// Code generated by stanc v2.31.0
#include <stan/model/model_header.hpp>
namespace minimalODEExampleExternal_model_namespace {

struct odefunc_functor__
{
  template<typename T0__, typename T1__, typename T2__,
           stan::require_all_t<stan::is_stan_scalar<T0__>, stan::is_col_vector<T1__>,
                               stan::is_vt_not_complex<T1__>,
                               stan::is_stan_scalar<T2__>>* = nullptr>
  Eigen::Matrix<stan::promote_args_t<T0__, stan::base_type_t<T1__>, T2__>, -1, 1> operator()(
    const T0__& t, const T1__& y, const T2__& theta,
    std::ostream* pstream__) const;
};


// Specialization for var types
template<typename T1__, stan::require_all_t<stan::is_col_vector<T1__>,
                                            stan::is_vt_not_complex<T1__>,
                                            stan::is_var<stan::scalar_type_t<T1__>>>* = nullptr>
Eigen::Matrix<stan::math::var, -1, 1>
odefunc(const double& t, const T1__& y, const double& theta,
        std::ostream* pstream__) {
  // All matrices used in reverse pass callback must be arena allocated
  stan::arena_t<Eigen::Matrix<stan::math::var, -1, 1>> dydt(2);
  dydt[0] = y[1].val();
  dydt[1] = -theta * y[0].val();

  stan::arena_t<Eigen::Matrix<double, -1, -1>> jacobianT = Eigen::MatrixXd::Zero(2, 2);
  jacobianT(1, 0) = 1.0;
  jacobianT(0, 1) = -theta;

  stan::arena_t<T1__> y_arena = y;
  // Use reverse_pass_callback since our return type is an Eigen matrix
  // This adds the reverse pass to our callback stack when we call grad() after building the autodiff tree
  stan::math::reverse_pass_callback([y_arena, jacobianT, dydt]() mutable {
    y_arena.adj() += jacobianT * dydt.adj();
  });
  // Make a hard copy of dydt to avoid overwriting values used in reverse pass
  return Eigen::Matrix<stan::math::var, -1, 1>(dydt);
}


/**
 *  Only doing the forward pass of above. Supports double and fvar types
 */
template<typename T1__, stan::require_all_t<stan::is_col_vector<T1__>,
                                            stan::is_vt_not_complex<T1__>>* = nullptr,
                        stan::require_not_vt_var<T1__>* = nullptr>
Eigen::Matrix<stan::scalar_type_t<T1__>, -1, 1>
odefunc(const double& t, const T1__& y, const double& theta,
        std::ostream* pstream__) {
  using scalar_t = stan::scalar_type_t<T1__>;
  Eigen::Matrix<scalar_t, -1, 1> dydt = Eigen::Matrix<scalar_t, -1, 1>::Zero(2);
  dydt[0] = y[1];
  dydt[1] = -theta * y[0];
  return dydt;
}



template<
  typename T0__, typename T1__, typename T2__,
  stan::require_all_t<stan::is_stan_scalar<T0__>, stan::is_col_vector<T1__>,
                      stan::is_vt_not_complex<T1__>, stan::is_stan_scalar<T2__>>*>
Eigen::Matrix<stan::promote_args_t<T0__, stan::base_type_t<T1__>, T2__>, -1, 1> odefunc_functor__::
operator()(const T0__& t, const T1__& y, const T2__& theta,
           std::ostream* pstream__) const
{
  return odefunc(t, y, theta, pstream__);
}

} //namespace