xml_parser_utils.cpp

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// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (c) 2026-present FERS Contributors (see AUTHORS.md).
//
// See the GNU GPLv2 LICENSE file in the FERS project root for more information.
 
#include "xml_parser_utils.h"
 
#include <GeographicLib/UTMUPS.hpp>
#include <algorithm>
#include <cmath>
#include <exception>
#include <filesystem>
#include <format>
#include <limits>
#include <optional>
#include <string_view>
 
#include "antenna/antenna_factory.h"
#include "core/config.h"
#include "core/logging.h"
#include "core/world.h"
#include "fers_xml_dtd.h"
#include "fers_xml_xsd.h"
#include "math/coord.h"
#include "math/geometry_ops.h"
#include "math/path.h"
#include "math/rotation_path.h"
#include "radar/platform.h"
#include "radar/radar_obj.h"
#include "radar/receiver.h"
#include "radar/target.h"
#include "radar/transmitter.h"
#include "serial/fmcw_validation.h"
#include "serial/rotation_angle_utils.h"
#include "serial/rotation_warning_utils.h"
#include "serial/waveform_factory.h"
#include "signal/radar_signal.h"
#include "timing/prototype_timing.h"
#include "timing/timing.h"
 
namespace fs = std::filesystem;
 
namespace serial::xml_parser_utils
{
    namespace
    {
        /// Parses the mutually exclusive radar operation mode elements.
        radar::OperationMode parse_mode_elements(const XmlElement& parent, const std::string& owner)
        {
            std::optional<radar::OperationMode> selected_mode;
            const auto select_mode = [&](const char* const element_name, const radar::OperationMode mode)
            {
                if (!parent.childElement(element_name, 0).isValid())
                {
                    return;
                }
                if (selected_mode.has_value())
                {
                    throw XmlException(owner +
                                       " must specify exactly one radar mode (<pulsed_mode>, <cw_mode>, "
                                       "<fmcw_mode>, or <sfcw_mode>).");
                }
                selected_mode = mode;
            };
 
            select_mode("pulsed_mode", radar::OperationMode::PULSED_MODE);
            select_mode("cw_mode", radar::OperationMode::CW_MODE);
            select_mode("fmcw_mode", radar::OperationMode::FMCW_MODE);
            select_mode("sfcw_mode", radar::OperationMode::SFCW_MODE);
            if (!selected_mode.has_value())
            {
                throw XmlException(owner +
                                   " must specify exactly one radar mode (<pulsed_mode>, <cw_mode>, "
                                   "<fmcw_mode>, or <sfcw_mode>).");
            }
            return *selected_mode;
        }
 
        void reject_non_empty_sfcw_mode(const XmlElement& parent, const std::string& owner)
        {
            const XmlElement sfcw_mode = parent.childElement("sfcw_mode", 0);
            if (sfcw_mode.isValid() && sfcw_mode.childElement("", 0).isValid())
            {
                throw XmlException(owner + " sfcw_mode must be empty.");
            }
        }
 
        /// Returns true when an FMCW mode block carries receiver-side FMCW fields.
        bool has_dechirp_fields(const XmlElement& fmcw_mode)
        {
            return XmlElement::getOptionalAttribute(fmcw_mode, "dechirp_mode").has_value() ||
                fmcw_mode.childElement("dechirp_reference", 0).isValid() ||
                fmcw_mode.childElement("if_sample_rate", 0).isValid() ||
                fmcw_mode.childElement("if_filter_bandwidth", 0).isValid() ||
                fmcw_mode.childElement("if_filter_transition_width", 0).isValid();
        }
 
        /// Parses an optional positive scalar child under <fmcw_mode>.
        std::optional<RealType> parse_optional_fmcw_if_child(const XmlElement& fmcw_mode, const std::string& child_name,
                                                             const std::string& owner)
        {
            const XmlElement element = fmcw_mode.childElement(child_name, 0);
            if (!element.isValid())
            {
                return std::nullopt;
            }
            if (fmcw_mode.childElement(child_name, 1).isValid())
            {
                throw XmlException(owner + " must declare at most one <" + child_name + ">.");
            }
            const std::string text = element.getText();
            if (text.empty())
            {
                throw XmlException("Element " + child_name + " is empty!");
            }
            const RealType value = std::stod(text);
            if (value <= 0.0 || !std::isfinite(value))
            {
                throw XmlException(owner + " <" + child_name + "> must be a finite positive value.");
            }
            return value;
        }
 
        bool has_if_chain_fields(const radar::Receiver::FmcwIfChainRequest& if_chain) noexcept
        {
            return if_chain.sample_rate_hz.has_value() || if_chain.filter_bandwidth_hz.has_value() ||
                if_chain.filter_transition_width_hz.has_value();
        }
 
        void reject_disabled_dechirp_fields(const XmlElement& ref_element,
                                            const radar::Receiver::FmcwIfChainRequest& if_chain,
                                            const std::string& owner)
        {
            if (ref_element.isValid())
            {
                throw XmlException(owner + " declares <dechirp_reference> while dechirp_mode is 'none'.");
            }
            if (has_if_chain_fields(if_chain))
            {
                throw XmlException(owner + " declares IF-chain fields while dechirp_mode is 'none'.");
            }
        }
 
        void validate_if_chain_request(const radar::Receiver::FmcwIfChainRequest& if_chain, const std::string& owner)
        {
            if ((if_chain.filter_bandwidth_hz.has_value() || if_chain.filter_transition_width_hz.has_value()) &&
                !if_chain.sample_rate_hz.has_value())
            {
                throw XmlException(owner + " IF filter fields require <if_sample_rate>.");
            }
            if (if_chain.sample_rate_hz.has_value())
            {
                const RealType sim_rate = params::rate() * params::oversampleRatio();
                if (*if_chain.sample_rate_hz > sim_rate)
                {
                    throw XmlException(owner + " <if_sample_rate> must not exceed the simulation sample rate.");
                }
            }
            if (if_chain.sample_rate_hz.has_value() && if_chain.filter_bandwidth_hz.has_value() &&
                *if_chain.filter_bandwidth_hz >= *if_chain.sample_rate_hz / 2.0)
            {
                throw XmlException(owner + " <if_filter_bandwidth> must be less than half <if_sample_rate>.");
            }
        }
 
        radar::Receiver::DechirpReference
        parse_dechirp_reference(const XmlElement& fmcw_mode, const XmlElement& ref_element, const std::string& owner)
        {
            if (!ref_element.isValid())
            {
                throw XmlException(owner + " enables dechirping but does not declare <dechirp_reference>.");
            }
            if (fmcw_mode.childElement("dechirp_reference", 1).isValid())
            {
                throw XmlException(owner + " must declare at most one <dechirp_reference>.");
            }
 
            radar::Receiver::DechirpReference reference;
            try
            {
                reference.source =
                    radar::parseDechirpReferenceSourceToken(XmlElement::getSafeAttribute(ref_element, "source"));
            }
            catch (const std::exception& e)
            {
                throw XmlException(owner + " has invalid dechirp_reference. " + e.what());
            }
 
            const auto transmitter_name = XmlElement::getOptionalAttribute(ref_element, "transmitter_name");
            const auto waveform_name = XmlElement::getOptionalAttribute(ref_element, "waveform_name");
            switch (reference.source)
            {
            case radar::Receiver::DechirpReferenceSource::Attached:
                if (transmitter_name.has_value() || waveform_name.has_value())
                {
                    throw XmlException(owner +
                                       " attached dechirp_reference must not set transmitter_name or "
                                       "waveform_name.");
                }
                break;
            case radar::Receiver::DechirpReferenceSource::Transmitter:
                if (!transmitter_name.has_value() || transmitter_name->empty() || waveform_name.has_value())
                {
                    throw XmlException(owner + " transmitter dechirp_reference requires transmitter_name only.");
                }
                reference.name = *transmitter_name;
                break;
            case radar::Receiver::DechirpReferenceSource::Custom:
                if (!waveform_name.has_value() || waveform_name->empty() || transmitter_name.has_value())
                {
                    throw XmlException(owner + " custom dechirp_reference requires waveform_name only.");
                }
                reference.name = *waveform_name;
                break;
            case radar::Receiver::DechirpReferenceSource::None:
                throw XmlException(owner + " dechirp_reference source must be attached, transmitter, or custom.");
            }
 
            return reference;
        }
 
        /// Parses receiver-side dechirp settings from an FMCW mode block.
        void parse_receiver_dechirp_config(const XmlElement& parent, radar::Receiver& receiver,
                                           const std::string& owner)
        {
            if (receiver.getMode() != radar::OperationMode::FMCW_MODE)
            {
                receiver.setDechirpMode(radar::Receiver::DechirpMode::None);
                return;
            }
 
            const XmlElement fmcw_mode = parent.childElement("fmcw_mode", 0);
            if (!fmcw_mode.isValid())
            {
                receiver.setDechirpMode(radar::Receiver::DechirpMode::None);
                return;
            }
 
            radar::Receiver::DechirpMode mode = radar::Receiver::DechirpMode::None;
            if (const auto mode_attr = XmlElement::getOptionalAttribute(fmcw_mode, "dechirp_mode"))
            {
                try
                {
                    mode = radar::parseDechirpModeToken(*mode_attr);
                }
                catch (const std::exception& e)
                {
                    throw XmlException(owner + " has invalid dechirp_mode. " + e.what());
                }
            }
 
            const XmlElement ref_element = fmcw_mode.childElement("dechirp_reference", 0);
            radar::Receiver::FmcwIfChainRequest if_chain{
                .sample_rate_hz = parse_optional_fmcw_if_child(fmcw_mode, "if_sample_rate", owner),
                .filter_bandwidth_hz = parse_optional_fmcw_if_child(fmcw_mode, "if_filter_bandwidth", owner),
                .filter_transition_width_hz =
                    parse_optional_fmcw_if_child(fmcw_mode, "if_filter_transition_width", owner)};
            if (mode == radar::Receiver::DechirpMode::None)
            {
                reject_disabled_dechirp_fields(ref_element, if_chain, owner);
                receiver.setDechirpMode(mode);
                return;
            }
 
            validate_if_chain_request(if_chain, owner);
            auto reference = parse_dechirp_reference(fmcw_mode, ref_element, owner);
 
            receiver.setDechirpMode(mode);
            receiver.setDechirpReference(std::move(reference));
            receiver.setFmcwIfChainRequest(if_chain);
        }
 
        /// Throws an XML validation exception with the provided message.
        void throw_xml_validation_error(const std::string& message) { throw XmlException(message); }
 
        /// Validates an FMCW waveform while adapting validation errors to XmlException.
        void validate_fmcw_waveform(const fers_signal::RadarSignal& wave, const std::string& owner)
        {
            serial::fmcw_validation::validateWaveform(wave, owner, throw_xml_validation_error);
        }
 
        /// Validates waveform/mode compatibility while adapting validation errors to XmlException.
        void validate_waveform_mode_match(const fers_signal::RadarSignal& wave, const radar::OperationMode mode,
                                          const std::string& owner)
        {
            serial::fmcw_validation::validateWaveformModeMatch(wave, mode, owner, throw_xml_validation_error);
        }
 
        /// Validates an FMCW schedule while adapting validation errors to XmlException.
        void validate_fmcw_schedule(const std::vector<radar::SchedulePeriod>& schedule,
                                    const fers_signal::RadarSignal& wave, const std::string& owner)
        {
            serial::fmcw_validation::validateSchedule(schedule, wave, owner, throw_xml_validation_error);
        }
 
        /// Draws the next unsigned seed from the master random generator.
        [[nodiscard]] unsigned next_seed(std::mt19937& master_seeder)
        {
            static_assert(std::mt19937::max() <= std::numeric_limits<unsigned>::max(),
                          "std::mt19937 output must fit into unsigned seeds.");
            return static_cast<unsigned>(master_seeder());
        }
 
        /// Resolves or instantiates a shared timing instance by prototype SimId.
        std::shared_ptr<timing::Timing> resolve_timing_instance(const SimId timing_id, ParserContext& ctx,
                                                                const std::string& owner)
        {
            if (const auto it = ctx.timing_instances.find(timing_id); it != ctx.timing_instances.end())
            {
                return it->second;
            }
 
            const timing::PrototypeTiming* proto = ctx.world->findTiming(timing_id);
            if (proto == nullptr)
            {
                throw XmlException("Timing ID '" + std::to_string(timing_id) + "' not found for " + owner + "'");
            }
 
            auto timing_obj =
                std::make_shared<timing::Timing>(proto->getName(), next_seed(*ctx.master_seeder), proto->getId());
            timing_obj->initializeModel(proto);
            ctx.timing_instances.emplace(timing_id, timing_obj);
            return timing_obj;
        }
    }
 
    RealType get_child_real_type(const XmlElement& element, const std::string& elementName)
    {
        const std::string text = element.childElement(elementName, 0).getText();
        if (text.empty())
        {
            throw XmlException("Element " + elementName + " is empty!");
        }
        return std::stod(text);
    }
 
    bool get_attribute_bool(const XmlElement& element, const std::string& attributeName, const bool defaultVal)
    {
        const auto attr_value = XmlElement::getOptionalAttribute(element, attributeName);
        if (!attr_value.has_value())
        {
            LOG(logging::Level::DEBUG, "Attribute '{}' not specified. Defaulting to {}.", attributeName, defaultVal);
            return defaultVal;
        }
        if (*attr_value == "true")
        {
            return true;
        }
        if (*attr_value == "false")
        {
            return false;
        }
 
        LOG(logging::Level::WARNING, "Invalid boolean value '{}' for attribute '{}'. Defaulting to {}.", *attr_value,
            attributeName, defaultVal);
        return defaultVal;
    }
 
    SimId assign_id_from_attribute(const std::string& owner, ObjectType type)
    {
        const SimId id = SimIdGenerator::instance().generateId(type);
        LOG(logging::Level::TRACE, "Assigned ID {} to {} (generated)", id, owner);
        return id;
    }
 
    SimId resolve_reference_id(const XmlElement& element, const std::string& attributeName, const std::string& owner,
                               const std::unordered_map<std::string, SimId>& name_map)
    {
        const std::string value = XmlElement::getSafeAttribute(element, attributeName);
        if (value.empty())
        {
            throw XmlException("Missing " + attributeName + " for " + owner + ".");
        }
        const auto it = name_map.find(value);
        if (it != name_map.end())
        {
            return it->second;
        }
        throw XmlException("Unknown " + attributeName + " '" + value + "' for " + owner + ".");
    }
 
    std::vector<radar::SchedulePeriod> parseSchedule(const XmlElement& parent, const std::string& parentName,
                                                     const bool isPulsed, const RealType pri)
    {
        std::vector<radar::SchedulePeriod> raw_periods;
        if (const XmlElement schedule_element = parent.childElement("schedule", 0); schedule_element.isValid())
        {
            unsigned p_idx = 0;
            while (true)
            {
                XmlElement const period_element = schedule_element.childElement("period", p_idx++);
                if (!period_element.isValid())
                {
                    break;
                }
                try
                {
                    const RealType start = std::stod(XmlElement::getSafeAttribute(period_element, "start"));
                    const RealType end = std::stod(XmlElement::getSafeAttribute(period_element, "end"));
                    raw_periods.push_back({start, end});
                }
                catch (const std::exception& e)
                {
                    LOG(logging::Level::WARNING, "Failed to parse schedule period for '{}': {}", parentName, e.what());
                }
            }
        }
        return radar::processRawSchedule(raw_periods, parentName, isPulsed, pri);
    }
 
    unsigned parseUnsignedParameter(const std::string_view param_name, const RealType raw_value)
    {
        if (!std::isfinite(raw_value))
        {
            throw XmlException(std::format("Parameter '{}' must be finite.", param_name));
        }
        if (raw_value < 0.0)
        {
            throw XmlException(std::format("Parameter '{}' must be non-negative.", param_name));
        }
 
        const RealType floored_value = std::floor(raw_value);
        if (floored_value > static_cast<RealType>(std::numeric_limits<unsigned>::max()))
        {
            throw XmlException(std::format("Parameter '{}' exceeds the supported unsigned range.", param_name));
        }
 
        return static_cast<unsigned>(floored_value);
    }
 
    template <typename Setter>
    void setOptionalRealParameter(const XmlElement& parameters, const std::string& param_name,
                                  const RealType default_value, Setter setter)
    {
        if (!parameters.childElement(param_name, 0).isValid())
        {
            LOG(logging::Level::DEBUG, "Parameter '{}' not specified. Using default value {}.", param_name,
                default_value);
            return;
        }
 
        setter(get_child_real_type(parameters, param_name));
    }
 
    template <typename Setter>
    void setOptionalUnsignedParameter(const XmlElement& parameters, const std::string& param_name,
                                      const unsigned default_value, Setter setter)
    {
        if (!parameters.childElement(param_name, 0).isValid())
        {
            LOG(logging::Level::DEBUG, "Parameter '{}' not specified. Using default value {}.", param_name,
                default_value);
            return;
        }
 
        setter(parseUnsignedParameter(param_name, get_child_real_type(parameters, param_name)));
    }
 
    void parseOptionalNumericParameters(const XmlElement& parameters, params::Parameters& params_out)
    {
        setOptionalRealParameter(parameters, "c", params::Parameters::DEFAULT_C,
                                 [&](const RealType value)
                                 {
                                     params_out.c = value;
                                     LOG(logging::Level::INFO, "Propagation speed (c) set to: {:.5f}", value);
                                 });
 
        setOptionalRealParameter(parameters, "simSamplingRate", 1000.0,
                                 [&](const RealType value)
                                 {
                                     params_out.sim_sampling_rate = value;
                                     LOG(logging::Level::DEBUG, "Simulation sampling rate set to: {:.5f} Hz", value);
                                 });
 
        if (parameters.childElement("randomseed", 0).isValid())
        {
            const auto seed = parseUnsignedParameter("randomseed", get_child_real_type(parameters, "randomseed"));
            params_out.random_seed = seed;
            LOG(logging::Level::DEBUG, "Random seed set to: {}", seed);
        }
 
        setOptionalUnsignedParameter(parameters, "adc_bits", 0,
                                     [&](const unsigned value)
                                     {
                                         params_out.adc_bits = value;
                                         LOG(logging::Level::DEBUG, "ADC quantization bits set to: {}", value);
                                     });
 
        setOptionalUnsignedParameter(parameters, "oversample", 1,
                                     [&](const unsigned value)
                                     {
                                         params::validateOversampleRatio(value);
                                         params_out.oversample_ratio = value;
                                         LOG(logging::Level::DEBUG, "Oversampling enabled with ratio: {}", value);
                                     });
    }
 
    void parseRotationAngleUnit(const XmlElement& parameters, params::Parameters& params_out)
    {
        try
        {
            const auto unit_token = parameters.childElement("rotationangleunit", 0).getText();
            if (!unit_token.empty())
            {
                if (const auto unit = params::rotationAngleUnitFromToken(unit_token))
                {
                    params_out.rotation_angle_unit = *unit;
                }
                else
                {
                    throw XmlException("Unsupported rotation angle unit '" + unit_token + "'.");
                }
            }
        }
        catch (const XmlException&)
        {
        }
    }
 
    bool parseOriginParameter(const XmlElement& parameters, params::Parameters& params_out)
    {
        bool origin_set = false;
        if (const XmlElement origin_element = parameters.childElement("origin", 0); origin_element.isValid())
        {
            try
            {
                params_out.origin_latitude = std::stod(XmlElement::getSafeAttribute(origin_element, "latitude"));
                params_out.origin_longitude = std::stod(XmlElement::getSafeAttribute(origin_element, "longitude"));
                if (const auto altitude = XmlElement::getOptionalAttribute(origin_element, "altitude"))
                {
                    params_out.origin_altitude = std::stod(*altitude);
                }
                else
                {
                    params_out.origin_altitude = 0.0;
                    LOG(logging::Level::DEBUG, "KML origin altitude not specified. Defaulting to 0.");
                }
                origin_set = true;
                LOG(logging::Level::INFO, "KML origin set to lat: {}, lon: {}, alt: {}", params_out.origin_latitude,
                    params_out.origin_longitude, params_out.origin_altitude);
            }
            catch (const std::exception& e)
            {
                LOG(logging::Level::WARNING, "Could not parse KML origin from XML, using defaults. Error: {}",
                    e.what());
            }
        }
        return origin_set;
    }
 
    void parseUtmCoordinateSystem(const XmlElement& cs_element, params::Parameters& params_out)
    {
        params_out.coordinate_frame = params::CoordinateFrame::UTM;
        params_out.utm_zone = std::stoi(XmlElement::getSafeAttribute(cs_element, "zone"));
        const std::string hem_str = XmlElement::getSafeAttribute(cs_element, "hemisphere");
 
        if (params_out.utm_zone < GeographicLib::UTMUPS::MINUTMZONE ||
            params_out.utm_zone > GeographicLib::UTMUPS::MAXUTMZONE)
        {
            throw XmlException("KML UTM zone " + std::to_string(params_out.utm_zone) +
                               " is invalid; must be in [1, 60].");
        }
        if (hem_str == "N" || hem_str == "n")
        {
            params_out.utm_north_hemisphere = true;
        }
        else if (hem_str == "S" || hem_str == "s")
        {
            params_out.utm_north_hemisphere = false;
        }
        else
        {
            throw XmlException("KML UTM hemisphere '" + hem_str + "' is invalid; must be 'N' or 'S'.");
        }
        LOG(logging::Level::INFO, "KML coordinate system set to UTM, zone {}{}", params_out.utm_zone,
            params_out.utm_north_hemisphere ? 'N' : 'S');
    }
 
    void parseCoordinateSystemParameter(const XmlElement& parameters, params::Parameters& params_out,
                                        const bool origin_set)
    {
        if (const XmlElement cs_element = parameters.childElement("coordinatesystem", 0); cs_element.isValid())
        {
            try
            {
                const std::string frame_str = XmlElement::getSafeAttribute(cs_element, "frame");
                if (frame_str == "UTM")
                {
                    parseUtmCoordinateSystem(cs_element, params_out);
                }
                else if (frame_str == "ECEF")
                {
                    params_out.coordinate_frame = params::CoordinateFrame::ECEF;
                    LOG(logging::Level::INFO, "KML coordinate system set to ECEF.");
                }
                else if (frame_str == "ENU")
                {
                    params_out.coordinate_frame = params::CoordinateFrame::ENU;
                    if (!origin_set)
                    {
                        LOG(logging::Level::WARNING,
                            "ENU KML frame specified but no <origin> tag found. Using default KML origin at UCT.");
                    }
                    LOG(logging::Level::INFO, "KML coordinate system set to ENU local tangent plane.");
                }
                else
                {
                    throw XmlException("Unsupported KML coordinate frame: " + frame_str);
                }
            }
            catch (const std::exception& e)
            {
                LOG(logging::Level::WARNING,
                    "Could not parse KML <coordinatesystem> from XML: {}. Defaulting KML export to ENU.", e.what());
                params_out.coordinate_frame = params::CoordinateFrame::ENU;
                params_out.utm_zone = 0;
                params_out.utm_north_hemisphere = true;
            }
        }
    }
 
    void parseParameters(const XmlElement& parameters, params::Parameters& params_out)
    {
        params_out.start = get_child_real_type(parameters, "starttime");
        params_out.end = get_child_real_type(parameters, "endtime");
        LOG(logging::Level::INFO, "Simulation time set from {:.5f} to {:.5f} seconds", params_out.start,
            params_out.end);
 
        params_out.rate = get_child_real_type(parameters, "rate");
        if (params_out.rate <= 0)
        {
            throw std::runtime_error("Sampling rate must be > 0");
        }
        LOG(logging::Level::DEBUG, "Sample rate set to: {:.5f}", params_out.rate);
 
        parseOptionalNumericParameters(parameters, params_out);
        parseRotationAngleUnit(parameters, params_out);
        const bool origin_set = parseOriginParameter(parameters, params_out);
        parseCoordinateSystemParameter(parameters, params_out, origin_set);
    }
 
    void parseWaveform(const XmlElement& waveform, ParserContext& ctx)
    {
        const std::string name = XmlElement::getSafeAttribute(waveform, "name");
        const SimId id = assign_id_from_attribute("waveform '" + name + "'", ObjectType::Waveform);
 
        const auto power = get_child_real_type(waveform, "power");
        const auto carrier = get_child_real_type(waveform, "carrier_frequency");
 
        if (const XmlElement pulsed_file = waveform.childElement("pulsed_from_file", 0); pulsed_file.isValid())
        {
            const std::string filename_str = XmlElement::getSafeAttribute(pulsed_file, "filename");
            fs::path pulse_path(filename_str);
 
            if (!fs::exists(pulse_path))
            {
                pulse_path = ctx.base_dir / filename_str;
            }
 
            // Defer to dependency-injected file loader
            auto wave = ctx.loaders.loadWaveform(name, pulse_path, power, carrier, id);
            ctx.world->add(std::move(wave));
        }
        else if (waveform.childElement("cw", 0).isValid())
        {
            auto cw_signal = std::make_unique<fers_signal::CwSignal>();
            auto wave = std::make_unique<fers_signal::RadarSignal>(
                name, power, carrier, ctx.parameters.end - ctx.parameters.start, std::move(cw_signal), id);
            ctx.world->add(std::move(wave));
        }
        else if (const XmlElement sfcw_element = waveform.childElement("stepped_frequency", 0); sfcw_element.isValid())
        {
            const RealType start_frequency_offset = get_child_real_type(sfcw_element, "start_frequency_offset");
            const RealType step_size = get_child_real_type(sfcw_element, "step_size");
            const RealType raw_step_count = get_child_real_type(sfcw_element, "step_count");
            if (raw_step_count <= 0.0 || std::floor(raw_step_count) != raw_step_count)
            {
                throw XmlException("Waveform '" + name + "' has an invalid step_count.");
            }
            const RealType dwell_time = get_child_real_type(sfcw_element, "dwell_time");
            const RealType step_period = get_child_real_type(sfcw_element, "step_period");
 
            std::optional<std::size_t> sweep_count;
            if (const auto sweep_count_element = sfcw_element.childElement("sweep_count", 0);
                sweep_count_element.isValid())
            {
                const RealType raw_count = get_child_real_type(sfcw_element, "sweep_count");
                if (raw_count <= 0.0 || std::floor(raw_count) != raw_count)
                {
                    throw XmlException("Waveform '" + name + "' has an invalid sweep_count.");
                }
                sweep_count = static_cast<std::size_t>(raw_count);
            }
 
            auto sfcw_signal = std::make_unique<fers_signal::SteppedFrequencySignal>(
                start_frequency_offset, step_size, static_cast<std::size_t>(raw_step_count), dwell_time, step_period,
                sweep_count);
            auto wave = std::make_unique<fers_signal::RadarSignal>(name, power, carrier, sfcw_signal->getDwellTime(),
                                                                   std::move(sfcw_signal), id);
            validate_fmcw_waveform(*wave, "Waveform '" + name + "'");
            ctx.world->add(std::move(wave));
        }
        else if (const XmlElement fmcw_element = waveform.childElement("fmcw_linear_chirp", 0); fmcw_element.isValid())
        {
            const auto direction =
                fers_signal::parseFmcwChirpDirection(XmlElement::getSafeAttribute(fmcw_element, "direction"));
            const RealType chirp_bandwidth = get_child_real_type(fmcw_element, "chirp_bandwidth");
            const RealType chirp_duration = get_child_real_type(fmcw_element, "chirp_duration");
            const RealType chirp_period = get_child_real_type(fmcw_element, "chirp_period");
 
            RealType start_frequency_offset = 0.0;
            if (const auto start_offset = fmcw_element.childElement("start_frequency_offset", 0);
                start_offset.isValid())
            {
                start_frequency_offset = get_child_real_type(fmcw_element, "start_frequency_offset");
            }
 
            std::optional<std::size_t> chirp_count;
            if (const auto chirp_count_element = fmcw_element.childElement("chirp_count", 0);
                chirp_count_element.isValid())
            {
                const RealType raw_count = get_child_real_type(fmcw_element, "chirp_count");
                if (raw_count <= 0.0 || std::floor(raw_count) != raw_count)
                {
                    throw XmlException("Waveform '" + name + "' has an invalid chirp_count.");
                }
                chirp_count = static_cast<std::size_t>(raw_count);
            }
 
            auto fmcw_signal = std::make_unique<fers_signal::FmcwChirpSignal>(
                chirp_bandwidth, chirp_duration, chirp_period, start_frequency_offset, chirp_count, direction);
            // RadarSignal length is the active chirp duration, not T_rep. The repeat period only spaces chirps.
            auto wave = std::make_unique<fers_signal::RadarSignal>(name, power, carrier, chirp_duration,
                                                                   std::move(fmcw_signal), id);
            validate_fmcw_waveform(*wave, "Waveform '" + name + "'");
            ctx.world->add(std::move(wave));
        }
        else if (const XmlElement fmcw_triangle_element = waveform.childElement("fmcw_triangle", 0);
                 fmcw_triangle_element.isValid())
        {
            const RealType chirp_bandwidth = get_child_real_type(fmcw_triangle_element, "chirp_bandwidth");
            const RealType chirp_duration = get_child_real_type(fmcw_triangle_element, "chirp_duration");
 
            RealType start_frequency_offset = 0.0;
            if (const auto start_offset = fmcw_triangle_element.childElement("start_frequency_offset", 0);
                start_offset.isValid())
            {
                start_frequency_offset = get_child_real_type(fmcw_triangle_element, "start_frequency_offset");
            }
 
            std::optional<std::size_t> triangle_count;
            if (const auto triangle_count_element = fmcw_triangle_element.childElement("triangle_count", 0);
                triangle_count_element.isValid())
            {
                const RealType raw_count = get_child_real_type(fmcw_triangle_element, "triangle_count");
                if (raw_count <= 0.0 || std::floor(raw_count) != raw_count)
                {
                    throw XmlException("Waveform '" + name + "' has an invalid triangle_count.");
                }
                triangle_count = static_cast<std::size_t>(raw_count);
            }
 
            auto fmcw_signal = std::make_unique<fers_signal::FmcwTriangleSignal>(
                chirp_bandwidth, chirp_duration, start_frequency_offset, triangle_count);
            auto wave = std::make_unique<fers_signal::RadarSignal>(
                name, power, carrier, fmcw_signal->getTrianglePeriod(), std::move(fmcw_signal), id);
            validate_fmcw_waveform(*wave, "Waveform '" + name + "'");
            ctx.world->add(std::move(wave));
        }
        else
        {
            LOG(logging::Level::FATAL, "Unsupported waveform type for '{}'", name);
            throw XmlException("Unsupported waveform type for '" + name + "'");
        }
    }
 
    void parseTiming(const XmlElement& timing, ParserContext& ctx)
    {
        const std::string name = XmlElement::getSafeAttribute(timing, "name");
        const SimId id = assign_id_from_attribute("timing '" + name + "'", ObjectType::Timing);
        const RealType freq = get_child_real_type(timing, "frequency");
        auto timing_obj = std::make_unique<timing::PrototypeTiming>(name, id);
 
        timing_obj->setFrequency(freq);
 
        unsigned noise_index = 0;
        while (true)
        {
            XmlElement const noise_element = timing.childElement("noise_entry", noise_index++);
            if (!noise_element.isValid())
            {
                break;
            }
 
            timing_obj->setAlpha(get_child_real_type(noise_element, "alpha"),
                                 get_child_real_type(noise_element, "weight"));
        }
 
        const auto set_optional_timing_parameter =
            [&](const std::string& element_name, const std::string& description, auto setter)
        {
            if (!timing.childElement(element_name, 0).isValid())
            {
                LOG(logging::Level::DEBUG, "Clock section '{}' does not specify {}.", name, description);
                return;
            }
            try
            {
                setter(get_child_real_type(timing, element_name));
            }
            catch (const XmlException&)
            {
                LOG(logging::Level::WARNING, "Clock section '{}' has an empty {}. Using default.", name, description);
            }
        };
 
        set_optional_timing_parameter("freq_offset", "frequency offset",
                                      [&](const RealType value) { timing_obj->setFreqOffset(value); });
        set_optional_timing_parameter("random_freq_offset_stdev", "random frequency offset",
                                      [&](const RealType value) { timing_obj->setRandomFreqOffsetStdev(value); });
        set_optional_timing_parameter("phase_offset", "phase offset",
                                      [&](const RealType value) { timing_obj->setPhaseOffset(value); });
        set_optional_timing_parameter("random_phase_offset_stdev", "random phase offset",
                                      [&](const RealType value) { timing_obj->setRandomPhaseOffsetStdev(value); });
 
        if (get_attribute_bool(timing, "synconpulse", false))
        {
            timing_obj->setSyncOnPulse();
        }
 
        ctx.world->add(std::move(timing_obj));
    }
 
    void parseAntenna(const XmlElement& antenna, ParserContext& ctx)
    {
        const std::string name = XmlElement::getSafeAttribute(antenna, "name");
        const SimId id = assign_id_from_attribute("antenna '" + name + "'", ObjectType::Antenna);
        const std::string pattern = XmlElement::getSafeAttribute(antenna, "pattern");
 
        std::unique_ptr<antenna::Antenna> ant;
 
        LOG(logging::Level::DEBUG, "Adding antenna '{}' with pattern '{}'", name, pattern);
        if (pattern == "isotropic")
        {
            ant = std::make_unique<antenna::Isotropic>(name, id);
        }
        else if (pattern == "sinc")
        {
            ant = std::make_unique<antenna::Sinc>(name, get_child_real_type(antenna, "alpha"),
                                                  get_child_real_type(antenna, "beta"),
                                                  get_child_real_type(antenna, "gamma"), id);
        }
        else if (pattern == "gaussian")
        {
            ant = std::make_unique<antenna::Gaussian>(name, get_child_real_type(antenna, "azscale"),
                                                      get_child_real_type(antenna, "elscale"), id);
        }
        else if (pattern == "squarehorn")
        {
            ant = std::make_unique<antenna::SquareHorn>(name, get_child_real_type(antenna, "diameter"), id);
        }
        else if (pattern == "parabolic")
        {
            ant = std::make_unique<antenna::Parabolic>(name, get_child_real_type(antenna, "diameter"), id);
        }
        else if (pattern == "xml")
        {
            ant = ctx.loaders.loadXmlAntenna(name, XmlElement::getSafeAttribute(antenna, "filename"), id);
        }
        else if (pattern == "file")
        {
            ant = ctx.loaders.loadH5Antenna(name, XmlElement::getSafeAttribute(antenna, "filename"), id);
        }
        else
        {
            LOG(logging::Level::FATAL, "Unsupported antenna pattern: {}", pattern);
            throw XmlException("Unsupported antenna pattern: " + pattern);
        }
 
        if (!antenna.childElement("efficiency", 0).isValid())
        {
            LOG(logging::Level::DEBUG, "Antenna '{}' does not specify efficiency, assuming unity.", name);
        }
        else
        {
            try
            {
                ant->setEfficiencyFactor(get_child_real_type(antenna, "efficiency"));
            }
            catch (const XmlException&)
            {
                LOG(logging::Level::WARNING, "Antenna '{}' has an empty efficiency, assuming unity.", name);
            }
        }
 
        ctx.world->add(std::move(ant));
    }
 
    void parseMotionPath(const XmlElement& motionPath, radar::Platform* platform)
    {
        math::Path* path = platform->getMotionPath();
        if (const auto interp_value = XmlElement::getOptionalAttribute(motionPath, "interpolation"))
        {
            if (*interp_value == "linear")
            {
                path->setInterp(math::Path::InterpType::INTERP_LINEAR);
            }
            else if (*interp_value == "cubic")
            {
                path->setInterp(math::Path::InterpType::INTERP_CUBIC);
            }
            else if (*interp_value == "static")
            {
                path->setInterp(math::Path::InterpType::INTERP_STATIC);
            }
            else
            {
                LOG(logging::Level::ERROR, "Unsupported interpolation type: {} for platform {}. Defaulting to static",
                    *interp_value, platform->getName());
                path->setInterp(math::Path::InterpType::INTERP_STATIC);
            }
        }
        else
        {
            LOG(logging::Level::DEBUG,
                "MotionPath interpolation type for platform {} not specified. Defaulting to static.",
                platform->getName());
            path->setInterp(math::Path::InterpType::INTERP_STATIC);
        }
 
        unsigned waypoint_index = 0;
        while (true)
        {
            XmlElement const waypoint = motionPath.childElement("positionwaypoint", waypoint_index);
            if (!waypoint.isValid())
            {
                break;
            }
 
            try
            {
                math::Coord coord;
                coord.t = get_child_real_type(waypoint, "time");
                coord.pos = math::Vec3(get_child_real_type(waypoint, "x"), get_child_real_type(waypoint, "y"),
                                       get_child_real_type(waypoint, "altitude"));
                path->addCoord(coord);
                LOG(logging::Level::TRACE, "Added waypoint {} to motion path for platform {}.", waypoint_index,
                    platform->getName());
            }
            catch (const XmlException& e)
            {
                LOG(logging::Level::ERROR, "Failed to add waypoint to motion path. Discarding waypoint. {}", e.what());
            }
 
            waypoint_index++;
        }
        path->finalize();
    }
 
    void parseRotationPath(const XmlElement& rotation, radar::Platform* platform, const params::RotationAngleUnit unit)
    {
        math::RotationPath* path = platform->getRotationPath();
        try
        {
            if (const std::string interp = XmlElement::getSafeAttribute(rotation, "interpolation"); interp == "linear")
            {
                path->setInterp(math::RotationPath::InterpType::INTERP_LINEAR);
            }
            else if (interp == "cubic")
            {
                path->setInterp(math::RotationPath::InterpType::INTERP_CUBIC);
            }
            else if (interp == "static")
            {
                path->setInterp(math::RotationPath::InterpType::INTERP_STATIC);
            }
            else
            {
                throw XmlException("Unsupported interpolation type: " + interp);
            }
        }
        catch (XmlException&)
        {
            LOG(logging::Level::ERROR,
                "Failed to set RotationPath interpolation type for platform {}. Defaulting to static",
                platform->getName());
            path->setInterp(math::RotationPath::InterpType::INTERP_STATIC);
        }
 
        unsigned waypoint_index = 0;
        while (true)
        {
            XmlElement const waypoint = rotation.childElement("rotationwaypoint", waypoint_index);
            if (!waypoint.isValid())
            {
                break;
            }
 
            try
            {
                LOG(logging::Level::TRACE, "Adding waypoint {} to rotation path for platform {}.", waypoint_index,
                    platform->getName());
 
                const RealType az_deg = get_child_real_type(waypoint, "azimuth");
                const RealType el_deg = get_child_real_type(waypoint, "elevation");
                const RealType time = get_child_real_type(waypoint, "time");
                const std::string owner =
                    std::format("platform '{}' rotation waypoint {}", platform->getName(), waypoint_index);
 
                rotation_warning_utils::maybe_warn_about_rotation_value(
                    az_deg, unit, rotation_warning_utils::ValueKind::Angle, "XML", owner, "azimuth");
                rotation_warning_utils::maybe_warn_about_rotation_value(
                    el_deg, unit, rotation_warning_utils::ValueKind::Angle, "XML", owner, "elevation");
 
                path->addCoord(rotation_angle_utils::external_rotation_to_internal(az_deg, el_deg, time, unit));
            }
            catch (const XmlException& e)
            {
                LOG(logging::Level::ERROR, "Failed to add waypoint to rotation path. Discarding waypoint. {}",
                    e.what());
            }
            waypoint_index++;
        }
        path->finalize();
    }
 
    void parseFixedRotation(const XmlElement& rotation, radar::Platform* platform, const params::RotationAngleUnit unit)
    {
        math::RotationPath* path = platform->getRotationPath();
        try
        {
            const RealType start_az_deg = get_child_real_type(rotation, "startazimuth");
            const RealType start_el_deg = get_child_real_type(rotation, "startelevation");
            const RealType rate_az_deg_s = get_child_real_type(rotation, "azimuthrate");
            const RealType rate_el_deg_s = get_child_real_type(rotation, "elevationrate");
            const std::string owner = std::format("platform '{}' fixedrotation", platform->getName());
 
            rotation_warning_utils::maybe_warn_about_rotation_value(
                start_az_deg, unit, rotation_warning_utils::ValueKind::Angle, "XML", owner, "startazimuth");
            rotation_warning_utils::maybe_warn_about_rotation_value(
                start_el_deg, unit, rotation_warning_utils::ValueKind::Angle, "XML", owner, "startelevation");
            rotation_warning_utils::maybe_warn_about_rotation_value(
                rate_az_deg_s, unit, rotation_warning_utils::ValueKind::Rate, "XML", owner, "azimuthrate");
            rotation_warning_utils::maybe_warn_about_rotation_value(
                rate_el_deg_s, unit, rotation_warning_utils::ValueKind::Rate, "XML", owner, "elevationrate");
            const math::RotationCoord start =
                rotation_angle_utils::external_rotation_to_internal(start_az_deg, start_el_deg, 0.0, unit);
            const math::RotationCoord rate =
                rotation_angle_utils::external_rotation_rate_to_internal(rate_az_deg_s, rate_el_deg_s, 0.0, unit);
 
            path->setConstantRate(start, rate);
            LOG(logging::Level::DEBUG, "Added fixed rotation to platform {}", platform->getName());
        }
        catch (XmlException& e)
        {
            LOG(logging::Level::FATAL, "Failed to set fixed rotation for platform {}. {}", platform->getName(),
                e.what());
            throw XmlException("Failed to set fixed rotation for platform " + platform->getName());
        }
    }
 
    /// Parses a transmitter after its operation mode has already been determined.
    static radar::Transmitter* parseTransmitterWithMode(const XmlElement& transmitter, radar::Platform* platform,
                                                        ParserContext& ctx, const ReferenceLookup& refs,
                                                        const radar::OperationMode mode)
    {
        const std::string name = XmlElement::getSafeAttribute(transmitter, "name");
        const SimId id = assign_id_from_attribute("transmitter '" + name + "'", ObjectType::Transmitter);
        const XmlElement pulsed_mode_element = transmitter.childElement("pulsed_mode", 0);
        const bool is_pulsed = mode == radar::OperationMode::PULSED_MODE;
 
        auto transmitter_obj = std::make_unique<radar::Transmitter>(platform, name, mode, id);
 
        const SimId waveform_id =
            resolve_reference_id(transmitter, "waveform", "transmitter '" + name + "'", *refs.waveforms);
        fers_signal::RadarSignal* wave = ctx.world->findWaveform(waveform_id);
        if (wave == nullptr)
        {
            throw XmlException("Waveform ID '" + std::to_string(waveform_id) + "' not found for transmitter '" + name +
                               "'");
        }
        validate_fmcw_waveform(*wave, "Waveform '" + wave->getName() + "'");
        validate_waveform_mode_match(*wave, mode, "Transmitter '" + name + "'");
        transmitter_obj->setWave(wave);
 
        if (is_pulsed)
        {
            transmitter_obj->setPrf(get_child_real_type(pulsed_mode_element, "prf"));
        }
 
        const SimId antenna_id =
            resolve_reference_id(transmitter, "antenna", "transmitter '" + name + "'", *refs.antennas);
        const antenna::Antenna* ant = ctx.world->findAntenna(antenna_id);
        if (ant == nullptr)
        {
            throw XmlException("Antenna ID '" + std::to_string(antenna_id) + "' not found for transmitter '" + name +
                               "'");
        }
        transmitter_obj->setAntenna(ant);
 
        const SimId timing_id =
            resolve_reference_id(transmitter, "timing", "transmitter '" + name + "'", *refs.timings);
        transmitter_obj->setTiming(resolve_timing_instance(timing_id, ctx, "transmitter '" + name + "'"));
 
        RealType const pri = is_pulsed ? (1.0 / transmitter_obj->getPrf()) : 0.0;
        auto schedule = parseSchedule(transmitter, name, is_pulsed, pri);
        if (wave->isFmcwFamily() || wave->isSteppedFrequency())
        {
            validate_fmcw_schedule(schedule, *wave, "Transmitter '" + name + "'");
        }
        if (!schedule.empty())
        {
            transmitter_obj->setSchedule(std::move(schedule));
        }
 
        ctx.world->add(std::move(transmitter_obj));
        return ctx.world->getTransmitters().back().get();
    }
 
    radar::Transmitter* parseTransmitter(const XmlElement& transmitter, radar::Platform* platform, ParserContext& ctx,
                                         const ReferenceLookup& refs)
    {
        const std::string name = XmlElement::getSafeAttribute(transmitter, "name");
        const radar::OperationMode mode = parse_mode_elements(transmitter, "Transmitter '" + name + "'");
        reject_non_empty_sfcw_mode(transmitter, "Transmitter '" + name + "'");
        if (const XmlElement fmcw_mode = transmitter.childElement("fmcw_mode", 0);
            fmcw_mode.isValid() && has_dechirp_fields(fmcw_mode))
        {
            throw XmlException("Transmitter '" + name + "' fmcw_mode must not contain dechirp configuration.");
        }
        return parseTransmitterWithMode(transmitter, platform, ctx, refs, mode);
    }
 
    /// Parses a receiver after its operation mode has already been determined.
    static radar::Receiver* parseReceiverWithMode(const XmlElement& receiver, radar::Platform* platform,
                                                  ParserContext& ctx, const ReferenceLookup& refs,
                                                  const radar::OperationMode mode)
    {
        const std::string name = XmlElement::getSafeAttribute(receiver, "name");
        const SimId id = assign_id_from_attribute("receiver '" + name + "'", ObjectType::Receiver);
        const XmlElement pulsed_mode_element = receiver.childElement("pulsed_mode", 0);
        const bool is_pulsed = mode == radar::OperationMode::PULSED_MODE;
 
        auto receiver_obj = std::make_unique<radar::Receiver>(platform, name, next_seed(*ctx.master_seeder), mode, id);
 
        const SimId ant_id = resolve_reference_id(receiver, "antenna", "receiver '" + name + "'", *refs.antennas);
        const antenna::Antenna* antenna = ctx.world->findAntenna(ant_id);
        if (antenna == nullptr)
        {
            throw XmlException("Antenna ID '" + std::to_string(ant_id) + "' not found for receiver '" + name + "'");
        }
        receiver_obj->setAntenna(antenna);
 
        if (!receiver.childElement("noise_temp", 0).isValid())
        {
            LOG(logging::Level::DEBUG, "Receiver '{}' does not specify noise temperature",
                receiver_obj->getName().c_str());
        }
        else
        {
            try
            {
                receiver_obj->setNoiseTemperature(get_child_real_type(receiver, "noise_temp"));
            }
            catch (const XmlException&)
            {
                LOG(logging::Level::WARNING, "Receiver '{}' has an empty noise temperature; using default.",
                    receiver_obj->getName().c_str());
            }
        }
 
        if (is_pulsed)
        {
            const RealType window_length = get_child_real_type(pulsed_mode_element, "window_length");
            if (window_length <= 0)
            {
                throw XmlException("<window_length> must be positive for receiver '" + name + "'");
            }
 
            const RealType prf = get_child_real_type(pulsed_mode_element, "prf");
            if (prf <= 0)
            {
                throw XmlException("<prf> must be positive for receiver '" + name + "'");
            }
 
            const RealType window_skip = get_child_real_type(pulsed_mode_element, "window_skip");
            if (window_skip < 0)
            {
                throw XmlException("<window_skip> must not be negative for receiver '" + name + "'");
            }
            receiver_obj->setWindowProperties(window_length, prf, window_skip);
        }
        const SimId timing_id = resolve_reference_id(receiver, "timing", "receiver '" + name + "'", *refs.timings);
        receiver_obj->setTiming(resolve_timing_instance(timing_id, ctx, "receiver '" + name + "'"));
 
        if (get_attribute_bool(receiver, "nodirect", false))
        {
            receiver_obj->setFlag(radar::Receiver::RecvFlag::FLAG_NODIRECT);
            LOG(logging::Level::DEBUG, "Ignoring direct signals for receiver '{}'", receiver_obj->getName().c_str());
        }
 
        if (get_attribute_bool(receiver, "nopropagationloss", false))
        {
            receiver_obj->setFlag(radar::Receiver::RecvFlag::FLAG_NOPROPLOSS);
            LOG(logging::Level::DEBUG, "Ignoring propagation losses for receiver '{}'",
                receiver_obj->getName().c_str());
        }
 
        RealType const pri = is_pulsed ? (1.0 / receiver_obj->getWindowPrf()) : 0.0;
        auto schedule = parseSchedule(receiver, name, is_pulsed, pri);
        if (!schedule.empty())
        {
            receiver_obj->setSchedule(std::move(schedule));
        }
 
        parse_receiver_dechirp_config(receiver, *receiver_obj, "Receiver '" + name + "'");
 
        ctx.world->add(std::move(receiver_obj));
        return ctx.world->getReceivers().back().get();
    }
 
    radar::Receiver* parseReceiver(const XmlElement& receiver, radar::Platform* platform, ParserContext& ctx,
                                   const ReferenceLookup& refs)
    {
        const std::string name = XmlElement::getSafeAttribute(receiver, "name");
        const radar::OperationMode mode = parse_mode_elements(receiver, "Receiver '" + name + "'");
        reject_non_empty_sfcw_mode(receiver, "Receiver '" + name + "'");
        return parseReceiverWithMode(receiver, platform, ctx, refs, mode);
    }
 
    void parseMonostatic(const XmlElement& monostatic, radar::Platform* platform, ParserContext& ctx,
                         const ReferenceLookup& refs)
    {
        const std::string name = XmlElement::getSafeAttribute(monostatic, "name");
        const radar::OperationMode monostatic_mode = parse_mode_elements(monostatic, "Monostatic '" + name + "'");
        reject_non_empty_sfcw_mode(monostatic, "Monostatic '" + name + "'");
        radar::Transmitter* trans = parseTransmitterWithMode(monostatic, platform, ctx, refs, monostatic_mode);
        radar::Receiver* recv = parseReceiverWithMode(monostatic, platform, ctx, refs, monostatic_mode);
        if (trans->getMode() != monostatic_mode || recv->getMode() != monostatic_mode)
        {
            throw XmlException("Monostatic '" + name + "' parsed inconsistent transmitter/receiver modes.");
        }
        if (trans->getSignal() != nullptr)
        {
            validate_waveform_mode_match(*trans->getSignal(), trans->getMode(),
                                         "Monostatic '" + trans->getName() + "'");
        }
        trans->setAttached(recv);
        recv->setAttached(trans);
    }
 
    void parseTarget(const XmlElement& target, radar::Platform* platform, ParserContext& ctx)
    {
        const std::string name = XmlElement::getSafeAttribute(target, "name");
        const SimId id = assign_id_from_attribute("target '" + name + "'", ObjectType::Target);
 
        const XmlElement rcs_element = target.childElement("rcs", 0);
        if (!rcs_element.isValid())
        {
            throw XmlException("<rcs> element is required in <target>!");
        }
 
        const std::string rcs_type = XmlElement::getSafeAttribute(rcs_element, "type");
        std::unique_ptr<radar::Target> target_obj;
        const unsigned seed = next_seed(*ctx.master_seeder);
 
        if (rcs_type == "isotropic")
        {
            target_obj = radar::createIsoTarget(platform, name, get_child_real_type(rcs_element, "value"), seed, id);
        }
        else if (rcs_type == "file")
        {
            // Defer to dependency-injected file loader
            target_obj = ctx.loaders.loadFileTarget(platform, name,
                                                    XmlElement::getSafeAttribute(rcs_element, "filename"), seed, id);
        }
        else
        {
            throw XmlException("Unsupported RCS type: " + rcs_type);
        }
 
        if (const XmlElement model = target.childElement("model", 0); model.isValid())
        {
            if (const std::string model_type = XmlElement::getSafeAttribute(model, "type"); model_type == "constant")
            {
                target_obj->setFluctuationModel(std::make_unique<radar::RcsConst>());
            }
            else if (model_type == "chisquare" || model_type == "gamma")
            {
                target_obj->setFluctuationModel(
                    std::make_unique<radar::RcsChiSquare>(target_obj->getRngEngine(), get_child_real_type(model, "k")));
            }
            else
            {
                throw XmlException("Unsupported model type: " + model_type);
            }
        }
 
        LOG(logging::Level::DEBUG, "Added target {} with RCS type {} to platform {}", name, rcs_type,
            platform->getName());
        ctx.world->add(std::move(target_obj));
    }
 
    void parsePlatformElements(const XmlElement& platform, ParserContext& ctx, radar::Platform* plat,
                               const std::function<void(const XmlElement&, std::string_view)>& register_name,
                               const ReferenceLookup& refs)
    {
        auto parseChildrenWithRefs = [&](const std::string& elementName, auto parseFunc)
        {
            unsigned index = 0;
            while (true)
            {
                const XmlElement element = platform.childElement(elementName, index++);
                if (!element.isValid())
                    break;
                register_name(element, elementName);
                parseFunc(element, plat, ctx, refs);
            }
        };
 
        auto parseChildrenWithoutRefs = [&](const std::string& elementName, auto parseFunc)
        {
            unsigned index = 0;
            while (true)
            {
                const XmlElement element = platform.childElement(elementName, index++);
                if (!element.isValid())
                    break;
                register_name(element, elementName);
                parseFunc(element, plat, ctx);
            }
        };
 
        parseChildrenWithRefs("monostatic", parseMonostatic);
        parseChildrenWithRefs("transmitter", parseTransmitter);
        parseChildrenWithRefs("receiver", parseReceiver);
        parseChildrenWithoutRefs("target", parseTarget);
    }
 
    void parsePlatform(const XmlElement& platform, ParserContext& ctx,
                       const std::function<void(const XmlElement&, std::string_view)>& register_name,
                       const ReferenceLookup& refs)
    {
        std::string const name = XmlElement::getSafeAttribute(platform, "name");
        const SimId id = assign_id_from_attribute("platform '" + name + "'", ObjectType::Platform);
        auto plat = std::make_unique<radar::Platform>(name, id);
 
        parsePlatformElements(platform, ctx, plat.get(), register_name, refs);
 
        if (const XmlElement motion_path = platform.childElement("motionpath", 0); motion_path.isValid())
        {
            parseMotionPath(motion_path, plat.get());
        }
 
        const XmlElement rot_path = platform.childElement("rotationpath", 0);
        if (const XmlElement fixed_rot = platform.childElement("fixedrotation", 0);
            rot_path.isValid() && fixed_rot.isValid())
        {
            LOG(logging::Level::ERROR,
                "Both <rotationpath> and <fixedrotation> are declared for platform {}. Only <rotationpath> will be "
                "used.",
                plat->getName());
            parseRotationPath(rot_path, plat.get(), ctx.parameters.rotation_angle_unit);
        }
        else if (rot_path.isValid())
        {
            parseRotationPath(rot_path, plat.get(), ctx.parameters.rotation_angle_unit);
        }
        else if (fixed_rot.isValid())
        {
            parseFixedRotation(fixed_rot, plat.get(), ctx.parameters.rotation_angle_unit);
        }
 
        ctx.world->add(std::move(plat));
    }
 
    void collectIncludeElements(const XmlDocument& doc, const fs::path& currentDir, std::vector<fs::path>& includePaths)
    {
        unsigned index = 0;
        while (true)
        {
            XmlElement const include_element = doc.getRootElement().childElement("include", index++);
            if (!include_element.isValid())
                break;
 
            std::string const include_filename = include_element.getText();
            if (include_filename.empty())
            {
                LOG(logging::Level::ERROR, "<include> element is missing the filename!");
                continue;
            }
 
            fs::path const include_path = currentDir / include_filename;
            includePaths.push_back(include_path);
 
            XmlDocument included_doc;
            if (!included_doc.loadFile(include_path.string()))
            {
                LOG(logging::Level::ERROR, "Failed to load included XML file: {}", include_path.string());
                continue;
            }
 
            collectIncludeElements(included_doc, include_path.parent_path(), includePaths);
        }
    }
 
    bool addIncludeFilesToMainDocument(const XmlDocument& mainDoc, const fs::path& currentDir)
    {
        std::vector<fs::path> include_paths;
        collectIncludeElements(mainDoc, currentDir, include_paths);
        bool did_combine = false;
 
        for (const auto& include_path : include_paths)
        {
            XmlDocument included_doc;
            if (!included_doc.loadFile(include_path.string()))
            {
                throw XmlException("Failed to load included XML file: " + include_path.string());
            }
 
            mergeXmlDocuments(mainDoc, included_doc);
            did_combine = true;
        }
 
        removeIncludeElements(mainDoc);
        return did_combine;
    }
 
    void validateXml(const bool didCombine, const XmlDocument& mainDoc)
    {
        LOG(logging::Level::DEBUG, "Validating the{}XML file...", didCombine ? " combined " : " ");
        if (!mainDoc.validateWithDtd(fers_xml_dtd))
        {
            LOG(logging::Level::FATAL, "{} XML file failed DTD validation!", didCombine ? "Combined" : "Main");
            throw XmlException("XML file failed DTD validation!");
        }
        LOG(logging::Level::DEBUG, "{} XML file passed DTD validation.", didCombine ? "Combined" : "Main");
 
        if (!mainDoc.validateWithXsd(fers_xml_xsd))
        {
            LOG(logging::Level::FATAL, "{} XML file failed XSD validation!", didCombine ? "Combined" : "Main");
            throw XmlException("XML file failed XSD validation!");
        }
        LOG(logging::Level::DEBUG, "{} XML file passed XSD validation.", didCombine ? "Combined" : "Main");
    }
 
    void processParsedDocument(const XmlDocument& doc, ParserContext& ctx)
    {
        const XmlElement root = doc.getRootElement();
        if (root.name() != "simulation")
        {
            throw XmlException("Root element is not <simulation>!");
        }
 
        std::unordered_map<std::string, std::string> name_registry;
        name_registry.reserve(64); // TODO: reserve 64?
        const auto register_name = [&](const XmlElement& element, const std::string_view kind)
        {
            const std::string name = XmlElement::getSafeAttribute(element, "name");
            const auto [iter, inserted] = name_registry.emplace(name, std::string(kind));
            if (!inserted)
            {
                throw XmlException("Duplicate name '" + name + "' found for " + std::string(kind) +
                                   "; previously used by " + iter->second + ".");
            }
        };
 
        try
        {
            ctx.parameters.simulation_name = XmlElement::getSafeAttribute(root, "name");
            if (!ctx.parameters.simulation_name.empty())
            {
                LOG(logging::Level::INFO, "Simulation name set to: {}", ctx.parameters.simulation_name);
            }
        }
        catch (const XmlException&)
        {
            LOG(logging::Level::WARNING, "No 'name' attribute found in <simulation> tag. KML name will default.");
        }
 
        parseParameters(root.childElement("parameters", 0), ctx.parameters);
 
        params::params = ctx.parameters;
 
        auto parseElements =
            [](const XmlElement& parent, const std::string& elementName, ParserContext& parser_ctx, auto parseFunction)
        {
            unsigned index = 0;
            while (true)
            {
                XmlElement const element = parent.childElement(elementName, index++);
                if (!element.isValid())
                    break;
                parseFunction(element, parser_ctx);
            }
        };
 
        parseElements(root, "waveform", ctx,
                      [&](const XmlElement& p, ParserContext& c)
                      {
                          register_name(p, "waveform");
                          parseWaveform(p, c);
                      });
 
        parseElements(root, "timing", ctx,
                      [&](const XmlElement& p, ParserContext& c)
                      {
                          register_name(p, "timing");
                          parseTiming(p, c);
                      });
 
        parseElements(root, "antenna", ctx,
                      [&](const XmlElement& p, ParserContext& c)
                      {
                          register_name(p, "antenna");
                          parseAntenna(p, c);
                      });
 
        std::unordered_map<std::string, SimId> waveform_refs;
        std::unordered_map<std::string, SimId> antenna_refs;
        std::unordered_map<std::string, SimId> timing_refs;
        waveform_refs.reserve(ctx.world->getWaveforms().size());
        antenna_refs.reserve(ctx.world->getAntennas().size());
        timing_refs.reserve(ctx.world->getTimings().size());
 
        for (const auto& [id, waveform] : ctx.world->getWaveforms())
            waveform_refs.emplace(waveform->getName(), id);
        for (const auto& [id, antenna] : ctx.world->getAntennas())
            antenna_refs.emplace(antenna->getName(), id);
        for (const auto& [id, timing] : ctx.world->getTimings())
            timing_refs.emplace(timing->getName(), id);
 
        const ReferenceLookup refs{&waveform_refs, &antenna_refs, &timing_refs};
 
        parseElements(root, "platform", ctx,
                      [&](const XmlElement& p, ParserContext& c)
                      {
                          register_name(p, "platform");
                          parsePlatform(p, c, register_name, refs);
                      });
 
        ctx.world->resolveReceiverDechirpReferences();
 
        ctx.world->scheduleInitialEvents();
 
        LOG(logging::Level::DEBUG, "Initial Event Queue State:\n{}", ctx.world->dumpEventQueue());
    }
 
    AssetLoaders createDefaultAssetLoaders()
    {
        return {.loadWaveform = [](const std::string& name, const fs::path& pulse_path, RealType power,
                                   RealType carrierFreq, SimId id)
                { return serial::loadWaveformFromFile(name, pulse_path.string(), power, carrierFreq, id); },
                .loadXmlAntenna = [](const std::string& name, const std::string& filename, SimId id)
                { return std::make_unique<antenna::XmlAntenna>(name, filename, id); },
                .loadH5Antenna = [](const std::string& name, const std::string& filename, SimId id)
                { return std::make_unique<antenna::H5Antenna>(name, filename, id); },
                .loadFileTarget = [](radar::Platform* platform, const std::string& name, const std::string& filename,
                                     unsigned seed, SimId id)
                { return radar::createFileTarget(platform, name, filename, seed, id); }};
    }
}