/*
 * (C) Copyright 2025- ECMWF and individual contributors.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 * In applying this licence, ECMWF does not waive the privileges and immunities
 * granted to it by virtue of its status as an intergovernmental organisation nor
 * does it submit to any jurisdiction.
 */

///
/// @file sectionInitializerRegistry.h
/// @brief Static registries and dispatch logic for GRIB section initializers.
///
/// This header defines the **section initializer registry layer** of the
/// mars2grib backend.
///
/// It provides:
/// - compile-time registries mapping *(section, template number)* pairs
/// to concrete section initializer functions
/// - a generic lookup utility for registry tables
/// - a unified dispatch function used by the encoder to resolve
/// the correct initializer at runtime
///
/// Each GRIB section exposes a sorted, constexpr registry associating
/// template numbers with their corresponding initializer functions.
/// These registries are intentionally static, allocation-free, and
/// trivially inspectable.
///
/// This file contains **no encoding logic** itself; it only orchestrates
/// the selection of the appropriate initializer.
///
/// @ingroup mars2grib_backend_sections
///
#pragma once

// System includes
#include <cstddef>

#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer0.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer1.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer2.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer3.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer4.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializer5.h"
#include "metkit/mars2grib/backend/sections/initializers/sectionInitializerCore.h"
#include "metkit/mars2grib/utils/generalUtils.h"

#include "metkit/mars2grib/utils/mars2gribExceptions.h"

namespace metkit::mars2grib::backend::sections::initializers {

///
/// @brief Registry for GRIB Section 0 initializers.
///
/// Section 0 does not require initialization logic; this registry
/// contains a single placeholder entry.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec0Reg[] = {
    {0, &allocateTemplateNumber0<0, 0, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Registry for GRIB Section 1 initializers.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec1Reg[] = {
    {0, &allocateTemplateNumber1<1, 0, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Registry for GRIB Section 2 (Local Use Section) initializers.
///
/// Includes both official and *virtual* template numbers used internally
/// by the encoder (e.g. DestinE extensions).
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec2Reg[] = {
    {1, &allocateTemplateNumber2<2, 1, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {15, &allocateTemplateNumber2<2, 15, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {20, &allocateTemplateNumber2<2, 20, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {24, &allocateTemplateNumber2<2, 24, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {25, &allocateTemplateNumber2<2, 25, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {36, &allocateTemplateNumber2<2, 36, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {37, &allocateTemplateNumber2<2, 37, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {38, &allocateTemplateNumber2<2, 38, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {39, &allocateTemplateNumber2<2, 39, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {1000, &allocateTemplateNumber2<2, 1000, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {1001, &allocateTemplateNumber2<2, 1001, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {1002, &allocateTemplateNumber2<2, 1002, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {1004, &allocateTemplateNumber2<2, 1004, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Registry for GRIB Section 3 (Grid Definition Section) initializers.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec3Reg[] = {
    {0, &allocateTemplateNumber3<3, 0, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {40, &allocateTemplateNumber3<3, 40, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {50, &allocateTemplateNumber3<3, 50, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {101, &allocateTemplateNumber3<3, 101, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {150, &allocateTemplateNumber3<3, 150, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Registry for GRIB Section 4 (Product Definition Section) initializers.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec4Reg[] = {
    {0, &allocateTemplateNumber4<4, 0, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {1, &allocateTemplateNumber4<4, 1, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {2, &allocateTemplateNumber4<4, 2, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {8, &allocateTemplateNumber4<4, 8, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {11, &allocateTemplateNumber4<4, 11, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {12, &allocateTemplateNumber4<4, 12, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {32, &allocateTemplateNumber4<4, 32, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {33, &allocateTemplateNumber4<4, 33, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {40, &allocateTemplateNumber4<4, 40, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {41, &allocateTemplateNumber4<4, 41, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {42, &allocateTemplateNumber4<4, 42, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {43, &allocateTemplateNumber4<4, 43, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {50, &allocateTemplateNumber4<4, 50, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {45, &allocateTemplateNumber4<4, 45, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {46, &allocateTemplateNumber4<4, 46, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {85, &allocateTemplateNumber4<4, 85, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {48, &allocateTemplateNumber4<4, 48, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {49, &allocateTemplateNumber4<4, 49, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {60, &allocateTemplateNumber4<4, 60, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {61, &allocateTemplateNumber4<4, 61, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {76, &allocateTemplateNumber4<4, 76, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {77, &allocateTemplateNumber4<4, 77, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {78, &allocateTemplateNumber4<4, 78, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {79, &allocateTemplateNumber4<4, 79, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {99, &allocateTemplateNumber4<4, 99, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {100, &allocateTemplateNumber4<4, 100, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {103, &allocateTemplateNumber4<4, 103, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {104, &allocateTemplateNumber4<4, 104, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {107, &allocateTemplateNumber4<4, 107, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {121, &allocateTemplateNumber4<4, 121, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {122, &allocateTemplateNumber4<4, 122, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {142, &allocateTemplateNumber4<4, 142, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {143, &allocateTemplateNumber4<4, 143, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Registry for GRIB Section 5 (Data Representation Section) initializers.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
inline constexpr Entry<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> Sec5Reg[] = {
    {0, &allocateTemplateNumber5<5, 0, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {42, &allocateTemplateNumber5<5, 42, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>},
    {51, &allocateTemplateNumber5<5, 51, MarsDict_t, ParDict_t, OptDict_t, OutDict_t>}};

///
/// @brief Lookup a section initializer function by template number.
///
/// Performs a linear search over a compile-time registry table and
/// returns the corresponding initializer function pointer.
///
/// @tparam EntryT Registry entry type
/// @tparam N      Registry size
///
/// @param table Registry table
/// @param templ Template number
///
/// @return Initializer function pointer, or `nullptr` if not found.
///
template <class EntryT, std::size_t N>
constexpr auto lookup(const EntryT (&table)[N], std::size_t templ) -> decltype(table[0].callback) {
    for (std::size_t i = 0; i < N; ++i) {
        if (table[i].templateNumber == templ)
            return table[i].callback;
    }
    return nullptr;
}

///
/// @brief Resolve a section initializer function.
///
/// Dispatches to the appropriate section registry based on the
/// GRIB section number and resolves the initializer corresponding
/// to the provided template number.
///
/// @tparam MarsDict_t Type of the MARS dictionary
/// @tparam ParDict_t  Type of the parameter dictionary
/// @tparam OptDict_t  Type of the options dictionary
/// @tparam OutDict_t  Type of the output GRIB dictionary
///
/// @param section GRIB section number
/// @param templ   Template number
///
/// @return Initializer function pointer, or `nullptr` if not found.
///
/// @throws Mars2GribGenericException
/// If an error occurs during dispatch.
///
template <class MarsDict_t, class ParDict_t, class OptDict_t, class OutDict_t>
Fn<MarsDict_t, ParDict_t, OptDict_t, OutDict_t> sectionRegistry(std::size_t section, std::size_t templ) {

    using metkit::mars2grib::utils::exceptions::Mars2GribGenericException;

    try {
        switch (section) {
            case 0:
                return lookup(Sec0Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            case 1:
                return lookup(Sec1Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            case 2:
                return lookup(Sec2Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            case 3:
                return lookup(Sec3Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            case 4:
                return lookup(Sec4Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            case 5:
                return lookup(Sec5Reg<MarsDict_t, ParDict_t, OptDict_t, OutDict_t>, templ);
            default:
                return nullptr;
        }
    }
    catch (...) {
        std::throw_with_nested(Mars2GribGenericException("Error getting section initializer function for section " +
                                                             std::to_string(section) + " template " +
                                                             std::to_string(templ),
                                                         Here()));
    }
}

}  // namespace metkit::mars2grib::backend::sections::initializers
