// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <cstdint>
#include <vector>

#include "../../common/CrystalLattice.h"
#include "../../common/DiffractionGeometry.h"
#include "../../common/UnitCell.h"
#include "gemmi/symmetry.hpp"

// Offline global (multi-frame) geometry refinement for serial stills. Pass 1 indexes many frames
// independently; this joint bundle adjustment then determines the ONE shared detector geometry (beam
// centre, distance, cell scale) that per-image refinement cannot reach from a single sparse still, so
// re-indexing with it converts more frames. Mirrors the validated Python prototype: one Ceres problem
// with shared beam/distance/cell blocks and a per-frame orientation block, robust loss, and a cell
// regularizer that anchors the (known) cell to break the distance<->cell-scale degeneracy at low
// resolution. Detector tilt (rot1/rot2) is NOT refined (gauge-coupled with the beam; zero indexing gain).

struct GeomRefineSpot {
    float x = 0, y = 0;         // observed (raw) spot position, pixels
    int32_t h = 0, k = 0, l = 0; // integer Miller index assigned in pass 1
};

struct GeomRefineFrame {
    CrystalLattice lattice;             // per-frame indexed lattice (real space), for the orientation seed
    std::vector<GeomRefineSpot> spots;  // indexed spots on this frame
};

struct GeometryRefinerSettings {
    gemmi::CrystalSystem crystal_system = gemmi::CrystalSystem::Triclinic;
    // Cell-scale regularizer strength (anchors the cell lengths to the input cell so the otherwise
    // degenerate distance is determined). Large => cell effectively fixed (the validated safe regime).
    double cell_reg_coeff = 30.0;
    int rounds = 3;                 // hkl-reassignment / tolerance-tightening rounds
    double beam_range_px = 8.0;     // beam bound around the nominal value
    double distance_range_mm = 8.0; // distance bound around the nominal value
    int min_spots_total = 100;      // refuse to refine below this many indexed spots
    int num_threads = 1;
};

struct GeometryRefinerResult {
    bool ok = false;
    double beam_x_px = 0, beam_y_px = 0;   // refined beam centre (== direct beam, tilt not refined)
    double distance_mm = 0;
    UnitCell cell{};                       // refined cell
    int frames_used = 0;
    int spots_used = 0;
    double median_residual_px = 0;         // final per-spot detector residual (fit quality)
};

// nominal_geom supplies the starting beam/distance/tilt/wavelength/pixel size; input_cell is anchored by
// the regularizer. Returns ok=false (and leaves the caller's geometry untouched) on any failure.
GeometryRefinerResult RefineGlobalGeometry(const DiffractionGeometry &nominal_geom,
                                           const UnitCell &input_cell,
                                           const std::vector<GeomRefineFrame> &frames,
                                           const GeometryRefinerSettings &settings);