#pragma once

#include <expected>
#include <limits>
#include <memory>
#include <ranges>
#include <vector>

namespace mcc::fitpack
{

extern "C" {
void curfit(int* iopt,
            int* m,
            double* x,
            double* y,
            double* w,
            double* xb,
            double* xe,
            int* k,
            double* s,
            int* nest,
            int* n,
            double* t,
            double* c,
            double* fp,
            double* wrk,
            int* lwrk,
            int* iwrk,
            int* ier);

void splev(double* t, int* n, double* c, int* k, double* x, double* y, int* m, int* e, int* ier);

void splder(double* t, int* n, double* c, int* k, int* nu, double* x, double* y, int* m, int* e, double* wrk, int* ier);

void surfit(int* iopt,
            int* m,
            double* x,
            double* y,
            double* z,
            double* w,
            double* xb,
            double* xe,
            double* yb,
            double* ye,
            int* kx,
            int* ky,
            double* s,
            int* nxest,
            int* nyest,
            int* nmax,
            double* eps,
            int* nx,
            double* tx,
            int* ny,
            double* ty,
            double* c,
            double* fp,
            double* wrk1,
            int* lwrk1,
            double* wrk2,
            int* lwrk2,
            int* iwrk,
            int* kwrk,
            int* ier);

void bispev(double* tx,
            int* nx,
            double* ty,
            int* ny,
            double* c,
            int* kx,
            int* ky,
            double* x,
            int* mx,
            double* y,
            int* my,
            double* z,
            double* wrk,
            int* lwrk,
            int* iwrk,
            int* kwrk,
            int* ier);

void parder(double* tx,
            int* nx,
            double* ty,
            int* ny,
            double* c,
            int* kx,
            int* ky,
            int* nux,
            int* nuy,
            double* x,
            int* mx,
            double* y,
            int* my,
            double* z,
            double* wrk,
            int* lwrk,
            int* iwrk,
            int* kwrk,
            int* ier);


void sphere(int* iopt,
            int* m,
            double* teta,
            double* phi,
            double* r,
            double* w,
            double* s,
            int* ntest,
            int* npest,
            double* eps,
            int* nt,
            double* tt,
            int* np,
            double* tp,
            double* c,
            double* fp,
            double* wrk1,
            int* lwrk1,
            double* wrk2,
            int* lwrk2,
            int* iwrk,
            int* kwrk,
            int* ier);
}



template <std::ranges::contiguous_range TethaT,
          std::ranges::contiguous_range PhiT,
          std::ranges::contiguous_range FuncT,
          typename WeightT,
          std::ranges::contiguous_range TKnotT,
          std::ranges::contiguous_range PKnotT,
          std::ranges::contiguous_range CoeffT>
int fitpack_sphere_smooth(const TethaT& tetha,
                          const PhiT& phi,
                          const FuncT& func,
                          const WeightT& weight,
                          double s_par,
                          int& ntest,
                          int& npest,
                          TKnotT& tetha_knots,
                          PKnotT& phi_knots,
                          CoeffT& coeffs,
                          double& resi2_sum,
                          double eps = std::numeric_limits<double>::epsilon())
    requires((std::ranges::contiguous_range<WeightT> || std::convertible_to<WeightT, double>) &&
             std::ranges::output_range<CoeffT, double>)
{
    static_assert(std::same_as<std::ranges::range_value_t<TethaT>, double> &&
                      std::same_as<std::ranges::range_value_t<PhiT>, double> &&
                      std::same_as<std::ranges::range_value_t<FuncT>, double> &&
                      std::same_as<std::ranges::range_value_t<TKnotT>, double> &&
                      std::same_as<std::ranges::range_value_t<PKnotT>, double>,
                  "Input ranges elements type must be double!");

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        static_assert(std::same_as<std::ranges::range_value_t<WeightT>, double>,
                      "Input ranges elements type must be double!");
    }

    auto m = std::min(std::min(std::ranges::size(tetha), std::ranges::size(phi)), std::ranges::size(func));
    if (m < 2) {
        return 10;
    }

    int res = 0;

    /*   do checking here to avoid possibly unnecessary memory allocations  */

    // number of knots must be >= 8 for the qubic b-splines
    if (ntest < 8 || npest < 8) {
        return 10;
    }

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        m = std::min(m, std::ranges::size(weight));
        if (m < 2) {
            return 10;
        }
    }

    if (s_par <= 0.0) {
        return 10;
    }

    if (eps <= 0.0 || eps >= 1.0) {
        return 10;
    }

    const auto nt = std::ranges::size(tetha_knots);
    const auto np = std::ranges::size(phi_knots);

    if (nt < ntest) {
        std::ranges::fill_n(std::back_inserter(tetha_knots), ntest - nt, 0.0);
    }
    if (np < npest) {
        std::ranges::fill_n(std::back_inserter(phi_knots), npest - np, 0.0);
    }


    // compute working arrays sizes according to sphere.f
    const int u = ntest - 7;
    const int v = npest - 7;
    const int uv = u * v;
    const int v2 = v * v;

    const int lwrk1 = 185 + 52 * v + 10 * u + 14 * uv + 8 * (u - 1) * v2 + 8 * m;
    const int lwrk2 = 48 + 21 * v + 7 * uv + 4 * (u - 1) * v2;
    const int kwrk = m + uv;

    std::unique_ptr<double> wrk1{new double(lwrk1)};
    std::unique_ptr<double> wrk2{new double(lwrk2)};
    std::unique_ptr<int> iwrk{new int(kwrk)};

    const int n_coeffs = (ntest - 4) * (npest - 4);
    if (std::ranges::size(coeffs) < n_coeffs) {  // resize
        std::ranges::fill_n(std::back_inserter(coeffs), n_coeffs - std::ranges::size(coeffs), 0.0);
    }

    const int iopt = 0;

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        res = sphere(&iopt, &m, std::ranges::data(tetha), std::ranges::data(phi), std::ranges::data(func),
                     std::ranges::data(weight), &s_par, &ntest, &npest, &eps, &ntest, std::ranges::data(tetha_knots),
                     &npest, std::ranges::data(phi_knots), std::ranges::data(coeffs), &resi2_sum, wrk1.get(), &lwrk1,
                     wrk2.get(), &lwrk2, iwrk.get(), &kwrk, &res);
    } else {
        std::vector<double> weight_vec(m, weight);

        res = sphere(&iopt, &m, std::ranges::data(tetha), std::ranges::data(phi), std::ranges::data(func),
                     weight_vec.data(), &s_par, &ntest, &npest, &eps, &ntest, std::ranges::data(tetha_knots), &npest,
                     std::ranges::data(phi_knots), std::ranges::data(coeffs), &resi2_sum, wrk1.get(), &lwrk1,
                     wrk2.get(), &lwrk2, iwrk.get(), &kwrk, &res);
    }


    return res;
}

/*
    least-squares fitting (iopt=-1)
*/
template <std::ranges::contiguous_range TethaT,
          std::ranges::contiguous_range PhiT,
          std::ranges::contiguous_range FuncT,
          typename WeightT,
          std::ranges::contiguous_range TKnotT,
          std::ranges::contiguous_range PKnotT,
          std::ranges::contiguous_range CoeffT>
int fitpack_sphere_fit(const TethaT& tetha,
                       const PhiT& phi,
                       const FuncT& func,
                       const WeightT& weight,
                       const TKnotT& tetha_knots,
                       const PKnotT& phi_knots,
                       CoeffT& coeffs,
                       double& resi2_sum,
                       double eps = std::numeric_limits<double>::epsilon())
{
    const double s = 100.0;
    int nt = std::ranges::size(tetha_knots);
    int np = std::ranges::size(phi_knots);

    return fitpack_sphere_smooth(tetha, phi, func, weight, s, nt, np, tetha_knots, phi_knots, coeffs, resi2_sum, eps);
}

/*

template <std::ranges::contiguous_range TethaT,
          std::ranges::contiguous_range PhiT,
          std::ranges::contiguous_range FuncT,
          typename WeightT,
          std::ranges::contiguous_range TKnotT,
          std::ranges::contiguous_range PKnotT,
          std::ranges::contiguous_range CoeffT>
int fitpack_sphere_fit(const TethaT& tetha,
                       const PhiT& phi,
                       const FuncT& func,
                       const WeightT& weight,
                       const TKnotT& tetha_knots,
                       const PKnotT& phi_knots,
                       CoeffT& coeffs,
                       double& resi2_sum,
                       double eps = std::numeric_limits<double>::epsilon())
    requires((std::ranges::contiguous_range<WeightT> || std::convertible_to<WeightT, double>) &&
             std::ranges::output_range<CoeffT, double>)
{
    static_assert(std::same_as<std::ranges::range_value_t<TethaT>, double> &&
                      std::same_as<std::ranges::range_value_t<PhiT>, double> &&
                      std::same_as<std::ranges::range_value_t<FuncT>, double> &&
                      std::same_as<std::ranges::range_value_t<TKnotT>, double> &&
                      std::same_as<std::ranges::range_value_t<PKnotT>, double>,
                  "Input ranges elements type must be double!");

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        static_assert(std::same_as<std::ranges::range_value_t<WeightT>, double>,
                      "Input ranges elements type must be double!");
    }

    auto m = std::min(std::min(std::ranges::size(tetha), std::ranges::size(phi)), std::ranges::size(func));
    if (m < 2) {
        return 10;
    }

    int res = 0;

    const auto nt = std::ranges::size(tetha_knots);
    const auto np = std::ranges::size(phi_knots);

    // number of knots must be >= 8 for the qubic b-splines
    if (std::min(nt, np) < 8) {
        return 10;
    }

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        m = std::min(m, std::ranges::size(weight));
        if (m < 2) {
            return 10;
        }
    }

    // compute working arrays sizes according to sphere.f
    const int u = nt - 7;
    const int v = np - 7;
    const int uv = u * v;
    const int v2 = v * v;

    const int lwrk1 = 185 + 52 * v + 10 * u + 14 * uv + 8 * (u - 1) * v2 + 8 * m;
    const int lwrk2 = 48 + 21 * v + 7 * uv + 4 * (u - 1) * v2;
    const int kwrk = m + uv;

    std::unique_ptr<double> wrk1{new double(lwrk1)};
    std::unique_ptr<double> wrk2{new double(lwrk2)};
    std::unique_ptr<int> iwrk{new int(kwrk)};

    const int n_coeffs = (nt - 4) * (np - 4);
    if (std::ranges::size(coeffs) < n_coeffs) {  // resize
        std::ranges::fill_n(std::back_inserter(coeffs), n_coeffs - std::ranges::size(coeffs), 0.0);
    }

    const int iopt = -1;
    const double s = 100.0;

    if constexpr (std::ranges::contiguous_range<WeightT>) {
        res = sphere(&iopt, &m, std::ranges::data(tetha), std::ranges::data(phi), std::ranges::data(func),
                     std::ranges::data(weight), &s, &nt, &np, &eps, &nt, std::ranges::data(tetha_knots), &np,
                     std::ranges::data(phi_knots), std::ranges::data(coeffs), &resi2_sum, wrk1.get(), &lwrk1,
                     wrk2.get(), &lwrk2, iwrk.get(), &kwrk, &res);
    } else {
        std::vector<double> weight_vec(m, weight);

        res = sphere(&iopt, &m, std::ranges::data(tetha), std::ranges::data(phi), std::ranges::data(func),
                     weight_vec.data(), &s, &nt, &np, &eps, &nt, std::ranges::data(tetha_knots), &np,
                     std::ranges::data(phi_knots), std::ranges::data(coeffs), &resi2_sum, wrk1.get(), &lwrk1,
                     wrk2.get(), &lwrk2, iwrk.get(), &kwrk, &res);
    }


    return res;
}

*/

}  // namespace mcc::fitpack