skip calculating index from id when index already present

battlesnake/src/types/simulation.rs

@@ -204,25 +204,19 @@ impl Board {
     }
 
     pub fn valid_actions(&self, id: u8) -> impl Iterator<Item = Direction> + use<'_> {
-        let head = self
-            .snakes
-            .binary_search_by_key(&id, |snake| snake.id)
-            .ok()
-            .map(|index| self.snakes[index].head());
-        if head.is_none() {
-            warn!(
-                "Asked for an action for a snake that doesn't exist: {id} not in {:?}",
-                self.snakes
-            );
+        let index = self.snakes.binary_search_by_key(&id, |snake| snake.id).ok();
+        if index.is_none() {
+            warn!("Asked for a snake that doesn't exist");
         }
-        enum_iterator::all::<Direction>()
-            .filter_map(move |direction| {
-                head.and_then(|head| head.apply(direction))
-                    .map(|tile| (direction, tile))
-            })
-            .filter(|(_, tile)| tile.x < self.width && tile.y < self.height)
-            .filter(|(_, tile)| self.is_free(*tile))
-            .map(|(direction, _)| direction)
+        index
+            .into_iter()
+            .flat_map(|index| self.valid_actions_index(index))
+    }
+
+    pub fn random_actions(
+        &self,
+    ) -> impl Iterator<Item = (u8, impl Iterator<Item = Direction> + use<'_>)> {
+        (0..self.snakes.len()).map(|index| (self.snakes[index].id, self.valid_actions_index(index)))
     }
 
     pub fn simulate_random<T>(&mut self, stop: impl Fn(&Self) -> Option<T>) -> T {
@@ -245,12 +239,21 @@ impl Board {
         self.turn += 1;
     }
 
+    fn valid_actions_index(&self, index: usize) -> impl Iterator<Item = Direction> + use<'_> {
+        let head = self.snakes[index].head();
+        enum_iterator::all::<Direction>()
+            .map(move |direction| (direction, head.wrapping_apply(direction)))
+            .filter(|(_, tile)| self.is_in_bounds(*tile))
+            .filter(|(_, tile)| self.is_free(*tile))
+            .map(|(direction, _)| direction)
+    }
+
     fn move_standard(&mut self, actions: &[(u8, Direction)]) {
         for i in 0..self.snakes.len() {
             let snake = &self.snakes[i];
             let action = actions.iter().find(|(id, _)| *id == snake.id).map_or_else(
                 || {
-                    self.valid_actions(snake.id)
+                    self.valid_actions_index(i)
                         .choose(&mut thread_rng())
                         .unwrap_or(Direction::Up)
                 },