/*
 *  This file is a part of TiledArray.
 *  Copyright (C) 2013  Virginia Tech
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  Justus Calvin
 *  Department of Chemistry, Virginia Tech
 *
 *  noop.h
 *  June 27, 2013
 *
 */

#ifndef TILEDARRAY_TILE_OP_NOOP_H__INCLUDED
#define TILEDARRAY_TILE_OP_NOOP_H__INCLUDED

#include <TiledArray/tile_op/tile_interface.h>

namespace TiledArray {

  /// Tile no operation (noop)

  /// This no operation will return the original or apply a permutation to the
  /// result tensor. If no permutation is given or the permutation is null,
  /// then the result is not permuted.
  /// \tparam Arg The argument type
  /// \tparam Consumable Flag that is \c true when Arg is consumable
  template <typename Arg, bool Consumable>
  class Noop {
  public:
    typedef Noop<Arg, Consumable> Noop_; ///< This object type
    typedef Arg argument_type; ///< The argument type
    typedef Arg result_type; ///< The result tile type

    static constexpr bool is_consumable = Consumable;

  private:

    // Permuting tile evaluation function
    // These operations cannot consume the argument tile since this operation
    // requires temporary storage space.

    static result_type eval(const Arg& arg, const Permutation& perm) {
      using TiledArray::permute;
      return permute(arg, perm);
    }

    // Non-permuting tile evaluation functions
    // The compiler will select the correct functions based on the
    // consumability of the arguments.

    template <bool C, typename std::enable_if<!C>::type* = nullptr>
    static result_type eval(const Arg& arg) {
      using TiledArray::clone;
      return clone(arg);
    }

    template <bool C, typename std::enable_if<C>::type* = nullptr>
    static result_type eval(Arg& arg) { return arg; }

  public:

    /// Permute operator

    /// \tparam A The tile argument type
    /// \param arg The tile argument
    /// \param perm The permutation applied to the result tile
    /// \return A permuted copy of `arg`
    result_type operator()(const argument_type& arg, const Permutation& perm) const {
      return eval(arg, perm);
    }

    /// Clone operator

    /// \tparam A The tile argument type
    /// \param arg The tile argument
    /// \return A clone of the `arg`
    template <typename A>
    result_type operator()(A&& arg) const {
      return Noop_::template eval<is_consumable>(arg);
    }

    /// Pass-through operations (shallow copy)

    /// \param arg The tile argument
    /// \return `arg`
    result_type consume(argument_type& arg) const {
      return Noop_::template eval<is_consumable_tile<Arg>::value>(arg);
    }

  }; // class Noop

} // namespace TiledArray

#endif // TILEDARRAY_TILE_OP_NOOP_H__INCLUDED
