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

#pragma once

#include <optional>

#include <gemmi/symmetry.hpp>

#include "../../common/Coord.h"
#include "../../common/CrystalLattice.h"

// The exact, orbit-based counterpart of the per-image spindle severity. A still has to assume the
// worst - that the nearest plausible lattice row is a lone 2-fold - but by the time a rotation run
// is merged the point group and the indexed orientation are KNOWN, so nothing needs guessing: apply
// the group's proper rotations to the sweep's blind double cone in the crystal's actual orientation
// and count what no operator maps onto measured territory. A unique reflection is lost exactly when
// its whole orbit stays inside the cone (Friedel never helps: the cone is double-sided, so the
// inversion maps it onto itself).
struct SpindleCuspLoss {
    // Fraction of all unique reflections to d_min that the mounting made unmeasurable. Weighted by
    // reciprocal volume: each shell has its own, narrower cone theta(d) = asin(lambda/2d), so a
    // direction at angle a from the spindle is only blind past q = 2 sin(a) / lambda.
    double lost_unique_fraction = 0;
    // The same loss as a fraction of the blind cone's own unique content: 1 = the group repaired
    // nothing (P1, or a lone diad on or perpendicular to the spindle), 0 = symmetry recovers the
    // whole cone. This is what severity means independent of how wide the cone happens to be.
    double cone_fraction = 0;
    double theta_max_deg = 0;
};

std::optional<SpindleCuspLoss> SpindleUnrepairedFraction(const gemmi::SpaceGroup &sg,
                                                         const CrystalLattice &lattice,
                                                         const Coord &spindle,
                                                         double wavelength_A,
                                                         double d_min_A);