//! Shared in-memory `DocApiBackend` for the runnable examples.
//!
//! Lets the examples run without the host binary: an in-process mock document
//! (HashMap<ObjectId, Body> + a kind table) behind the `InProcess` transport.
//! Not for production use — the real backend lives in the host (`src/app/doc_api.rs`).

use std::collections::HashMap;

use ocs_doc_api::backend::{DocApiBackend, KernelBody};
use ocs_doc_api::{
    normalize_layer_name, Aabb, ApiError, ApiResult, Curve2Spec, EntityView, GeometryErrorKind,
    GeometryRevision, LayerInfo, ObjectId, PlacementSpec,
};


#[derive(Clone)]
pub struct MockBackend {
    next_id: u64,
    revision: u64,
    undo_steps: u32,
    bodies: HashMap<ObjectId, KernelBody>,
    kinds: HashMap<ObjectId, String>,
    /// Stored 2D curve specs so `bounds()` works on non-solid entities too.
    curves: HashMap<ObjectId, Curve2Spec>,
    /// Stored text content for Text/MText annotations.
    text_values: HashMap<ObjectId, String>,
    /// Stored hatch boundary loops.
    hatch_boundaries: HashMap<ObjectId, Vec<Vec<[f64; 2]>>>,
    /// Stored dimension measurements.
    dimension_measurements: HashMap<ObjectId, f64>,
    /// Stored insert attributes.
    attributes_store: HashMap<ObjectId, Vec<(String, String)>>,
    /// Stored viewport views (target, height).
    viewport_views: HashMap<ObjectId, ([f64; 3], f64)>,
    /// Stored XDATA records keyed by (entity id, application name).
    xdata_store: HashMap<(ObjectId, String), ocs_doc_api::XDataRecord>,
    /// Stored XRECORD payloads keyed by entity id.
    xrecord_store: HashMap<ObjectId, ocs_doc_api::XRecordSpec>,
    /// Stored layer table.
    layers: HashMap<String, LayerInfo>,
    /// Layer name assigned to each entity.
    entity_layers: HashMap<ObjectId, String>,
}

impl Default for MockBackend {
    fn default() -> Self {
        let mut backend = Self {
            next_id: 0,
            revision: 0,
            undo_steps: 0,
            bodies: HashMap::new(),
            kinds: HashMap::new(),
            curves: HashMap::new(),
            text_values: HashMap::new(),
            hatch_boundaries: HashMap::new(),
            dimension_measurements: HashMap::new(),
            attributes_store: HashMap::new(),
            viewport_views: HashMap::new(),
            xdata_store: HashMap::new(),
            xrecord_store: HashMap::new(),
            layers: HashMap::new(),
            entity_layers: HashMap::new(),
        };
        backend.layers.insert("0".to_string(), LayerInfo::new("0"));
        backend
    }
}

impl MockBackend {
    fn alloc(&mut self, kind: &str) -> ObjectId {
        self.next_id += 1;
        let id = ObjectId::from_u64(self.next_id);
        self.kinds.insert(id, kind.to_string());
        id
    }
    fn body(&self, id: ObjectId) -> ApiResult<&KernelBody> {
        self.bodies.get(&id).ok_or(ApiError::UnknownId(id))
    }
    #[allow(dead_code)]
    pub fn undo_steps(&self) -> u32 {
        self.undo_steps
    }
}

/// Coarse bounds for a stored 2D curve spec (mirrors the host's entity_bounds).
fn curve_bounds(spec: &Curve2Spec) -> Aabb {
    match spec {
        Curve2Spec::Line { start, end, .. } => Aabb {
            min: [
                start[0].min(end[0]),
                start[1].min(end[1]),
                start[2].min(end[2]),
            ],
            max: [
                start[0].max(end[0]),
                start[1].max(end[1]),
                start[2].max(end[2]),
            ],
        },
        Curve2Spec::Circle { centre, radius, .. } => Aabb {
            min: [centre[0] - radius, centre[1] - radius, centre[2]],
            max: [centre[0] + radius, centre[1] + radius, centre[2]],
        },
        Curve2Spec::Point { position, .. } => Aabb {
            min: *position,
            max: *position,
        },
        Curve2Spec::Polyline { points, .. } => {
            let mut min = [f64::INFINITY; 3];
            let mut max = [f64::NEG_INFINITY; 3];
            for p in points {
                for i in 0..3 {
                    min[i] = min[i].min(p[i]);
                    max[i] = max[i].max(p[i]);
                }
            }
            Aabb { min, max }
        }
        Curve2Spec::Arc { centre, radius, .. } => Aabb {
            min: [centre[0] - radius, centre[1] - radius, centre[2]],
            max: [centre[0] + radius, centre[1] + radius, centre[2]],
        },
        Curve2Spec::Ellipse {
            centre, major_axis, ..
        } => {
            let r = (major_axis[0] * major_axis[0]
                + major_axis[1] * major_axis[1]
                + major_axis[2] * major_axis[2])
                .sqrt();
            Aabb {
                min: [centre[0] - r, centre[1] - r, centre[2] - r],
                max: [centre[0] + r, centre[1] + r, centre[2] + r],
            }
        }
        Curve2Spec::Spline { control_points, .. } => {
            let mut min = [f64::INFINITY; 3];
            let mut max = [f64::NEG_INFINITY; 3];
            for p in control_points {
                for i in 0..3 {
                    min[i] = min[i].min(p[i]);
                    max[i] = max[i].max(p[i]);
                }
            }
            Aabb { min, max }
        }
        Curve2Spec::Ray { origin, .. } | Curve2Spec::XLine { origin, .. } => Aabb {
            min: *origin,
            max: *origin,
        },
    }
}

impl DocApiBackend for MockBackend {
    fn resolve_body(&mut self, id: ObjectId) -> ApiResult<KernelBody> {
        Ok(self.body(id)?.clone())
    }
    fn store_solid(&mut self, body: &KernelBody) -> ApiResult<ObjectId> {
        let id = self.alloc("Solid3D");
        self.bodies.insert(id, body.clone());
        Ok(id)
    }
    fn update_solid(&mut self, id: ObjectId, body: &KernelBody) -> ApiResult<()> {
        if self.bodies.insert(id, body.clone()).is_none() {
            return Err(ApiError::UnknownId(id));
        }
        Ok(())
    }
    fn create_many(&mut self, specs: &[ocs_doc_api::EntitySpec]) -> ApiResult<Vec<ObjectId>> {
        // Validate per-spec layers up front so the op is atomic.
        for spec in specs {
            if let Some(name) = spec.layer() {
                self.lookup_layer(name).map_err(|e| ApiError::validation(
                    "CreateMany",
                    e.to_string(),
                ))?;
            }
        }
        let mut next = self.clone();
        let ids = specs
            .iter()
            .map(|spec| match spec {
                ocs_doc_api::EntitySpec::Solid(spec) => {
                    next.store_solid(&ocs_doc_api::geom::make_solid(spec)?)
                }
                ocs_doc_api::EntitySpec::Curve(spec) => {
                    ocs_doc_api::convert::curve_spec_to_entity(spec)?;
                    next.add_curve(spec)
                }
            })
            .collect::<ApiResult<Vec<_>>>()?;
        next.push_undo("CreateMany");
        next.finalize_op();
        *self = next;
        Ok(ids)
    }
    fn transform_many(&mut self, ids: &[ObjectId], placement: &PlacementSpec) -> ApiResult<()> {
        let mut next = self.clone();
        for &id in ids {
            next.transform_entity(id, placement)?;
        }
        next.push_undo("TransformMany");
        next.finalize_op();
        *self = next;
        Ok(())
    }
    fn add_curve(&mut self, spec: &Curve2Spec) -> ApiResult<ObjectId> {
        let kind = match spec {
            Curve2Spec::Line { .. } => "Line",
            Curve2Spec::Circle { .. } => "Circle",
            Curve2Spec::Polyline { .. } => "LwPolyline",
            Curve2Spec::Point { .. } => "Point",
            Curve2Spec::Arc { .. } => "Arc",
            Curve2Spec::Ellipse { .. } => "Ellipse",
            Curve2Spec::Spline { .. } => "Spline",
            Curve2Spec::Ray { .. } => "Ray",
            Curve2Spec::XLine { .. } => "XLine",
        };
        let layer = spec
            .layer()
            .map(|name| {
                self.lookup_layer(name).map(|info| info.normalized_name())
            })
            .transpose()?;
        let id = self.alloc(kind);
        self.curves.insert(id, spec.clone());
        self.entity_layers
            .insert(id, layer.unwrap_or_else(|| "0".to_string()));
        Ok(id)
    }

    fn lookup_layer(&self, name: &str) -> ApiResult<LayerInfo> {
        let norm = normalize_layer_name(name);
        if norm.is_empty() {
            return Err(ApiError::validation("LookupLayer", "empty layer name"));
        }
        self.layers
            .get(&norm)
            .cloned()
            .ok_or_else(|| ApiError::validation("LookupLayer", format!("layer '{name}' does not exist")))
    }
    fn add_insert(&mut self, spec: &ocs_doc_api::ops::InsertSpec) -> ApiResult<ObjectId> {
        if spec.block_name.is_empty() {
            return Err(ApiError::validation("CreateInsert", "empty block name"));
        }
        Ok(self.alloc("Insert"))
    }
    fn add_viewport(&mut self, spec: &ocs_doc_api::ops::ViewportSpec) -> ApiResult<ObjectId> {
        let id = self.alloc("Viewport");
        self.viewport_views
            .insert(id, (spec.view_target, spec.view_height));
        Ok(id)
    }
    fn add_text(&mut self, spec: &ocs_doc_api::ops::TextSpec) -> ApiResult<ObjectId> {
        let id = self.alloc("Text");
        self.text_values.insert(id, spec.value.clone());
        Ok(id)
    }
    fn add_mtext(&mut self, spec: &ocs_doc_api::ops::MTextSpec) -> ApiResult<ObjectId> {
        let id = self.alloc("MText");
        self.text_values.insert(id, spec.value.clone());
        Ok(id)
    }
    fn set_text_content(&mut self, id: ObjectId, value: &str) -> ApiResult<()> {
        if let std::collections::hash_map::Entry::Occupied(mut e) = self.text_values.entry(id) {
            e.insert(value.to_string());
            Ok(())
        } else {
            Err(ApiError::UnknownId(id))
        }
    }
    fn text_content(&self, id: ObjectId) -> ApiResult<String> {
        self.text_values
            .get(&id)
            .cloned()
            .ok_or(ApiError::UnknownId(id))
    }
    fn add_hatch(&mut self, spec: &ocs_doc_api::ops::HatchSpec) -> ApiResult<ObjectId> {
        let id = self.alloc("Hatch");
        self.hatch_boundaries
            .insert(id, vec![spec.boundary.clone()]);
        Ok(id)
    }
    fn hatch_boundary(&self, id: ObjectId) -> ApiResult<Vec<Vec<[f64; 2]>>> {
        self.hatch_boundaries
            .get(&id)
            .cloned()
            .ok_or(ApiError::UnknownId(id))
    }
    fn add_dimension_linear(
        &mut self,
        spec: &ocs_doc_api::ops::DimensionSpec,
    ) -> ApiResult<ObjectId> {
        let id = self.alloc("Dimension");
        let d = ((spec.first_point[0] - spec.second_point[0]).powi(2)
            + (spec.first_point[1] - spec.second_point[1]).powi(2)
            + (spec.first_point[2] - spec.second_point[2]).powi(2))
        .sqrt();
        self.dimension_measurements.insert(id, d);
        Ok(id)
    }
    fn add_dimension_radius(
        &mut self,
        spec: &ocs_doc_api::ops::DimensionRadialSpec,
    ) -> ApiResult<ObjectId> {
        let id = self.alloc("Dimension");
        let d = ((spec.center[0] - spec.point[0]).powi(2)
            + (spec.center[1] - spec.point[1]).powi(2)
            + (spec.center[2] - spec.point[2]).powi(2))
        .sqrt();
        self.dimension_measurements.insert(id, d);
        Ok(id)
    }
    fn add_dimension_diameter(
        &mut self,
        spec: &ocs_doc_api::ops::DimensionRadialSpec,
    ) -> ApiResult<ObjectId> {
        self.add_dimension_radius(spec)
    }
    fn add_dimension_angular(
        &mut self,
        _spec: &ocs_doc_api::ops::DimensionAngularSpec,
    ) -> ApiResult<ObjectId> {
        let id = self.alloc("Dimension");
        self.dimension_measurements.insert(id, 90.0);
        Ok(id)
    }
    fn dimension_measurement(&self, id: ObjectId) -> ApiResult<f64> {
        self.dimension_measurements
            .get(&id)
            .copied()
            .ok_or(ApiError::UnknownId(id))
    }
    fn add_attribute_definition(
        &mut self,
        spec: &ocs_doc_api::ops::AttributeDefinitionSpec,
    ) -> ApiResult<ObjectId> {
        if spec.tag.is_empty() {
            return Err(ApiError::validation(
                "CreateAttributeDefinition",
                "empty tag",
            ));
        }
        Ok(self.alloc("AttributeDefinition"))
    }
    fn add_dimension_angular2ln(
        &mut self,
        _spec: &ocs_doc_api::ops::DimensionAngularSpec,
    ) -> ApiResult<ObjectId> {
        let id = self.alloc("Dimension");
        self.dimension_measurements.insert(id, 90.0);
        Ok(id)
    }
    fn add_table(&mut self, spec: &ocs_doc_api::ops::TableSpec) -> ApiResult<ObjectId> {
        let cols = spec.data.first().map(|r| r.len()).unwrap_or(0);
        if spec.data.is_empty() || cols == 0 || spec.data.iter().any(|r| r.len() != cols) {
            return Err(ApiError::validation(
                "CreateTable",
                "table needs a non-empty rectangular grid",
            ));
        }
        Ok(self.alloc("Table"))
    }
    fn set_attribute(&mut self, id: ObjectId, tag: &str, value: &str) -> ApiResult<()> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        let attrs = self.attributes_store.entry(id).or_default();
        if let Some(a) = attrs.iter_mut().find(|(t, _)| t == tag) {
            a.1 = value.to_string();
        } else {
            attrs.push((tag.to_string(), value.to_string()));
        }
        Ok(())
    }
    fn attributes(&self, id: ObjectId) -> ApiResult<Vec<(String, String)>> {
        self.attributes_store
            .get(&id)
            .cloned()
            .ok_or(ApiError::UnknownId(id))
    }
    fn block_entities(&self, _block_name: &str) -> ApiResult<Vec<EntityView>> {
        Ok(Vec::new())
    }
    fn add_raster_image(
        &mut self,
        _spec: &ocs_doc_api::ops::RasterImageSpec,
    ) -> ApiResult<ObjectId> {
        Ok(self.alloc("RasterImage"))
    }
    fn loft(
        &mut self,
        sections: &[(cadkernel::space::Plane, Vec<cadkernel::geom2d::Curve>)],
    ) -> ApiResult<ObjectId> {
        if sections.len() < 2 {
            return Err(ApiError::validation("Loft", "loft needs >= 2 profiles"));
        }
        let body = cadkernel::brep::make::cuboid([0.0, 0.0, 0.0], [1.0; 3])
            .ok_or_else(|| ApiError::geometry(GeometryErrorKind::InvalidInput, "make cuboid"))?;
        self.store_solid(&body)
    }
    fn set_viewport_view(
        &mut self,
        id: ObjectId,
        view_target: [f64; 3],
        view_height: f64,
    ) -> ApiResult<()> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        self.viewport_views.insert(id, (view_target, view_height));
        Ok(())
    }
    fn viewport_view(&self, id: ObjectId) -> ApiResult<([f64; 3], f64)> {
        self.viewport_views
            .get(&id)
            .copied()
            .ok_or(ApiError::UnknownId(id))
    }
    fn set_xdata(
        &mut self,
        id: ObjectId,
        application_name: &str,
        record: Option<&ocs_doc_api::XDataRecord>,
    ) -> ApiResult<()> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        let key = (id, application_name.to_string());
        match record {
            Some(r) => {
                self.xdata_store.insert(key, r.clone());
            }
            None => {
                self.xdata_store.remove(&key);
            }
        }
        Ok(())
    }
    fn xdata(
        &self,
        id: ObjectId,
        application_name: &str,
    ) -> ApiResult<Option<ocs_doc_api::XDataRecord>> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        Ok(self
            .xdata_store
            .get(&(id, application_name.to_string()))
            .cloned())
    }
    fn add_xrecord(&mut self, spec: &ocs_doc_api::XRecordSpec) -> ApiResult<ObjectId> {
        let id = self.alloc("XRecord");
        self.xrecord_store.insert(id, spec.clone());
        Ok(id)
    }
    fn set_xrecord(&mut self, id: ObjectId, spec: &ocs_doc_api::XRecordSpec) -> ApiResult<()> {
        if !self.object_exists(id) {
            return Err(ApiError::validation(
                "SetXRecord",
                format!("unknown ObjectId {id:?}"),
            ));
        }
        self.xrecord_store.insert(id, spec.clone());
        Ok(())
    }
    fn xrecord(&self, id: ObjectId) -> ApiResult<Option<ocs_doc_api::XRecordSpec>> {
        if !self.object_exists(id) {
            return Err(ApiError::validation(
                "GetXRecord",
                format!("unknown ObjectId {id:?}"),
            ));
        }
        Ok(self.xrecord_store.get(&id).cloned())
    }
    fn create_layer(&mut self, info: &LayerInfo) -> ApiResult<()> {
        let name = normalize_layer_name(&info.name);
        if name.is_empty() {
            return Err(ApiError::validation("CreateLayer", "empty layer name"));
        }
        if self.layers.contains_key(&name) {
            return Err(ApiError::validation(
                "CreateLayer",
                format!("layer '{name}' already exists"),
            ));
        }
        let mut stored = info.clone();
        stored.name = name.clone();
        self.layers.insert(name, stored);
        Ok(())
    }
    fn update_layer(&mut self, name: &str, info: &LayerInfo) -> ApiResult<()> {
        let name_upper = normalize_layer_name(name);
        if !self.layers.contains_key(&name_upper) {
            return Err(ApiError::validation(
                "UpdateLayer",
                format!("layer '{name}' does not exist"),
            ));
        }
        let mut stored = info.clone();
        stored.name = name_upper.clone();
        self.layers.insert(name_upper, stored);
        Ok(())
    }
    fn delete_layer(&mut self, name: &str) -> ApiResult<()> {
        let name_upper = normalize_layer_name(name);
        if name_upper == "0" {
            return Err(ApiError::validation("DeleteLayer", "cannot delete layer 0"));
        }
        if self.entity_layers.values().any(|l| normalize_layer_name(l) == name_upper) {
            return Err(ApiError::validation(
                "DeleteLayer",
                format!("layer '{name_upper}' still in use"),
            ));
        }
        if self.layers.remove(&name_upper).is_none() {
            return Err(ApiError::validation(
                "DeleteLayer",
                format!("layer '{name}' does not exist"),
            ));
        }
        Ok(())
    }
    fn set_entity_layer(&mut self, id: ObjectId, layer: &str) -> ApiResult<()> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        let layer_upper = normalize_layer_name(layer);
        let target = self
            .layers
            .get(&layer_upper)
            .ok_or_else(|| {
                ApiError::validation(
                    "SetEntityLayer",
                    format!("layer '{layer_upper}' does not exist"),
                )
            })?;
        if target.flags.locked {
            return Err(ApiError::Unsupported(format!(
                "entity {id:?} cannot be moved to locked layer '{layer_upper}'"
            )));
        }
        self.entity_layers.insert(id, layer_upper);
        Ok(())
    }
    fn layers(&self) -> ApiResult<Vec<LayerInfo>> {
        let mut v: Vec<_> = self.layers.values().cloned().collect();
        v.sort_by(|a, b| a.name.cmp(&b.name));
        Ok(v)
    }
    fn entity_layer(&self, id: ObjectId) -> ApiResult<String> {
        self.entity_layers
            .get(&id)
            .cloned()
            .ok_or(ApiError::UnknownId(id))
    }
    fn add_vertex(&mut self, id: ObjectId, _at: usize, _point: [f64; 3]) -> ApiResult<()> {
        if self.entity_exists(id) {
            Ok(())
        } else {
            Err(ApiError::UnknownId(id))
        }
    }
    fn remove_entity(&mut self, id: ObjectId) -> ApiResult<bool> {
        self.bodies.remove(&id);
        self.xdata_store.retain(|(k, _), _| *k != id);
        self.xrecord_store.remove(&id);
        self.entity_layers.remove(&id);
        Ok(self.kinds.remove(&id).is_some())
    }
    fn enumerate_entities(
        &self,
        kind: Option<&str>,
        layer: Option<&str>,
        include_bounds: bool,
    ) -> ApiResult<Vec<EntityView>> {
        let mut out = Vec::new();
        for (id, kind_name) in &self.kinds {
            if let Some(k) = kind {
                if !k.eq_ignore_ascii_case(kind_name) {
                    continue;
                }
            }
            let entity_layer = self
                .entity_layers
                .get(id)
                .cloned()
                .unwrap_or_else(|| "0".to_string());
            if let Some(l) = layer {
                if !l.eq_ignore_ascii_case(&entity_layer) {
                    continue;
                }
            }
            let bounds = if include_bounds {
                self.curves.get(id).map(curve_bounds)
            } else {
                None
            };
            out.push(EntityView {
                id: *id,
                kind: kind_name.clone(),
                layer: entity_layer,
                bounds,
            });
        }
        Ok(out)
    }
    fn point_position(&self, id: ObjectId) -> ApiResult<[f64; 3]> {
        let spec = self.curves.get(&id).ok_or(ApiError::UnknownId(id))?;
        match spec {
            Curve2Spec::Point { position, .. } => Ok(*position),
            _ => Err(ApiError::Unsupported(
                "GetPointPosition is only for Point entities".into(),
            )),
        }
    }
    fn line_geometry(&self, id: ObjectId) -> ApiResult<([f64; 3], [f64; 3])> {
        let spec = self.curves.get(&id).ok_or(ApiError::UnknownId(id))?;
        match spec {
            Curve2Spec::Line { start, end, .. } => Ok((*start, *end)),
            _ => Err(ApiError::Unsupported(
                "GetLineGeometry is only for Line entities".into(),
            )),
        }
    }
    fn get_entity(&mut self, id: ObjectId) -> ApiResult<EntityView> {
        let kind = self.kinds.get(&id).ok_or(ApiError::UnknownId(id))?.clone();
        let layer = self
            .entity_layers
            .get(&id)
            .cloned()
            .unwrap_or_else(|| "0".to_string());
        let bounds = self.bodies.get(&id).and_then(|b| {
            cadkernel::brep::body_bounds(b).map(|bb| Aabb {
                min: bb.min,
                max: bb.max,
            })
        });
        Ok(EntityView {
            id,
            kind,
            layer,
            bounds,
        })
    }
    fn transform_entity(&mut self, id: ObjectId, placement: &PlacementSpec) -> ApiResult<()> {
        if !self.entity_exists(id) {
            return Err(ApiError::UnknownId(id));
        }
        if let Some(body) = self.bodies.get(&id).cloned() {
            let place = cadkernel::brep::Placement {
                x_axis: placement.x_axis,
                y_axis: placement.y_axis,
                z_axis: placement.z_axis,
                origin: placement.origin,
            };
            let moved = cadkernel::brep::transform(&body, &place).ok_or_else(|| {
                ApiError::geometry(GeometryErrorKind::InvalidInput, "transform failed")
            })?;
            self.bodies.insert(id, moved);
        }
        Ok(())
    }
    fn profile_curves(&self, _id: ObjectId) -> ApiResult<Vec<cadkernel::geom2d::Curve>> {
        Err(ApiError::Unsupported("profiles not mocked".into()))
    }
    fn bounds(&mut self, id: ObjectId) -> ApiResult<Aabb> {
        // Solids via the kernel body; 2D curves from their stored spec.
        if let Some(body) = self.bodies.get(&id) {
            let bb = cadkernel::brep::body_bounds(body)
                .ok_or_else(|| ApiError::geometry(GeometryErrorKind::Empty, "no bounds"))?;
            return Ok(Aabb {
                min: bb.min,
                max: bb.max,
            });
        }
        if let Some(spec) = self.curves.get(&id) {
            return Ok(curve_bounds(spec));
        }
        Err(ApiError::UnknownId(id))
    }
    fn centroid(&mut self, id: ObjectId) -> ApiResult<[f64; 3]> {
        let body = self.body(id)?;
        Ok(mesh_vc(&cadkernel::brep::mesh_body(body, 0.5, 1e-3)).1)
    }
    fn volume(&mut self, id: ObjectId) -> ApiResult<f64> {
        let body = self.body(id)?;
        Ok(mesh_vc(&cadkernel::brep::mesh_body(body, 0.5, 1e-3)).0)
    }
    fn entity_exists(&self, id: ObjectId) -> bool {
        self.kinds.contains_key(&id)
    }
    fn object_exists(&self, id: ObjectId) -> bool {
        self.xrecord_store.contains_key(&id)
    }
    fn revision(&self) -> GeometryRevision {
        GeometryRevision(self.revision)
    }
    fn push_undo(&mut self, _label: &str) {}
    fn finalize_op(&mut self) {
        self.undo_steps += 1;
        self.revision += 1;
    }
}

/// Signed volume + centroid of a closed mesh — delegates to the crate's single
/// source of truth (divergence theorem) so the example mock can't drift.
fn mesh_vc(mesh: &cadkernel::brep::Mesh) -> (f64, [f64; 3]) {
    ocs_doc_api::geom::mesh_volume_centroid(mesh)
}