Jungfraujoch/rugnux/ModelValidation.h

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

#pragma once

#include <optional>
#include <string>
#include <vector>

#include "gemmi/symmetry.hpp"

#include "../common/Reflection.h"   // MergedReflection
#include "../common/UnitCell.h"

class Logger;

// Result of validating merged intensities against an atomic model.
struct ModelValidationResult {
    bool ok = false;
    std::string model_path;        // the file that was asked for, so the report can name it
    // Why it did not run, when ok is false: the file could not be read, had no atoms, no cell or no
    // usable space group. A caller that asked for a model must be able to say so rather than finish
    // quietly with no R-free and no maps, which reads exactly like a run that was never asked.
    std::string failure_reason;
    double r_work = 0.0;
    double r_free = 0.0;
    double k_sol = 0.0;
    double b_sol = 0.0;
    double k_overall = 0.0;
    int n_work = 0;
    int n_free = 0;
    double mean_atom_density_sigma = 0.0;  // mean 2Fo-Fc value at atom centres, in sigma
    std::string maps_prefix;               // where the .ccp4 / _maps.mtz were written

    // The anomalous difference map read at the model's own atoms: the strongest sites, highest
    // first. Empty when the merge kept no Bijvoet split, and so had nothing to make the map from.
    struct AnomalousSite {
        std::string label;   // atom, residue and chain, e.g. "SG CYS A7"
        double sigma = 0.0;  // height of the anomalous map at that atom, in map sigma
    };
    std::vector<AnomalousSite> anomalous_sites;
    int anomalous_pairs = 0;               // Bijvoet pairs the anomalous map was computed from

    // Set when the anomalous map is inverted at the model's atoms - deeper troughs than peaks - which
    // says the data and the model are in opposite hands. Named so the report can quote the evidence.
    bool anomalous_hands_disagree = false;
    std::string anomalous_deepest_site;
    double anomalous_deepest_sigma = 0.0;

    // The alternative-indexing operator picked by R-free, identity where none was needed.
    // AdoptModelFrame below applies it to the reflections that are written out, so the file, the
    // R-factors and the maps all describe one indexing.
    gemmi::Op indexing_op = gemmi::Op::identity();
    // Set when the data were merged in the enantiomorph of the model's space group and the model's
    // group is adopted for the written reflections. This is a change of LABEL only: the two groups
    // have the same rotation operations, so they index and split into Bijvoet hands identically, and
    // the reflections themselves must not move. See the note in ValidateAgainstModel.
    bool adopted_model_enantiomorph = false;
    int model_space_group_number = 0;
};

// Given merged intensities and an atomic model (PDB or mmCIF, gzipped or not - the format is taken
// from the file's content), scale the model structure factors (with an
// optimized flat bulk-solvent contribution and an overall anisotropic B) to the observed
// amplitudes, then report R-work / R-free and write 2Fo-Fc and Fo-Fc electron-density maps
// (CCP4) plus an MTZ of map coefficients next to output_prefix.
//
// No refinement of the structure itself is done. The model is only re-fractionalized into the
// data unit cell (a cheap rigid cell adjustment) so a deposited model with a slightly different
// cell still lines up with the processed data. Returns ok=false (and logs) on any failure.
// data_space_group_number is the space group the data was merged in. If it is the enantiomorph of
// the model's space group (e.g. data P4(1)2(1)2, model P4(3)2(1)2 - indistinguishable from merged
// intensities), the model's group is adopted as a label, without touching the reflections.
//
// probe_indexing_ambiguity controls how a merohedral (alternative-indexing) ambiguity is resolved.
// Pass false when a reference (MTZ) already fixed the indexing - the data are then kept in that
// authoritative indexing. Pass true (model only, no reference) to resolve it here as a fallback, by
// fitting each candidate reindexing to the model and keeping the lowest R-free. Holohedral crystals
// (no twin laws) are unaffected either way.
ModelValidationResult ValidateAgainstModel(const std::vector<MergedReflection> &merged,
                                           const UnitCell &cell,
                                           const std::string &model_path,
                                           const std::string &output_prefix,
                                           Logger &logger,
                                           std::optional<int> data_space_group_number = std::nullopt,
                                           bool probe_indexing_ambiguity = true);

// Reindex `merged` into the frame ValidateAgainstModel reported, so the reflection files that are
// written describe the same indexing as the R-factors and the maps. Returns the space group they are
// now in - the model's, where its enantiomorph was adopted, and `data_space_group_number` otherwise
// (a change of indexing is metric- and group-preserving). A no-op where the model needed neither.
int AdoptModelFrame(const ModelValidationResult &validation,
                    std::vector<MergedReflection> &merged,
                    int data_space_group_number,
                    bool merge_friedel,
                    Logger &logger);

// Reference intensities computed from an atomic model: |F_model|^2, with a flat bulk-solvent
// contribution at the standard constants, for every reflection to `d_min`. This is the same
// information a reference MTZ carries, and it is what lets a model break the indexing ambiguity of a
// serial-stills run: there the ambiguity has to be broken per image, at integration time, long before
// there is a merge to fit a model to. `cell` and `space_group_number` override the model's own, where
// the run already knows them. Empty on any failure (which is logged).
std::vector<MergedReflection> ModelReferenceIntensities(const std::string &model_path,
                                                        const std::optional<UnitCell> &cell,
                                                        std::optional<int> space_group_number,
                                                        double d_min,
                                                        Logger &logger);