cadmpeg-asm 0.6.2

// SPDX-License-Identifier: Apache-2.0
//! Core cached B-spline surface and curve block decoding and their writer-facing patch layouts.
//!
//! The token-space functions decode model values from framed payload tokens
//! and serve the decode path. The byte-space functions additionally record
//! native payload offsets and serve the retained-source patch writer, which
//! edits the original binary stream in place and is therefore byte-addressed
//! by nature.

use crate::kernel_header::RefWidth;
use crate::nurbs::reader::{
    construction_marker_positions, is_periodic, marker_at, marker_positions, read_control_points,
    read_knots, take_tagged_int, BsplineMarker, KnotLayout, ReadPoles3, INT_WIDTHS, LEN_TO_MM,
};
use crate::nurbs::subtypes;
use crate::nurbs::toks;
use crate::nurbs::toks::Cur;
use crate::sab::Token;
use cadmpeg_ir::geometry::nurbs::{NurbsCurve, NurbsSurface, NurbsSurfaceAxis};
use cadmpeg_ir::math::Point3;

use crate::nurbs::toks::take_knot_table as knots;

const MAX_RECOVERY_SURFACE_POLES: u64 = 200_000;

macro_rules! propagate_resource {
    ($result:expr) => {
        match $result {
            Ok(value) => value,
            Err(error) => return Some(Err(error)),
        }
    };
}

/// Read `count` control points in the marker-selected form, scaling positions to
/// millimetres. Token-space counterpart of [`read_control_points`].
fn control_points(cur: &mut Cur<'_>, count: usize, marker: BsplineMarker) -> Option<ReadPoles3> {
    let mut poles = ReadPoles3::empty(marker.rational());
    for _ in 0..count {
        let mut comps = [0.0f64; 4];
        for comp in comps.iter_mut().take(marker.cp_dims()) {
            *comp = cur.take_f64()?;
        }
        poles.push(
            Point3::new(
                comps[0] * LEN_TO_MM,
                comps[1] * LEN_TO_MM,
                comps[2] * LEN_TO_MM,
            ),
            comps[3],
        )?;
    }
    Some(poles)
}

/// Decode a surface `nubs`/`nurbs` block at token `marker_pos`, returning the
/// surface and the token index just past the block. Token-space counterpart of
/// [`decode_surface_block`].
pub(super) fn surface_block(toks: &[Token], marker_pos: usize) -> Option<(NurbsSurface, usize)> {
    let marker = toks::marker_at(toks, marker_pos)?;
    let mut cur = Cur::at(toks, marker_pos + 1);

    let degree_u = cur.take_long()?;
    let degree_v = cur.take_long()?;
    if !(1..=20).contains(&degree_u) || !(1..=20).contains(&degree_v) {
        return None;
    }
    // Some caches carry an optional scope identifier (`u`/`v`/`both`) before
    // the enum block; skip it so knot counts stay aligned.
    if matches!(cur.peek(), Some(Token::Ident(_))) {
        cur.bump();
    }
    let mut enums = [0i64; 4];
    for e in &mut enums {
        *e = cur.take_enum()?;
    }
    let n_uniq_u = cur.take_long()?;
    let n_uniq_v = cur.take_long()?;
    if n_uniq_u < 1 || n_uniq_v < 1 {
        return None;
    }

    let (u_knots, n_poles_u) = knots(&mut cur, usize::try_from(n_uniq_u).ok()?, degree_u)?;
    let (v_knots, n_poles_v) = knots(&mut cur, usize::try_from(n_uniq_v).ok()?, degree_v)?;
    // A larger cached grid is not recovered; the surface keeps its native
    // carrier, as in the binary path.
    let pole_count = n_poles_u.checked_mul(n_poles_v)?;
    if cadmpeg_core::decode::u64_from_index(pole_count) > MAX_RECOVERY_SURFACE_POLES {
        return None;
    }

    // Grid is stored v-major (v outer, u inner); transpose to the IR's u-major
    // order where index `u * v_count + v` is pole `(u, v)`.
    let poles = control_points(&mut cur, pole_count, marker)?;
    let grid = poles.into_counted_transposed_grid(n_poles_u, n_poles_v)?;
    let surface = NurbsSurface::new(
        NurbsSurfaceAxis::new(
            u32::try_from(degree_u).ok()?,
            u_knots,
            is_periodic(enums[0]),
        ),
        NurbsSurfaceAxis::new(
            u32::try_from(degree_v).ok()?,
            v_knots,
            is_periodic(enums[1]),
        ),
        grid,
        false,
    )
    .ok()?;
    Some((surface, cur.pos()))
}

/// Decode a curve `nubs`/`nurbs` block at token `marker_pos`, returning the
/// curve and the token index just past the block. Token-space counterpart of
/// [`decode_curve_block`].
pub(super) fn curve_block(toks: &[Token], marker_pos: usize) -> Option<(NurbsCurve, usize)> {
    let marker = toks::marker_at(toks, marker_pos)?;
    let mut cur = Cur::at(toks, marker_pos + 1);

    let degree = cur.take_long()?;
    if !(1..=20).contains(&degree) {
        return None;
    }
    let closure = cur.take_enum()?;
    let n_uniq = cur.take_long()?;
    if n_uniq < 1 {
        return None;
    }
    let (knot_vector, n_poles) = knots(&mut cur, usize::try_from(n_uniq).ok()?, degree)?;
    let poles = control_points(&mut cur, n_poles, marker)?;

    let curve = NurbsCurve::new(
        u32::try_from(degree).ok()?,
        knot_vector,
        poles.into_lane(),
        is_periodic(closure),
    )
    .ok()?;
    Some((curve, cur.pos()))
}

/// Decode the face-surface cache of a spline surface record from its payload
/// tokens: the LAST valid surface block (the final `setSurfaceShape` cache;
/// earlier blocks are support surfaces or 2D pcurves), except in a
/// `comp_spl_sur` compound, whose own cache comes first.
pub(super) fn surface_cache(toks: &[Token]) -> Option<NurbsSurface> {
    let scope = toks::cache_scope(toks)?;
    let positions = toks::owned_marker_positions(scope)?;
    let compound = scope.iter().any(|token| {
        matches!(token, Token::Ident(name) | Token::SubIdent(name) if name == "comp_spl_sur")
    });
    if compound {
        positions
            .into_iter()
            .find_map(|pos| surface_block(scope, pos).map(|(surface, _)| surface))
    } else {
        positions
            .into_iter()
            .rev()
            .find_map(|pos| surface_block(scope, pos).map(|(surface, _)| surface))
    }
}

/// Decode a subtype's own surface cache. Variable blends select the cache
/// clause read by their grammar; an inline support is a separate surface.
pub(super) fn owned_surface_cache(
    ctx: &cadmpeg_core::decode::DecodeContext<'_>,
    scope: toks::SubtypeScope<'_>,
    table: Option<&toks::SubtypeTable>,
) -> Option<Result<NurbsSurface, cadmpeg_core::CodecError>> {
    let tokens = scope.tokens();
    if matches!(scope.interior().first(), Some(Token::Ident(name) | Token::SubIdent(name))
        if crate::nurbs::blend::VARIABLE_BLEND_NAMES.contains(&name.as_str()))
    {
        let _depth = propagate_resource!(ctx.enter_nested("admit ASM variable-blend cache"));
        let cache_marker = propagate_resource!(crate::nurbs::blend::var_blend_spl_sur(
            ctx,
            tokens,
            table,
            crate::nurbs::blend::SupportCaches::Skip,
        )
        .transpose()
        .map(|decoded| decoded.and_then(|decoded| decoded.current_cache_marker)));
        return surface_block(tokens, cache_marker?).map(|(surface, _)| Ok(surface));
    }
    scope
        .owned_marker_positions()
        .into_iter()
        .find_map(|pos| surface_block(tokens, pos).map(|(surface, _)| Ok(surface)))
}

/// Decode the 3D curve cache of a procedural curve record from its payload
/// tokens: the FIRST valid curve block (surface and 2D pcurve blocks do not
/// parse as a 3D curve block).
pub(super) fn curve_cache(toks: &[Token]) -> Option<NurbsCurve> {
    let scope = toks::cache_scope(toks)?;
    toks::owned_marker_positions(scope)?
        .into_iter()
        .find_map(|pos| curve_block(scope, pos).map(|(curve, _)| curve))
}

/// Decode the 3D curve cache a subtype scope itself owns: the first curve
/// block outside every construction the scope nests.
pub(super) fn owned_curve_cache(scope: toks::SubtypeScope<'_>) -> Option<NurbsCurve> {
    let tokens = scope.tokens();
    scope
        .owned_marker_positions()
        .into_iter()
        .find_map(|pos| curve_block(tokens, pos).map(|(curve, _)| curve))
}

/// A scope either supplies a cache, allows a reference search, or rejects
/// cache recovery. Rejection must not substitute one of its support caches.
enum CacheLookup<T> {
    Found(T),
    Missing,
    Rejected,
}

/// Decode the cache of each scope the `{ref N}` references in `toks` reach,
/// depth first in stream order. A visited set breaks reference cycles.
///
/// [`toks::SubtypeTable::span`] answers with the balanced scope the reference
/// names, so `decode_scope` reads a proven scope and needs no walk of its own
/// to establish one.
fn cache_from_subtype_refs<T, E>(
    toks: &[Token],
    table: &toks::SubtypeTable,
    decode_scope: impl Fn(toks::SubtypeScope<'_>) -> Result<CacheLookup<T>, E>,
) -> Option<Result<T, E>> {
    let mut seen = std::collections::HashSet::new();
    let mut pending = Vec::new();
    pending.push(toks::subtype_refs(toks));
    while let Some(references) = pending.last_mut() {
        let Some(index) = references.next() else {
            pending.pop();
            continue;
        };
        if !seen.insert(index) {
            continue;
        }
        // The doc states what the index means. `docs/formats/asm.md`: "A named
        // `ref N` scope or compact `0x0F LONG N 0x10` scope nested inside a
        // surface, curve, or pcurve body indexes a per-file subtype table, not
        // a byte offset. Each subtype definition -- a `0x0F` opening followed
        // by a `0x0d`/`0x0e` name token other than `ref` -- contributes one
        // table entry in stream order." An index at or beyond the table's
        // length therefore names no definition the stream states. What the
        // decoder does about it is the decoder's decision: the search refuses
        // the stream rather than skipping the reference and reading the one
        // behind it.
        let target = table.span(index)?;
        match decode_scope(target) {
            Ok(CacheLookup::Found(decoded)) => return Some(Ok(decoded)),
            Ok(CacheLookup::Rejected) => return None,
            Ok(CacheLookup::Missing) => {}
            Err(error) => return Some(Err(error)),
        }
        pending.push(toks::subtype_refs(target.tokens()));
    }
    None
}

/// Decode a surface cache, following subtype-table references.
pub fn surface_cache_resolving_refs(
    ctx: &cadmpeg_core::decode::DecodeContext<'_>,
    toks: &[Token],
    table: &toks::SubtypeTable,
) -> Option<Result<NurbsSurface, cadmpeg_core::CodecError>> {
    if let Some((start, _)) =
        toks::find_owned_subtype_marker(toks, crate::nurbs::blend::VARIABLE_BLEND_NAMES)
    {
        return owned_surface_cache(ctx, toks::subtype_span(toks, start)?, Some(table));
    }
    surface_cache(toks).map(Ok).or_else(|| {
        cache_from_subtype_refs(toks, table, |scope| {
            if matches!(scope.interior().first(), Some(Token::Ident(name) | Token::SubIdent(name))
                if crate::nurbs::blend::VARIABLE_BLEND_NAMES.contains(&name.as_str()))
            {
                owned_surface_cache(ctx, scope, Some(table))
                    .transpose()
                    .map(|cache| cache.map_or(CacheLookup::Rejected, CacheLookup::Found))
            } else {
                Ok(surface_cache(scope.tokens()).map_or(CacheLookup::Missing, CacheLookup::Found))
            }
        })
    })
}

/// Read the owned cache, resolving a direct subtype-table alias.
pub(super) fn owned_surface_cache_resolving_refs(
    ctx: &cadmpeg_core::decode::DecodeContext<'_>,
    scope: toks::SubtypeScope<'_>,
    table: &toks::SubtypeTable,
) -> Option<Result<NurbsSurface, cadmpeg_core::CodecError>> {
    if let Some(cache) = owned_surface_cache(ctx, scope, Some(table)) {
        return Some(cache);
    }
    // Only a reference scope aliases another construction. References inside
    // a named construction are its supports or guides, whose caches use their
    // own parameter charts and cannot stand in for the owner's missing cache.
    let index = match scope.interior() {
        [Token::Ident(name), Token::Long(index)] if name == "ref" => *index,
        [Token::Long(index)] => *index,
        _ => return None,
    };
    let target = table.span(usize::try_from(index).ok()?)?;
    owned_surface_cache(ctx, target, Some(table))
}

/// Decode a curve cache, following subtype-table references.
pub fn curve_cache_resolving_refs(
    toks: &[Token],
    table: &toks::SubtypeTable,
) -> Option<NurbsCurve> {
    curve_cache(toks).or_else(|| {
        let Ok(curve) = cache_from_subtype_refs(toks, table, |scope| {
            Ok::<_, std::convert::Infallible>(
                curve_cache(scope.tokens()).map_or(CacheLookup::Missing, CacheLookup::Found),
            )
        })?;
        Some(curve)
    })
}

/// [`owned_curve_cache`], following subtype-table references.
pub(super) fn owned_curve_cache_resolving_refs(
    scope: toks::SubtypeScope<'_>,
    table: &toks::SubtypeTable,
) -> Option<NurbsCurve> {
    owned_curve_cache(scope).or_else(|| {
        let Ok(curve) = cache_from_subtype_refs(scope.tokens(), table, |scope| {
            Ok::<_, std::convert::Infallible>(
                owned_curve_cache(scope).map_or(CacheLookup::Missing, CacheLookup::Found),
            )
        })?;
        Some(curve)
    })
}

/// Decode a surface `nubs`/`nurbs` block at `marker_pos`, or `None` if the bytes
/// there are not a well-formed surface block.
pub struct SurfacePatchLayout {
    /// Decoded surface cache.
    pub surface: NurbsSurface,
    control_start: usize,
    /// Native payload offsets for U knots.
    pub u_knots: KnotLayout,
    /// Native payload offsets for V knots.
    pub v_knots: KnotLayout,
    /// Payload offsets for the U/V closure enums.
    pub periodic_value_offsets: [usize; 2],
    /// Payload offsets for the U/V degree integers.
    pub degree_value_offsets: [usize; 2],
}

impl SurfacePatchLayout {
    /// Offset immediately after the final control component.
    pub fn end(&self) -> usize {
        self.control_start + self.control_value_offsets().len() * 9
    }

    /// Native v-major tagged-double payload offsets, excluding each tag byte.
    pub fn control_value_offsets(&self) -> impl ExactSizeIterator<Item = usize> + '_ {
        let components = if self.surface.weights().is_some() {
            4
        } else {
            3
        };
        (0..self.surface.poles().len() * components)
            .map(|ordinal| self.control_start + ordinal * 9 + 1)
    }
}

pub(super) fn decode_surface_block(
    b: &[u8],
    marker_pos: usize,
    int_width: RefWidth,
) -> Option<SurfacePatchLayout> {
    // Byte-addressed patch inspection uses an independent desktop writer policy.
    let marker = marker_at(b, marker_pos)?;
    let mut pos = marker_pos + marker.byte_len();

    let degree_u_offset = pos + 1;
    let degree_u = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    let degree_v_offset = pos + 1;
    let degree_v = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    if !(1..=20).contains(&degree_u) || !(1..=20).contains(&degree_v) {
        return None;
    }
    // Some caches carry an optional scope identifier (`u`/`v`/`both`) before the
    // enum block; skip it so knot counts stay aligned.
    if b.get(pos) == Some(&0x0d) {
        let len = usize::from(*b.get(pos + 1)?);
        pos += 2 + len;
    }
    let mut enums = [0i64; 4];
    let mut enum_value_offsets = [0usize; 4];
    for (ordinal, e) in enums.iter_mut().enumerate() {
        enum_value_offsets[ordinal] = pos + 1;
        *e = take_tagged_int(b, &mut pos, 0x15, int_width)?;
    }
    let n_uniq_u = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    let n_uniq_v = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    if n_uniq_u < 1 || n_uniq_v < 1 {
        return None;
    }

    let (u_knots, n_poles_u, u_knot_layout) = read_knots(
        b,
        &mut pos,
        usize::try_from(n_uniq_u).ok()?,
        degree_u,
        int_width,
    )?;
    let (v_knots, n_poles_v, v_knot_layout) = read_knots(
        b,
        &mut pos,
        usize::try_from(n_uniq_v).ok()?,
        degree_v,
        int_width,
    )?;
    if n_poles_u.checked_mul(n_poles_v).is_none_or(|n| n > 200_000) {
        return None;
    }

    // Grid is stored v-major (v outer, u inner); transpose to the IR's u-major
    // order where index `u * v_count + v` is pole `(u, v)`.
    let control_start = pos;
    let poles = read_control_points(b, &mut pos, n_poles_u * n_poles_v, marker)?;
    let grid = poles.into_transposed_grid(n_poles_u, n_poles_v)?;
    let surface = NurbsSurface::new(
        NurbsSurfaceAxis::new(
            u32::try_from(degree_u).ok()?,
            u_knots,
            is_periodic(enums[0]),
        ),
        NurbsSurfaceAxis::new(
            u32::try_from(degree_v).ok()?,
            v_knots,
            is_periodic(enums[1]),
        ),
        grid,
        false,
    )
    .ok()?;
    Some(SurfacePatchLayout {
        surface,
        control_start,
        u_knots: u_knot_layout,
        v_knots: v_knot_layout,
        periodic_value_offsets: [enum_value_offsets[0], enum_value_offsets[1]],
        degree_value_offsets: [degree_u_offset, degree_v_offset],
    })
}

/// Locate the final valid `nubs`/`nurbs` surface block at the stream's known
/// integer width.
pub fn final_surface_patch_layout(
    record: &[u8],
    int_width: RefWidth,
) -> Option<SurfacePatchLayout> {
    construction_marker_positions(record, int_width)?
        .into_iter()
        .filter_map(|position| decode_surface_block(record, position, int_width))
        .next_back()
}

/// Locate the surface block at `ordinal` among valid surface caches at the
/// stream's known integer width.
pub fn surface_patch_layout_at(
    record: &[u8],
    ordinal: usize,
    int_width: RefWidth,
) -> Option<SurfacePatchLayout> {
    construction_marker_positions(record, int_width)?
        .into_iter()
        .filter_map(|position| decode_surface_block(record, position, int_width))
        .nth(ordinal)
}

/// Decode a curve `nubs`/`nurbs` block at `marker_pos`, or `None` if the bytes
/// there are not a well-formed 3D curve block.
pub struct CurvePatchLayout {
    /// Decoded curve cache.
    pub curve: NurbsCurve,
    control_start: usize,
    /// Native unique-knot payloads.
    pub knots: KnotLayout,
    /// Payload offset for the closure enum.
    pub periodic_value_offset: usize,
    /// Payload offset for the degree integer.
    pub degree_value_offset: usize,
}

impl CurvePatchLayout {
    /// Offset immediately after the final control component.
    pub fn end(&self) -> usize {
        self.control_start + self.control_value_offsets().len() * 9
    }

    /// Tagged-double payload offsets in pole/component order.
    pub fn control_value_offsets(&self) -> impl ExactSizeIterator<Item = usize> + '_ {
        let components = if self.curve.weights().is_some() { 4 } else { 3 };
        (0..self.curve.control_points().len() * components)
            .map(|ordinal| self.control_start + ordinal * 9 + 1)
    }
}

pub(super) fn decode_curve_block(
    b: &[u8],
    marker_pos: usize,
    int_width: RefWidth,
) -> Option<CurvePatchLayout> {
    // Byte-addressed patch inspection uses an independent desktop writer policy.
    let marker = marker_at(b, marker_pos)?;
    let mut pos = marker_pos + marker.byte_len();

    let degree_value_offset = pos + 1;
    let degree = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    if !(1..=20).contains(&degree) {
        return None;
    }
    let periodic_value_offset = pos + 1;
    let closure = take_tagged_int(b, &mut pos, 0x15, int_width)?;
    let n_uniq = take_tagged_int(b, &mut pos, 0x04, int_width)?;
    if n_uniq < 1 {
        return None;
    }
    let (knots, n_poles, knot_layout) = read_knots(
        b,
        &mut pos,
        usize::try_from(n_uniq).ok()?,
        degree,
        int_width,
    )?;
    let control_start = pos;
    let poles = read_control_points(b, &mut pos, n_poles, marker)?;

    let curve = NurbsCurve::new(
        u32::try_from(degree).ok()?,
        knots,
        poles.into_lane(),
        is_periodic(closure),
    )
    .ok()?;
    Some(CurvePatchLayout {
        curve,
        control_start,
        knots: knot_layout,
        periodic_value_offset,
        degree_value_offset,
    })
}

/// Locate the first valid 3D curve cache at the stream's known integer width.
pub fn first_curve_patch_layout(record: &[u8], int_width: RefWidth) -> Option<CurvePatchLayout> {
    construction_marker_positions(record, int_width)?
        .into_iter()
        .find_map(|position| decode_curve_block(record, position, int_width))
}

/// Locate the final valid 3D curve cache at the stream's known integer width.
pub fn final_curve_patch_layout(record: &[u8], int_width: RefWidth) -> Option<CurvePatchLayout> {
    construction_marker_positions(record, int_width)?
        .into_iter()
        .filter_map(|position| decode_curve_block(record, position, int_width))
        .next_back()
}

/// Decode the unique well-formed surface cache across both integer widths.
///
/// This generic entry point has no stream-width, owning-scope, or family-role
/// witness. It therefore withholds when more than one `(width, marker)`
/// candidate decodes.
pub fn decode_surface_cache(record_bytes: &[u8]) -> Option<NurbsSurface> {
    decode_unique_cache(record_bytes, |bytes, position, width| {
        decode_surface_block(bytes, position, width).map(|candidate| candidate.surface)
    })
}

/// Decode the surface cache a subtype scope itself owns: the first surface
/// block outside every construction the scope nests. A scope whose supports are
/// nested constructions carries their caches too, and those are not its own.
pub(super) fn decode_owned_surface_cache_at(
    scope: subtypes::SubtypeScope<'_>,
    int_width: RefWidth,
) -> Option<NurbsSurface> {
    let bytes = scope.bytes();
    scope
        .owned_marker_positions(int_width)
        .into_iter()
        .find_map(|pos| decode_surface_block(bytes, pos, int_width).map(|decoded| decoded.surface))
}

/// Decode the unique well-formed 3D curve cache across both integer widths.
///
/// This generic entry point has no stream-width or owning-scope witness. It
/// therefore withholds when more than one `(width, marker)` candidate decodes.
pub fn decode_curve_cache(record_bytes: &[u8]) -> Option<NurbsCurve> {
    decode_unique_cache(record_bytes, |bytes, position, width| {
        decode_curve_block(bytes, position, width).map(|candidate| candidate.curve)
    })
}

/// Decode the 3D curve cache a subtype scope itself owns: the first curve block
/// outside every construction the scope nests.
pub fn decode_owned_curve_cache_at(
    scope: subtypes::SubtypeScope<'_>,
    int_width: RefWidth,
) -> Option<NurbsCurve> {
    let bytes = scope.bytes();
    scope
        .owned_marker_positions(int_width)
        .into_iter()
        .find_map(|pos| decode_curve_block(bytes, pos, int_width).map(|decoded| decoded.curve))
}

fn decode_unique_cache<T>(
    record_bytes: &[u8],
    decode: impl Fn(&[u8], usize, RefWidth) -> Option<T>,
) -> Option<T> {
    let positions = marker_positions(record_bytes);
    let mut decoded = None;
    for width in INT_WIDTHS {
        for &position in &positions {
            if let Some(candidate) = decode(record_bytes, position, width) {
                if decoded.is_some() {
                    return None;
                }
                decoded = Some(candidate);
            }
        }
    }
    decoded
}

#[cfg(test)]
mod tests {

    use crate::nurbs::toks::SubtypeTable;
    use cadmpeg_core::decode::{DecodeArena, DecodeContext, DecodePolicy, ResourceDimension};
    use cadmpeg_core::CodecError;

    #[test]
    fn cacheless_surface_does_not_borrow_a_referenced_support_cache() {
        use crate::sab::{Record, Token};
        let arena = DecodeArena::new();
        let (ctx, _) =
            DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
        let mut tokens = vec![
            Token::SubtypeOpen,
            Token::Ident("exact_spl_sur".into()),
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Long(1),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Long(2),
            Token::Long(2),
        ];
        for _ in 0..2 {
            tokens.extend([
                Token::Double(0.0),
                Token::Long(1),
                Token::Double(1.0),
                Token::Long(1),
            ]);
        }
        for point in [[0., 0., 0.], [1., 0., 0.], [0., 1., 0.], [1., 1., 0.]] {
            tokens.extend(point.map(Token::Double));
        }
        tokens.push(Token::SubtypeClose);
        let record = Record {
            index: 0,
            name: "spline-surface".into(),
            tokens: tokens.into(),
            offset: 0,
            len: 0,
        };
        let table = SubtypeTable::from_records(&[record]);
        for reference in [
            vec![
                Token::SubtypeOpen,
                Token::Ident("ref".into()),
                Token::Long(0),
                Token::SubtypeClose,
            ],
            vec![Token::SubtypeOpen, Token::Long(0), Token::SubtypeClose],
        ] {
            let scope = crate::nurbs::toks::subtype_span(&reference, 0).unwrap();
            assert!(
                super::owned_surface_cache_resolving_refs(&ctx, scope, &table)
                    .unwrap()
                    .is_ok()
            );
            let mut owner = vec![
                Token::SubtypeOpen,
                Token::Ident("srf_srf_v_bl_spl_sur".into()),
            ];
            owner.extend(reference);
            owner.push(Token::SubtypeClose);
            let scope = crate::nurbs::toks::subtype_span(&owner, 0).unwrap();
            assert!(super::owned_surface_cache_resolving_refs(&ctx, scope, &table).is_none());
        }
    }

    #[test]
    fn cached_nurbs_recovery_admits_large_knot_tables() {
        use crate::sab::Token;
        let mut curve = vec![
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Enum(0),
            Token::Long(1_001),
        ];
        for index in 0_u32..1_001 {
            curve.extend([Token::Double(f64::from(index)), Token::Long(1)]);
        }
        for index in 0_u32..1_001 {
            curve.extend([
                Token::Double(f64::from(index)),
                Token::Double(0.0),
                Token::Double(0.0),
            ]);
        }
        let (decoded, end) = super::curve_block(&curve, 0).unwrap();
        assert_eq!(decoded.control_points().len(), 1_001);
        assert_eq!(decoded.knots().len(), 1_003);
        assert_eq!(end, curve.len());
        for width in [
            crate::kernel_header::RefWidth::Four,
            crate::kernel_header::RefWidth::Eight,
        ] {
            let bytes = knot_block_bytes(&curve, width);
            let decoded = super::decode_curve_block(&bytes, 0, width).unwrap();
            assert_eq!(decoded.curve.control_points().len(), 1_001);
            assert_eq!(decoded.knots.value_offsets.len(), 1_001);
            assert_eq!(decoded.end(), bytes.len());
        }
        let mut surface = vec![
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Long(1),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Long(2),
            Token::Long(1_001),
        ];
        for count in [2_u32, 1_001] {
            for index in 0..count {
                surface.extend([Token::Double(f64::from(index)), Token::Long(1)]);
            }
        }
        for v in 0_u32..1_001 {
            for u in 0_u32..2 {
                surface.extend([
                    Token::Double(f64::from(u)),
                    Token::Double(f64::from(v)),
                    Token::Double(0.0),
                ]);
            }
        }
        let (decoded, end) = super::surface_block(&surface, 0).unwrap();
        assert_eq!(decoded.poles().len(), 2_002);
        assert_eq!(decoded.v_knots().len(), 1_003);
        assert_eq!(end, surface.len());
        for width in [
            crate::kernel_header::RefWidth::Four,
            crate::kernel_header::RefWidth::Eight,
        ] {
            let bytes = knot_block_bytes(&surface, width);
            let decoded = super::decode_surface_block(&bytes, 0, width).unwrap();
            assert_eq!(decoded.surface.poles().len(), 2_002);
            assert_eq!(decoded.v_knots.value_offsets.len(), 1_001);
            assert_eq!(decoded.end(), bytes.len());
        }
    }

    #[test]
    fn cached_surface_past_the_pole_limit_is_not_recovered() {
        use crate::sab::Token;
        let mut grid = vec![
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Long(1),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Long(449),
            Token::Long(449),
        ];
        for _ in 0..2 {
            for index in 0_u32..449 {
                grid.extend([Token::Double(f64::from(index)), Token::Long(1)]);
            }
        }
        grid.extend(std::iter::repeat_n(Token::Double(0.0), 449 * 449 * 3));
        let arena = DecodeArena::new();
        let (ctx, _) =
            DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).expect("root");
        assert!(
            super::surface_block(&grid, 0).is_none(),
            "a grid past the pole ceiling is not recovered"
        );
        assert!(ctx.resource_refusal().is_none());
    }

    fn knot_block_bytes(
        tokens: &[crate::sab::Token],
        width: crate::kernel_header::RefWidth,
    ) -> Vec<u8> {
        use crate::sab::Token;
        let mut bytes = Vec::new();
        for token in tokens {
            match token {
                Token::Ident(name) => {
                    bytes.extend([0x0d, u8::try_from(name.len()).unwrap()]);
                    bytes.extend(name.as_bytes());
                }
                Token::Double(value) => {
                    bytes.push(0x06);
                    bytes.extend(value.to_le_bytes());
                }
                Token::Long(value) | Token::Enum(value) => {
                    bytes.push(if matches!(token, Token::Long(_)) {
                        0x04
                    } else {
                        0x15
                    });
                    match width {
                        crate::kernel_header::RefWidth::Four => {
                            bytes.extend(i32::try_from(*value).unwrap().to_le_bytes());
                        }
                        crate::kernel_header::RefWidth::Eight => bytes.extend(value.to_le_bytes()),
                    }
                }
                _ => panic!("not a knot-block token"),
            }
        }
        bytes
    }

    #[test]
    fn knot_counts_without_complete_source_fields_do_not_allocate() {
        use crate::sab::Token;
        let curve = [
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Enum(0),
            Token::Long(i64::MAX),
            Token::Double(0.0),
            Token::Long(1),
        ];
        assert!(super::curve_block(&curve, 0).is_none());
        let surface = [
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Long(1),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Long(i64::MAX),
            Token::Long(2),
            Token::Double(0.0),
            Token::Long(1),
        ];
        assert!(super::surface_block(&surface, 0).is_none());
        for width in [
            crate::kernel_header::RefWidth::Four,
            crate::kernel_header::RefWidth::Eight,
        ] {
            let mut truncated = curve.clone();
            truncated[3] = Token::Long(i64::from(i32::MAX));
            assert!(
                super::decode_curve_block(&knot_block_bytes(&truncated, width), 0, width).is_none()
            );
        }
    }

    fn variable_blend_tokens(name: &str, current: i64) -> Vec<crate::sab::Token> {
        use crate::sab::Token;
        let mut tokens = vec![
            Token::SubtypeOpen,
            Token::Ident(name.into()),
            Token::Long(1),
        ];
        for _ in 0..2 {
            tokens.extend([
                Token::Str("blend_support_zero_curve".into()),
                Token::Ident("null_surface".into()),
                Token::Ident("null_curve".into()),
                Token::Ident("nullbs".into()),
                Token::Position([0.0; 3]),
                Token::Ident("nullbs".into()),
            ]);
        }
        tokens.extend([
            Token::Ident("straight".into()),
            Token::Position([0.0; 3]),
            Token::Vector3([1.0, 0.0, 0.0]),
            Token::Double(0.0),
            Token::Double(1.0),
            Token::Double(0.0),
            Token::Double(0.0),
            Token::Enum(0),
            Token::Str("two_ends".into()),
            Token::Enum(0),
            Token::True,
            Token::Double(0.0),
            Token::Double(1.0),
            Token::Double(1.0),
            Token::Double(1.0),
            Token::Enum(7),
            Token::Double(1.0),
            Token::Double(1.0),
            Token::Double(0.0),
            Token::Double(1.0),
            Token::Double(0.0),
            Token::False,
            Token::Long(current),
            Token::Double(0.001),
            Token::Double(0.001),
            Token::Long(1),
            Token::Enum(0),
            Token::Ident("nubs".into()),
            Token::Long(1),
            Token::Long(1),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Long(2),
            Token::Long(2),
        ]);
        for _ in 0..2 {
            tokens.extend([
                Token::Double(0.0),
                Token::Long(1),
                Token::Double(1.0),
                Token::Long(1),
            ]);
        }
        for point in [[7., 0., 0.], [8., 0., 0.], [7., 1., 0.], [8., 1., 0.]] {
            tokens.extend(point.map(Token::Double));
        }
        tokens.extend([
            Token::Double(0.001),
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::False,
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::Ident("null_curve".into()),
            Token::True,
            Token::True,
            Token::False,
            Token::False,
            Token::Ident("nullbs".into()),
            Token::Ident("nullbs".into()),
            Token::SubtypeClose,
        ]);
        tokens
    }

    #[test]
    fn embedded_variable_blend_cache_admission_matches_top_level() {
        use crate::sab::{Record, Token};
        use cadmpeg_ir::geometry::{SolvedSurfaceGeometry, SurfaceGeometry};
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            for current in [0, 1, 2] {
                let scope = variable_blend_tokens(name, current);
                let record = |index, name: &str, tokens: Vec<Token>| Record {
                    index,
                    name: name.into(),
                    tokens: tokens.into(),
                    offset: 0,
                    len: 0,
                };
                let mut surface =
                    vec![Token::Ref(-1), Token::Long(0), Token::Ref(-1), Token::False];
                surface.extend(scope.clone());
                surface.extend([Token::False, Token::False, Token::False, Token::False]);
                let records = [
                    record(
                        0,
                        "face",
                        vec![
                            Token::Ref(-1),
                            Token::Long(0),
                            Token::Ref(-1),
                            Token::Ref(-1),
                            Token::Ref(-1),
                            Token::Ref(2),
                            Token::Ref(-1),
                            Token::Ref(1),
                            Token::False,
                            Token::False,
                        ],
                    ),
                    record(1, "spline", surface),
                    record(
                        2,
                        "shell",
                        vec![
                            Token::Ref(-1),
                            Token::Long(0),
                            Token::Ref(-1),
                            Token::Ref(-1),
                            Token::Ref(-1),
                            Token::Ref(0),
                            Token::Ref(-1),
                            Token::Ref(3),
                        ],
                    ),
                    record(
                        3,
                        "lump",
                        vec![
                            Token::Ref(-1),
                            Token::Long(0),
                            Token::Ref(-1),
                            Token::Ref(-1),
                            Token::Ref(2),
                            Token::Ref(4),
                        ],
                    ),
                    record(
                        4,
                        "body",
                        vec![
                            Token::Ref(-1),
                            Token::Long(0),
                            Token::Ref(-1),
                            Token::Ref(3),
                            Token::Ref(-1),
                            Token::Ref(-1),
                        ],
                    ),
                ];
                let arena = DecodeArena::new();
                let (ctx, _) =
                    DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
                let out = crate::brep::decode_with_header(
                    &ctx,
                    &records,
                    &[],
                    None,
                    "source",
                    crate::asm_format!("sat"),
                    crate::brep::DecodePurpose::Model,
                )
                .unwrap();
                let carrier = out
                    .surfaces
                    .iter()
                    .find(|s| s.id.as_str() == "sat:brep:entity#1")
                    .unwrap();
                assert_eq!(out.faces.len(), 1);
                if current == 0 {
                    assert!(matches!(
                        carrier.geometry,
                        SurfaceGeometry::Procedural { cache: None, .. }
                    ));
                } else {
                    assert!(matches!(
                        carrier.geometry,
                        SurfaceGeometry::Solved(SolvedSurfaceGeometry::Nurbs(_))
                    ));
                }
                let table = SubtypeTable::from_records(&records);
                for reference in [
                    vec![
                        Token::SubtypeOpen,
                        Token::Ident("ref".into()),
                        Token::Long(0),
                        Token::SubtypeClose,
                    ],
                    vec![Token::SubtypeOpen, Token::Long(0), Token::SubtypeClose],
                    scope.clone(),
                ] {
                    let mut support = vec![Token::Ident("spline".into()), Token::False];
                    support.extend(reference);
                    support.extend([Token::False, Token::False, Token::False, Token::False]);
                    let mut cursor = crate::nurbs::toks::Cur::at(&support, 0);
                    let decoded = crate::nurbs::proc_curve::optional_embedded_surface_with_bounds(
                        &ctx,
                        &mut cursor,
                        &table,
                    )
                    .unwrap()
                    .unwrap();
                    assert_eq!(
                        decoded.surface.into_surface().is_some(),
                        current != 0,
                        "{name}, current={current}"
                    );
                    assert_eq!(cursor.pos(), support.len());
                }
            }
        }
    }

    #[test]
    fn variable_blend_current_cache_is_not_an_inline_support_surface() {
        use crate::sab::{Record, Token};
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            for current in [0, 1, 2] {
                let mut owner = variable_blend_tokens(name, current);
                let marker = owner
                    .iter()
                    .position(|token| matches!(token, Token::Ident(name) if name == "nubs"))
                    .unwrap();
                let mut support = owner[marker..marker + 29].to_vec();
                for token in &mut support[17..] {
                    if let Token::Double(value) = token {
                        *value += 100.0;
                    }
                }
                let mut surface = vec![Token::Ident("spline".into())];
                surface.extend(support);
                surface.extend([Token::False, Token::False, Token::False, Token::False]);
                owner[3] = Token::Str("blend_support_surface".into());
                owner.splice(4..5, surface);
                let records = [Record {
                    index: 0,
                    name: "spline".into(),
                    tokens: owner.clone().into(),
                    offset: 0,
                    len: 0,
                }];
                let arena = DecodeArena::new();
                let (ctx, _) =
                    DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
                let table = SubtypeTable::from_records(&records);
                assert!(
                    crate::nurbs::proc_surface::procedural_surface_resolving_refs(
                        &ctx, &owner, &table
                    )
                    .is_some()
                );
                for payload in [
                    owner,
                    vec![
                        Token::SubtypeOpen,
                        Token::Ident("ref".into()),
                        Token::Long(0),
                        Token::SubtypeClose,
                    ],
                    vec![Token::SubtypeOpen, Token::Long(0), Token::SubtypeClose],
                ] {
                    let cache = super::surface_cache_resolving_refs(&ctx, &payload, &table);
                    if current == 0 {
                        assert!(cache.is_none());
                    } else {
                        let surface = cache.unwrap().unwrap();
                        assert_eq!(
                            surface.poles()[0].get(),
                            cadmpeg_ir::math::Point3::new(70., 0., 0.)
                        );
                    }
                }
            }
        }
    }

    #[test]
    fn bounded_second_interval_keeps_the_variable_blend_cache() {
        use crate::sab::{Record, Token};
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            let mut owner = variable_blend_tokens(name, 1);
            let upper = owner
                .iter()
                .position(|token| matches!(token, Token::False))
                .unwrap();
            owner.splice(upper..=upper, [Token::True, Token::Double(1.0)]);
            let records = [Record {
                index: 0,
                name: "spline".into(),
                tokens: owner.clone().into(),
                offset: 0,
                len: 0,
            }];
            let arena = DecodeArena::new();
            let (ctx, _) =
                DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
            let table = SubtypeTable::from_records(&records);
            assert!(
                crate::nurbs::proc_surface::procedural_surface_resolving_refs(&ctx, &owner, &table)
                    .is_none(),
                "{name}"
            );
            let surface = super::surface_cache_resolving_refs(&ctx, &owner, &table)
                .unwrap()
                .unwrap();
            assert_eq!(
                surface.poles()[0].get(),
                cadmpeg_ir::math::Point3::new(70., 0., 0.),
                "{name}"
            );
        }
    }

    #[test]
    fn uncached_spline_support_keeps_the_variable_blend_cache() {
        use crate::sab::{Record, Token};
        let mut support = vec![
            Token::Ident("spline".into()),
            Token::True,
            Token::SubtypeOpen,
            Token::Ident("cyl_spl_sur".into()),
            Token::Long(1),
            Token::Ident("intcurve".into()),
            Token::True,
            Token::SubtypeOpen,
            Token::Ident("ref".into()),
            Token::Long(0),
            Token::SubtypeClose,
            Token::True,
            Token::Double(-1.0),
            Token::True,
            Token::Double(1.0),
            Token::Vector3([0.0, 1.0, 0.0]),
            Token::Position([0.0; 3]),
            Token::Enum(2),
        ];
        for bound in [-1.0, 1.0, 0.0, 0.1] {
            support.extend([Token::True, Token::Double(bound)]);
        }
        support.extend([
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
            Token::Enum(0),
        ]);
        support.extend([Token::Long(0), Token::Long(1), Token::Double(0.5)]);
        support.extend([
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
            Token::Long(0),
        ]);
        support.extend([Token::False, Token::SubtypeClose]);
        support.extend([Token::False, Token::False, Token::False, Token::False]);
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            for side in [3, 9] {
                let mut owner = variable_blend_tokens(name, 1);
                owner[side] = Token::Str("blend_support_surface".into());
                owner.splice(side + 1..side + 2, support.clone());
                let records = [Record {
                    index: 0,
                    name: "spline".into(),
                    tokens: owner.clone().into(),
                    offset: 0,
                    len: 0,
                }];
                let arena = DecodeArena::new();
                let (ctx, _) =
                    DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
                let table = SubtypeTable::from_records(&records);
                assert!(
                    crate::nurbs::proc_surface::procedural_surface_resolving_refs(
                        &ctx, &owner, &table
                    )
                    .is_none(),
                    "{name}, side token {side}"
                );
                let surface = super::surface_cache_resolving_refs(&ctx, &owner, &table)
                    .unwrap()
                    .unwrap();
                assert_eq!(
                    surface.poles()[0].get(),
                    cadmpeg_ir::math::Point3::new(70., 0., 0.),
                    "{name}, side token {side}"
                );
            }
        }
    }

    #[test]
    fn post_curve_follows_the_null_post_pcurve() {
        use crate::sab::{Record, Token};
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            let mut owner = variable_blend_tokens(name, 1);
            let post = owner.len() - 2;
            owner.splice(
                post..=post,
                [
                    Token::Ident("nubs".into()),
                    Token::Long(1),
                    Token::Enum(0),
                    Token::Long(2),
                    Token::Double(0.0),
                    Token::Long(1),
                    Token::Double(1.0),
                    Token::Long(1),
                    Token::Double(1.0),
                    Token::Double(2.0),
                    Token::Double(3.0),
                    Token::Double(4.0),
                    Token::Double(5.0),
                    Token::Double(6.0),
                ],
            );
            let records = [Record {
                index: 0,
                name: "spline".into(),
                tokens: owner.clone().into(),
                offset: 0,
                len: 0,
            }];
            let arena = DecodeArena::new();
            let (ctx, _) =
                DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
            let table = SubtypeTable::from_records(&records);
            let surface =
                crate::nurbs::proc_surface::procedural_surface_resolving_refs(&ctx, &owner, &table)
                    .unwrap()
                    .unwrap();
            let crate::nurbs::proc_surface::DecodedProceduralSurfaceDefinition::VariableBlend(
                construction,
            ) = surface.definition()
            else {
                panic!("{name}: expected a variable blend");
            };
            assert!(construction.post_pcurve.is_none(), "{name}");
            let post_curve = construction.post_curve.as_ref().expect("post curve");
            assert_eq!(
                post_curve.control_points()[1].get(),
                cadmpeg_ir::math::Point3::new(40., 50., 60.),
                "{name}"
            );
            assert!(super::surface_cache_resolving_refs(&ctx, &owner, &table).is_some());
        }
    }

    #[test]
    fn untyped_variable_blend_cache_is_rejected_for_owner_and_alias() {
        use crate::sab::{Record, Token};
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            for current in [0, 1, 2] {
                let mut tokens = variable_blend_tokens(name, current);
                let tail = tokens.len() - 2;
                tokens[tail] = Token::Ident("unsupported_pcurve".into());
                let records = [Record {
                    index: 0,
                    name: "spline".into(),
                    tokens: tokens.clone().into(),
                    offset: 0,
                    len: 0,
                }];
                let arena = DecodeArena::new();
                let (ctx, _) =
                    DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
                let table = SubtypeTable::from_records(&records);
                assert!(
                    crate::nurbs::proc_surface::procedural_surface_resolving_refs(
                        &ctx, &tokens, &table,
                    )
                    .is_none()
                );
                for payload in [
                    tokens.clone(),
                    vec![
                        Token::SubtypeOpen,
                        Token::Ident("ref".into()),
                        Token::Long(0),
                        Token::SubtypeClose,
                    ],
                    vec![Token::SubtypeOpen, Token::Long(0), Token::SubtypeClose],
                ] {
                    assert!(super::surface_cache_resolving_refs(&ctx, &payload, &table).is_none());
                }
            }
        }
    }

    #[test]
    fn rejected_blend_alias_does_not_substitute_its_support_cache() {
        use crate::sab::{Record, Token};
        for current in [0, 1] {
            for malformed in [false, true] {
                let mut owner = variable_blend_tokens("var_blend_spl_sur", current);
                if malformed {
                    let tail = owner.len() - 2;
                    owner[tail] = Token::Ident("unsupported_pcurve".into());
                }
                owner.splice(
                    4..5,
                    [
                        Token::Ident("spline".into()),
                        Token::False,
                        Token::SubtypeOpen,
                        Token::Ident("ref".into()),
                        Token::Long(1),
                        Token::SubtypeClose,
                        Token::False,
                        Token::False,
                        Token::False,
                        Token::False,
                    ],
                );
                let record = |index, tokens: Vec<Token>| Record {
                    index,
                    name: "spline".into(),
                    tokens: tokens.into(),
                    offset: 0,
                    len: 0,
                };
                let records = [
                    record(0, owner.clone()),
                    record(1, variable_blend_tokens("var_blend_spl_sur", 1)),
                ];
                let arena = DecodeArena::new();
                let (ctx, _) =
                    DecodeContext::from_root_bytes(&[], &arena, &DecodePolicy::service()).unwrap();
                let table = SubtypeTable::from_records(&records);
                assert_eq!(
                    crate::nurbs::proc_surface::procedural_surface_resolving_refs(
                        &ctx, &owner, &table
                    )
                    .is_some(),
                    !malformed,
                );
                for payload in [
                    owner.clone(),
                    vec![
                        Token::SubtypeOpen,
                        Token::Ident("ref".into()),
                        Token::Long(0),
                        Token::SubtypeClose,
                    ],
                    vec![Token::SubtypeOpen, Token::Long(0), Token::SubtypeClose],
                ] {
                    assert_eq!(
                        super::surface_cache_resolving_refs(&ctx, &payload, &table).is_some(),
                        current != 0 && !malformed,
                    );
                }
            }
        }
    }

    #[test]
    fn stale_variable_blend_cache_uses_only_temporary_storage() {
        let tokens = variable_blend_tokens("var_blend_spl_sur", 0);
        let scope = crate::nurbs::toks::subtype_span(&tokens, 0).unwrap();
        let arena = DecodeArena::new();
        let mut policy = DecodePolicy::service();
        policy.limits.max_retained_bytes = 0;
        let (ctx, _) = DecodeContext::from_root_bytes(&[], &arena, &policy).unwrap();
        assert!(super::owned_surface_cache(&ctx, scope, None).is_none());
    }

    #[test]
    fn variable_blend_cache_reference_cycles_do_not_recurse() {
        use crate::sab::{Record, Token};
        fn records(name: &str, side: usize) -> [Record; 1] {
            let mut tokens = variable_blend_tokens(name, 1);
            tokens.splice(
                side + 1..side + 2,
                [
                    Token::Ident("spline".into()),
                    Token::False,
                    Token::SubtypeOpen,
                    Token::Ident("ref".into()),
                    Token::Long(0),
                    Token::SubtypeClose,
                    Token::False,
                    Token::False,
                    Token::False,
                    Token::False,
                ],
            );
            [Record {
                index: 0,
                name: "spline".into(),
                tokens: tokens.into(),
                offset: 0,
                len: 0,
            }]
        }
        let mut policy = DecodePolicy::service();
        // One procedural reference, one cache admission and one blend value;
        // the cycle adds no depth.
        policy.limits.max_recursion_depth = 3;
        for name in crate::nurbs::blend::VARIABLE_BLEND_NAMES {
            for side in [3, 9] {
                let records = records(name, side);
                let table = SubtypeTable::from_records(&records);
                let scope = table.span(0).unwrap();
                let arena = DecodeArena::new();
                let (ctx, _) = DecodeContext::from_root_bytes(&[], &arena, &policy).unwrap();
                let surface = super::owned_surface_cache_resolving_refs(&ctx, scope, &table)
                    .unwrap()
                    .unwrap();
                assert_eq!(
                    surface.poles()[0].get(),
                    cadmpeg_ir::math::Point3::new(70., 0., 0.),
                    "{name}, side token {side}"
                );
                if let Some(Err(error)) =
                    crate::nurbs::proc_surface::procedural_surface_resolving_refs(
                        &ctx,
                        &records[0].tokens,
                        &table,
                    )
                {
                    panic!("{name}, side token {side}: {error:?}");
                }
            }
        }

        let records = records("var_blend_spl_sur", 3);
        let table = SubtypeTable::from_records(&records);
        let scope = table.span(0).unwrap();
        policy.limits.max_recursion_depth = 0;
        let arena = DecodeArena::new();
        let (ctx, _) = DecodeContext::from_root_bytes(&[], &arena, &policy).unwrap();
        let error = super::owned_surface_cache_resolving_refs(&ctx, scope, &table)
            .unwrap()
            .unwrap_err();
        let CodecError::ResourceLimit(limit) = error else {
            panic!("depth refusal: {error:?}");
        };
        assert_eq!(limit.dimension, ResourceDimension::RecursionDepth);
        assert_eq!(limit.operation, "admit ASM variable-blend cache");
    }
}