// SPDX-FileCopyrightText: 2025 Paul Scherrer Institute
// SPDX-License-Identifier: GPL-3.0-only

#include "WriteReflections.h"
#include "scale_merge/Merge.h"
#include "scale_merge/HKLKey.h"
#include "scale_merge/TwinningAnalysis.h"

#include <cmath>
#include <map>
#include <tuple>
#include <fstream>
#include <iomanip>
#include <sstream>
#include <stdexcept>
#include <ctime>
#include <chrono>

#include <gemmi/mtz.hpp>

#include "../common/GitInfo.h"

namespace {

/// Current date in ISO-8601 (YYYY-MM-DD) for the _audit block.
std::string CurrentDateISO() {
    auto now = std::chrono::system_clock::now();
    auto t   = std::chrono::system_clock::to_time_t(now);
    std::tm tm{};
#ifdef _WIN32
    gmtime_s(&tm, &t);
#else
    gmtime_r(&t, &tm);
#endif
    char buf[32];
    std::strftime(buf, sizeof(buf), "%Y-%m-%d", &tm);
    return buf;
}

/// Format a double with given decimal places; returns "?" for non-finite.
std::string Fmt(double val, int decimals = 4) {
    if (!std::isfinite(val))
        return "?";
    std::ostringstream ss;
    ss << std::fixed << std::setprecision(decimals) << val;
    return ss.str();
}

/// Quote a CIF string value; returns "?" for empty.
std::string CifStr(const std::string& s) {
    if (s.empty())
        return "?";
    // If it contains spaces or special chars, single-quote it
    if (s.find(' ') != std::string::npos ||
        s.find('\'') != std::string::npos ||
        s.find('#') != std::string::npos)
        return "'" + s + "'";
    return s;
}

} // namespace


void WriteMmcifReflections(const std::vector<MergedReflection> &reflections,
                           const UnitCell &unitCell,
                           const DiffractionExperiment &experiment,
                           const MergeStatistics &statistics,
                           const std::string &isa,
                           const TwinningAnalysisResult &twinning,
                           const std::string &filename) {

    std::ofstream out(filename);
    if (!out)
        throw std::runtime_error("WriteMmcifReflections: cannot open " + filename);

    out << std::fixed;

    // ---------- data block ----------
    out << "data_sample" << "\n";
    out << "#\n";

    // ---------- _audit ----------
    out << "_audit.revision_id     1\n";
    out << "_audit.creation_date   " << CurrentDateISO() << "\n";
    out << "_audit.update_record   'Initial release'\n";
    out << "#\n";

    // ---------- _software ----------
    out << "_software.name         'Jungfraujoch'\n";

    out << "_software.version      " << CifStr(jfjoch_version()) << "\n";
    out << "_software.classification reduction\n";
    out << "#\n";

    // ---------- _cell ----------
    out << "_cell.length_a     " << Fmt(unitCell.a, 3) << "\n";
    out << "_cell.length_b     " << Fmt(unitCell.b, 3) << "\n";
    out << "_cell.length_c     " << Fmt(unitCell.c, 3) << "\n";
    out << "_cell.angle_alpha  " << Fmt(unitCell.alpha, 2) << "\n";
    out << "_cell.angle_beta   " << Fmt(unitCell.beta, 2) << "\n";
    out << "_cell.angle_gamma  " << Fmt(unitCell.gamma, 2) << "\n";

    auto *sg = gemmi::find_spacegroup_by_number(experiment.GetSpaceGroupNumber().value_or(1));
    if (sg == nullptr)
        throw std::runtime_error("WriteMmcifReflections: invalid space group number");

    // ---------- _symmetry ----------
    out << "_symmetry.space_group_name_H-M  " << CifStr(sg->hm) << "\n";
    out << "_symmetry.Int_Tables_number      " << sg->number << "\n";
    out << "#\n";

    // ---------- _diffrn_source / _diffrn_detector ----------
    if (!experiment.GetSourceName().empty())
        out << "_diffrn_source.pdbx_synchrotron_site  " << CifStr(experiment.GetSourceName()) << "\n";

    if (!experiment.GetInstrumentName().empty())
        out << "_diffrn_source.pdbx_synchrotron_beamline  " << CifStr(experiment.GetInstrumentName()) << "\n";

    out << "_diffrn_radiation_wavelength.wavelength  " << Fmt(experiment.GetWavelength_A(), 5) << "\n";
    out << "_diffrn_detector.detector  " << CifStr(experiment.GetDetectorDescription()) << "\n";
    out << "#\n";

    // ---------- merging statistics (_reflns overall + _reflns_shell loop) ----------
    // cc_half and r_meas are stored as fractions (0-1), which is the mmCIF convention. ISa (the
    // Diederichs asymptotic I/sigma, 1/b of the a*sigma^2 + (b*I)^2 error model) and the twinning
    // indicators below have no standard mmCIF item. They are written under the "jfjoch" reserved
    // prefix (_reflns.jfjoch_*), the IUCr-sanctioned local-data-name extension for private items -
    // NOT the "pdbx_" prefix, which is owned by the wwPDB PDBx/mmCIF dictionary and must not label
    // items that dictionary does not define. (The other pdbx_ items here are genuine PDBx items.)
    const auto mult = [](const MergeStatisticsShell &s) {
        return s.unique_reflections > 0 ? static_cast<double>(s.total_observations) / s.unique_reflections : 0.0; };
    const auto compl_pct = [](const MergeStatisticsShell &s) {
        return s.possible_unique_reflections > 0
               ? 100.0 * static_cast<double>(s.unique_reflections) / s.possible_unique_reflections : 0.0; };
    if (!statistics.shells.empty()) {
        const auto &ov = statistics.overall;
        out << "_reflns.d_resolution_high         " << Fmt(ov.d_min, 2) << "\n";
        out << "_reflns.d_resolution_low          " << Fmt(ov.d_max, 2) << "\n";
        out << "_reflns.number_obs                " << ov.unique_reflections << "\n";
        out << "_reflns.pdbx_number_measured_all  " << ov.total_observations << "\n";
        out << "_reflns.pdbx_redundancy           " << Fmt(mult(ov), 2) << "\n";
        out << "_reflns.percent_possible_obs      " << Fmt(compl_pct(ov), 1) << "\n";
        out << "_reflns.pdbx_netI_over_sigmaI     " << Fmt(ov.mean_i_over_sigma, 2) << "\n";
        out << "_reflns.pdbx_Rrim_I_all           " << Fmt(ov.r_meas, 4) << "\n";
        out << "_reflns.pdbx_CC_half              " << Fmt(ov.cc_half, 4) << "\n";
        out << "_reflns.jfjoch_diffrn_ISa             " << CifStr(isa) << "   # asymptotic I/sigma (Diederichs)\n";
        // Twinning indicators (no standard mmCIF item; same jfjoch local prefix as ISa above).
        if (twinning.l_test_pairs > 0) {
            out << "_reflns.jfjoch_L_test_mean_abs_L      " << Fmt(twinning.mean_abs_l, 3)
                << "   # Padilla-Yeates <|L|> (untwinned 0.500, perfect twin 0.375)\n";
            out << "_reflns.jfjoch_L_test_mean_L_squared  " << Fmt(twinning.mean_l_squared, 3)
                << "   # <L^2> (untwinned 0.333, perfect twin 0.200)\n";
        }
        if (twinning.moment_reflections > 0)
            out << "_reflns.jfjoch_second_moment_I        " << Fmt(twinning.second_moment, 3)
                << "   # <I^2>/<I>^2 (untwinned 2.00, perfect twin 1.50)\n";
        out << "#\n";

        out << "loop_\n";
        out << "_reflns_shell.d_res_high\n";
        out << "_reflns_shell.d_res_low\n";
        out << "_reflns_shell.number_measured_obs\n";
        out << "_reflns_shell.number_unique_obs\n";
        out << "_reflns_shell.pdbx_redundancy\n";
        out << "_reflns_shell.percent_possible_obs\n";
        out << "_reflns_shell.meanI_over_sigI_obs\n";
        out << "_reflns_shell.pdbx_Rrim_I_all\n";
        out << "_reflns_shell.pdbx_CC_half\n";
        for (const auto &s : statistics.shells) {
            if (s.unique_reflections == 0)
                continue;
            out << Fmt(s.d_min, 2) << " " << Fmt(s.d_max, 2) << " "
                << s.total_observations << " " << s.unique_reflections << " "
                << Fmt(mult(s), 2) << " " << Fmt(compl_pct(s), 1) << " "
                << Fmt(s.mean_i_over_sigma, 2) << " " << Fmt(s.r_meas, 4) << " " << Fmt(s.cc_half, 4) << "\n";
        }
        out << "#\n";
    }

    // ---------- _refln loop ----------
    out << "loop_\n";
    out << "_refln.index_h\n";
    out << "_refln.index_k\n";
    out << "_refln.index_l\n";
    out << "_refln.intensity_meas\n";
    out << "_refln.intensity_sigma\n";
    out << "_refln.F_meas_au\n";
    out << "_refln.F_meas_sigma_au\n";
    out << "_refln.status_free\n";
    out << "_refln.status\n";

    for (const auto& r : reflections) {
        out << std::setw(5) << r.h << " "
            << std::setw(5) << r.k << " "
            << std::setw(5) << r.l << " "
            << std::setw(14) << Fmt(r.I, 4) << " "
            << std::setw(14) << Fmt(r.sigma, 4) << " "
            << std::setw(14) << Fmt(r.F, 4) << " "
            << std::setw(14) << Fmt(r.sigmaF, 4) << " "
            << (r.rfree_flag ? 1 : 0) << " "
            << "o"  // 'o' = observed
            << "\n";
    }

    out << "#\n";
    out << "# End of reflections\n";
    out.close();
}

void WriteMtzReflections(const std::vector<MergedReflection> &reflections,
                         const UnitCell &unitCell,
                         const DiffractionExperiment &experiment,
                         const std::string &filename) {
    gemmi::Mtz mtz;

    // Optional but recommended metadata
    mtz.spacegroup = gemmi::find_spacegroup_by_number(
        experiment.GetSpaceGroupNumber().value_or(1));
    mtz.set_cell_for_all(unitCell);

    // Add dataset
    gemmi::Mtz::Dataset& ds = mtz.add_dataset("native");
    ds.crystal_name = experiment.GetSampleName();
    ds.wavelength = experiment.GetWavelength_A();

    const int dataset_id = ds.id;

    // In anomalous mode the merge keeps the two Friedel mates as separate rows (I+ under the ASU
    // representative hkl, I- under -hkl). Emitting those verbatim gives a file with two rows per
    // reflection that downstream tools have to re-collapse. Instead pair the mates into one row per
    // reflection with the standard CCP4 anomalous layout (IMEAN + I(+)/I(-), and the same split for
    // the French-Wilson amplitude), which aimless / ctruncate / mtz2sca / ANODE read directly.
    if (experiment.GetScalingSettings().GetMergeFriedel()) {
        mtz.add_column("H", 'H', dataset_id, -1, false);
        mtz.add_column("K", 'H', dataset_id, -1, false);
        mtz.add_column("L", 'H', dataset_id, -1, false);
        mtz.add_column("IMEAN", 'J', dataset_id, -1, false);
        mtz.add_column("SIGIMEAN", 'Q', dataset_id, -1, false);
        mtz.add_column("F", 'F', dataset_id, -1, false);      // French-Wilson amplitude
        mtz.add_column("SIGF", 'Q', dataset_id, -1, false);
        mtz.add_column("FreeR_flag", 'I', dataset_id, -1, false);

        mtz.nreflections = static_cast<int>(reflections.size());
        mtz.data.reserve(reflections.size() * 8);
        for (const auto& r : reflections) {
            mtz.data.push_back(static_cast<float>(r.h));
            mtz.data.push_back(static_cast<float>(r.k));
            mtz.data.push_back(static_cast<float>(r.l));
            mtz.data.push_back(r.I);
            mtz.data.push_back(r.sigma);
            mtz.data.push_back(r.F);
            mtz.data.push_back(r.sigmaF);
            mtz.data.push_back(r.rfree_flag ? 1.0f : 0.0f);
        }
        mtz.write_to_file(filename);
        return;
    }

    // Anomalous: group the two mates by their (shared) Friedel-merged ASU representative. A single
    // generator gives both the group key (its hkl, identical for +hkl and -hkl) and which mate this
    // row is (.plus).
    const HKLKeyGenerator key_gen(false, experiment.GetSpaceGroupNumber().value_or(1));

    struct AnomRow {
        int h = 0, k = 0, l = 0;
        float Ip = NAN, sIp = NAN, Im = NAN, sIm = NAN;
        float Fp = NAN, sFp = NAN, Fm = NAN, sFm = NAN;
        int rfree = 0;
    };
    std::map<std::tuple<int, int, int>, AnomRow> rows;
    for (const auto& r : reflections) {
        const HKLKey key = key_gen(r);
        AnomRow& row = rows[{key.h, key.k, key.l}];
        row.h = key.h; row.k = key.k; row.l = key.l;
        row.rfree = r.rfree_flag ? 1 : 0;
        if (key.plus) { row.Ip = r.I; row.sIp = r.sigma; row.Fp = r.F; row.sFp = r.sigmaF; }
        else          { row.Im = r.I; row.sIm = r.sigma; row.Fm = r.F; row.sFm = r.sigmaF; }
    }

    // Friedel-mean of the two mates by inverse variance (the single mate, if only one was measured).
    const auto combine = [](float a, float sa, float b, float sb, float& val, float& sig) {
        const bool ok_a = std::isfinite(a) && sa > 0.0f;
        const bool ok_b = std::isfinite(b) && sb > 0.0f;
        if (ok_a && ok_b) {
            const double wa = 1.0 / (static_cast<double>(sa) * sa);
            const double wb = 1.0 / (static_cast<double>(sb) * sb);
            val = static_cast<float>((wa * a + wb * b) / (wa + wb));
            sig = static_cast<float>(1.0 / std::sqrt(wa + wb));
        } else if (ok_a) { val = a; sig = sa; }
        else if (ok_b)   { val = b; sig = sb; }
        else             { val = NAN; sig = NAN; }
    };

    mtz.add_column("H", 'H', dataset_id, -1, false);
    mtz.add_column("K", 'H', dataset_id, -1, false);
    mtz.add_column("L", 'H', dataset_id, -1, false);
    mtz.add_column("IMEAN", 'J', dataset_id, -1, false);
    mtz.add_column("SIGIMEAN", 'Q', dataset_id, -1, false);
    mtz.add_column("I(+)", 'K', dataset_id, -1, false);
    mtz.add_column("SIGI(+)", 'M', dataset_id, -1, false);
    mtz.add_column("I(-)", 'K', dataset_id, -1, false);
    mtz.add_column("SIGI(-)", 'M', dataset_id, -1, false);
    mtz.add_column("F", 'F', dataset_id, -1, false);       // French-Wilson amplitude (mean)
    mtz.add_column("SIGF", 'Q', dataset_id, -1, false);
    mtz.add_column("F(+)", 'G', dataset_id, -1, false);
    mtz.add_column("SIGF(+)", 'L', dataset_id, -1, false);
    mtz.add_column("F(-)", 'G', dataset_id, -1, false);
    mtz.add_column("SIGF(-)", 'L', dataset_id, -1, false);
    mtz.add_column("FreeR_flag", 'I', dataset_id, -1, false);

    mtz.nreflections = static_cast<int>(rows.size());
    mtz.data.reserve(rows.size() * 16);
    for (const auto& [hkl, row] : rows) {
        float i_mean, sig_i_mean, f_mean, sig_f_mean;
        combine(row.Ip, row.sIp, row.Im, row.sIm, i_mean, sig_i_mean);
        combine(row.Fp, row.sFp, row.Fm, row.sFm, f_mean, sig_f_mean);
        mtz.data.push_back(static_cast<float>(row.h));
        mtz.data.push_back(static_cast<float>(row.k));
        mtz.data.push_back(static_cast<float>(row.l));
        mtz.data.push_back(i_mean);
        mtz.data.push_back(sig_i_mean);
        mtz.data.push_back(row.Ip);
        mtz.data.push_back(row.sIp);
        mtz.data.push_back(row.Im);
        mtz.data.push_back(row.sIm);
        mtz.data.push_back(f_mean);
        mtz.data.push_back(sig_f_mean);
        mtz.data.push_back(row.Fp);
        mtz.data.push_back(row.sFp);
        mtz.data.push_back(row.Fm);
        mtz.data.push_back(row.sFm);
        mtz.data.push_back(static_cast<float>(row.rfree));
    }
    mtz.write_to_file(filename);
}

void WriteReflections(const std::vector<MergedReflection> &reflections,
                      const UnitCell &unitCell,
                      const DiffractionExperiment &experiment,
                      const MergeStatistics &statistics,
                      const std::string &isa,
                      const TwinningAnalysisResult &twinning,
                      const std::string &filename) {
    // Always write both an MTZ and an mmCIF - each has its uses downstream (MTZ for the CCP4 /
    // phenix reflection tools, mmCIF for deposition and as the self-describing native format).
    WriteMtzReflections(reflections, unitCell, experiment, filename + ".mtz");
    WriteMmcifReflections(reflections, unitCell, experiment, statistics, isa, twinning, filename + ".cif");
}