cadmpeg-asm 0.6.1

// SPDX-License-Identifier: Apache-2.0

use crate::kernel_header::RefWidth;
use crate::nurbs::core::curve_cache;
use crate::nurbs::core::decode_curve_cache;
use crate::nurbs::core::decode_surface_cache;
use crate::nurbs::core::final_curve_patch_layout;
use crate::nurbs::core::final_surface_patch_layout;
use crate::nurbs::core::first_curve_patch_layout;
use crate::nurbs::core::surface_cache;
use crate::nurbs::core::surface_patch_layout_at;
use crate::nurbs::pcurve::tests::curve_block;
use crate::nurbs::pcurve::tests::curve_block_with_endpoint;
use crate::nurbs::pcurve::tests::pcurve_block;
use crate::nurbs::pcurve::tests::push_f64;
use crate::nurbs::pcurve::tests::push_ident;
use crate::nurbs::pcurve::tests::push_int;
use crate::nurbs::pcurve::tests::push_string;
use crate::nurbs::pcurve::tests::push_vector;
use crate::nurbs::pcurve::tests::surface_block;
use crate::nurbs::pcurve::tests::surface_block_with_x_offset;
use crate::nurbs::proc_curve::procedural_curve_resolving_refs;
use crate::nurbs::toks::lex_test_span;
use crate::nurbs::toks::test_table;

#[test]
fn curve_cache_decodes_in_both_integer_widths() {
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let block = curve_block(int_width);
        let curve = decode_curve_cache(&block)
            .unwrap_or_else(|| panic!("curve cache at width {int_width}"));
        assert_eq!(curve.degree(), 1);
        assert_eq!(curve.control_points().len(), 2);
        assert_eq!(curve.control_points()[1].x, 10.0); // cm→mm ×10
        assert_eq!(curve.knots().as_slice(), [0.0, 0.0, 1.0, 1.0]);
        assert!(first_curve_patch_layout(&block, int_width).is_some());
        assert!(final_curve_patch_layout(&block, int_width).is_some());
        let other_width = match int_width {
            RefWidth::Four => RefWidth::Eight,
            RefWidth::Eight => RefWidth::Four,
        };
        assert!(first_curve_patch_layout(&block, other_width).is_none());
        assert!(final_curve_patch_layout(&block, other_width).is_none());
    }
}

#[test]
fn generic_curve_and_pcurve_caches_withhold_multiple_candidates() {
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut curves = curve_block(int_width);
        curves.extend_from_slice(&curve_block(int_width));
        assert!(decode_curve_cache(&curves).is_none());

        let mut pcurves = pcurve_block(int_width);
        pcurves.extend_from_slice(&pcurve_block(int_width));
        assert!(super::decode_pcurve_cache(&pcurves).is_none());

        let block = pcurve_block(int_width);
        assert!(super::final_pcurve_patch_layout(&block, int_width).is_some());
        let other_width = match int_width {
            RefWidth::Four => RefWidth::Eight,
            RefWidth::Eight => RefWidth::Four,
        };
        assert!(super::final_pcurve_patch_layout(&block, other_width).is_none());

        let mut surfaces = b"comp_spl_sur".to_vec();
        surfaces.extend_from_slice(&surface_block(int_width));
        surfaces.extend_from_slice(&surface_block(int_width));
        assert!(decode_surface_cache(&surfaces).is_none());
    }
}

#[test]
fn wrapper_directrix_fields_reject_nested_curve_substitution() {
    let asm_decode_arena = cadmpeg_core::decode::DecodeArena::new();
    let (asm_decode_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &asm_decode_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut subset = vec![0x0f];
        push_ident(&mut subset, "subset_int_cur");
        subset.push(0x0f);
        push_ident(&mut subset, "support");
        subset.extend_from_slice(&curve_block(int_width));
        subset.push(0x10);
        push_f64(&mut subset, -1.0);
        push_f64(&mut subset, 2.0);
        subset.extend_from_slice(&curve_block(int_width));
        push_f64(&mut subset, 0.001);
        subset.push(0x10);
        let subset_tokens =
            lex_test_span(&subset, int_width).expect("valid single-record byte fixture");
        let subset_decoded = procedural_curve_resolving_refs(
            &asm_decode_ctx,
            &subset_tokens,
            &test_table(&subset, int_width).expect("valid single-record byte fixture"),
        )
        .transpose()
        .expect("resource allocation did not fail")
        .unwrap_or_else(|| panic!("nested subset source at width {int_width}"));
        assert!(!matches!(
            subset_decoded.construction,
            crate::nurbs::proc_curve::ProceduralCurveConstruction::Subset(_)
        ));

        let mut offset = vec![0x0f];
        push_ident(&mut offset, "offset_int_cur");
        offset.push(0x0b);
        offset.push(0x0f);
        push_ident(&mut offset, "support");
        offset.extend_from_slice(&curve_block(int_width));
        offset.push(0x10);
        push_f64(&mut offset, -1.0);
        push_f64(&mut offset, 2.0);
        push_vector(&mut offset, [1.0, 2.0, 3.0]);
        push_string(&mut offset, "first");
        push_int(&mut offset, 0x04, 4, int_width);
        push_string(&mut offset, "second");
        push_int(&mut offset, 0x04, 5, int_width);
        offset.extend_from_slice(&curve_block(int_width));
        push_f64(&mut offset, 0.001);
        offset.push(0x10);
        let offset_tokens =
            lex_test_span(&offset, int_width).expect("valid single-record byte fixture");
        let offset_decoded = procedural_curve_resolving_refs(
            &asm_decode_ctx,
            &offset_tokens,
            &test_table(&offset, int_width).expect("valid single-record byte fixture"),
        )
        .transpose()
        .expect("resource allocation did not fail")
        .unwrap_or_else(|| panic!("nested vector-offset source at width {int_width}"));
        assert!(!matches!(
            offset_decoded.construction,
            crate::nurbs::proc_curve::ProceduralCurveConstruction::VectorOffset(_)
        ));
    }
}

#[test]
fn pcurve_fit_tolerance_withholds_nested_only_cache() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exp_par_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&pcurve_block(int_width));
        push_f64(&mut bytes, 0.9);
        bytes.push(0x10);
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let scope = crate::nurbs::toks::subtype_span(&tokens, 0)
            .expect("the fixture opens one balanced scope");
        assert!(super::pcurve_fit_tolerance(&resource_ctx, scope).is_none());
    }
}

#[test]
fn patch_layout_roles_exclude_nested_construction_caches() {
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut surfaces = Vec::new();
        push_ident(&mut surfaces, "spline");
        surfaces.push(0x0f);
        push_ident(&mut surfaces, "auxiliary");
        surfaces.push(0x10);
        surfaces.push(0x0f);
        push_ident(&mut surfaces, "carrier");
        surfaces.extend_from_slice(&surface_block(int_width));
        let surface_end = surfaces.len();
        surfaces.push(0x0f);
        push_ident(&mut surfaces, "support");
        surfaces.extend_from_slice(&surface_block_with_x_offset(int_width, 9.0));
        surfaces.extend_from_slice(&[0x10, 0x10]);
        assert_eq!(
            final_surface_patch_layout(&surfaces, int_width)
                .expect("owned surface layout")
                .end(),
            surface_end
        );
        assert!(surface_patch_layout_at(&surfaces, 1, int_width).is_none());
        let mut ambiguous_surfaces = surfaces.clone();
        ambiguous_surfaces.push(0x0f);
        push_ident(&mut ambiguous_surfaces, "competing");
        ambiguous_surfaces.extend_from_slice(&surface_block(int_width));
        ambiguous_surfaces.push(0x10);
        assert!(final_surface_patch_layout(&ambiguous_surfaces, int_width).is_none());

        let mut curves = Vec::new();
        push_ident(&mut curves, "intcurve");
        curves.push(0x0f);
        push_ident(&mut curves, "auxiliary");
        curves.push(0x10);
        curves.push(0x0f);
        push_ident(&mut curves, "carrier");
        curves.extend_from_slice(&curve_block(int_width));
        let curve_end = curves.len();
        curves.push(0x0f);
        push_ident(&mut curves, "support");
        curves.extend_from_slice(&curve_block_with_endpoint(int_width, [9.0, 0.0, 0.0]));
        curves.extend_from_slice(&[0x10, 0x10]);
        assert_eq!(
            first_curve_patch_layout(&curves, int_width)
                .expect("first owned curve layout")
                .end(),
            curve_end
        );
        assert_eq!(
            final_curve_patch_layout(&curves, int_width)
                .expect("final owned curve layout")
                .end(),
            curve_end
        );

        let mut pcurves = Vec::new();
        push_ident(&mut pcurves, "pcurve");
        pcurves.push(0x0f);
        push_ident(&mut pcurves, "auxiliary");
        pcurves.push(0x10);
        pcurves.push(0x0f);
        push_ident(&mut pcurves, "carrier");
        pcurves.extend_from_slice(&pcurve_block(int_width));
        let pcurve_end = pcurves.len();
        pcurves.push(0x0f);
        push_ident(&mut pcurves, "support");
        pcurves.extend_from_slice(&pcurve_block(int_width));
        pcurves.extend_from_slice(&[0x10, 0x10]);
        assert_eq!(
            super::final_pcurve_patch_layout(&pcurves, int_width)
                .expect("final owned pcurve layout")
                .control_end(),
            pcurve_end
        );
    }
}

#[test]
fn surface_cache_decodes_in_both_integer_widths() {
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let block = surface_block(int_width);
        let surface = decode_surface_cache(&block)
            .unwrap_or_else(|| panic!("surface cache at width {int_width}"));
        assert_eq!((surface.u_degree(), surface.v_degree()), (1, 1));
        assert_eq!((surface.u_count(), surface.v_count()), (2, 2));
        assert!(final_surface_patch_layout(&block, int_width).is_some());
        let other_width = match int_width {
            RefWidth::Four => RefWidth::Eight,
            RefWidth::Eight => RefWidth::Four,
        };
        assert!(final_surface_patch_layout(&block, other_width).is_none());
    }
}

#[test]
fn token_curve_cache_ignores_nested_support_scope() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exact_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [2.0, 0.0, 0.0]));
        bytes.push(0x10);
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [7.0, 0.0, 0.0]));
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let curve = curve_cache(&resource_ctx, &tokens)
            .transpose()
            .expect("resource allocation")
            .unwrap_or_else(|| panic!("owned curve cache at width {int_width}"));

        assert!((curve.control_points()[1].x - 70.0).abs() < f64::EPSILON);
    }
}

#[test]
fn procedural_curve_cache_ignores_nested_support_scope() {
    let asm_decode_arena = cadmpeg_core::decode::DecodeArena::new();
    let (asm_decode_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &asm_decode_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "spring_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [2.0, 0.0, 0.0]));
        bytes.push(0x10);
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [7.0, 0.0, 0.0]));
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let decoded = procedural_curve_resolving_refs(
            &asm_decode_ctx,
            &tokens,
            &test_table(&bytes, int_width).expect("valid single-record byte fixture"),
        )
        .transpose()
        .expect("resource allocation did not fail")
        .unwrap_or_else(|| panic!("procedural curve at width {int_width}"));

        assert!((decoded.curve.control_points()[1].x - 70.0).abs() < f64::EPSILON);
    }
}

#[test]
fn procedural_curve_with_only_nested_cache_is_withheld() {
    let asm_decode_arena = cadmpeg_core::decode::DecodeArena::new();
    let (asm_decode_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &asm_decode_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "spring_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block(int_width));
        bytes.push(0x10);
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");

        assert!(procedural_curve_resolving_refs(
            &asm_decode_ctx,
            &tokens,
            &test_table(&bytes, int_width).expect("valid single-record byte fixture")
        )
        .transpose()
        .expect("resource allocation did not fail")
        .is_none());
    }
}

#[test]
fn token_surface_cache_ignores_later_nested_support_scope() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "off_spl_sur");
        bytes.extend_from_slice(&surface_block_with_x_offset(int_width, 5.0));
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&surface_block_with_x_offset(int_width, 9.0));
        bytes.push(0x10);
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let surface = surface_cache(&resource_ctx, &tokens)
            .transpose()
            .expect("resource allocation")
            .unwrap_or_else(|| panic!("owned surface cache at width {int_width}"));

        assert!((surface.poles()[0].x - 50.0).abs() < f64::EPSILON);
    }
}

/// `docs/formats/asm.md` states construction-cache ownership: "the outer
/// non-`ref` procedural subtype owns the record's solved curve or surface
/// cache". Two cache-bearing owned scopes name no single owner, so the record
/// states no cache and every route that reads one refuses. The record's own
/// stream is not a second answer.
#[test]
fn two_cache_bearing_owned_scopes_state_no_record_cache() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    let asm_decode_arena = cadmpeg_core::decode::DecodeArena::new();
    let (asm_decode_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &asm_decode_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exact_int_cur");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [2.0, 0.0, 0.0]));
        bytes.push(0x10);
        bytes.push(0x0f);
        push_ident(&mut bytes, "exact_int_cur");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [7.0, 0.0, 0.0]));
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        assert!(crate::nurbs::toks::cache_scope(&resource_ctx, &tokens)
            .transpose()
            .unwrap()
            .is_none());
        assert!(curve_cache(&resource_ctx, &tokens).is_none());
        assert!(procedural_curve_resolving_refs(
            &asm_decode_ctx,
            &tokens,
            &test_table(&bytes, int_width).expect("valid single-record byte fixture")
        )
        .transpose()
        .expect("resource allocation did not fail")
        .is_none());

        let mut surfaces = vec![0x0f];
        push_ident(&mut surfaces, "off_spl_sur");
        surfaces.extend_from_slice(&surface_block_with_x_offset(int_width, 5.0));
        surfaces.push(0x10);
        surfaces.push(0x0f);
        push_ident(&mut surfaces, "off_spl_sur");
        surfaces.extend_from_slice(&surface_block_with_x_offset(int_width, 9.0));
        surfaces.push(0x10);

        let surface_tokens =
            lex_test_span(&surfaces, int_width).expect("valid single-record byte fixture");
        assert!(
            crate::nurbs::toks::cache_scope(&resource_ctx, &surface_tokens)
                .transpose()
                .unwrap()
                .is_none()
        );
        assert!(surface_cache(&resource_ctx, &surface_tokens).is_none());
    }
}

/// A record that owns a construction whose scopes bear no B-spline marker
/// states no cache: the blocks that remain belong to nested support, source,
/// guide or child fields, which the ownership sentence excludes.
#[test]
fn a_construction_with_no_cache_bearing_owned_scope_states_no_record_cache() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "spring_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block(int_width));
        bytes.push(0x10);
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        assert!(crate::nurbs::toks::cache_scope(&resource_ctx, &tokens)
            .transpose()
            .unwrap()
            .is_none());
        assert!(curve_cache(&resource_ctx, &tokens).is_none());
        assert!(surface_cache(&resource_ctx, &tokens).is_none());
    }
}

/// A record that owns no non-`ref` subtype states no construction, so no
/// construction's ownership rule applies to its blocks and its own stream is
/// the cache span.
#[test]
fn a_record_with_no_construction_carries_its_cache_in_its_own_stream() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let bytes = curve_block(int_width);
        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");

        assert_eq!(
            crate::nurbs::toks::cache_scope(&resource_ctx, &tokens)
                .transpose()
                .unwrap(),
            Some(&tokens[..])
        );
        let curve = curve_cache(&resource_ctx, &tokens)
            .transpose()
            .expect("resource allocation")
            .unwrap_or_else(|| panic!("record-stream curve cache at width {int_width}"));
        assert_eq!(curve.degree(), 1);
    }
}

/// The token-space owned-cache decoder reads the scope, not a raw stream.
/// `subtype_span` is its only source, so the balance the raw walk refuses is a
/// state the argument cannot hold and the decoder states no refusal for it.
#[test]
fn a_token_scope_decodes_the_curve_cache_it_owns_through_the_scope_type() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exact_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [2.0, 0.0, 0.0]));
        bytes.push(0x10);
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [7.0, 0.0, 0.0]));
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let scope = crate::nurbs::toks::subtype_span(&tokens, 0).expect("balanced scope");
        let curve = crate::nurbs::core::owned_curve_cache(&resource_ctx, scope)
            .transpose()
            .expect("resource allocation")
            .unwrap_or_else(|| panic!("owned curve cache at width {int_width}"));

        assert!((curve.control_points()[1].x - 70.0).abs() < f64::EPSILON);
    }
}

/// The byte-space owned-cache decoder reads the scope, not a raw stream.
#[test]
fn a_byte_scope_decodes_the_curve_cache_it_owns_through_the_scope_type() {
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exact_int_cur");
        bytes.push(0x0f);
        push_ident(&mut bytes, "support");
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [2.0, 0.0, 0.0]));
        bytes.push(0x10);
        bytes.extend_from_slice(&curve_block_with_endpoint(int_width, [7.0, 0.0, 0.0]));
        bytes.push(0x10);

        let scope =
            crate::nurbs::subtypes::subtype_span(&bytes, 0, int_width).expect("balanced scope");
        let curve = crate::nurbs::core::decode_owned_curve_cache_at(scope, int_width)
            .unwrap_or_else(|| panic!("owned curve cache at width {int_width}"));

        assert!((curve.control_points()[1].x - 70.0).abs() < f64::EPSILON);
    }
}

/// The explicit-pcurve decoder reads an `exp_par_cur` scope, not a raw stream.
/// `subtype_span` and `payload_subtype_toks` are its only sources, so the
/// unbalanced stream the free walk refuses is a state the argument cannot hold.
#[test]
fn an_exp_par_cur_scope_decodes_its_own_bs2_field_through_the_scope_type() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut bytes = vec![0x0f];
        push_ident(&mut bytes, "exp_par_cur");
        bytes.extend_from_slice(&pcurve_block(int_width));
        bytes.push(0x10);

        let tokens = lex_test_span(&bytes, int_width).expect("valid single-record byte fixture");
        let scope = crate::nurbs::toks::subtype_span(&tokens, 0).expect("balanced scope");
        let pcurve = crate::nurbs::pcurve::explicit_pcurve_cache(&resource_ctx, scope)
            .transpose()
            .expect("resource allocation")
            .unwrap_or_else(|| panic!("explicit pcurve cache at width {int_width}"));

        assert_eq!(pcurve.degree(), 1);
        assert_eq!(pcurve.knots().as_slice(), [0.0, 0.0, 1.0, 1.0]);
    }
}

/// Each subtype definition contributes one table entry in stream order, so an
/// index at or beyond the table's length names no definition the stream states
/// (`docs/formats/asm.md`). The decoder's decision at such an index: the
/// reference search refuses the stream there and does not go on to the
/// resolvable reference behind it.
#[test]
fn an_unresolvable_subtype_reference_refuses_the_search_behind_it() {
    let resource_arena = cadmpeg_core::decode::DecodeArena::new();
    let (resource_ctx, _) = cadmpeg_core::decode::DecodeContext::from_root_bytes(
        &[],
        &resource_arena,
        &cadmpeg_core::decode::DecodePolicy::default(),
    )
    .expect("test decode context");
    for int_width in [RefWidth::Four, RefWidth::Eight] {
        let mut definition = vec![0x0f];
        push_ident(&mut definition, "exact_int_cur");
        definition.extend_from_slice(&curve_block(int_width));
        definition.push(0x10);

        let mut references = vec![0x0f];
        push_ident(&mut references, "ref");
        push_int(&mut references, 0x04, 99, int_width);
        references.push(0x10);
        references.push(0x0f);
        push_ident(&mut references, "ref");
        push_int(&mut references, 0x04, 0, int_width);
        references.push(0x10);

        let definition_tokens =
            lex_test_span(&definition, int_width).expect("valid single-record byte fixture");
        let reference_tokens =
            lex_test_span(&references, int_width).expect("valid single-record byte fixture");
        let records = [
            crate::sab::Record {
                index: 0,
                name: String::new(),
                tokens: definition_tokens,
                offset: 0,
                len: 0,
            },
            crate::sab::Record {
                index: 1,
                name: String::new(),
                tokens: reference_tokens.clone(),
                offset: 0,
                len: 0,
            },
        ];
        let table =
            crate::nurbs::toks::SubtypeTable::from_records(&resource_ctx, &records).unwrap();

        // Entry zero is the cache-bearing definition, and the record states
        // `{ref 99}` before `{ref 0}`.
        assert!(table.span(0).is_some());
        assert!(table.span(99).is_none());
        assert!(
            crate::nurbs::core::curve_cache_resolving_refs(
                &resource_ctx,
                &reference_tokens,
                &table
            )
            .is_none(),
            "the unresolvable reference at width {int_width} must refuse the search"
        );
    }
}