// SPDX-License-Identifier: Apache-2.0
// 
// Copyright 2008-2016 Conrad Sanderson (https://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
// https://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 diagmat_proxy
//! @{



template<typename T1>
struct diagmat_proxy_default
  {
  typedef typename T1::elem_type                   elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  inline
  diagmat_proxy_default(const T1& X)
    : P       ( X )
    , P_is_vec( (resolves_to_vector<T1>::yes) || (P.get_n_rows() == 1) || (P.get_n_cols() == 1) )
    , P_is_col( T1::is_col || (P.get_n_cols() == 1) )
    , n_rows  ( P_is_vec ? P.get_n_elem() : P.get_n_rows() )
    , n_cols  ( P_is_vec ? P.get_n_elem() : P.get_n_cols() )
    {
    arma_debug_sigprint();
    }
  
  
  arma_inline
  elem_type
  operator[](const uword i) const
    {
    if(Proxy<T1>::use_at == false)
      {
      return P_is_vec ? P[i] : P.at(i,i);
      }
    else
      {
      if(P_is_vec)
        {
        return (P_is_col) ? P.at(i,0) : P.at(0,i);
        }
      else
        {
        return P.at(i,i);
        }
      }
    }
  
  
  arma_inline
  elem_type
  at(const uword row, const uword col) const
    {
    if(row == col)
      {
      if(Proxy<T1>::use_at == false)
        {
        return (P_is_vec) ? P[row] : P.at(row,row);
        }
      else
        {
        if(P_is_vec)
          {
          return (P_is_col) ? P.at(row,0) : P.at(0,row);
          }
        else
          {
          return P.at(row,row);
          }
        }
      }
    else
      {
      return elem_type(0);
      }
    }
  
  
  inline bool is_alias(const Mat<elem_type>& X) const { return P.is_alias(X); }
  
  const Proxy<T1> P;
  const bool      P_is_vec;
  const bool      P_is_col;
  const uword     n_rows;
  const uword     n_cols;
  };



template<typename T1>
struct diagmat_proxy_fixed
  {
  typedef typename T1::elem_type                   elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  inline
  diagmat_proxy_fixed(const T1& X)
    : P(X)
    {
    arma_debug_sigprint();
    }
  
  
  arma_inline
  elem_type
  operator[](const uword i) const
    {
    return (P_is_vec) ? P[i] : P.at(i,i);
    }
  
  
  arma_inline
  elem_type
  at(const uword row, const uword col) const
    {
    if(row == col)
      {
      return (P_is_vec) ? P[row] : P.at(row,row);
      }
    else
      {
      return elem_type(0);
      }
    }
  
  arma_inline bool is_alias(const Mat<elem_type>& X) const { return (void_ptr(&X) == void_ptr(&P)); }
  
  const T1& P;
  
  //// this may require T1::n_elem etc to be declared as static constexpr inline variables (C++17)
  //// see also the notes in Mat::fixed
  // static constexpr bool  P_is_vec = (T1::n_rows == 1) || (T1::n_cols == 1);
  // static constexpr uword n_rows   = P_is_vec ? T1::n_elem : T1::n_rows;
  // static constexpr uword n_cols   = P_is_vec ? T1::n_elem : T1::n_cols;
  
  static const bool  P_is_vec = (T1::n_rows == 1) || (T1::n_cols == 1);
  static const uword n_rows   = P_is_vec ? T1::n_elem : T1::n_rows;
  static const uword n_cols   = P_is_vec ? T1::n_elem : T1::n_cols;
  };



template<typename T1, bool condition>
struct diagmat_proxy_redirect {};

template<typename T1>
struct diagmat_proxy_redirect<T1, false> { typedef diagmat_proxy_default<T1> result; };

template<typename T1>
struct diagmat_proxy_redirect<T1, true>  { typedef diagmat_proxy_fixed<T1>   result; };


template<typename T1>
struct diagmat_proxy : public diagmat_proxy_redirect<T1, is_Mat_fixed<T1>::value>::result
  {
  inline diagmat_proxy(const T1& X)
    : diagmat_proxy_redirect<T1, is_Mat_fixed<T1>::value>::result(X)
    {
    }
  };



template<typename eT>
struct diagmat_proxy< Mat<eT> >
  {
  typedef          eT                              elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  inline
  diagmat_proxy(const Mat<eT>& X)
    : P       ( X )
    , P_is_vec( (X.n_rows == 1) || (X.n_cols == 1) )
    , n_rows  ( P_is_vec ? X.n_elem : X.n_rows )
    , n_cols  ( P_is_vec ? X.n_elem : X.n_cols )
    {
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P_is_vec ? P[i] : P.at(i,i);                                         }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? ( P_is_vec ? P[row] : P.at(row,row) ) : elem_type(0); }
  
  arma_inline bool is_alias(const Mat<eT>& X) const { return (void_ptr(&X) == void_ptr(&P)); }
  
  const Mat<eT>& P;
  const bool     P_is_vec;
  const uword    n_rows;
  const uword    n_cols;
  };



template<typename eT>
struct diagmat_proxy< Row<eT> >
  {
  typedef          eT                              elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  
  inline
  diagmat_proxy(const Row<eT>& X)
    : P(X)
    , n_rows(X.n_elem)
    , n_cols(X.n_elem)
    {
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
  
  arma_inline bool is_alias(const Mat<eT>& X) const { return (void_ptr(&X) == void_ptr(&P)); }
  
  static constexpr bool P_is_vec = true;
  
  const Row<eT>& P;
  const uword    n_rows;
  const uword    n_cols;
  };



template<typename eT>
struct diagmat_proxy< Col<eT> >
  {
  typedef          eT                              elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  
  inline
  diagmat_proxy(const Col<eT>& X)
    : P(X)
    , n_rows(X.n_elem)
    , n_cols(X.n_elem)
    {
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
  
  arma_inline bool is_alias(const Mat<eT>& X) const { return (void_ptr(&X) == void_ptr(&P)); }
  
  static constexpr bool P_is_vec = true;
  
  const Col<eT>& P;
  const uword    n_rows;
  const uword    n_cols;
  };



template<typename eT>
struct diagmat_proxy< subview_row<eT> >
  {
  typedef          eT                              elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  
  inline
  diagmat_proxy(const subview_row<eT>& X)
    : P(X)
    , n_rows(X.n_elem)
    , n_cols(X.n_elem)
    {
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
  
  arma_inline bool is_alias(const Mat<eT>& X) const { return (void_ptr(&X) == void_ptr(&(P.m))); }
  
  static constexpr bool P_is_vec = true;
  
  const subview_row<eT>& P;
  const uword            n_rows;
  const uword            n_cols;
  };



template<typename eT>
struct diagmat_proxy< subview_col<eT> >
  {
  typedef          eT                              elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  
  inline
  diagmat_proxy(const subview_col<eT>& X)
    : P(X)
    , n_rows(X.n_elem)
    , n_cols(X.n_elem)
    {
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
  
  arma_inline bool is_alias(const Mat<eT>& X) const { return (void_ptr(&X) == void_ptr(&(P.m))); }
  
  static constexpr bool P_is_vec = true;
  
  const subview_col<eT>& P;
  const uword            n_rows;
  const uword            n_cols;
  };



template<typename T1, typename T2>
struct diagmat_proxy< Glue<T1,T2,glue_times> >
  {
  typedef typename T1::elem_type                   elem_type;
  typedef typename get_pod_type<elem_type>::result pod_type;
  
  inline
  diagmat_proxy(const Glue<T1,T2,glue_times>& X)
    {
    op_diagmat::apply_times(P, X.A, X.B);
    
    n_rows = P.n_rows;
    n_cols = P.n_cols;
    
    arma_debug_sigprint();
    }
  
  arma_inline elem_type operator[] (const uword i)                    const { return P.at(i,i);                                   }
  arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P.at(row,row) : elem_type(0); }
  
  constexpr bool is_alias(const Mat<elem_type>&) const { return false; }
  
  static constexpr bool P_is_vec = false;
  
  Mat<elem_type> P;
  uword          n_rows;
  uword          n_cols;
  };



//! @}
