] = i;

		for (SizeType i = 0; i < ipConnected.size(); i++) {
			A.setRow(i, counter);
			SizeType ii = ipConnected[i];
			for (int k = reflection_.getRowPtr(ii); k < reflection_.getRowPtr(ii + 1); k++) {
				ComplexOrRealType val = reflection_.getValue(k);
				int col = ipConnectedInverse[reflection_.getCol(k)];
				if (col < 0)
					continue;
				A.pushCol(col);
				A.pushValue(val);
				counter++;
			}
		}
		A.setRow(A.rank(), counter);
		A.checkValidity();
	}

	void findIsolated()
	{
		for (SizeType i = 0; i < reflection_.rank(); i++) {
			SizeType nz = 0;
			bool hasDiagonal = false;
			for (int k = reflection_.getRowPtr(i); k < reflection_.getRowPtr(i + 1); k++) {
				ComplexOrRealType val = reflection_.getValue(k);
				SizeType col = reflection_.getCol(k);
				if (i == col) {
					val = val + 1.0;
					hasDiagonal = true;
				}
				if (isAlmostZero(val, 1e-4))
					continue;
				nz++;
			}
			if (!hasDiagonal)
				nz++;
			if (nz == 1)
				ipIsolated_.push_back(i);
			else
				ipConnected_.push_back(i);
		}
	}

	SizeType gencolorLabel(const SparseMatrixType& A, SizeType firstColor)
	{
		ilabel_.assign(A.rank(), AVAILABLE);

		SizeType ncolor = firstColor - 1;
		typename PsimagLite::Vector<SizeType>::Type ilist;
		RealType eps = 1e-3;

		// while (any( ilabel == unlabeled))
		for (SizeType ii = 0; ii < ilabel_.size(); ii++) {
			if (ilabel_[ii] != AVAILABLE)
				continue;
			ncolor++;
			SizeType icolor = ncolor;
			ilist.clear();
			findWithLabel(ilist, ilabel_, AVAILABLE);
			SizeType ifound = 0;
			for (SizeType i = 0; i < ilist.size(); i++) {
				//				if (ifound >= maxsize) break;

				SizeType ni = ilist[i];
				if (ilabel_[ni] == AVAILABLE) {
					ilabel_[ni] = icolor;
					ifound++;
					// --------------
					// mark neighbors
					// --------------
					typename PsimagLite::Vector<SizeType>::Type jlist;
					findConnected(jlist, ni, A, eps);
					//					jlist = find( A(ni,:) );
					for (SizeType j = 0; j < jlist.size(); j++) {
						SizeType nj = jlist[j];
						if (ilabel_[nj] == AVAILABLE) {
							ilabel_[nj] = NOT_AVAILABLE;
						}
					}
				}
			}
			ilist.clear();
			findWithLabel(ilist, ilabel_, NOT_AVAILABLE);
			//			ilist = find( ilabel == isseen);
			for (SizeType jj = 0; jj < ilist.size(); jj++) {
				ilabel_[ilist[jj]] = AVAILABLE;
			}
			//			if (ilist.size() >= 1) {
			//			   ilabel(ilist) = unlabeled;
			//			}
		}
		return ncolor;
	}

	void findConnected(typename PsimagLite::Vector<SizeType>::Type& jlist,
	    SizeType ni,
	    const SparseMatrixType& A,
	    const RealType& eps) const
	{
		bool hasDiagonal = false;
		for (int k = A.getRowPtr(ni); k < A.getRowPtr(ni + 1); k++) {
			ComplexOrRealType val = A.getValue(k);
			SizeType col = A.getCol(k);
			if (ni == col) {
				hasDiagonal = true;
				val += 1.0;
			}
			if (isAlmostZero(val, eps))
				continue;
			jlist.push_back(col);
		}
		if (!hasDiagonal)
			jlist.push_back(ni);
	}

	void gencolorCheck(const typename PsimagLite::Vector<SizeType>::Type& ilabel, SizeType ncolor) const
	{
		// ------------
		// RealType check
		// ------------
		typename PsimagLite::Vector<SizeType>::Type ilist;
		findWithLabel(ilist, ilabel, ncolor);
		//		isok = max( ilabel == ncolor);
		SizeType isok = *std::max(ilist.begin(), ilist.end());
		if (isok == 0) {
			PsimagLite::String s = "ncolor " + ttos(ncolor) + " max(ilabel) " + ttos(isok) + "\n";
			// throw PsimagLite::RuntimeError(s.c_str());
		}
	}

	void findWithLabel(typename PsimagLite::Vector<SizeType>::Type& ilist,
	    const typename PsimagLite::Vector<SizeType>::Type& ilabel,
	    SizeType icolor) const
	{
		for (SizeType i = 0; i < ilabel.size(); i++)
			if (ilabel[i] == icolor)
				ilist.push_back(i);
	}

	//	void gencolorPerm(const typename PsimagLite::Vector<SizeType>::Type& ilabel,
	//			  SizeType firstColor,
	//			  SizeType ncolor)
	//	{
	//		// find size:
	//		typename PsimagLite::Vector<SizeType>::Type ilist;
	//		SizeType ip = 0;
	//		iperm_.resize(reflection_.rank());

	//		for (SizeType icolor=firstColor;icolor<=ncolor;icolor++) {
	//			//			ilist = find( ilabel == icolor);
	//			ilist.clear();
	//			findWithLabel(ilist,ilabel,icolor);
	//			SizeType nc = ilist.size();
	//			//			nc = length(ilist);
	//			for (SizeType j=ip;j<ip+nc;j++) iperm_[j]=ilist[j-ip];

	//			// omitting check
	//			ip += nc;
	//		}
	//		if (!idebug_) return;

	//		//		% ----------------
	//		//		% print statistics
	//		//		% ----------------
	//		std::cout<<"ncolor="<<ncolor<<"\n";
	//		for (SizeType icolor=firstColor;icolor<ncolor;icolor++) {
	//			ilist.clear();
	//			findWithLabel(ilist,ilabel,icolor);
	//			std::cout<<"color="<<icolor<<" size="<<ilist.size()<<"\n";
	//		}

	//	}

	const SparseMatrixType& reflection_;
	bool idebug_;
	typename PsimagLite::Vector<SizeType>::Type ipIsolated_, ipConnected_;
	typename PsimagLite::Vector<SizeType>::Type ilabel_;
	//	typename PsimagLite::Vector<SizeType>::Type iperm_;
	typename PsimagLite::Vector<SizeType>::Type ipcolor_;
}; // class ReflectionColor

} // namespace Dmrg

/*@}*/
#endif // REFLECTION_COLOR_H