1 files changed, 212 insertions, 0 deletions
diff --git a/src/mekh.rs b/src/mekh.rs
new file mode 100644
index 0000000..9b23115
--- /dev/null
+++ b/src/mekh.rs
@@ -0,0 +1,212 @@
+use crate::*;
+
+pub struct Mekh<'brand, 'arena, V> {
+    pub shell: ptr!(Shell),
+    pub into_loop: ptr!(Loop),
+    pub into_vertex: ptr!(Vertex),
+    pub hole_loop: own!(Loop),
+    pub hole_vertex: ptr!(Vertex),
+}
+
+impl<'brand, 'arena, V> Mekh<'brand, 'arena, V> {
+    pub fn new(
+        shell: ptr!(Shell),
+        into_loop: ptr!(Loop),
+        into_vertex: ptr!(Vertex),
+        hole_loop: own!(Loop),
+        hole_vertex: ptr!(Vertex),
+    ) -> Self {
+        Self {
+            shell,
+            into_loop,
+            into_vertex,
+            hole_loop,
+            hole_vertex,
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+pub enum MekhError {
+    #[error("cannot join loop with itself")]
+    SameLoop,
+    #[error("loops do not share the same face")]
+    LoopFaceMismatch,
+    #[error("hole loop is an outer loop")]
+    HoleIsOuter,
+    #[error("vertex is not part of loop")]
+    VertexLoopMismatch,
+}
+
+impl<'brand, 'arena, V> Operator<'brand, 'arena, V> for Mekh<'brand, 'arena, V> {
+    type Inverse = Kemh<'brand, 'arena, V>;
+    type Error = MekhError;
+    type Check = [ptr!(HalfEdge); 2];
+
+    fn check(&self, dcel: &Dcel<'brand, 'arena, V>) -> Result<Self::Check, Self::Error> {
+        use MekhError::*;
+
+        let into_loop = self.into_loop.lens(dcel);
+        or_err(!into_loop.eq(*self.hole_loop), SameLoop)?;
+        or_err(
+            into_loop.face().eq(self.hole_loop.face(dcel)),
+            LoopFaceMismatch,
+        )?;
+        or_err(!self.hole_loop.is_outer(dcel), HoleIsOuter)?;
+
+        let into_he = self
+            .into_vertex
+            .find_outgoing(self.into_loop, dcel)
+            .ok_or(VertexLoopMismatch)?;
+        let hole_he = self
+            .hole_vertex
+            .find_outgoing(*self.hole_loop, dcel)
+            .ok_or(VertexLoopMismatch)?;
+
+        Ok([into_he, hole_he])
+    }
+
+    fn apply(
+        self,
+        dcel: &mut Dcel<'brand, 'arena, V>,
+    ) -> Result<Self::Inverse, OperatorErr<Self, Self::Error>> {
+        let [b0, a2] = try_check!(self, dcel);
+
+        let Mekh {
+            shell,
+            into_loop,
+            into_vertex,
+            hole_loop,
+            hole_vertex,
+        } = self;
+
+        let (edge, [a1, b1]) = Edge::create(shell, dcel);
+
+        let a0 = b0.prev(dcel);
+        let b2 = a2.prev(dcel);
+
+        a1.update_origin(into_vertex, dcel);
+        dcel.follow(a0, a1);
+        dcel.follow(a1, a2);
+
+        b1.update_origin(hole_vertex, dcel);
+        dcel.follow(b2, b1);
+        dcel.follow(b1, b0);
+
+        into_loop.update_connectivity(dcel);
+
+        hole_loop.face(dcel).remove_inner_loop(*hole_loop, dcel);
+        hole_loop.free(dcel);
+
+        Ok(Kemh {
+            shell,
+            edge,
+            loop_: into_loop,
+            hole_vertex,
+        })
+    }
+}
+
+pub struct Kemh<'brand, 'arena, V> {
+    pub shell: ptr!(Shell),
+    pub edge: own!(Edge),
+    pub loop_: ptr!(Loop),
+    pub hole_vertex: ptr!(Vertex),
+}
+
+#[derive(Error, Debug)]
+pub enum KemhError {
+    #[error("vertex is not part of edge")]
+    HalfEdgeVertexMismatch,
+    #[error("both half edges need to be part of loop")]
+    HalfEdgeLoopMismatch,
+}
+
+impl<'brand, 'arena, V> Kemh<'brand, 'arena, V> {
+    pub fn new(
+        shell: ptr!(Shell),
+        edge: own!(Edge),
+        loop_: ptr!(Loop),
+        hole_vertex: ptr!(Vertex),
+    ) -> Self {
+        Self {
+            shell,
+            edge,
+            loop_,
+            hole_vertex,
+        }
+    }
+}
+
+impl<'brand, 'arena, V> Operator<'brand, 'arena, V> for Kemh<'brand, 'arena, V> {
+    type Inverse = Mekh<'brand, 'arena, V>;
+    type Error = KemhError;
+    type Check = [ptr!(HalfEdge); 2];
+
+    fn check(&self, dcel: &Dcel<'brand, 'arena, V>) -> Result<Self::Check, Self::Error> {
+        use KemhError::*;
+        let Kemh {
+            edge,
+            loop_,
+            hole_vertex,
+            ..
+        } = self;
+
+        let [mut a, mut b] = edge.lens(dcel).half_edges();
+
+        if a.origin().eq(*hole_vertex) {
+            [b, a] = [a, b];
+        } else {
+            or_err(b.origin().eq(*hole_vertex), HalfEdgeVertexMismatch)?;
+        }
+
+        or_err(
+            a.loop_().eq(*loop_) && b.loop_().eq(*loop_),
+            HalfEdgeLoopMismatch,
+        )?;
+
+        Ok([a.item, b.item])
+    }
+
+    fn apply(
+        self,
+        dcel: &mut Dcel<'brand, 'arena, V>,
+    ) -> Result<Self::Inverse, OperatorErr<Self, Self::Error>> {
+        let [a1, b1] = try_check!(self, dcel);
+        let Kemh {
+            shell,
+            edge,
+            loop_: into_loop,
+            hole_vertex,
+        } = self;
+
+        let hole_loop = into_loop.face(dcel).add_new_inner_loop(dcel);
+        let into_vertex = a1.origin(dcel);
+
+        let a0 = a1.prev(dcel);
+        let a2 = a1.next(dcel);
+
+        let b0 = b1.next(dcel);
+        let b2 = b1.prev(dcel);
+
+        dcel.follow(a0, b0);
+        dcel.follow(b2, a2);
+
+        b0.update_origin(into_vertex, dcel);
+        a2.update_origin(hole_vertex, dcel);
+
+        hole_loop.set_half_edges(a2, dcel);
+        hole_loop.update_connectivity(dcel);
+
+        shell.remove_edge(*edge, dcel);
+        edge.destroy(dcel);
+
+        Ok(Mekh {
+            shell,
+            into_loop,
+            into_vertex,
+            hole_loop,
+            hole_vertex,
+        })
+    }
+}