1 files changed, 186 insertions, 0 deletions

diff --git a/src/msev.rs b/src/msev.rs
new file mode 100644
index 0000000..9abc5a4
--- /dev/null
+++ b/src/msev.rs
@@ -0,0 +1,186 @@
+// Make Split Edge Vertex
+
+use crate::*;
+
+pub struct Msev<'brand, 'arena, V> {
+    pub shell: ptr!(Shell),
+    pub vertex: ptr!(Vertex),
+    pub loops: [ptr!(Loop); 2],
+    pub data: V,
+}
+
+impl<'brand, 'arena, V> Msev<'brand, 'arena, V> {
+    pub fn new(shell: ptr!(Shell), vertex: ptr!(Vertex), loops: [ptr!(Loop); 2], data: V) -> Self {
+        Self {
+            shell,
+            vertex,
+            loops,
+            data,
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+pub enum MsevError {
+    #[error("vertex is not part of loop")]
+    VertexLoopMismatch,
+}
+
+impl<'brand, 'arena, V> Operator<'brand, 'arena, V> for Msev<'brand, 'arena, V> {
+    type Inverse = Ksev<'brand, 'arena, V>;
+    type Error = MsevError;
+    type Check = [ptr!(HalfEdge); 2];
+
+    fn check(&self, dcel: &Dcel<'brand, 'arena, V>) -> Result<Self::Check, Self::Error> {
+        use MsevError::*;
+
+        let a = self
+            .vertex
+            .find_outgoing(self.loops[0], dcel)
+            .ok_or(VertexLoopMismatch)?;
+        let b = self
+            .vertex
+            .find_outgoing(self.loops[1], dcel)
+            .ok_or(VertexLoopMismatch)?;
+
+        Ok([a, b])
+    }
+
+    fn apply(
+        self,
+        dcel: &mut Dcel<'brand, 'arena, V>,
+    ) -> Result<Self::Inverse, OperatorErr<Self, Self::Error>> {
+        let [a2, b0] = try_check!(self, dcel);
+        let a0 = a2.prev(dcel);
+        let b2 = b0.prev(dcel);
+
+        let (edge, [a1, b1]) = Edge::create(self.shell, dcel);
+        let v = self.shell.add_new_vertex(self.data, dcel);
+
+        a1.update_origin(self.vertex, dcel);
+        b2.twin(dcel).update_origin(*v, dcel);
+        b1.update_origin(*v, dcel);
+        a2.update_origin(*v, dcel);
+
+        dcel.follow(a0, a1);
+        dcel.follow(a1, a2);
+
+        dcel.follow(b2, b1);
+        dcel.follow(b1, b0);
+
+        a1.set_loop_(self.loops[0], dcel);
+        b1.set_loop_(self.loops[1], dcel);
+
+        Ok(Ksev {
+            shell: self.shell,
+            loops: self.loops,
+            old_vertex: self.vertex,
+            new_vertex: v,
+            edge,
+        })
+    }
+}
+
+pub struct Ksev<'brand, 'arena, V> {
+    pub shell: ptr!(Shell),
+    pub loops: [ptr!(Loop); 2],
+    pub old_vertex: ptr!(Vertex),
+    pub new_vertex: own!(Vertex),
+    pub edge: own!(Edge),
+}
+
+impl<'brand, 'arena, V> Ksev<'brand, 'arena, V> {
+    pub fn new(
+        shell: ptr!(Shell),
+        loops: [ptr!(Loop); 2],
+        old_vertex: ptr!(Vertex),
+        new_vertex: own!(Vertex),
+        edge: own!(Edge),
+    ) -> Self {
+        Self {
+            shell,
+            loops,
+            old_vertex,
+            new_vertex,
+            edge,
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+pub enum KsevError {
+    #[error("edge does not match vertices")]
+    EdgeVertexMismatch,
+    #[error("edge does not match loops")]
+    EdgeLoopMismatch,
+}
+
+impl<'brand, 'arena, V> Operator<'brand, 'arena, V> for Ksev<'brand, 'arena, V> {
+    type Inverse = Msev<'brand, 'arena, V>;
+    type Error = KsevError;
+    type Check = [ptr!(HalfEdge); 2];
+
+    fn check(&self, dcel: &Dcel<'brand, 'arena, V>) -> Result<Self::Check, Self::Error> {
+        use KsevError::*;
+
+        let [mut a, mut b] = self.edge.lens(dcel).half_edges();
+        if a.origin().eq(*self.new_vertex) {
+            [a, b] = [b, a];
+        }
+
+        or_err(
+            a.origin().eq(self.old_vertex) && b.origin().eq(*self.new_vertex),
+            EdgeVertexMismatch,
+        )?;
+
+        or_err(
+            (a.loop_().eq(self.loops[0]) && b.loop_().eq(self.loops[1]))
+                || (a.loop_().eq(self.loops[1]) && b.loop_().eq(self.loops[0])),
+            EdgeLoopMismatch,
+        )?;
+
+        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 Ksev {
+            shell,
+            old_vertex,
+            new_vertex,
+            edge,
+            ..
+        } = self;
+
+        let loops = [a1.loop_(dcel), b1.loop_(dcel)];
+
+        let a0 = a1.prev(dcel);
+        let a2 = a1.next(dcel);
+
+        let b0 = b1.next(dcel);
+        let b2 = b1.prev(dcel);
+
+        dcel.follow(a0, a2);
+        dcel.follow(b2, b0);
+
+        a2.update_origin(old_vertex, dcel);
+        b2.twin(dcel).update_origin(old_vertex, dcel);
+
+        loops[0].set_half_edges(a0, dcel);
+        loops[1].set_half_edges(b0, dcel);
+
+        edge.destroy(dcel);
+        let data = new_vertex.destroy(dcel);
+
+        Ok(Msev {
+            shell,
+            vertex: old_vertex,
+            loops,
+            data,
+        })
+    }
+}