// 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 fn_as_scalar
//! @{

template <uword N>
struct as_scalar_redirect {
  template <typename T1>
  inline static typename T1::elem_type apply(const T1& X);
};

template <>
struct as_scalar_redirect<2> {
  template <typename T1, typename T2>
  inline static typename T1::elem_type apply(const Glue<T1, T2, glue_times>& X);
};

template <>
struct as_scalar_redirect<3> {
  template <typename T1, typename T2, typename T3>
  inline static typename T1::elem_type apply(
      const Glue<Glue<T1, T2, glue_times>, T3, glue_times>& X);
};

template <uword N>
template <typename T1>
inline typename T1::elem_type as_scalar_redirect<N>::apply(const T1& X) {
  arma_extra_debug_sigprint();

  const Proxy<T1> P(X);

  arma_debug_check((P.get_n_elem() != 1),
                   "as_scalar(): expression must evaluate to exactly one element");

  return (Proxy<T1>::use_at) ? P.at(0, 0) : P[0];
}

template <typename T1, typename T2>
inline typename T1::elem_type as_scalar_redirect<2>::apply(
    const Glue<T1, T2, glue_times>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  // T1 must result in a matrix with one row
  // T2 must result in a matrix with one column

  const bool has_all_mat = (is_Mat<T1>::value || is_Mat_trans<T1>::value) &&
                           (is_Mat<T2>::value || is_Mat_trans<T2>::value);

  const bool use_at = (Proxy<T1>::use_at || Proxy<T2>::use_at);

  const bool do_partial_unwrap = (has_all_mat || use_at);

  if (do_partial_unwrap) {
    const partial_unwrap<T1> tmp1(X.A);
    const partial_unwrap<T2> tmp2(X.B);

    typedef typename partial_unwrap<T1>::stored_type TA;
    typedef typename partial_unwrap<T2>::stored_type TB;

    const TA& A = tmp1.M;
    const TB& B = tmp2.M;

    const uword A_n_rows = (tmp1.do_trans == false) ? (TA::is_row ? 1 : A.n_rows)
                                                    : (TA::is_col ? 1 : A.n_cols);
    const uword A_n_cols = (tmp1.do_trans == false) ? (TA::is_col ? 1 : A.n_cols)
                                                    : (TA::is_row ? 1 : A.n_rows);

    const uword B_n_rows = (tmp2.do_trans == false) ? (TB::is_row ? 1 : B.n_rows)
                                                    : (TB::is_col ? 1 : B.n_cols);
    const uword B_n_cols = (tmp2.do_trans == false) ? (TB::is_col ? 1 : B.n_cols)
                                                    : (TB::is_row ? 1 : B.n_rows);

    arma_debug_check((A_n_rows != 1) || (B_n_cols != 1) || (A_n_cols != B_n_rows),
                     "as_scalar(): incompatible dimensions");

    const eT val = op_dot::direct_dot(A.n_elem, A.memptr(), B.memptr());

    return (tmp1.do_times || tmp2.do_times) ? (val * tmp1.get_val() * tmp2.get_val())
                                            : val;
  } else {
    const Proxy<T1> PA(X.A);
    const Proxy<T2> PB(X.B);

    arma_debug_check((PA.get_n_rows() != 1) || (PB.get_n_cols() != 1) ||
                         (PA.get_n_cols() != PB.get_n_rows()),
                     "as_scalar(): incompatible dimensions");

    return op_dot::apply_proxy(PA, PB);
  }
}

template <typename T1, typename T2, typename T3>
inline typename T1::elem_type as_scalar_redirect<3>::apply(
    const Glue<Glue<T1, T2, glue_times>, T3, glue_times>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  // T1 * T2 must result in a matrix with one row
  // T3 must result in a matrix with one column

  typedef typename strip_inv<T2>::stored_type T2_stripped_1;
  typedef typename strip_diagmat<T2_stripped_1>::stored_type T2_stripped_2;

  const strip_inv<T2> strip1(X.A.B);
  const strip_diagmat<T2_stripped_1> strip2(strip1.M);

  const bool tmp2_do_inv_gen = strip1.do_inv_gen && arma_config::optimise_invexpr;
  const bool tmp2_do_diagmat = strip2.do_diagmat;

  if (tmp2_do_diagmat == false) {
    const Mat<eT> tmp(X);

    arma_debug_check((tmp.n_elem != 1),
                     "as_scalar(): expression must evaluate to exactly one element");

    return tmp[0];
  } else {
    const partial_unwrap<T1> tmp1(X.A.A);
    const partial_unwrap<T2_stripped_2> tmp2(strip2.M);
    const partial_unwrap<T3> tmp3(X.B);

    const Mat<eT>& A = tmp1.M;
    const Mat<eT>& B = tmp2.M;
    const Mat<eT>& C = tmp3.M;

    const uword A_n_rows = (tmp1.do_trans == false) ? A.n_rows : A.n_cols;
    const uword A_n_cols = (tmp1.do_trans == false) ? A.n_cols : A.n_rows;

    const bool B_is_vec = B.is_vec();

    const uword B_n_rows =
        (B_is_vec) ? B.n_elem : ((tmp2.do_trans == false) ? B.n_rows : B.n_cols);
    const uword B_n_cols =
        (B_is_vec) ? B.n_elem : ((tmp2.do_trans == false) ? B.n_cols : B.n_rows);

    const uword C_n_rows = (tmp3.do_trans == false) ? C.n_rows : C.n_cols;
    const uword C_n_cols = (tmp3.do_trans == false) ? C.n_cols : C.n_rows;

    const eT val = tmp1.get_val() * tmp2.get_val() * tmp3.get_val();

    arma_debug_check((A_n_rows != 1) || (C_n_cols != 1) || (A_n_cols != B_n_rows) ||
                         (B_n_cols != C_n_rows),
                     "as_scalar(): incompatible dimensions");

    if (B_is_vec) {
      if (tmp2_do_inv_gen) {
        return val * op_dotext::direct_rowvec_invdiagvec_colvec(A.mem, B, C.mem);
      } else {
        return val * op_dot::direct_dot(A.n_elem, A.mem, B.mem, C.mem);
      }
    } else {
      if (tmp2_do_inv_gen) {
        return val * op_dotext::direct_rowvec_invdiagmat_colvec(A.mem, B, C.mem);
      } else {
        return val * op_dotext::direct_rowvec_diagmat_colvec(A.mem, B, C.mem);
      }
    }
  }
}

template <typename T1>
inline typename T1::elem_type as_scalar_diag(const Base<typename T1::elem_type, T1>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  const unwrap<T1> tmp(X.get_ref());
  const Mat<eT>& A = tmp.M;

  arma_debug_check((A.n_elem != 1),
                   "as_scalar(): expression must evaluate to exactly one element");

  return A.mem[0];
}

template <typename T1, typename T2, typename T3>
inline typename T1::elem_type as_scalar_diag(
    const Glue<Glue<T1, T2, glue_times_diag>, T3, glue_times>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  // T1 * T2 must result in a matrix with one row
  // T3 must result in a matrix with one column

  typedef typename strip_diagmat<T2>::stored_type T2_stripped;

  const strip_diagmat<T2> strip(X.A.B);

  const partial_unwrap<T1> tmp1(X.A.A);
  const partial_unwrap<T2_stripped> tmp2(strip.M);
  const partial_unwrap<T3> tmp3(X.B);

  const Mat<eT>& A = tmp1.M;
  const Mat<eT>& B = tmp2.M;
  const Mat<eT>& C = tmp3.M;

  const uword A_n_rows = (tmp1.do_trans == false) ? A.n_rows : A.n_cols;
  const uword A_n_cols = (tmp1.do_trans == false) ? A.n_cols : A.n_rows;

  const bool B_is_vec = B.is_vec();

  const uword B_n_rows =
      (B_is_vec) ? B.n_elem : ((tmp2.do_trans == false) ? B.n_rows : B.n_cols);
  const uword B_n_cols =
      (B_is_vec) ? B.n_elem : ((tmp2.do_trans == false) ? B.n_cols : B.n_rows);

  const uword C_n_rows = (tmp3.do_trans == false) ? C.n_rows : C.n_cols;
  const uword C_n_cols = (tmp3.do_trans == false) ? C.n_cols : C.n_rows;

  const eT val = tmp1.get_val() * tmp2.get_val() * tmp3.get_val();

  arma_debug_check((A_n_rows != 1) || (C_n_cols != 1) || (A_n_cols != B_n_rows) ||
                       (B_n_cols != C_n_rows),
                   "as_scalar(): incompatible dimensions");

  if (B_is_vec) {
    return val * op_dot::direct_dot(A.n_elem, A.mem, B.mem, C.mem);
  } else {
    return val * op_dotext::direct_rowvec_diagmat_colvec(A.mem, B, C.mem);
  }
}

template <typename T1, typename T2>
arma_warn_unused inline typename T1::elem_type as_scalar(
    const Glue<T1, T2, glue_times>& X,
    const typename arma_not_cx<typename T1::elem_type>::result* junk = nullptr) {
  arma_extra_debug_sigprint();
  arma_ignore(junk);

  if (is_glue_times_diag<T1>::value) {
    return as_scalar_diag(X);
  }

  constexpr uword N_mat = 1 + depth_lhs<glue_times, Glue<T1, T2, glue_times> >::num;

  arma_extra_debug_print(arma_str::format("N_mat = %u") % N_mat);

  return as_scalar_redirect<N_mat>::apply(X);
}

template <typename T1>
arma_warn_unused inline typename T1::elem_type as_scalar(
    const Base<typename T1::elem_type, T1>& X) {
  arma_extra_debug_sigprint();

  const Proxy<T1> P(X.get_ref());

  arma_debug_check((P.get_n_elem() != 1),
                   "as_scalar(): expression must evaluate to exactly one element");

  return (Proxy<T1>::use_at) ? P.at(0, 0) : P[0];
}

template <typename T1>
arma_warn_unused inline typename T1::elem_type as_scalar(
    const BaseCube<typename T1::elem_type, T1>& X) {
  arma_extra_debug_sigprint();

  const ProxyCube<T1> P(X.get_ref());

  arma_debug_check((P.get_n_elem() != 1),
                   "as_scalar(): expression must evaluate to exactly one element");

  return (ProxyCube<T1>::use_at) ? P.at(0, 0, 0) : P[0];
}

template <typename T>
arma_warn_unused arma_inline typename arma_scalar_only<T>::result as_scalar(const T& x) {
  return x;
}

template <typename T1>
arma_warn_unused inline typename T1::elem_type as_scalar(
    const SpBase<typename T1::elem_type, T1>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  const unwrap_spmat<T1> tmp(X.get_ref());
  const SpMat<eT>& A = tmp.M;

  arma_debug_check((A.n_elem != 1),
                   "as_scalar(): expression must evaluate to exactly one element");

  return A.at(0, 0);
}

//! @}
