brep_kernel/edit/direct_edit/

delete_faces.rs

//! Deleting a SET of faces — the multi-select half of Golovanov §6.12.
//!
//! [`delete_face_and_heal`](super::delete_face_and_heal) removes ONE face and
//! heals by re-intersecting its neighbours. That is the right heal for a
//! transition strip, and the wrong question entirely for the case the app
//! sends most often: a user has selected every face of a POCKET — its walls and
//! its floor — and wants the pocket gone.
//!
//! Such a selection is not a strip between neighbours; it is a PATCH. Its free
//! boundary is not four edges belonging to four other faces, it is one whole
//! HOLE LOOP of one surviving face — the mouth the pocket was sunk through. So
//! the heal is not to re-intersect anything, it is to CAP: drop the patch, drop
//! the hole loop, and the face the pocket was sunk into is the whole face
//! again. Nothing is refit; every surviving carrier and loop is bit-identical
//! to what it was.
//!
//! This is the same closed form [`cap_through_wall`](super::closed_heal) already
//! uses for a bore's wall, stated for an arbitrary set of faces instead of one:
//! a bore wall is simply the patch whose free boundary is TWO hole loops, in the
//! two faces the drill went in and out of. A blind pocket, a blind bore (wall +
//! floor disc), and a BOSS (a pad's wall + top, whose mouth is a hole loop in
//! the face it was grown from) are all the same operation.
//!
//! ## The lane gate
//!
//! Structural, decided before any geometry is touched:
//!
//! * every survivor loop that touches the selection must be ENTIRELY consumed
//!   by it. A loop that keeps some of its edges means the selection cut a face
//!   rather than lifting a patch off it — that is the transition-strip
//!   question, and it routes to the one-face-at-a-time chain.
//!
//! Once the gate says "patch", this lane OWNS the answer, refusals included —
//! the checks below name what is wrong instead of falling back to a heal that
//! was written for a different shape:
//!
//! * a consumed loop must be a HOLE in its face, not the loop that bounds the
//!   face's material. Selecting a pocket's three walls but not its floor makes
//!   the floor's OUTER loop the free boundary; capping that would leave a face
//!   with no boundary at all, so the refusal names the floor and says to select
//!   it too.
//! * the shell must stay CONNECTED. `validate()` deliberately does not ask
//!   (see `faces_are_connected`), and a patch whose removal severs the body is
//!   a thing this operation cannot represent.
//! * the GENUS must come out of the Euler accounting as a whole number ≥ 0.
//!   Capping a blind pocket leaves the genus alone; capping a through feature
//!   drops it by one. Neither is assumed — both fall out of the same count.

use super::*;

/// A selection that passed the structural gate: the faces to lift off, the
/// survivor loops their free boundary consumes, and the edges that go with
/// them.
struct FacePatch {
    /// The shell the patch lives in (all its faces share one).
    shell_index: usize,
    /// Ids of the selected faces.
    face_ids: HashSet<u64>,
    /// `(shell, face position, loop index)` of every survivor loop the patch's
    /// free boundary consumes whole — the hole loops that go with it.
    dropped_loops: Vec<(usize, usize, usize)>,
    /// Every edge the patch uses: its interior edges and its free boundary.
    /// All of them lose both their coedges, so all of them go.
    edges: HashSet<u64>,
}

/// How many coedges a given edge gets from the selection and from the rest of
/// the solid.
#[derive(Clone, Copy, Default)]
struct EdgeCensus {
    selected: usize,
    kept: usize,
}

fn census(solid: &BrepSolid, face_ids: &HashSet<u64>) -> HashMap<u64, EdgeCensus> {
    let mut counts: HashMap<u64, EdgeCensus> = HashMap::default();
    for face in solid.shells.iter().flat_map(|shell| &shell.faces) {
        let selected = face_ids.contains(&face.id);
        for coedge in face.loops.iter().flat_map(|loop_record| &loop_record.coedges) {
            let entry = counts.entry(coedge.edge_id).or_default();
            if selected {
                entry.selected += 1;
            } else {
                entry.kept += 1;
            }
        }
    }
    counts
}

/// Decide whether `face_ids` is a PATCH — a set whose free boundary consumes
/// whole loops of the faces around it — and if so gather what its removal
/// takes with it. `None` routes the caller to the one-face-at-a-time chain.
fn classify_patch(solid: &BrepSolid, face_ids: &[u64]) -> Option<FacePatch> {
    let selected: HashSet<u64> = face_ids.iter().copied().collect();
    let mut shells = face_ids
        .iter()
        .filter_map(|face_id| find_face(solid, *face_id))
        .map(|(shell_index, _)| shell_index);
    let shell_index = shells.next()?;
    if shells.any(|other| other != shell_index) {
        // A patch is a piece of ONE shell's surface.
        return None;
    }

    let counts = census(solid, &selected);
    let mut dropped_loops = Vec::new();
    for (shell_position, shell) in solid.shells.iter().enumerate() {
        for (face_position, face) in shell.faces.iter().enumerate() {
            if selected.contains(&face.id) {
                continue;
            }
            for (loop_index, loop_record) in face.loops.iter().enumerate() {
                let mut touches = false;
                let mut whole = true;
                for coedge in &loop_record.coedges {
                    if counts
                        .get(&coedge.edge_id)
                        .is_some_and(|count| count.selected > 0)
                    {
                        touches = true;
                    } else {
                        whole = false;
                    }
                }
                if !touches {
                    continue;
                }
                if !whole {
                    // The selection stops part-way along a survivor's loop: it
                    // is a strip between neighbours, not a patch lifted off
                    // them. The chain owns that question.
                    return None;
                }
                dropped_loops.push((shell_position, face_position, loop_index));
            }
        }
    }
    if dropped_loops.is_empty() {
        // Nothing outside the selection borders it — the "patch" is a whole
        // closed shell. Capping has nothing to cap onto.
        return None;
    }

    let edges: HashSet<u64> = counts
        .iter()
        .filter(|(_, count)| count.selected > 0)
        .map(|(edge_id, _)| *edge_id)
        .collect();
    Some(FacePatch {
        shell_index,
        face_ids: selected,
        dropped_loops,
        edges,
    })
}

/// `V - E + F - H` on the reduced complex `validate()`'s Euler check uses:
/// degenerate (pole) edges and the vertices only they reference are not
/// independent cells, and each loop past a face's first is a hole.
fn euler_characteristic(solid: &BrepSolid) -> i64 {
    let referenced: HashSet<u64> = solid
        .edges
        .iter()
        .filter(|edge| !edge.degenerate)
        .flat_map(|edge| [edge.start_vertex_id, edge.end_vertex_id])
        .collect();
    let vertices = solid
        .vertices
        .iter()
        .filter(|vertex| referenced.contains(&vertex.id))
        .count() as i64;
    let edges = solid.edges.iter().filter(|edge| !edge.degenerate).count() as i64;
    let faces = solid
        .shells
        .iter()
        .map(|shell| shell.faces.len())
        .sum::<usize>() as i64;
    let holes: i64 = solid
        .shells
        .iter()
        .flat_map(|shell| &shell.faces)
        .map(|face| face.loops.len().saturating_sub(1) as i64)
        .sum();
    vertices - edges + faces - holes
}

/// How a face is named in a refusal: its persistent name when it has one, its
/// id otherwise.
fn face_label(face: &FaceRecord) -> String {
    match &face.name {
        Some(name) => format!("`{name}`"),
        None => format!("face {}", face.id),
    }
}

/// Lift `patch` off the solid and close the hole loops it was sunk through.
fn cap_face_patch(solid: &BrepSolid, patch: &FacePatch, op: &str) -> Result<BrepSolid, String> {
    // --- Every consumed loop must be a HOLE in its face --------------------
    // Grouped per face, because "would this face keep a loop" is a question
    // about the face, not about one loop.
    let mut per_face: HashMap<(usize, usize), Vec<usize>> = HashMap::default();
    for (shell_position, face_position, loop_index) in &patch.dropped_loops {
        per_face
            .entry((*shell_position, *face_position))
            .or_default()
            .push(*loop_index);
    }
    for ((shell_position, face_position), loop_indices) in &per_face {
        let face = &solid.shells[*shell_position].faces[*face_position];
        if loop_indices.len() >= face.loops.len() {
            return Err(format!(
                "{op}: the selection is the whole boundary of {} — it is part of the \
                 pocket, not the face the pocket was sunk into. Select it as well \
                 (a patch is capped by the face AROUND it, which has to keep a loop).",
                face_label(face)
            ));
        }
        let mut areas = Vec::with_capacity(face.loops.len());
        for index in 0..face.loops.len() {
            areas.push(loop_signed_area(face, index)?);
        }
        let host = (0..areas.len())
            .max_by(|a, b| areas[*a].abs().total_cmp(&areas[*b].abs()))
            .expect("the face has at least two loops here");
        for loop_index in loop_indices {
            if *loop_index == host || areas[host] * areas[*loop_index] >= 0.0 {
                return Err(format!(
                    "{op}: the loop the selection would leave open in {} bounds that \
                     face's material rather than a hole in it — capping it would erase \
                     the face (deferred)",
                    face_label(face)
                ));
            }
        }
    }

    let mut healed = solid.clone();

    // --- Drop the hole loops, then the patch, then their edges -------------
    // Loops go first, by descending index within each face, so no removal
    // disturbs a position resolved against the original topology; dropping a
    // loop cannot move a face, and the faces go by id.
    for ((shell_position, face_position), loop_indices) in &per_face {
        let mut loop_indices = loop_indices.clone();
        loop_indices.sort_unstable_by(|a, b| b.cmp(a));
        for loop_index in loop_indices {
            healed.shells[*shell_position].faces[*face_position]
                .loops
                .remove(loop_index);
        }
    }
    for shell in &mut healed.shells {
        shell.faces.retain(|face| !patch.face_ids.contains(&face.id));
    }
    healed.edges.retain(|edge| !patch.edges.contains(&edge.id));
    let used: HashSet<u64> = healed
        .edges
        .iter()
        .flat_map(|edge| [edge.start_vertex_id, edge.end_vertex_id])
        .collect();
    healed.vertices.retain(|vertex| used.contains(&vertex.id));

    // --- The two things `validate()` will not ask for us -------------------
    if !faces_are_connected(&healed.shells[patch.shell_index].faces) {
        return Err(format!(
            "{op}: the selected faces are what joins two otherwise separate parts of \
             the body — removing them would sever the solid, which this operation \
             cannot represent (deferred)"
        ));
    }
    // Genus is not assumed either way: capping a blind pocket leaves it alone,
    // capping a through feature drops it by one, and both fall out of the same
    // Euler count over the reduced complex.
    let shift = euler_characteristic(solid) - euler_characteristic(&healed);
    if shift % 2 != 0 {
        return Err(format!(
            "{op}: the selection does not close into whole handles \
             (Euler characteristic shifts by an odd {shift}) — refusing rather than \
             emitting a solid whose genus is a guess"
        ));
    }
    healed.genus += shift / 2;
    if healed.genus < 0 {
        return Err(format!(
            "{op}: capping the selection leaves genus {}, so the solid's stated genus \
             did not account for the feature it carries (deferred)",
            healed.genus
        ));
    }

    let issues = healed.validate();
    if !issues.is_empty() {
        return Err(format!("{op}: the capped solid failed validation: {issues:?}"));
    }
    Ok(healed)
}

/// Delete a SET of faces and heal, in one operation.
///
/// Two lanes, chosen by the selection's own shape (see the module docs):
///
/// * a PATCH — a set whose free boundary consumes whole hole loops of the
///   faces around it (a pocket's walls + floor, a boss's wall + top, a bore's
///   wall) — is CAPPED: the patch and those loops go, and nothing else is
///   touched;
/// * anything else is healed one face at a time by
///   [`delete_face_and_heal`](super::delete_face_and_heal), which extends and
///   re-intersects each face's neighbours. Face ids are stable across a heal,
///   so the chain re-uses the ids it was given.
///
/// A single-face selection always takes the second lane — a lone face is
/// exactly the question `delete_face_and_heal` was written for, and its
/// through-wall cap already covers the one-face patch there is.
pub fn delete_faces_and_heal(solid: &BrepSolid, face_ids: &[u64]) -> Result<BrepSolid, String> {
    let op = "delete_faces_and_heal";
    let mut seen: HashSet<u64> = HashSet::default();
    let face_ids: Vec<u64> = face_ids
        .iter()
        .copied()
        .filter(|face_id| seen.insert(*face_id))
        .collect();
    if face_ids.is_empty() {
        return Err(format!("{op}: no faces selected"));
    }
    for face_id in &face_ids {
        if find_face(solid, *face_id).is_none() {
            return Err(format!("{op}: no face with id {face_id}"));
        }
    }
    if face_ids.len() == 1 {
        return delete_face_and_heal(solid, face_ids[0]);
    }
    if let Some(patch) = classify_patch(solid, &face_ids) {
        return cap_face_patch(solid, &patch, op);
    }
    let mut healed = solid.clone();
    for face_id in &face_ids {
        healed = delete_face_and_heal(&healed, *face_id)?;
    }
    Ok(healed)
}

// ---------------------------------------------------------------------------
// Tests — the lane gate and each named refusal, on the smallest solids that
// wear the signature. The reported document itself is pinned end-to-end
// through the feature engine in
// `tests/suites/inbox_20260905_cone_pocket_delete_faces.rs`.
// ---------------------------------------------------------------------------
#[cfg(test)]
mod delete_faces_tests {
    use super::*;
    use crate::{
        boolean_operation, chamfer_edge, make_box_brep, make_cylinder_brep,
        solid_mass_properties, BooleanOperation, BooleanOptions,
    };

    fn volume(solid: &BrepSolid) -> f64 {
        solid_mass_properties(solid)
            .expect("mass properties")
            .volume
    }

    fn face_count(solid: &BrepSolid) -> usize {
        solid.shells.iter().map(|shell| shell.faces.len()).sum()
    }

    /// A 20 mm cube with a square blind pocket sunk 5 mm into its top face:
    /// four walls and a floor, whose mouth is a hole loop in `Box_PZ`.
    fn cube_with_square_pocket() -> BrepSolid {
        let cube = make_box_brep(Vec3::default(), 20.0, 20.0, 20.0).unwrap();
        // The cutter starts ABOVE the top face and reaches down to z = 15, so
        // the pocket is blind: its floor is inside the material.
        let cutter = make_box_brep(Vec3::new(5.0, 5.0, 15.0), 8.0, 8.0, 10.0).unwrap();
        let cut = boolean_operation(
            &cube,
            &cutter,
            BooleanOperation::Subtract,
            &BooleanOptions::default(),
        )
        .unwrap();
        assert!(cut.validate().is_empty(), "{:?}", cut.validate());
        cut
    }

    /// The ids of every face whose WHOLE trimmed boundary satisfies `inside` —
    /// the honest way to pick a feature's faces, since a face's carrier plane
    /// reaches well past the region it is trimmed to.
    fn faces_bounded_within(solid: &BrepSolid, inside: impl Fn(Vec3) -> bool) -> Vec<u64> {
        solid
            .shells
            .iter()
            .flat_map(|shell| &shell.faces)
            .filter(|face| {
                face.loops
                    .iter()
                    .flat_map(|loop_record| &loop_record.coedges)
                    .all(|coedge| {
                        solid
                            .edges
                            .iter()
                            .find(|edge| edge.id == coedge.edge_id)
                            .and_then(|edge| edge.curve.evaluate(0.5 * (edge.t0 + edge.t1)).ok())
                            .map(&inside)
                            .unwrap_or(false)
                    })
            })
            .map(|face| face.id)
            .collect()
    }

    /// The pocket's five faces: everything trimmed to inside the pocket's
    /// footprint and at or above its floor.
    fn pocket_faces(solid: &BrepSolid) -> Vec<u64> {
        faces_bounded_within(solid, |point| {
            point.x > 4.0 && point.x < 14.0 && point.y > 4.0 && point.y < 14.0 && point.z > 14.0
        })
    }

    /// The reported operation, on the simplest solid that wears its shape:
    /// select every face of a blind pocket and the pocket is gone, the face it
    /// was sunk through closes, and the cube is back.
    #[test]
    fn capping_a_blind_pocket_restores_the_cube() {
        let cut = cube_with_square_pocket();
        let pocket = pocket_faces(&cut);
        assert_eq!(pocket.len(), 5, "four walls and a floor");
        assert_eq!(face_count(&cut), 11, "the cube's six plus the pocket's five");

        let healed = delete_faces_and_heal(&cut, &pocket).expect("the pocket caps");
        assert!(healed.validate().is_empty(), "{:?}", healed.validate());
        assert_eq!(face_count(&healed), 6, "the cube's six faces");
        assert!(
            healed
                .shells
                .iter()
                .flat_map(|shell| &shell.faces)
                .all(|face| face.loops.len() == 1),
            "no face keeps the pocket's mouth loop"
        );
        assert_eq!(healed.genus, 0, "a pocket is not a handle");
        // Nothing on this path is refit, so the volume is the cube's to the
        // mass integrator's own round-off over six planes.
        assert!(
            (volume(&healed) - 8000.0).abs() < 1e-9,
            "the cube is back: {}",
            volume(&healed)
        );
    }

    /// The same pocket with the FLOOR left out of the selection. The floor's
    /// only loop would be the free boundary, and capping it would erase the
    /// face — so the refusal names the floor and says to select it.
    #[test]
    fn refuses_a_pocket_whose_floor_was_not_selected() {
        let cut = cube_with_square_pocket();
        let pocket = pocket_faces(&cut);
        let floor = cut
            .shells
            .iter()
            .flat_map(|shell| &shell.faces)
            .find(|face| {
                pocket.contains(&face.id)
                    && face
                        .surface
                        .evaluate(0.5, 0.5)
                        .map(|point| (point.z - 15.0).abs() < 1e-9)
                        .unwrap_or(false)
            })
            .expect("the pocket floor")
            .id;
        let walls: Vec<u64> = pocket.iter().copied().filter(|id| *id != floor).collect();
        assert_eq!(walls.len(), 4);

        let error = delete_faces_and_heal(&cut, &walls).unwrap_err();
        assert!(
            error.contains("Select it as well"),
            "the refusal must say what to do: {error}"
        );
    }

    /// A selection that is NOT a patch — the two rim chamfers of a cylinder —
    /// still goes through the one-at-a-time chain, and still heals. The gate
    /// must not swallow the case the chain was written for.
    #[test]
    fn a_non_patch_selection_still_chains() {
        let cylinder =
            make_cylinder_brep(Vec3::default(), Vec3::new(0.0, 0.0, 1.0), 4.0, 6.0).unwrap();
        let full = volume(&cylinder);
        let rim_at = |solid: &BrepSolid, z: f64| {
            solid
                .edges
                .iter()
                .find(|edge| {
                    !edge.degenerate
                        && edge.start_vertex_id == edge.end_vertex_id
                        && edge
                            .curve
                            .evaluate(0.5 * (edge.t0 + edge.t1))
                            .map(|point| (point.z - z).abs() < 1e-9)
                            .unwrap_or(false)
                })
                .map(|edge| edge.id)
                .expect("closed rim")
        };
        let top = rim_at(&cylinder, 6.0);
        let chamfered = chamfer_edge(&cylinder, top, 1.0, Some("C1")).unwrap();
        let bottom = rim_at(&chamfered, 0.0);
        let chamfered = chamfer_edge(&chamfered, bottom, 1.0, Some("C2")).unwrap();
        assert!(chamfered.validate().is_empty(), "{:?}", chamfered.validate());

        let strips: Vec<u64> = chamfered
            .shells
            .iter()
            .flat_map(|shell| &shell.faces)
            .filter(|face| matches!(face.name.as_deref(), Some("C1") | Some("C2")))
            .map(|face| face.id)
            .collect();
        assert_eq!(strips.len(), 2, "both chamfer strips are named");
        // Not a patch: each strip's rims are shared with loops its neighbours
        // keep the rest of, so the gate hands this to the chain.
        assert!(
            classify_patch(&chamfered, &strips).is_none(),
            "two chamfer strips are not a patch"
        );

        let healed = delete_faces_and_heal(&chamfered, &strips).expect("the chain heals both");
        assert!(healed.validate().is_empty(), "{:?}", healed.validate());
        assert_eq!(face_count(&healed), 3, "wall, top, bottom");
        assert!(
            (volume(&healed) - full).abs() <= 1e-6 * full,
            "the cylinder is back: {} vs {full}",
            volume(&healed)
        );
    }

    /// The patch lane must not be confined to a blind pocket: a through bore's
    /// wall is the patch whose free boundary is TWO hole loops, and the same
    /// count that leaves a pocket's genus alone drops this one's by the handle
    /// it closes. Selected here WITH a second, unrelated pocket so the
    /// selection is genuinely a multi-face one.
    #[test]
    fn capping_a_through_bore_and_a_pocket_together_drops_one_handle() {
        let plate = make_box_brep(Vec3::default(), 20.0, 20.0, 20.0).unwrap();
        let drill = make_cylinder_brep(
            Vec3::new(5.0, 5.0, -5.0),
            Vec3::new(0.0, 0.0, 1.0),
            2.0,
            30.0,
        )
        .unwrap();
        let drilled = boolean_operation(
            &plate,
            &drill,
            BooleanOperation::Subtract,
            &BooleanOptions::default(),
        )
        .unwrap();
        let pocket_cutter = make_box_brep(Vec3::new(12.0, 12.0, 15.0), 5.0, 5.0, 10.0).unwrap();
        let cut = boolean_operation(
            &drilled,
            &pocket_cutter,
            BooleanOperation::Subtract,
            &BooleanOptions::default(),
        )
        .unwrap();
        assert!(cut.validate().is_empty(), "{:?}", cut.validate());
        assert_eq!(cut.genus, 1, "the bore is a handle");

        // Everything that is not one of the plate's six outer planes.
        let outer = |point: Vec3| {
            point.x.abs() < 1e-9
                || (point.x - 20.0).abs() < 1e-9
                || point.y.abs() < 1e-9
                || (point.y - 20.0).abs() < 1e-9
                || point.z.abs() < 1e-9
                || (point.z - 20.0).abs() < 1e-9
        };
        let selection: Vec<u64> = cut
            .shells
            .iter()
            .flat_map(|shell| &shell.faces)
            .filter(|face| !face.surface.evaluate(0.5, 0.5).map(outer).unwrap_or(true))
            .map(|face| face.id)
            .collect();
        assert_eq!(selection.len(), 6, "the bore wall plus the pocket's five");

        let healed = delete_faces_and_heal(&cut, &selection).expect("both cap");
        assert!(healed.validate().is_empty(), "{:?}", healed.validate());
        assert_eq!(face_count(&healed), 6, "the plate's six faces");
        assert_eq!(healed.genus, 0, "closing the bore removes the handle");
        assert!(
            (volume(&healed) - 8000.0).abs() < 1e-6,
            "the plate is back: {}",
            volume(&healed)
        );
    }

    /// A post joining two plates wears a patch's exact signature — its four
    /// walls are bounded by one hole loop in each plate — and capping it would
    /// leave two closed surfaces in one shell record, which `validate()`
    /// accepts. The connectivity check is what refuses it.
    #[test]
    fn refuses_a_patch_whose_removal_would_sever_the_body() {
        let lower = make_box_brep(Vec3::new(0.0, 0.0, 0.0), 20.0, 20.0, 4.0).unwrap();
        let upper = make_box_brep(Vec3::new(0.0, 0.0, 12.0), 20.0, 20.0, 4.0).unwrap();
        // A SQUARE post, so its wall is four faces: the patch lane's question,
        // not the single-face cap's.
        let post = make_box_brep(Vec3::new(8.0, 8.0, 4.0), 4.0, 4.0, 8.0).unwrap();
        let options = BooleanOptions::default();
        let joined = boolean_operation(&lower, &post, BooleanOperation::Union, &options)
            .and_then(|solid| {
                boolean_operation(&solid, &upper, BooleanOperation::Union, &options)
            })
            .expect("the sandwich unions");
        assert!(joined.validate().is_empty(), "{:?}", joined.validate());

        let walls = faces_bounded_within(&joined, |point| {
            point.x >= 7.9 && point.x <= 12.1 && point.y >= 7.9 && point.y <= 12.1
        });
        assert_eq!(walls.len(), 4, "the post's four walls");
        assert!(
            classify_patch(&joined, &walls).is_some(),
            "the post's walls ARE a patch — the refusal has to come from the \
             connectivity check, not from the gate"
        );

        let error = delete_faces_and_heal(&joined, &walls).unwrap_err();
        assert!(
            error.contains("sever the solid"),
            "unexpected refusal: {error}"
        );
    }

    #[test]
    fn refuses_a_face_that_does_not_exist() {
        let cube = make_box_brep(Vec3::default(), 1.0, 1.0, 1.0).unwrap();
        let error = delete_faces_and_heal(&cube, &[999_999, 1]).unwrap_err();
        assert!(
            error.contains("no face with id 999999"),
            "unexpected refusal: {error}"
        );
    }

    #[test]
    fn refuses_an_empty_selection() {
        let cube = make_box_brep(Vec3::default(), 1.0, 1.0, 1.0).unwrap();
        let error = delete_faces_and_heal(&cube, &[]).unwrap_err();
        assert!(error.contains("no faces selected"), "{error}");
    }
}