// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include "BraggPrediction.h"

std::multimap<float, Reflection> CalcBraggPredictions(const DiffractionExperiment& experiment,
                                                      const CrystalLattice& lattice,
                                                      float high_res_A,
                                                      float ewald_dist_cutoff,
                                                      int max_hkl) {
    std::multimap<float, Reflection> reflections;

    auto geom = experiment.GetDiffractionGeometry();
    auto det_width_pxl = static_cast<float>(experiment.GetXPixelsNum());
    auto det_height_pxl = static_cast<float>(experiment.GetYPixelsNum());

    float one_over_dmax = 1.0f / high_res_A;
    float one_over_dmax_sq = one_over_dmax * one_over_dmax;

    Coord Astar = lattice.Astar();
    Coord Bstar = lattice.Bstar();
    Coord Cstar = lattice.Cstar();

    for (int h = -max_hkl; h < max_hkl; h++) {
        for (int k = -max_hkl; k < max_hkl; k++) {
            for (int l = -max_hkl; l < max_hkl; l++) {
                // (000) is not too interesting
                if (h == 0 && k == 0 && l == 0)
                    continue;

                Coord recip = Astar * static_cast<float>(h) + Bstar * static_cast<float>(k) + Cstar * static_cast<float>(l);
                if (recip * recip > one_over_dmax_sq)
                    continue;

                float d = 1.0f / recip.Length();

                float dist_ewald_sphere = std::fabs(geom.DistFromEwaldSphere(recip));

                if (!std::isfinite(dist_ewald_sphere) || dist_ewald_sphere > ewald_dist_cutoff )
                    continue;

                auto [x,y] = geom.RecipToDector(recip);

                if ((x < 0) || (x >= det_width_pxl) || (y < 0) || (y >= det_height_pxl))
                    continue;

                reflections.insert(std::make_pair(dist_ewald_sphere, Reflection{
                        .h = h,
                        .k = k,
                        .l = l,
                        .predicted_x = x,
                        .predicted_y = y,
                        .d = d
                }));
            }
        }
    }
    return reflections;
}