From 28f5d3ea1f9a6ad704c3e0182b0bbad1a77ec09c Mon Sep 17 00:00:00 2001
From: hheik <4469778+hheik@users.noreply.github.com>
Date: Tue, 5 May 2026 17:24:24 +0300
Subject: [PATCH] get_node() now returns Result<Option<&T>> to indicate tiles
 that are out of bounds. Fixed inconsistent spelling of neighbor -> neighbour

---
 src/lib.rs | 68 +++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 44 insertions(+), 24 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 41c433a..5b69801 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
-/// A trait for graph-like structures, where you can get a node by a unique value and find its neighbors.
+/// A trait for graph-like structures, where you can get a node by a unique value and find its
+/// neighbours.
 ///
 /// **Node** represents some settled data type. The graph should likely contain `Option<Node>`
 /// elements prepopulated with `None` values. For example `[[None; WIDTH]; HEIGHT]` for a 2D grid.
@@ -15,23 +16,33 @@ pub trait GraphLike<Node, NodeId> {
     /// Used in the default implementation of `full_generation`
     const MAX_RETRIES: usize = 5;
 
-    fn get_node(&self, id: NodeId) -> Option<&Node>;
+    fn get_node(&self, id: NodeId) -> Result<Option<&Node>, ()>;
     fn set_node(&mut self, id: NodeId, node: Option<Node>);
     fn iter_ids(&self) -> impl Iterator<Item = NodeId>;
-    fn iter_neighbor_ids(&self, id: NodeId) -> impl Iterator<Item = NodeId>;
+    fn iter_neighbour_ids(&self, id: NodeId) -> impl Iterator<Item = NodeId>;
 
     fn iter_nodes<'a>(&'a self) -> impl Iterator<Item = (NodeId, Option<&'a Node>)>
     where
         Node: 'a,
         NodeId: Copy,
     {
-        self.iter_ids().map(|id| (id, self.get_node(id)))
+        self.iter_ids().map(|id| {
+            (
+                id,
+                self.get_node(id)
+                    .expect("GraphLike::iter_ids() should only return valid ids"),
+            )
+        })
     }
     fn iter_empty(&self) -> impl Iterator<Item = NodeId>
     where
         NodeId: Copy,
     {
-        self.iter_ids().filter(|id| self.get_node(*id).is_none())
+        self.iter_ids().filter(|id| {
+            self.get_node(*id)
+                .expect("GraphLike::iter_ids() should only return valid ids")
+                .is_none()
+        })
     }
     fn iter_neighbour_nodes<'a>(
         &'a self,
@@ -41,7 +52,13 @@ pub trait GraphLike<Node, NodeId> {
         NodeId: Copy,
         Node: 'a,
     {
-        self.iter_neighbor_ids(id).map(|id| (id, self.get_node(id)))
+        self.iter_neighbour_ids(id).map(|id| {
+            (
+                id,
+                self.get_node(id)
+                    .expect("GraphLike::iter_neighbour_ids() should only return valid ids"),
+            )
+        })
     }
 
     fn single_step(
@@ -144,8 +161,11 @@ mod tests {
     }
 
     impl GraphLike<u8, (usize, usize)> for TestGraph {
-        fn get_node(&self, id: (usize, usize)) -> Option<&u8> {
-            self.tiles[id.0][id.1].as_ref()
+        fn get_node(&self, id: (usize, usize)) -> Result<Option<&u8>, ()> {
+            if id.0 >= 3 || id.1 >= 3 {
+                return Err(());
+            }
+            Ok(self.tiles[id.0][id.1].as_ref())
         }
 
         fn set_node(&mut self, id: (usize, usize), node: Option<u8>) {
@@ -156,25 +176,25 @@ mod tests {
             (0..3).flat_map(|i| (0..3).map(move |j| (i, j)))
         }
 
-        fn iter_neighbor_ids(&self, id: (usize, usize)) -> impl Iterator<Item = (usize, usize)> {
-            let mut neighbors = vec![];
+        fn iter_neighbour_ids(&self, id: (usize, usize)) -> impl Iterator<Item = (usize, usize)> {
+            let mut neighbours = vec![];
             if id.0 > 0 {
-                neighbors.push((id.0 - 1, id.1));
+                neighbours.push((id.0 - 1, id.1));
             }
             if id.0 < 2 {
-                neighbors.push((id.0 + 1, id.1));
+                neighbours.push((id.0 + 1, id.1));
             }
             if id.1 > 0 {
-                neighbors.push((id.0, id.1 - 1));
+                neighbours.push((id.0, id.1 - 1));
             }
             if id.1 < 2 {
-                neighbors.push((id.0, id.1 + 1));
+                neighbours.push((id.0, id.1 + 1));
             }
-            neighbors.into_iter()
+            neighbours.into_iter()
         }
     }
 
-    /// Entropy is the number of empty neighbors, and choose sets the value to the same value.
+    /// Entropy is the number of empty neighbours, and choose sets the value to the same value.
     /// Just for testing.
     struct TestRuleset;
 
@@ -184,11 +204,11 @@ mod tests {
             graph: &impl GraphLike<u8, (usize, usize)>,
             id: (usize, usize),
         ) -> Option<f32> {
-            let neighbors = graph
+            let neighbours = graph
                 .iter_neighbour_nodes(id)
                 .filter(|n| n.1.is_some())
                 .count();
-            Some(4_usize.strict_sub(neighbors) as f32)
+            Some(4_usize.strict_sub(neighbours) as f32)
         }
 
         fn choose(
@@ -197,11 +217,11 @@ mod tests {
             id: (usize, usize),
             _retry_count: Option<usize>,
         ) -> Option<u8> {
-            let neighbors = graph
+            let neighbours = graph
                 .iter_neighbour_nodes(id)
                 .filter(|n| n.1.is_some())
                 .count();
-            Some(4_usize.strict_sub(neighbors) as u8)
+            Some(4_usize.strict_sub(neighbours) as u8)
         }
     }
 
@@ -215,8 +235,8 @@ mod tests {
                 [None, None, None],
             ],
         };
-        assert_eq!(graph.get_node((0, 0)), None);
-        assert_eq!(graph.get_node((1, 2)), Some(&99));
+        assert_eq!(graph.get_node((0, 0)), Ok(None));
+        assert_eq!(graph.get_node((1, 2)), Ok(Some(&99)));
     }
 
     #[test]
@@ -290,14 +310,14 @@ mod tests {
     }
 
     #[test]
-    fn iter_neighbor_ids_works() {
+    fn iter_neighbour_ids_works() {
         // This really tests that the implementation itself works...
         let graph = TestGraph {
             tiles: [[None; 3]; 3],
         };
         assert_eq!(
             graph
-                .iter_neighbor_ids((1, 1))
+                .iter_neighbour_ids((1, 1))
                 .collect::<HashSet<(usize, usize)>>(),
             vec![(0, 1), (2, 1), (1, 0), (1, 2)]
                 .into_iter()