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

#pragma once

#include <optional>

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

#include "../../common/DiffractionExperiment.h"
#include "../../common/JFJochMessages.h"
#include "../../common/SpotToSave.h"
#include "SpindleBlindFraction.h"

struct IndexerResult {
    std::vector<CrystalLattice> lattice;
    float indexing_time_s;
    bool executed = false; // If indexing was not performed (due to indexer being not-available) mark it, so indexing result is marked accordingly
    // What the indexer threw, when it threw. A THIRD outcome, not a flavour of the other two: an
    // empty lattice list with no error is a real negative result about the frame - it was examined
    // and no lattice fits it - whereas an error says nothing about the frame at all, the indexer
    // never having got to look, and will recur on the next one.
    std::optional<std::string> error;
    // How much of a single sweep's blind cone this orientation makes unrecoverable, in [0,1].
    // Absent when the frame gives nothing to decide on (no spindle defined, no lattice rows).
    std::optional<float> spindle_blind_fraction;
    std::optional<float> spindle_row_length_A;
    std::optional<float> spindle_miss_angle_deg;
};

class Indexer {
protected:
    int64_t viable_cell_min_spots = 9;
    float indexing_tolerance = 0.1;
    float dist_tolerance_vs_reference = 0.05;
    bool index_ice_rings = true;

    DiffractionGeometry geom;
    std::optional<UnitCell> reference_unit_cell;
    // The rotation axis a subsequent sweep would use. Present on a grid scan too, where the axis is
    // defined but stationary - that is exactly the case the spindle severity is for.
    std::optional<Coord> spindle_axis;
    float wavelength_A = 0;
    // Half-angle of the blind double cone a sweep would leave: asin(lambda/2d) at the GEOMETRIC
    // resolution of the setup - the detector corner at the recorded distance and wavelength - not at
    // the still's own spot resolution. A weak, attenuated grid still reaching 3 A would score a row
    // at an 11 deg miss-angle as exactly 0 while the real sweep, at the detector's 1.8 A, loses a
    // fifth of its wider cone. The corner is an upper bound on any sweep collected without moving
    // the detector, it is there on every frame, and it is unbiased where the still's spot list is
    // systematically shallow; a wider cone errs towards reporting loss, which is the cheap error.
    // 0 when the geometry cannot give it.
    float spindle_theta_max_deg = 0;

    virtual void SetupUnitCell(const std::optional<UnitCell>& cell) = 0;
    virtual std::vector<CrystalLattice> RunInternal(const std::vector<Coord> &coord, size_t nspots) = 0;
    // Set by RunInternal when the implementation computes it; read out by Run.
    virtual std::optional<SpindleSeverity> GetSpindleSeverity() const { return {}; }
    // The row pass alone, over the whole of `coord`, to produce the spindle severity without
    // reducing or refining anything. Implemented by the FFT-family indexers, which own a row
    // search; the others have nothing to answer with and return nothing.
    virtual std::optional<SpindleSeverity> RunSeverityOnly(const std::vector<Coord> &coord) { return {}; }
public:
    virtual ~Indexer() = default;
    void Setup(const DiffractionExperiment& experiment);
    // severity_only = true runs RunSeverityOnly instead of indexing: no lattice comes back and
    // `executed` stays false, since nothing was an indexing attempt. Used when the seed escalation
    // indexed a frame from fewer spots than the severity's floor - the score must not be absent on
    // precisely the frames that index cleanly.
    IndexerResult Run(const std::vector<Coord> &coord, bool severity_only = false);
};