// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Desire Nuentsa <desire.nuentsa_wakam@inria.fr>
// Copyright (C) 2014 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_SUITESPARSEQRSUPPORT_H
#define EIGEN_SUITESPARSEQRSUPPORT_H

// IWYU pragma: private
#include "./InternalHeaderCheck.h"

namespace Eigen {

template <typename MatrixType>
class SPQR;
template <typename SPQRType>
struct SPQRMatrixQReturnType;
template <typename SPQRType>
struct SPQRMatrixQTransposeReturnType;
template <typename SPQRType, typename Derived>
struct SPQR_QProduct;
namespace internal {
template <typename SPQRType>
struct traits<SPQRMatrixQReturnType<SPQRType> > {
  typedef typename SPQRType::MatrixType ReturnType;
};
template <typename SPQRType>
struct traits<SPQRMatrixQTransposeReturnType<SPQRType> > {
  typedef typename SPQRType::MatrixType ReturnType;
};
template <typename SPQRType, typename Derived>
struct traits<SPQR_QProduct<SPQRType, Derived> > {
  typedef typename Derived::PlainObject ReturnType;
};
}  // End namespace internal

/**
 * \ingroup SPQRSupport_Module
 * \class SPQR
 * \brief Sparse QR factorization based on SuiteSparseQR library
 *
 * This class is used to perform a multithreaded and multifrontal rank-revealing QR decomposition
 * of sparse matrices. The result is then used to solve linear leasts_square systems.
 * Clearly, a QR factorization is returned such that A*P = Q*R where :
 *
 * P is the column permutation. Use colsPermutation() to get it.
 *
 * Q is the orthogonal matrix represented as Householder reflectors.
 * Use matrixQ() to get an expression and matrixQ().transpose() to get the transpose.
 * You can then apply it to a vector.
 *
 * R is the sparse triangular factor. Use matrixQR() to get it as SparseMatrix.
 * NOTE : The Index type of R is always SuiteSparse_long. You can get it with SPQR::Index
 *
 * \tparam MatrixType_ The type of the sparse matrix A, must be a column-major SparseMatrix<>
 *
 * \implsparsesolverconcept
 *
 *
 */
template <typename MatrixType_>
class SPQR : public SparseSolverBase<SPQR<MatrixType_> > {
 protected:
  typedef SparseSolverBase<SPQR<MatrixType_> > Base;
  using Base::m_isInitialized;

 public:
  typedef typename MatrixType_::Scalar Scalar;
  typedef typename MatrixType_::RealScalar RealScalar;
  typedef SuiteSparse_long StorageIndex;
  typedef SparseMatrix<Scalar, ColMajor, StorageIndex> MatrixType;
  typedef Map<PermutationMatrix<Dynamic, Dynamic, StorageIndex> > PermutationType;
  enum { ColsAtCompileTime = Dynamic, MaxColsAtCompileTime = Dynamic };

 public:
  SPQR()
      : m_analysisIsOk(false),
        m_factorizationIsOk(false),
        m_isRUpToDate(false),
        m_ordering(SPQR_ORDERING_DEFAULT),
        m_allow_tol(SPQR_DEFAULT_TOL),
        m_tolerance(NumTraits<Scalar>::epsilon()),
        m_cR(0),
        m_E(0),
        m_H(0),
        m_HPinv(0),
        m_HTau(0),
        m_useDefaultThreshold(true) {
    cholmod_l_start(&m_cc);
  }

  explicit SPQR(const MatrixType_& matrix)
      : m_analysisIsOk(false),
        m_factorizationIsOk(false),
        m_isRUpToDate(false),
        m_ordering(SPQR_ORDERING_DEFAULT),
        m_allow_tol(SPQR_DEFAULT_TOL),
        m_tolerance(NumTraits<Scalar>::epsilon()),
        m_cR(0),
        m_E(0),
        m_H(0),
        m_HPinv(0),
        m_HTau(0),
        m_useDefaultThreshold(true) {
    cholmod_l_start(&m_cc);
    compute(matrix);
  }

  ~SPQR() {
    SPQR_free();
    cholmod_l_finish(&m_cc);
  }
  void SPQR_free() {
    cholmod_l_free_sparse(&m_H, &m_cc);
    cholmod_l_free_sparse(&m_cR, &m_cc);
    cholmod_l_free_dense(&m_HTau, &m_cc);
    std::free(m_E);
    std::free(m_HPinv);
  }

  void compute(const MatrixType_& matrix) {
    if (m_isInitialized) SPQR_free();

    MatrixType mat(matrix);

    /* Compute the default threshold as in MatLab, see:
     * Tim Davis, "Algorithm 915, SuiteSparseQR: Multifrontal Multithreaded Rank-Revealing
     * Sparse QR Factorization, ACM Trans. on Math. Soft. 38(1), 2011, Page 8:3
     */
    RealScalar pivotThreshold = m_tolerance;
    if (m_useDefaultThreshold) {
      RealScalar max2Norm = 0.0;
      for (int j = 0; j < mat.cols(); j++) max2Norm = numext::maxi(max2Norm, mat.col(j).norm());
      if (numext::is_exactly_zero(max2Norm)) max2Norm = RealScalar(1);
      pivotThreshold = 20 * (mat.rows() + mat.cols()) * max2Norm * NumTraits<RealScalar>::epsilon();
    }
    cholmod_sparse A;
    A = viewAsCholmod(mat);
    m_rows = matrix.rows();
    Index col = matrix.cols();
    m_rank = SuiteSparseQR<Scalar>(m_ordering, pivotThreshold, col, &A, &m_cR, &m_E, &m_H, &m_HPinv, &m_HTau, &m_cc);

    if (!m_cR) {
      m_info = NumericalIssue;
      m_isInitialized = false;
      return;
    }
    m_info = Success;
    m_isInitialized = true;
    m_isRUpToDate = false;
  }
  /**
   * Get the number of rows of the input matrix and the Q matrix
   */
  inline Index rows() const { return m_rows; }

  /**
   * Get the number of columns of the input matrix.
   */
  inline Index cols() const { return m_cR->ncol; }

  template <typename Rhs, typename Dest>
  void _solve_impl(const MatrixBase<Rhs>& b, MatrixBase<Dest>& dest) const {
    eigen_assert(m_isInitialized && " The QR factorization should be computed first, call compute()");
    eigen_assert(b.cols() == 1 && "This method is for vectors only");

    // Compute Q^T * b
    typename Dest::PlainObject y, y2;
    y = matrixQ().transpose() * b;

    // Solves with the triangular matrix R
    Index rk = this->rank();
    y2 = y;
    y.resize((std::max)(cols(), Index(y.rows())), y.cols());
    y.topRows(rk) = this->matrixR().topLeftCorner(rk, rk).template triangularView<Upper>().solve(y2.topRows(rk));

    // Apply the column permutation
    // colsPermutation() performs a copy of the permutation,
    // so let's apply it manually:
    for (Index i = 0; i < rk; ++i) dest.row(m_E[i]) = y.row(i);
    for (Index i = rk; i < cols(); ++i) dest.row(m_E[i]).setZero();

    //       y.bottomRows(y.rows()-rk).setZero();
    //       dest = colsPermutation() * y.topRows(cols());

    m_info = Success;
  }

  /** \returns the sparse triangular factor R. It is a sparse matrix
   */
  const MatrixType matrixR() const {
    eigen_assert(m_isInitialized && " The QR factorization should be computed first, call compute()");
    if (!m_isRUpToDate) {
      m_R = viewAsEigen<Scalar, ColMajor, typename MatrixType::StorageIndex>(*m_cR);
      m_isRUpToDate = true;
    }
    return m_R;
  }
  /// Get an expression of the matrix Q
  SPQRMatrixQReturnType<SPQR> matrixQ() const { return SPQRMatrixQReturnType<SPQR>(*this); }
  /// Get the permutation that was applied to columns of A
  PermutationType colsPermutation() const {
    eigen_assert(m_isInitialized && "Decomposition is not initialized.");
    return PermutationType(m_E, m_cR->ncol);
  }
  /**
   * Gets the rank of the matrix.
   * It should be equal to matrixQR().cols if the matrix is full-rank
   */
  Index rank() const {
    eigen_assert(m_isInitialized && "Decomposition is not initialized.");
    return m_cc.SPQR_istat[4];
  }
  /// Set the fill-reducing ordering method to be used
  void setSPQROrdering(int ord) { m_ordering = ord; }
  /// Set the tolerance tol to treat columns with 2-norm < =tol as zero
  void setPivotThreshold(const RealScalar& tol) {
    m_useDefaultThreshold = false;
    m_tolerance = tol;
  }

  /** \returns a pointer to the SPQR workspace */
  cholmod_common* cholmodCommon() const { return &m_cc; }

  /** \brief Reports whether previous computation was successful.
   *
   * \returns \c Success if computation was successful,
   *          \c NumericalIssue if the sparse QR can not be computed
   */
  ComputationInfo info() const {
    eigen_assert(m_isInitialized && "Decomposition is not initialized.");
    return m_info;
  }

 protected:
  bool m_analysisIsOk;
  bool m_factorizationIsOk;
  mutable bool m_isRUpToDate;
  mutable ComputationInfo m_info;
  int m_ordering;                           // Ordering method to use, see SPQR's manual
  int m_allow_tol;                          // Allow to use some tolerance during numerical factorization.
  RealScalar m_tolerance;                   // treat columns with 2-norm below this tolerance as zero
  mutable cholmod_sparse* m_cR = nullptr;   // The sparse R factor in cholmod format
  mutable MatrixType m_R;                   // The sparse matrix R in Eigen format
  mutable StorageIndex* m_E = nullptr;      // The permutation applied to columns
  mutable cholmod_sparse* m_H = nullptr;    // The householder vectors
  mutable StorageIndex* m_HPinv = nullptr;  // The row permutation of H
  mutable cholmod_dense* m_HTau = nullptr;  // The Householder coefficients
  mutable Index m_rank;                     // The rank of the matrix
  mutable cholmod_common m_cc;              // Workspace and parameters
  bool m_useDefaultThreshold;               // Use default threshold
  Index m_rows;
  template <typename, typename>
  friend struct SPQR_QProduct;
};

template <typename SPQRType, typename Derived>
struct SPQR_QProduct : ReturnByValue<SPQR_QProduct<SPQRType, Derived> > {
  typedef typename SPQRType::Scalar Scalar;
  typedef typename SPQRType::StorageIndex StorageIndex;
  // Define the constructor to get reference to argument types
  SPQR_QProduct(const SPQRType& spqr, const Derived& other, bool transpose)
      : m_spqr(spqr), m_other(other), m_transpose(transpose) {}

  inline Index rows() const { return m_transpose ? m_spqr.rows() : m_spqr.cols(); }
  inline Index cols() const { return m_other.cols(); }
  // Assign to a vector
  template <typename ResType>
  void evalTo(ResType& res) const {
    cholmod_dense y_cd;
    cholmod_dense* x_cd;
    int method = m_transpose ? SPQR_QTX : SPQR_QX;
    cholmod_common* cc = m_spqr.cholmodCommon();
    y_cd = viewAsCholmod(m_other.const_cast_derived());
    x_cd = SuiteSparseQR_qmult<Scalar>(method, m_spqr.m_H, m_spqr.m_HTau, m_spqr.m_HPinv, &y_cd, cc);
    res = Matrix<Scalar, ResType::RowsAtCompileTime, ResType::ColsAtCompileTime>::Map(
        reinterpret_cast<Scalar*>(x_cd->x), x_cd->nrow, x_cd->ncol);
    cholmod_l_free_dense(&x_cd, cc);
  }
  const SPQRType& m_spqr;
  const Derived& m_other;
  bool m_transpose;
};
template <typename SPQRType>
struct SPQRMatrixQReturnType {
  SPQRMatrixQReturnType(const SPQRType& spqr) : m_spqr(spqr) {}
  template <typename Derived>
  SPQR_QProduct<SPQRType, Derived> operator*(const MatrixBase<Derived>& other) {
    return SPQR_QProduct<SPQRType, Derived>(m_spqr, other.derived(), false);
  }
  SPQRMatrixQTransposeReturnType<SPQRType> adjoint() const { return SPQRMatrixQTransposeReturnType<SPQRType>(m_spqr); }
  // To use for operations with the transpose of Q
  SPQRMatrixQTransposeReturnType<SPQRType> transpose() const {
    return SPQRMatrixQTransposeReturnType<SPQRType>(m_spqr);
  }
  const SPQRType& m_spqr;
};

template <typename SPQRType>
struct SPQRMatrixQTransposeReturnType {
  SPQRMatrixQTransposeReturnType(const SPQRType& spqr) : m_spqr(spqr) {}
  template <typename Derived>
  SPQR_QProduct<SPQRType, Derived> operator*(const MatrixBase<Derived>& other) {
    return SPQR_QProduct<SPQRType, Derived>(m_spqr, other.derived(), true);
  }
  const SPQRType& m_spqr;
};

}  // End namespace Eigen
#endif