#include "util.h"

template <typename ComplexOrRealType>
void csc_matmul_pre(char trans_A,
    const int nrow_A,
    const int ncol_A,
    const PsimagLite::Vector<int>::Type& acolptr,
    const PsimagLite::Vector<int>::Type& arow,
    const typename PsimagLite::Vector<ComplexOrRealType>::Type& aval,
    const int nrow_Y,
    const int ncol_Y,
    const PsimagLite::Matrix<ComplexOrRealType>& yin,
    const int nrow_X,
    const int ncol_X,
    PsimagLite::Matrix<ComplexOrRealType>& xout)
{
	/*
	 * -------------------------------------------------------
	 * A in compressed sparse COLUMN format
	 *
	 * compute   X +=  op(A) * Y
	 * where op(A) is transpose(A)   if trans_A = 'T' or 't'
	 *       op(A) is A              otherwise
	 *
	 * if need transpose(A) then
	 *   X(nrow_X,ncol_X) +=  tranpose(A(nrow_A,ncol_A))*Y(nrow_Y,ncol_Y)
	 *   requires nrow_X == ncol_A, ncol_X == ncol_Y, nrow_A == nrow_Y
	 *
	 * if need A then
	 *  X(nrow_X,ncol_X) += A(nrow_A,ncol_A) * Y(nrow_Y,ncol_Y)
	 *  requires  nrow_X == nrow_A, ncol_A == nrow_Y, ncol_X == ncol_Y
	 * -------------------------------------------------------
	 */

	const bool is_complex = PsimagLite::IsComplexNumber<ComplexOrRealType>::True;
	int isTranspose = (trans_A == 'T') || (trans_A == 't');
	int isConjTranspose = (trans_A == 'C') || (trans_A == 'c');

	if (isTranspose || isConjTranspose) {
		/*
		 *   ----------------------------------------------------------
		 *   X(nrow_X,ncol_X) +=  tranpose(A(nrow_A,ncol_A))*Y(nrow_Y,ncol_Y)
		 *   X(ix,jx) +=  transpose( A(ia,ja) ) * Y(iy,jy)
		 *   X(ja,jy) +=  sum( At(ja, ia) * Y(ia,jy), over ia)
		 *   ----------------------------------------------------------
		 */

		assert((nrow_X == ncol_A) && (nrow_A == nrow_Y) && (ncol_X == ncol_Y));

		int ja = 0;
		for (ja = 0; ja < ncol_A; ja++) {
			int istart = acolptr[ja];
			int iend = acolptr[ja + 1] - 1;
			int k = 0;
			for (k = istart; k <= iend; k++) {
				int ia = arow[k];
				assert((0 <= ia) && (ia < nrow_A));

				ComplexOrRealType aij = aval[k];
				ComplexOrRealType atji = aij;
				if (is_complex && isConjTranspose) {
					atji = PsimagLite::conj(atji);
				};

				int jy = 0;
				for (jy = 0; jy < ncol_Y; jy++) {
					int ix = ja;
					int jx = jy;
					xout(ix, jx) += (atji * yin(ia, jy));
				};
			};
		};
	} else {
		/*
		 * ---------------------------------------------
		 * X(nrow_X,ncol_X) += A(nrow_A,ncol_A) * Y(nrow_Y,ncol_Y)
		 * X(ia,jy) += sum( A(ia,ja)*Y(ja,jy), over ja )
		 * ---------------------------------------------
		 */
		assert((nrow_X == nrow_A) && (ncol_A == nrow_Y) && (ncol_X == ncol_Y));

		int ja = 0;
		for (ja = 0; ja < ncol_A; ja++) {
			int istart = acolptr[ja];
			int iend = acolptr[ja + 1] - 1;
			int k = 0;
			for (k = istart; k <= iend; k++) {
				ComplexOrRealType aij = aval[k];

				int ia = arow[k];
				assert((0 <= ia) && (ia < nrow_A));

				int jy = 0;
				for (jy = 0; jy < ncol_Y; jy++) {
					int ix = ia;
					int jx = jy;

					xout(ix, jx) += (aij * yin(ja, jy));
				};
			};
		};
	};
}

#undef X
#undef Y
