grib-reader 0.6.0

mod common;

use std::io::Write;

use common::{
    build_grib1_message, build_grib1_message_with_bitmap, build_grib2_complex_packing_message,
    build_grib2_complex_packing_message_with_missing, build_grib2_lambert_alternating_message,
    build_grib2_lambert_message, build_grib2_message, build_grib2_message_with_forecast,
    build_grib2_multifield_message, build_grib2_polar_stereographic_alternating_message,
    build_grib2_polar_stereographic_message, build_grib2_spatial_differencing_message,
};
use grib_reader::{
    Error, ForecastTimeUnit, GribFile, GridDefinition, LocalParameterEntry, OpenOptions,
    ParameterTableSource, ProductDefinitionTemplate,
};

#[test]
fn open_grib2_from_file_and_decode() {
    let dir = tempfile::tempdir().unwrap();
    let path = dir.path().join("sample.grib2");
    let mut file = std::fs::File::create(&path).unwrap();
    file.write_all(&build_grib2_message(&[1, 2, 3, 4])).unwrap();

    let opened = GribFile::open(&path).unwrap();
    assert_eq!(opened.edition(), 2);
    assert_eq!(opened.message_count(), 1);
    let field = opened.message(0).unwrap();
    assert_eq!(field.parameter_name(), "TMP");
    assert_eq!(field.reference_time().year, 2026);
    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0]
    );
    assert_eq!(
        field
            .read_data_as_f64()
            .unwrap()
            .iter()
            .copied()
            .collect::<Vec<_>>(),
        vec![1.0, 2.0, 3.0, 4.0]
    );
    assert_eq!(
        field
            .read_data_as_f32()
            .unwrap()
            .iter()
            .copied()
            .collect::<Vec<_>>(),
        vec![1.0_f32, 2.0, 3.0, 4.0]
    );
}

#[test]
fn open_grib1_from_file_and_decode() {
    let dir = tempfile::tempdir().unwrap();
    let path = dir.path().join("sample.grib1");
    let mut file = std::fs::File::create(&path).unwrap();
    file.write_all(&build_grib1_message(&[5, 6, 7, 8])).unwrap();

    let opened = GribFile::open(&path).unwrap();
    assert_eq!(opened.edition(), 1);
    assert_eq!(opened.message_count(), 1);
    let field = opened.message(0).unwrap();
    assert_eq!(field.parameter_name(), "TMP");
    assert_eq!(field.center_id(), 7);
    assert!(field.grib1_product_definition().is_some());
    assert_eq!(
        field
            .read_data_as_f64()
            .unwrap()
            .iter()
            .copied()
            .collect::<Vec<_>>(),
        vec![5.0, 6.0, 7.0, 8.0]
    );
}

#[test]
fn decode_into_reuses_caller_buffers_for_f32_and_f64() {
    let opened = GribFile::from_bytes(build_grib2_message(&[1, 2, 3, 4])).unwrap();
    let field = opened.message(0).unwrap();

    let mut as_f32 = [0.0_f32; 4];
    field.decode_into(&mut as_f32).unwrap();
    assert_eq!(as_f32, [1.0, 2.0, 3.0, 4.0]);

    let mut as_f64 = [0.0_f64; 4];
    field.decode_into(&mut as_f64).unwrap();
    assert_eq!(as_f64, [1.0, 2.0, 3.0, 4.0]);
}

#[test]
fn open_grib2_lambert_conformal_field_and_decode_flat_data() {
    let opened = GribFile::from_bytes(build_grib2_lambert_message()).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.grid_shape(), (3, 2));
    assert_eq!(field.latitudes().unwrap(), None);
    assert_eq!(field.longitudes().unwrap(), None);
    assert_eq!(
        field.projected_x_coordinates().unwrap().unwrap(),
        vec![0.0, 2_539.703, 5_079.406]
    );
    assert_eq!(
        field.projected_y_coordinates().unwrap().unwrap(),
        vec![-0.0, -2_539.703]
    );
    match field.grid_definition() {
        GridDefinition::LambertConformal(grid) => {
            assert_eq!(grid.number_of_points, 6);
            assert_eq!(grid.shape_of_earth, 1);
            assert_eq!(grid.scaled_value_radius, 6_371_200);
            assert_eq!(grid.nx, 3);
            assert_eq!(grid.ny, 2);
            assert_eq!(grid.lat_first, 12_190_000);
            assert_eq!(grid.lon_first, 226_541_000);
            assert_eq!(grid.lat_d, 25_000_000);
            assert_eq!(grid.lon_v, 265_000_000);
            assert_eq!(grid.dx, 2_539_703);
            assert_eq!(grid.dy, 2_539_703);
            assert_eq!(grid.latin1, 25_000_000);
            assert_eq!(grid.latin2, 25_000_000);
        }
        other => panic!("expected Lambert conformal grid, got {other:?}"),
    }

    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
    let array = field.read_data_as_f64().unwrap();
    assert_eq!(array.shape(), &[2, 3]);
    assert_eq!(
        array.iter().copied().collect::<Vec<_>>(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
}

#[test]
fn open_rejects_grid_above_configured_decoded_point_limit() {
    let err = match GribFile::from_bytes_with_options(
        build_grib2_message(&[1, 2, 3, 4]),
        OpenOptions::default().with_max_decoded_points(3),
    ) {
        Ok(_) => panic!("expected decoded point limit error"),
        Err(err) => err,
    };

    assert!(matches!(
        err,
        Error::LimitExceeded {
            what: "decoded grid points",
            requested: 4,
            limit: 3,
        }
    ));
}

#[test]
fn projected_coordinate_helpers_enforce_axis_limit() {
    let opened = GribFile::from_bytes_with_options(
        build_grib2_lambert_message(),
        OpenOptions::default().with_max_axis_points(2),
    )
    .unwrap();
    let field = opened.message(0).unwrap();

    let err = field.projected_x_coordinates().unwrap_err();
    assert!(matches!(
        err,
        Error::LimitExceeded {
            what: "projected x axis",
            requested: 3,
            limit: 2,
        }
    ));
}

#[test]
fn open_rejects_projected_grid_point_count_mismatch() {
    let mut bytes = build_grib2_lambert_message();
    let grid_offset = 16 + 21;
    bytes[grid_offset + 6..grid_offset + 10].copy_from_slice(&5u32.to_be_bytes());

    let err = match GribFile::from_bytes(bytes) {
        Ok(_) => panic!("expected projected grid point count mismatch"),
        Err(err) => err,
    };
    assert!(matches!(err, Error::InvalidSection { section: 3, .. }));
    assert!(err.to_string().contains("declares 5 points"));
}

#[test]
fn open_grib2_lambert_conformal_normalizes_alternating_scan_rows() {
    let opened = GribFile::from_bytes(build_grib2_lambert_alternating_message()).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
}

#[test]
fn open_grib2_polar_stereographic_field_and_decode_flat_data() {
    let opened = GribFile::from_bytes(build_grib2_polar_stereographic_message()).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.grid_shape(), (3, 2));
    assert_eq!(field.latitudes().unwrap(), None);
    assert_eq!(field.longitudes().unwrap(), None);
    assert_eq!(
        field.projected_x_coordinates().unwrap().unwrap(),
        vec![0.0, 3_000.0, 6_000.0]
    );
    assert_eq!(
        field.projected_y_coordinates().unwrap().unwrap(),
        vec![-0.0, -3_000.0]
    );
    match field.grid_definition() {
        GridDefinition::PolarStereographic(grid) => {
            assert_eq!(grid.number_of_points, 6);
            assert_eq!(grid.shape_of_earth, 6);
            assert_eq!(grid.nx, 3);
            assert_eq!(grid.ny, 2);
            assert_eq!(grid.lat_first, 41_612_949);
            assert_eq!(grid.lon_first, 185_117_126);
            assert_eq!(grid.lat_d, 60_000_000);
            assert_eq!(grid.lon_v, 225_000_000);
            assert_eq!(grid.dx, 3_000_000);
            assert_eq!(grid.dy, 3_000_000);
            assert_eq!(grid.projection_center_flag, 0);
        }
        other => panic!("expected polar stereographic grid, got {other:?}"),
    }

    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
    let array = field.read_data_as_f64().unwrap();
    assert_eq!(array.shape(), &[2, 3]);
    assert_eq!(
        array.iter().copied().collect::<Vec<_>>(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
}

#[test]
fn open_grib2_polar_stereographic_normalizes_alternating_scan_rows() {
    let opened =
        GribFile::from_bytes(build_grib2_polar_stereographic_alternating_message()).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    );
}

#[test]
fn open_grib2_simple_field_applies_decimal_scale_to_reference_and_values() {
    let mut bytes = build_grib2_message(&[0, 10, 20, 30]);
    let section5_offset = 16 + 21 + 72 + 34;
    bytes[section5_offset + 11..section5_offset + 15].copy_from_slice(&10f32.to_be_bytes());
    bytes[section5_offset + 15..section5_offset + 17].copy_from_slice(&0i16.to_be_bytes());
    bytes[section5_offset + 17..section5_offset + 19].copy_from_slice(&1i16.to_be_bytes());

    let opened = GribFile::from_bytes(bytes).unwrap();
    let decoded = opened
        .message(0)
        .unwrap()
        .read_data_as_f64()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<_>>();

    assert!((decoded[0] - 1.0).abs() < 1e-12);
    assert!((decoded[1] - 2.0).abs() < 1e-12);
    assert!((decoded[2] - 3.0).abs() < 1e-12);
    assert!((decoded[3] - 4.0).abs() < 1e-12);
}

#[test]
fn computes_valid_time_from_forecast_lead() {
    let opened =
        GribFile::from_bytes(build_grib2_message_with_forecast(&[1, 2, 3, 4], 18)).unwrap();
    let field = opened.message(0).unwrap();
    let valid = field.valid_time().unwrap();

    assert_eq!(field.forecast_time_unit(), Some(1));
    assert_eq!(
        field.forecast_time_unit_kind(),
        Some(ForecastTimeUnit::Hour)
    );
    assert_eq!(field.forecast_time(), Some(18));
    assert_eq!(valid.year, 2026);
    assert_eq!(valid.month, 3);
    assert_eq!(valid.day, 21);
    assert_eq!(valid.hour, 6);
    assert_eq!(valid.minute, 0);
    assert_eq!(valid.second, 0);
}

#[test]
fn computes_grib1_indicator_ten_valid_time_from_u16_lead() {
    let mut bytes = build_grib1_message(&[5, 6, 7, 8]);
    let pds_offset = 8;
    bytes[pds_offset + 18] = 0x01;
    bytes[pds_offset + 19] = 0x2c;
    bytes[pds_offset + 20] = 10;

    let opened = GribFile::from_bytes(bytes).unwrap();
    let field = opened.message(0).unwrap();
    let valid = field.valid_time().unwrap();

    assert_eq!(field.forecast_time_unit(), Some(1));
    assert_eq!(
        field.forecast_time_unit_kind(),
        Some(ForecastTimeUnit::Hour)
    );
    assert_eq!(field.forecast_time(), Some(300));
    assert_eq!(valid.year, 2026);
    assert_eq!(valid.month, 4);
    assert_eq!(valid.day, 2);
    assert_eq!(valid.hour, 0);
    assert_eq!(valid.minute, 0);
    assert_eq!(valid.second, 0);
}

#[test]
fn computes_grib1_quarter_hour_valid_time() {
    let mut bytes = build_grib1_message(&[5, 6, 7, 8]);
    let pds_offset = 8;
    bytes[pds_offset + 17] = 13;
    bytes[pds_offset + 18] = 2;
    bytes[pds_offset + 20] = 0;

    let opened = GribFile::from_bytes(bytes).unwrap();
    let field = opened.message(0).unwrap();
    let valid = field.valid_time().unwrap();

    assert_eq!(field.forecast_time_unit(), Some(13));
    assert_eq!(
        field.forecast_time_unit_kind(),
        Some(ForecastTimeUnit::QuarterHour)
    );
    assert_eq!(field.forecast_time(), Some(2));
    assert_eq!(valid.hour, 12);
    assert_eq!(valid.minute, 30);
    assert_eq!(valid.second, 0);
}

#[test]
fn computes_grib2_second_valid_time() {
    let mut bytes = build_grib2_message_with_forecast(&[1, 2, 3, 4], 30);
    let product_offset = 16 + 21 + 72;
    bytes[product_offset + 17] = 13;

    let opened = GribFile::from_bytes(bytes).unwrap();
    let field = opened.message(0).unwrap();
    let valid = field.valid_time().unwrap();

    assert_eq!(field.forecast_time_unit(), Some(13));
    assert_eq!(
        field.forecast_time_unit_kind(),
        Some(ForecastTimeUnit::Second)
    );
    assert_eq!(field.forecast_time(), Some(30));
    assert_eq!(valid.hour, 12);
    assert_eq!(valid.minute, 0);
    assert_eq!(valid.second, 30);
}

#[test]
fn opens_grib2_individual_ensemble_product_template() {
    let opened = GribFile::from_bytes(replace_grib2_product_section(
        build_grib2_message(&[1, 2, 3, 4]),
        product_section_template_one(),
    ))
    .unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.product_definition().unwrap().template_number(), 1);
    match &field.product_definition().unwrap().template {
        ProductDefinitionTemplate::IndividualEnsembleForecast(template) => {
            assert_eq!(template.type_of_ensemble_forecast, 1);
            assert_eq!(template.perturbation_number, 2);
            assert_eq!(template.number_of_forecasts_in_ensemble, 20);
        }
        other => panic!("expected template 4.1, got {other:?}"),
    }
    assert_eq!(
        field.read_flat_data_as_f64().unwrap(),
        vec![1.0, 2.0, 3.0, 4.0]
    );
}

#[test]
fn opens_grib2_statistical_process_product_template() {
    let opened = GribFile::from_bytes(replace_grib2_product_section(
        build_grib2_message(&[1, 2, 3, 4]),
        product_section_template_eight(),
    ))
    .unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.product_definition().unwrap().template_number(), 8);
    let valid = field.valid_time().unwrap();
    assert_eq!(valid.year, 2026);
    assert_eq!(valid.month, 3);
    assert_eq!(valid.day, 20);
    assert_eq!(valid.hour, 18);
    match &field.product_definition().unwrap().template {
        ProductDefinitionTemplate::StatisticalProcess(template) => {
            assert_eq!(template.time_ranges.len(), 1);
            assert_eq!(template.time_ranges[0].type_of_statistical_processing, 1);
            assert_eq!(template.time_ranges[0].time_range_length, 6);
        }
        other => panic!("expected template 4.8, got {other:?}"),
    }
}

#[test]
fn opens_grib2_ensemble_statistical_process_product_template() {
    let opened = GribFile::from_bytes(replace_grib2_product_section(
        build_grib2_message(&[1, 2, 3, 4]),
        product_section_template_eleven(),
    ))
    .unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.product_definition().unwrap().template_number(), 11);
    let valid = field.valid_time().unwrap();
    assert_eq!(valid.year, 2026);
    assert_eq!(valid.month, 3);
    assert_eq!(valid.day, 20);
    assert_eq!(valid.hour, 18);
    match &field.product_definition().unwrap().template {
        ProductDefinitionTemplate::EnsembleStatisticalProcess(template) => {
            assert_eq!(template.ensemble.perturbation_number, 3);
            assert_eq!(template.time_ranges.len(), 1);
        }
        other => panic!("expected template 4.11, got {other:?}"),
    }
}

#[test]
fn iterates_multifield_grib2_message() {
    let opened = GribFile::from_bytes(build_grib2_multifield_message()).unwrap();
    let names = opened
        .messages()
        .map(|message| message.parameter_name().to_owned())
        .collect::<Vec<_>>();
    assert_eq!(names, vec!["TMP", "POT"]);
}

#[test]
fn ncep_refc_resolves_from_builtin_local_table() {
    let mut bytes = build_grib2_message(&[1, 2, 3, 4]);
    set_grib2_identification(&mut bytes, 7, 0, 1);
    set_grib2_product_parameter(&mut bytes, 16, 196);

    let opened = GribFile::from_bytes(bytes).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.parameter_name(), "REFC");
    assert_eq!(
        field.parameter_description(),
        "Maximum/Composite radar reflectivity"
    );
    assert_eq!(
        field.parameter().source,
        ParameterTableSource::Local {
            center_id: 7,
            subcenter_id: 0,
            local_table_version: 1,
        }
    );
}

#[test]
fn unknown_local_grib2_parameter_remains_unknown_local() {
    let mut bytes = build_grib2_message(&[1, 2, 3, 4]);
    set_grib2_identification(&mut bytes, 8, 0, 1);
    set_grib2_product_parameter(&mut bytes, 16, 196);

    let opened = GribFile::from_bytes(bytes).unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.parameter_name(), "unknown");
    assert_eq!(field.parameter_description(), "Unknown parameter");
    assert_eq!(
        field.parameter().source,
        ParameterTableSource::UnknownLocal {
            center_id: 8,
            subcenter_id: 0,
            local_table_version: 1,
        }
    );
}

#[test]
fn caller_local_entries_resolve_unknown_center_local_parameters() {
    let mut bytes = build_grib2_message(&[1, 2, 3, 4]);
    set_grib2_identification(&mut bytes, 8, 0, 1);
    set_grib2_product_parameter(&mut bytes, 16, 196);

    let local_parameters = [LocalParameterEntry {
        center_id: 8,
        subcenter_id: Some(0),
        local_table_version: Some(1),
        discipline: 0,
        category: 16,
        number: 196,
        short_name: "LREFC",
        description: "Local composite reflectivity",
    }];
    let opened = GribFile::from_bytes_with_local_parameters(
        bytes,
        OpenOptions::default(),
        &local_parameters,
    )
    .unwrap();
    let field = opened.message(0).unwrap();

    assert_eq!(field.parameter_name(), "LREFC");
    assert_eq!(
        field.parameter_description(),
        "Local composite reflectivity"
    );
    assert_eq!(
        field.parameter().source,
        ParameterTableSource::Local {
            center_id: 8,
            subcenter_id: 0,
            local_table_version: 1,
        }
    );
}

#[test]
fn tolerant_open_skips_malformed_candidates() {
    let mut bytes = b"junkGRIB\x00\x00\x00\x02not-a-real-message".to_vec();
    bytes.extend_from_slice(&build_grib2_message(&[9, 8, 7, 6]));

    let opened = GribFile::from_bytes_with_options(
        bytes,
        OpenOptions {
            strict: false,
            ..OpenOptions::default()
        },
    )
    .unwrap();

    assert_eq!(opened.message_count(), 1);
    assert_eq!(
        opened
            .message(0)
            .unwrap()
            .read_data_as_f64()
            .unwrap()
            .iter()
            .copied()
            .collect::<Vec<_>>(),
        vec![9.0, 8.0, 7.0, 6.0]
    );
}

#[test]
fn tolerant_open_still_reports_unsupported_messages() {
    let mut bytes = build_grib2_message(&[1, 2, 3, 4]);
    let product_offset = 16 + 21 + 72;
    bytes[product_offset + 7..product_offset + 9].copy_from_slice(&99u16.to_be_bytes());
    bytes.extend_from_slice(&build_grib2_message(&[9, 8, 7, 6]));

    let err = match GribFile::from_bytes_with_options(
        bytes,
        OpenOptions {
            strict: false,
            ..OpenOptions::default()
        },
    ) {
        Ok(_) => panic!("expected unsupported product template error"),
        Err(err) => err,
    };

    assert!(matches!(err, Error::UnsupportedProductTemplate(99)));
}

#[test]
fn open_grib1_bitmap_field_ignores_padding_bits() {
    let opened = GribFile::from_bytes(build_grib1_message_with_bitmap(
        &[9, 7],
        3,
        1,
        Some(&[0b1011_1111]),
    ))
    .unwrap();

    let decoded = opened
        .message(0)
        .unwrap()
        .read_data_as_f64()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<_>>();
    assert_eq!(decoded.len(), 3);
    assert_eq!(decoded[0], 9.0);
    assert!(decoded[1].is_nan());
    assert_eq!(decoded[2], 7.0);
}

#[test]
fn open_grib2_complex_packing_field_and_decode() {
    let opened = GribFile::from_bytes(build_grib2_complex_packing_message()).unwrap();
    let decoded = opened
        .message(0)
        .unwrap()
        .read_data_as_f64()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<_>>();

    assert_eq!(decoded, vec![3.0, 4.0, 5.0, 9.0]);
}

#[test]
fn open_grib2_complex_packing_field_with_missing_values() {
    let opened = GribFile::from_bytes(build_grib2_complex_packing_message_with_missing()).unwrap();
    let decoded = opened
        .message(0)
        .unwrap()
        .read_data_as_f64()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<_>>();

    assert_eq!(decoded[0], 7.0);
    assert!(decoded[1].is_nan());
    assert_eq!(decoded[2], 9.0);
    assert!(decoded[3].is_nan());
}

#[test]
fn open_grib2_spatial_differencing_field_and_decode() {
    let opened = GribFile::from_bytes(build_grib2_spatial_differencing_message()).unwrap();
    let decoded = opened
        .message(0)
        .unwrap()
        .read_data_as_f64()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<_>>();

    assert_eq!(decoded, vec![10.0, 12.0, 15.0, 19.0]);
}

fn replace_grib2_product_section(mut bytes: Vec<u8>, section: Vec<u8>) -> Vec<u8> {
    let offset = grib2_section_offset(&bytes, 4);
    let old_len = u32::from_be_bytes(bytes[offset..offset + 4].try_into().unwrap()) as usize;
    bytes.splice(offset..offset + old_len, section);
    let total_len = bytes.len() as u64;
    bytes[8..16].copy_from_slice(&total_len.to_be_bytes());
    bytes
}

fn base_product_section() -> Vec<u8> {
    let bytes = build_grib2_message(&[1, 2, 3, 4]);
    let offset = grib2_section_offset(&bytes, 4);
    let len = u32::from_be_bytes(bytes[offset..offset + 4].try_into().unwrap()) as usize;
    bytes[offset..offset + len].to_vec()
}

fn product_section_template_one() -> Vec<u8> {
    let mut section = base_product_section();
    section.resize(37, 0);
    section[..4].copy_from_slice(&37u32.to_be_bytes());
    section[7..9].copy_from_slice(&1u16.to_be_bytes());
    section[34] = 1;
    section[35] = 2;
    section[36] = 20;
    section
}

fn product_section_template_eight() -> Vec<u8> {
    let mut section = base_product_section();
    section.resize(58, 0);
    section[..4].copy_from_slice(&58u32.to_be_bytes());
    section[7..9].copy_from_slice(&8u16.to_be_bytes());
    section[34..36].copy_from_slice(&2026u16.to_be_bytes());
    section[36] = 3;
    section[37] = 20;
    section[38] = 18;
    section[41] = 1;
    section[46] = 1;
    section[47] = 2;
    section[48] = 1;
    section[49..53].copy_from_slice(&6u32.to_be_bytes());
    section[53] = 255;
    section
}

fn product_section_template_eleven() -> Vec<u8> {
    let mut section = product_section_template_eight();
    section.resize(61, 0);
    section[..4].copy_from_slice(&61u32.to_be_bytes());
    section[7..9].copy_from_slice(&11u16.to_be_bytes());
    section.copy_within(34..58, 37);
    section[34] = 1;
    section[35] = 3;
    section[36] = 20;
    section
}

fn set_grib2_identification(
    bytes: &mut [u8],
    center_id: u16,
    subcenter_id: u16,
    local_table_version: u8,
) {
    let offset = grib2_section_offset(bytes, 1);
    bytes[offset + 5..offset + 7].copy_from_slice(&center_id.to_be_bytes());
    bytes[offset + 7..offset + 9].copy_from_slice(&subcenter_id.to_be_bytes());
    bytes[offset + 10] = local_table_version;
}

fn set_grib2_product_parameter(bytes: &mut [u8], category: u8, number: u8) {
    let offset = grib2_section_offset(bytes, 4);
    bytes[offset + 9] = category;
    bytes[offset + 10] = number;
}

fn grib2_section_offset(bytes: &[u8], section_number: u8) -> usize {
    let mut offset = 16;
    while offset + 5 <= bytes.len().saturating_sub(4) {
        let length = u32::from_be_bytes(bytes[offset..offset + 4].try_into().unwrap()) as usize;
        assert!(length >= 5, "invalid section length {length}");
        if bytes[offset + 4] == section_number {
            return offset;
        }
        offset += length;
    }

    panic!("section {section_number} not found");
}