// 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 SpValProxy
//! @{


// Sparse value proxy class, to prevent inserting 0s into sparse matrices.
// T1 must be either SpMat or SpSubview.
// This class uses T1::insert_element(), T1::delete_element(), T1::invalidate_cache()

template<typename T1>
class SpValProxy
  {
  public:
  
  typedef typename T1::elem_type eT; // Convenience typedef
  
  friend class SpMat<eT>;
  friend class SpSubview<eT>;
  
  /**
   * Create the sparse value proxy.
   * Otherwise, pass a pointer to a reference of the value.
   */
  arma_inline SpValProxy(uword row, uword col, T1& in_parent, eT* in_val_ptr = nullptr);
       inline SpValProxy() = delete;
  
  //! For swapping operations.
  arma_inline SpValProxy& operator=(const SpValProxy& rhs);
  template<typename T2>
  arma_inline SpValProxy& operator=(const SpValProxy<T2>& rhs);
  
  //! Overload all of the potential operators.
  
  //! First, the ones that could modify a value.
  inline SpValProxy& operator= (const eT rhs);
  inline SpValProxy& operator+=(const eT rhs);
  inline SpValProxy& operator-=(const eT rhs);
  inline SpValProxy& operator*=(const eT rhs);
  inline SpValProxy& operator/=(const eT rhs);
  
  inline SpValProxy& operator++();
  inline SpValProxy& operator--();
  
  inline eT          operator++(const int);
  inline eT          operator--(const int);
  
  //! This will work for any other operations that do not modify a value.
  arma_inline operator eT() const;
  
  arma_inline typename get_pod_type<eT>::result real() const;
  arma_inline typename get_pod_type<eT>::result imag() const;
  
  
  private:
  
  // Deletes the element if it is zero; NOTE: does not check if val_ptr == nullptr
  arma_inline void check_zero();
  
  const uword row;
  const uword col;
  
  arma_aligned eT* val_ptr;
  
  arma_aligned T1& parent; // We will call this object if we need to insert or delete an element.
  };



//! @}
