BREP_kernel 0.13.2

//! The offset shell's own refusals, minted as TYPED `KernelRefusal`s at their
//! origin with stable slugs (census item 4, 2026-09-27), and the predicates
//! `features/offset_shell.rs` dispatches on — the class and slug, never the
//! text:
//!
//! | feature branch | predicate | class |
//! |---|---|---|
//! | every face selected: warn and no-op | `is_offset_shell_no_retained_face` | `InvalidInput { what: "offset_shell_no_retained_face" }` |
//! | an open curved rim: the reorder advice | `is_offset_shell_open_curved_rim` | `NonIntegralGenus` (typed at `finalize_assembled_solid`, carried through every cause put in front of it) or `UnsupportedGeometry { what: "offset_shell_unwelded_curved_rim" }` |
//!
//! plus the outward guard's `Internal { what: "offset_shell_empty_shell" }`,
//! the sharp-side lane's `UnsupportedGeometry { what:
//! "offset_shell_sharp_side_continuation" }` and the certainty step's
//! `UnsupportedGeometry { what: "offset_shell_regularity_uncertain" }` and
//! `{ what: "offset_shell_fold_between_samples" }`, the selection's
//! `UnsupportedGeometry { what: "offset_shell_tangent_offsets" }` (two offsets
//! touch tangentially: the cavity pinches to a line) and the assembly's
//! `UnsupportedGeometry { what: "offset_shell_sealed_hollow" }` (a cavity skin
//! with no path to the opening, refused when the assembly fails), which no
//! feature branch matches — the last two so a refusal naming its cause never
//! takes the reorder advice.

use crate::{KernelRefusal, KernelStage};

pub(super) const NO_RETAINED_FACE: &str = "offset_shell_no_retained_face";
/// Two offsets touch tangentially, so the cavity would pinch to a line
/// (`BREP_OFFSET_TANGENT_TOUCH`).
pub(super) const TANGENT_OFFSETS: &str = "offset_shell_tangent_offsets";
/// A cavity skin is sealed off from the opening and the assembly failed
/// (`BREP_OFFSET_SEALED_HOLLOW`).
pub(super) const SEALED_HOLLOW: &str = "offset_shell_sealed_hollow";
pub(super) const UNWELDED_CURVED_RIM: &str = "offset_shell_unwelded_curved_rim";
pub(super) const EMPTY_SHELL: &str = "offset_shell_empty_shell";
/// The sharp-side lane could not continue a curved carrier past its sharp
/// outward side (`sharp_side_continued_source`): a named deferral.
pub(super) const SHARP_SIDE_CONTINUATION: &str = "offset_shell_sharp_side_continuation";
/// The regularity scan found nothing collapsed on a support but could not
/// certify it regular either (`offset/regularity.rs`, the certainty step): a
/// named deferral, so the support is neither built whole nor carved.
pub(super) const REGULARITY_UNCERTAIN: &str = "offset_shell_regularity_uncertain";

/// The certainty step's refinement found a collapsed sample the scan's census
/// and carve had not seen: the support folds between the samples.
pub(super) const FOLD_BETWEEN_SAMPLES: &str = "offset_shell_fold_between_samples";

pub(super) fn fold_between_samples(
    face_id: u64,
    distance: f64,
    sample: crate::offset_regularity::FoldSample,
) -> KernelRefusal {
    KernelRefusal::unsupported(
        KernelStage::Classify,
        FOLD_BETWEEN_SAMPLES,
        format!(
            "offset_shell: the offset of source face {face_id} by {distance:.6} folds between the \
             regularity scan's samples — the certainty step read 1 − δ·κ = {:.3e} at (u={:.6}, \
             v={:.6}), curvature radius {:.6} against the offset {:.6}, where the census and the \
             carve had found nothing to divide. The support is refused rather than built whole",
            sample.factor,
            sample.u,
            sample.v,
            sample.radius(),
            sample.displacement.abs()
        ),
    )
}

/// A support the scan could not certify: nothing collapsed, and either cells
/// were still risky at the scan's finest spacing or the dip descent ran out of
/// budget. Building it whole would ship a carrier that may fold between the
/// samples and validate.
pub(super) fn regularity_uncertain(
    face_id: u64,
    distance: f64,
    unresolved: usize,
    budget_exhausted: bool,
    least: Option<crate::offset_regularity::FoldSample>,
) -> KernelRefusal {
    let because = match (unresolved, budget_exhausted) {
        (0, _) => "the refinement budget ran out with prominent dips of the fold factor still \
                   unexplored"
            .to_string(),
        (cells, false) => format!(
            "{cells} cell(s) of the scan were still risky at its finest spacing — the fold \
             factor sits within a hair of the level over an area no sampling can decide"
        ),
        (cells, true) => format!(
            "{cells} cell(s) of the scan were still risky at its finest spacing and the \
             refinement budget ran out"
        ),
    };
    let least = least
        .map(|least| {
            format!(
                "; the least 1 − δ·κ seen is {:.3e} at (u={:.6}, v={:.6}), curvature radius {:.6} \
                 against the offset {:.6}",
                least.factor,
                least.u,
                least.v,
                least.radius(),
                least.displacement.abs()
            )
        })
        .unwrap_or_default();
    KernelRefusal::unsupported(
        KernelStage::Classify,
        REGULARITY_UNCERTAIN,
        format!(
            "offset_shell: the offset of source face {face_id} by {distance:.6} cannot be \
             certified regular over the face's trim — nothing collapsed at any sample, but \
             {because}{least}. The support is refused rather than built whole, because a \
             carrier folded between the samples welds into a shell that validates and bounds \
             the wrong solid"
        ),
    )
}

/// Every face was selected as an opening, so no support is left to offset.
pub(super) fn no_retained_face() -> KernelRefusal {
    KernelRefusal::input(
        KernelStage::Collect,
        NO_RETAINED_FACE,
        "offset_shell: removing every face cannot produce a shell",
    )
}

/// A one-use closed rim the welds could not close on a curved-solid opening.
pub(super) fn unwelded_curved_rim(edge_id: u64, anchor: crate::Vec3) -> KernelRefusal {
    KernelRefusal::unsupported(
        KernelStage::Sew,
        UNWELDED_CURVED_RIM,
        format!(
            "offset_shell: unwelded rim leaves a non-watertight shell \
             (one-use closed edge {} near ({:.3},{:.3},{:.3})); this \
             curved-solid opening is not yet supported",
            edge_id, anchor.x, anchor.y, anchor.z
        ),
    )
}

/// An outward result with shells that enclose no volume
/// (`outward_shell_is_connected`).
pub(super) fn empty_shell(shells: usize, empty: usize, floor: f64) -> KernelRefusal {
    // Internal, not `InvalidResultTopology`: that class is backed as an
    // arrangement degeneracy and so is perturbation-eligible (the boolean's
    // retry contract), which a builder's own verdict must not inherit, the
    // same ruling the loft's "failed validation" sites took.
    KernelRefusal::internal(
        KernelStage::Validate,
        EMPTY_SHELL,
        format!(
            "offset_shell: the outward shell assembled {shells} shells, {empty} of which enclose no volume \
             (under {floor:.1e}); those are fragments of an assembly that cannot be built as it stands"
        ),
    )
}

/// Whether `refusal` is the shell's "every face was selected" refusal: the
/// class and slug, never the text.
pub(crate) fn is_offset_shell_no_retained_face(refusal: &KernelRefusal) -> bool {
    matches!(&refusal.class, crate::RefusalClass::InvalidInput { what } if what == NO_RETAINED_FACE)
}

/// Whether `refusal` is an open curved rim the shell could not close: the
/// assembly's `NonIntegralGenus` (typed at `finalize_assembled_solid`, carried
/// through every cause put in front of it) or the unwelded curved rim. The
/// class, never the text; a genus sentence quoted under another class is not
/// this refusal.
pub(crate) fn is_offset_shell_open_curved_rim(refusal: &KernelRefusal) -> bool {
    match &refusal.class {
        crate::RefusalClass::NonIntegralGenus { .. } => true,
        crate::RefusalClass::UnsupportedGeometry { what } => what == UNWELDED_CURVED_RIM,
        _ => false,
    }
}