// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
// Copyright 2008-2016 National ICT Australia (NICTA)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ------------------------------------------------------------------------

//! \addtogroup glue_solve
//! @{

//
// glue_solve_gen_default

template <typename T1, typename T2>
inline void glue_solve_gen_default::apply(Mat<typename T1::elem_type>& out,
                                          const Glue<T1, T2, glue_solve_gen_default>& X) {
  arma_extra_debug_sigprint();

  const bool status = glue_solve_gen_default::apply(out, X.A, X.B);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("solve(): solution not found");
  }
}

template <typename eT, typename T1, typename T2>
inline bool glue_solve_gen_default::apply(Mat<eT>& out, const Base<eT, T1>& A_expr,
                                          const Base<eT, T2>& B_expr) {
  arma_extra_debug_sigprint();

  return glue_solve_gen_full::apply<eT, T1, T2, false>(out, A_expr, B_expr, uword(0));
}

//
// glue_solve_gen_full

template <typename T1, typename T2>
inline void glue_solve_gen_full::apply(Mat<typename T1::elem_type>& out,
                                       const Glue<T1, T2, glue_solve_gen_full>& X) {
  arma_extra_debug_sigprint();

  const bool status = glue_solve_gen_full::apply(out, X.A, X.B, X.aux_uword);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("solve(): solution not found");
  }
}

template <typename eT, typename T1, typename T2, const bool has_user_flags>
inline bool glue_solve_gen_full::apply(Mat<eT>& actual_out, const Base<eT, T1>& A_expr,
                                       const Base<eT, T2>& B_expr, const uword flags) {
  arma_extra_debug_sigprint();

  typedef typename get_pod_type<eT>::result T;

  if (has_user_flags == true) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): has_user_flags = true");
  }
  if (has_user_flags == false) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): has_user_flags = false");
  }

  const bool fast = has_user_flags && bool(flags & solve_opts::flag_fast);
  const bool equilibrate = has_user_flags && bool(flags & solve_opts::flag_equilibrate);
  const bool no_approx = has_user_flags && bool(flags & solve_opts::flag_no_approx);
  const bool no_band = has_user_flags && bool(flags & solve_opts::flag_no_band);
  const bool no_sympd = has_user_flags && bool(flags & solve_opts::flag_no_sympd);
  const bool allow_ugly = has_user_flags && bool(flags & solve_opts::flag_allow_ugly);
  const bool likely_sympd = has_user_flags && bool(flags & solve_opts::flag_likely_sympd);
  const bool refine = has_user_flags && bool(flags & solve_opts::flag_refine);
  const bool no_trimat = has_user_flags && bool(flags & solve_opts::flag_no_trimat);
  const bool force_approx = has_user_flags && bool(flags & solve_opts::flag_force_approx);

  if (has_user_flags) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): enabled flags:");

    if (fast) {
      arma_extra_debug_print("fast");
    }
    if (equilibrate) {
      arma_extra_debug_print("equilibrate");
    }
    if (no_approx) {
      arma_extra_debug_print("no_approx");
    }
    if (no_band) {
      arma_extra_debug_print("no_band");
    }
    if (no_sympd) {
      arma_extra_debug_print("no_sympd");
    }
    if (allow_ugly) {
      arma_extra_debug_print("allow_ugly");
    }
    if (likely_sympd) {
      arma_extra_debug_print("likely_sympd");
    }
    if (refine) {
      arma_extra_debug_print("refine");
    }
    if (no_trimat) {
      arma_extra_debug_print("no_trimat");
    }
    if (force_approx) {
      arma_extra_debug_print("force_approx");
    }

    arma_debug_check((fast && equilibrate),
                     "solve(): options 'fast' and 'equilibrate' are mutually exclusive");
    arma_debug_check((fast && refine),
                     "solve(): options 'fast' and 'refine' are mutually exclusive");
    arma_debug_check(
        (no_sympd && likely_sympd),
        "solve(): options 'no_sympd' and 'likely_sympd' are mutually exclusive");
  }

  Mat<eT> A = A_expr.get_ref();

  if (force_approx) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): forced approximate solution");

    arma_debug_check(
        no_approx,
        "solve(): options 'no_approx' and 'force_approx' are mutually exclusive");

    if (fast) {
      arma_debug_warn_level(
          2, "solve(): option 'fast' ignored for forced approximate solution");
    }
    if (equilibrate) {
      arma_debug_warn_level(
          2, "solve(): option 'equilibrate' ignored for forced approximate solution");
    }
    if (refine) {
      arma_debug_warn_level(
          2, "solve(): option 'refine' ignored for forced approximate solution");
    }
    if (likely_sympd) {
      arma_debug_warn_level(
          2, "solve(): option 'likely_sympd' ignored for forced approximate solution");
    }

    return auxlib::solve_approx_svd(actual_out, A, B_expr.get_ref());  // A is overwritten
  }

  // A_expr and B_expr can be used more than once (sympd optimisation fails or approximate
  // solution required), so ensure they are not overwritten in case we have aliasing

  bool is_alias = true;  // assume we have aliasing until we can prove otherwise

  if (is_Mat<T1>::value && is_Mat<T2>::value) {
    const quasi_unwrap<T1> UA(A_expr.get_ref());
    const quasi_unwrap<T2> UB(B_expr.get_ref());

    is_alias = UA.is_alias(actual_out) || UB.is_alias(actual_out);
  }

  Mat<eT> tmp;
  Mat<eT>& out = (is_alias) ? tmp : actual_out;

  T rcond = T(0);
  bool status = false;

  if (A.n_rows == A.n_cols) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): detected square system");

    uword KL = 0;
    uword KU = 0;

    const bool is_band =
        arma_config::optimise_band && ((no_band || auxlib::crippled_lapack(A))
                                           ? false
                                           : band_helper::is_band(KL, KU, A, uword(32)));

    const bool is_triu = (no_trimat || refine || equilibrate || likely_sympd || is_band)
                             ? false
                             : trimat_helper::is_triu(A);
    const bool is_tril =
        (no_trimat || refine || equilibrate || likely_sympd || is_band || is_triu)
            ? false
            : trimat_helper::is_tril(A);

    const bool try_sympd =
        arma_config::optimise_sym &&
        ((no_sympd || auxlib::crippled_lapack(A) || is_band || is_triu || is_tril)
             ? false
             : (likely_sympd ? true : sym_helper::guess_sympd(A, uword(16))));

    if (fast) {
      // fast mode: solvers without refinement and without rcond estimate

      arma_extra_debug_print("glue_solve_gen_full::apply(): fast mode");

      if (is_band) {
        if ((KL == 1) && (KU == 1)) {
          arma_extra_debug_print("glue_solve_gen_full::apply(): fast + tridiagonal");

          status = auxlib::solve_tridiag_fast(out, A, B_expr.get_ref());
        } else {
          arma_extra_debug_print("glue_solve_gen_full::apply(): fast + band");

          status = auxlib::solve_band_fast(out, A, KL, KU, B_expr.get_ref());
        }
      } else if (is_triu || is_tril) {
        if (is_triu) {
          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): fast + upper triangular matrix");
        }
        if (is_tril) {
          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): fast + lower triangular matrix");
        }

        const uword layout = (is_triu) ? uword(0) : uword(1);

        status = auxlib::solve_trimat_fast(out, A, B_expr.get_ref(), layout);
      } else if (try_sympd) {
        arma_extra_debug_print("glue_solve_gen_full::apply(): fast + try_sympd");

        status = auxlib::solve_sympd_fast(out, A, B_expr.get_ref());  // A is overwritten

        if (status == false) {
          // auxlib::solve_sympd_fast() may have failed because A isn't really sympd

          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): auxlib::solve_sympd_fast() failed; "
              "retrying");

          A = A_expr.get_ref();

          status =
              auxlib::solve_square_fast(out, A, B_expr.get_ref());  // A is overwritten
        }
      } else {
        arma_extra_debug_print("glue_solve_gen_full::apply(): fast + dense");

        status = auxlib::solve_square_fast(out, A, B_expr.get_ref());  // A is overwritten
      }
    } else if (refine || equilibrate) {
      // refine mode: solvers with refinement and with rcond estimate

      arma_extra_debug_print("glue_solve_gen_full::apply(): refine mode");

      if (is_band) {
        arma_extra_debug_print("glue_solve_gen_full::apply(): refine + band");

        status = auxlib::solve_band_refine(out, rcond, A, KL, KU, B_expr, equilibrate);
      } else if (try_sympd) {
        arma_extra_debug_print("glue_solve_gen_full::apply(): refine + try_sympd");

        status = auxlib::solve_sympd_refine(out, rcond, A, B_expr.get_ref(),
                                            equilibrate);  // A is overwritten

        if ((status == false) && (rcond == T(0))) {
          // auxlib::solve_sympd_refine() may have failed because A isn't really sympd;
          // in that case rcond is set to zero

          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): auxlib::solve_sympd_refine() failed; "
              "retrying");

          A = A_expr.get_ref();

          status = auxlib::solve_square_refine(out, rcond, A, B_expr.get_ref(),
                                               equilibrate);  // A is overwritten
        }
      } else {
        arma_extra_debug_print("glue_solve_gen_full::apply(): refine + dense");

        status = auxlib::solve_square_refine(out, rcond, A, B_expr,
                                             equilibrate);  // A is overwritten
      }
    } else {
      // default mode: solvers without refinement but with rcond estimate

      arma_extra_debug_print("glue_solve_gen_full::apply(): default mode");

      if (is_band) {
        arma_extra_debug_print("glue_solve_gen_full::apply(): rcond + band");

        status = auxlib::solve_band_rcond(out, rcond, A, KL, KU, B_expr.get_ref());
      } else if (is_triu || is_tril) {
        if (is_triu) {
          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): rcond + upper triangular matrix");
        }
        if (is_tril) {
          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): rcond + lower triangular matrix");
        }

        const uword layout = (is_triu) ? uword(0) : uword(1);

        status = auxlib::solve_trimat_rcond(out, rcond, A, B_expr.get_ref(), layout);
      } else if (try_sympd) {
        bool sympd_state = false;

        status = auxlib::solve_sympd_rcond(out, sympd_state, rcond, A,
                                           B_expr.get_ref());  // A is overwritten

        if ((status == false) && (sympd_state == false)) {
          arma_extra_debug_print(
              "glue_solve_gen_full::apply(): auxlib::solve_sympd_rcond() failed; "
              "retrying");

          A = A_expr.get_ref();

          status = auxlib::solve_square_rcond(out, rcond, A,
                                              B_expr.get_ref());  // A is overwritten
        }
      } else {
        status = auxlib::solve_square_rcond(out, rcond, A,
                                            B_expr.get_ref());  // A is overwritten
      }
    }
  } else {
    arma_extra_debug_print("glue_solve_gen_full::apply(): detected non-square system");

    if (equilibrate) {
      arma_debug_warn_level(
          2, "solve(): option 'equilibrate' ignored for non-square matrix");
    }
    if (refine) {
      arma_debug_warn_level(2, "solve(): option 'refine' ignored for non-square matrix");
    }
    if (likely_sympd) {
      arma_debug_warn_level(
          2, "solve(): option 'likely_sympd' ignored for non-square matrix");
    }

    if (fast) {
      status = auxlib::solve_rect_fast(out, A, B_expr.get_ref());  // A is overwritten
    } else {
      status =
          auxlib::solve_rect_rcond(out, rcond, A, B_expr.get_ref());  // A is overwritten
    }
  }

  if ((status == true) && (fast == false) && (allow_ugly == false) &&
      ((rcond < std::numeric_limits<T>::epsilon()) || arma_isnan(rcond))) {
    status = false;
  }

  if ((status == false) && (no_approx == false)) {
    arma_extra_debug_print("glue_solve_gen_full::apply(): solving rank deficient system");

    if (rcond == T(0)) {
      arma_debug_warn_level(2, "solve(): system is singular; attempting approx solution");
    } else {
      arma_debug_warn_level(2, "solve(): system is singular (rcond: ", rcond,
                            "); attempting approx solution");
    }

    // TODO: conditionally recreate A: have a separate state flag which indicates whether
    // A was previously overwritten

    A = A_expr.get_ref();  // as A may have been overwritten

    status = auxlib::solve_approx_svd(out, A, B_expr.get_ref());  // A is overwritten
  }

  if (is_alias) {
    actual_out.steal_mem(out);
  }

  return status;
}

//
// glue_solve_tri_default

template <typename T1, typename T2>
inline void glue_solve_tri_default::apply(Mat<typename T1::elem_type>& out,
                                          const Glue<T1, T2, glue_solve_tri_default>& X) {
  arma_extra_debug_sigprint();

  const bool status = glue_solve_tri_default::apply(out, X.A, X.B, X.aux_uword);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("solve(): solution not found");
  }
}

template <typename eT, typename T1, typename T2>
inline bool glue_solve_tri_default::apply(Mat<eT>& actual_out, const Base<eT, T1>& A_expr,
                                          const Base<eT, T2>& B_expr, const uword flags) {
  arma_extra_debug_sigprint();

  typedef typename get_pod_type<eT>::result T;

  const bool triu = bool(flags & solve_opts::flag_triu);
  const bool tril = bool(flags & solve_opts::flag_tril);

  arma_extra_debug_print("glue_solve_tri_default::apply(): enabled flags:");

  if (triu) {
    arma_extra_debug_print("triu");
  }
  if (tril) {
    arma_extra_debug_print("tril");
  }

  const quasi_unwrap<T1> UA(A_expr.get_ref());
  const Mat<eT>& A = UA.M;

  arma_debug_check((A.is_square() == false),
                   "solve(): matrix marked as triangular must be square sized");

  const uword layout = (triu) ? uword(0) : uword(1);

  bool is_alias = true;

  if (is_Mat<T2>::value) {
    const quasi_unwrap<T2> UB(B_expr.get_ref());

    is_alias = UA.is_alias(actual_out) || UB.is_alias(actual_out);
  }

  T rcond = T(0);
  bool status = false;

  Mat<eT> tmp;
  Mat<eT>& out = (is_alias) ? tmp : actual_out;

  status = auxlib::solve_trimat_rcond(out, rcond, A, B_expr.get_ref(),
                                      layout);  // A is not modified

  if ((status == true) &&
      ((rcond < std::numeric_limits<T>::epsilon()) || arma_isnan(rcond))) {
    status = false;
  }

  if (status == false) {
    arma_extra_debug_print(
        "glue_solve_tri_default::apply(): solving rank deficient system");

    if (rcond == T(0)) {
      arma_debug_warn_level(2, "solve(): system is singular; attempting approx solution");
    } else {
      arma_debug_warn_level(2, "solve(): system is singular (rcond: ", rcond,
                            "); attempting approx solution");
    }

    Mat<eT> triA =
        (triu) ? trimatu(A) : trimatl(A);  // trimatu() and trimatl() return the same type

    status =
        auxlib::solve_approx_svd(out, triA, B_expr.get_ref());  // triA is overwritten
  }

  if (is_alias) {
    actual_out.steal_mem(out);
  }

  return status;
}

//
// glue_solve_tri_full

template <typename T1, typename T2>
inline void glue_solve_tri_full::apply(Mat<typename T1::elem_type>& out,
                                       const Glue<T1, T2, glue_solve_tri_full>& X) {
  arma_extra_debug_sigprint();

  const bool status = glue_solve_tri_full::apply(out, X.A, X.B, X.aux_uword);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("solve(): solution not found");
  }
}

template <typename eT, typename T1, typename T2>
inline bool glue_solve_tri_full::apply(Mat<eT>& actual_out, const Base<eT, T1>& A_expr,
                                       const Base<eT, T2>& B_expr, const uword flags) {
  arma_extra_debug_sigprint();

  typedef typename get_pod_type<eT>::result T;

  const bool fast = bool(flags & solve_opts::flag_fast);
  const bool equilibrate = bool(flags & solve_opts::flag_equilibrate);
  const bool no_approx = bool(flags & solve_opts::flag_no_approx);
  const bool triu = bool(flags & solve_opts::flag_triu);
  const bool tril = bool(flags & solve_opts::flag_tril);
  const bool allow_ugly = bool(flags & solve_opts::flag_allow_ugly);
  const bool likely_sympd = bool(flags & solve_opts::flag_likely_sympd);
  const bool refine = bool(flags & solve_opts::flag_refine);
  const bool no_trimat = bool(flags & solve_opts::flag_no_trimat);
  const bool force_approx = bool(flags & solve_opts::flag_force_approx);

  arma_extra_debug_print("glue_solve_tri_full::apply(): enabled flags:");

  if (fast) {
    arma_extra_debug_print("fast");
  }
  if (equilibrate) {
    arma_extra_debug_print("equilibrate");
  }
  if (no_approx) {
    arma_extra_debug_print("no_approx");
  }
  if (triu) {
    arma_extra_debug_print("triu");
  }
  if (tril) {
    arma_extra_debug_print("tril");
  }
  if (allow_ugly) {
    arma_extra_debug_print("allow_ugly");
  }
  if (likely_sympd) {
    arma_extra_debug_print("likely_sympd");
  }
  if (refine) {
    arma_extra_debug_print("refine");
  }
  if (no_trimat) {
    arma_extra_debug_print("no_trimat");
  }
  if (force_approx) {
    arma_extra_debug_print("force_approx");
  }

  if (no_trimat || equilibrate || refine || force_approx) {
    const uword mask = ~(solve_opts::flag_triu | solve_opts::flag_tril);

    return glue_solve_gen_full::apply(
        actual_out, ((triu) ? trimatu(A_expr.get_ref()) : trimatl(A_expr.get_ref())),
        B_expr, (flags & mask));
  }

  if (likely_sympd) {
    arma_debug_warn_level(2,
                          "solve(): option 'likely_sympd' ignored for triangular matrix");
  }

  const quasi_unwrap<T1> UA(A_expr.get_ref());
  const Mat<eT>& A = UA.M;

  arma_debug_check((A.is_square() == false),
                   "solve(): matrix marked as triangular must be square sized");

  const uword layout = (triu) ? uword(0) : uword(1);

  bool is_alias = true;

  if (is_Mat<T2>::value) {
    const quasi_unwrap<T2> UB(B_expr.get_ref());

    is_alias = UA.is_alias(actual_out) || UB.is_alias(actual_out);
  }

  T rcond = T(0);
  bool status = false;

  Mat<eT> tmp;
  Mat<eT>& out = (is_alias) ? tmp : actual_out;

  if (fast) {
    status =
        auxlib::solve_trimat_fast(out, A, B_expr.get_ref(), layout);  // A is not modified
  } else {
    status = auxlib::solve_trimat_rcond(out, rcond, A, B_expr.get_ref(),
                                        layout);  // A is not modified
  }

  if ((status == true) && (fast == false) && (allow_ugly == false) &&
      ((rcond < std::numeric_limits<T>::epsilon()) || arma_isnan(rcond))) {
    status = false;
  }

  if ((status == false) && (no_approx == false)) {
    arma_extra_debug_print("glue_solve_tri_full::apply(): solving rank deficient system");

    if (rcond == T(0)) {
      arma_debug_warn_level(2, "solve(): system is singular; attempting approx solution");
    } else {
      arma_debug_warn_level(2, "solve(): system is singular (rcond: ", rcond,
                            "); attempting approx solution");
    }

    Mat<eT> triA =
        (triu) ? trimatu(A) : trimatl(A);  // trimatu() and trimatl() return the same type

    status =
        auxlib::solve_approx_svd(out, triA, B_expr.get_ref());  // triA is overwritten
  }

  if (is_alias) {
    actual_out.steal_mem(out);
  }

  return status;
}

//! @}
