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#ifndef TEMPLAT_LATTICE_ALGEBRA_OPERATORS_POWER_H
#define TEMPLAT_LATTICE_ALGEBRA_OPERATORS_POWER_H

/* This file is part of TempLat, available at https://cosmolattice.github.io/templat .
   Copyright 2021-2026 The TempLat authors, see AUTHORS.md.
   Released under the MIT license, see LICENSE.md. */

// File info: Main contributor(s): Wessel Valkenburg, Franz R. Sattler, Year: 2025

#include "TempLat/lattice/algebra/conditional/conditionalbinarygetter.h"
#include "TempLat/lattice/algebra/helpers/isstdgettable.h"
#include "TempLat/lattice/algebra/helpers/istemplatgettable.h"
#include "TempLat/lattice/algebra/operators/add.h"
#include "TempLat/lattice/algebra/operators/binaryoperator.h"
#include "TempLat/lattice/algebra/operators/subtract.h"
#include "TempLat/lattice/algebra/operators/unaryoperator.h"
#include "TempLat/util/rangeiteration/tagliteral.h"
#include "TempLat/util/powr.h"

namespace TempLat
{
  using device::pow;

  namespace Operators
  {
    template <typename R, typename T> class Power : public TempLat::BinaryOperator<R, T>
    {
    public:
      using BinaryOperator<R, T>::mR;
      using BinaryOperator<R, T>::mT;

      Power(const R &pR, const T &pT) : BinaryOperator<R, T>(pR, pT) {}

      template <typename... IDX>
        requires requires(std::decay_t<R> r, std::decay_t<T> t, IDX... idx) {
          requires IsVariadicIndex<IDX...>;
          DoEval::eval(r, idx...);
          DoEval::eval(t, idx...);
        }
      DEVICE_INLINE_FUNCTION auto eval(const IDX &...idx) const
      {
        using NT1 = std::decay_t<decltype(DoEval::eval(mR, idx...))>;
        using NT2 = std::decay_t<decltype(DoEval::eval(mT, idx...))>;
        using NT = decltype(NT1{} * NT2{});
        return pow(static_cast<NT>(DoEval::eval(mR, idx...)), static_cast<NT>(DoEval::eval(mT, idx...)));
      }

      virtual std::string operatorString() const override { return "^"; }

      template <typename U> auto d(const U &other)
      {
        /* so the compiler chooses without problems between std::log and TempLat::Operators::log */
        return GetDeriv::get(mR, other) * pow(mR, mT - OneType()) + GetDeriv::get(mT, other) * (*this) * log(mT);
      }
    };

    template <int N, typename R> class PowerN : public UnaryOperator<R>
    {
    public:
      using UnaryOperator<R>::mR;

      PowerN(const R &pR) : UnaryOperator<R>(pR) {}

      template <typename... IDX>
        requires requires(std::decay_t<R> r, IDX... idx) {
          requires IsVariadicIndex<IDX...>;
          DoEval::eval(r, idx...);
        }
      DEVICE_INLINE_FUNCTION auto eval(const IDX &...idx) const
      {
        return powr<N>(DoEval::eval(mR, idx...));
      }

      std::string toString() const { return "(" + GetString::get(mR) + ")^" + std::to_string(N); }

      template <typename U> auto d(const U &other) const
      {
        /* so the compiler chooses without problems between std::log and TempLat::Operators::log */
        return Tag<N>() * PowerN<N - 1, R>(mR) * GetDeriv::get(mR, other);
      }
    };
  } // namespace Operators

  template <typename R, typename T>
    requires ConditionalBinaryGetter<R, T>
  auto pow(const R &r, const T &t)
  {
    return Operators::Power<R, T>(r, t);
  }

  template <int N> constexpr ZeroType pow(ZeroType) { return {}; }

  template <typename T> constexpr OneType pow(const T &a, ZeroType b) { return {}; }

  template <typename T>
    requires std::is_same_v<T, ZeroType>
  constexpr auto pow(ZeroType a, const T &)
  {
    return ZeroType{};
  }

  // enable if is just so that we can overload to consitently write pow<3>(4)  for std::pow(4,3);
  template <int N, typename R>
    requires(HasEvalMethod<R> && N != 1 && N != 0)
  auto pow(const R &r)
  {
    return Operators::PowerN<N, R>(r);
  }

  // overload so that we can sonsitently write pow<3>(4)  for std::pow(4,3);
  template <int N, typename R>
    requires requires(R r) {
      requires !HasEvalMethod<R>;
      requires N != 0;
      requires N != 1;
      requires !(IsTempLatGettable<0, R> || IsSTDGettable<0, R>);
      powr<N>(r);
    }
  auto pow(const R &r)
  {
    return powr<N>(r);
  }

  template <int N, typename T>
    requires(N == 0)
  constexpr auto pow(const T &a)
  {
    return OneType{};
  }

  template <int N, typename T>
    requires(N == 1)
  T pow(const T &a)
  {
    return a;
  }
} // namespace TempLat

#endif