a

src/board.rs

@@ -39,6 +39,14 @@ impl Board {
         }
     }
 
+    pub const fn starting_pos(mut self) -> Self {
+        self.place_unchecked(3, 3, Piece::White);
+        self.place_unchecked(4, 3, Piece::Black);
+        self.place_unchecked(3, 4, Piece::Black);
+        self.place_unchecked(4, 4, Piece::White);
+        self
+    }
+
     /// Returns a mutable reference to a place on the [`Board`]
     /// at (i, j)
     pub const fn get_mut(&mut self, i: usize, j: usize) -> &mut Option<Piece> {
@@ -55,13 +63,21 @@ impl Board {
         *self.get_mut(i, j) = Some(piece);
     }
 
+    pub fn test_prop(&self, i: usize, j: usize, piece: Piece) -> bool {
+        let mut self_copy = self.clone();
+        if self_copy.get(i, j).is_some() {
+            return false;
+        }
+        self_copy.place_and_prop_unchecked(i, j, piece)
+    }
+
     /// Propegate piece captures originating from (i, j)
     /// DO NOT USE THIS ALONE, this should be called as a part of
     /// [`Board::place`] or [`Board::place_and_prop_unchecked`]
-    fn propegate_from(&mut self, i: usize, j: usize) {
+    fn propegate_from(&mut self, i: usize, j: usize) -> bool {
         // returns if that place is empty
         let Some(starting_color) = *self.get(i, j) else {
-            return;
+            return false;
         };
 
         // Create all chains from the piece being propegated from in `i` and `j` coordinates
@@ -69,6 +85,7 @@ impl Board {
             .into_iter()
             .map(|range| range.into_iter().map(|i| (i, j)).collect())
             .collect();
+
         chains.extend(
             split_from(0, BOARD_SIZE - 1, j)
                 .into_iter()
@@ -80,6 +97,7 @@ impl Board {
                 let Some(piece) = self.get(new_i, new_j) else {
                     break;
                 };
+
                 if piece == &starting_color {
                     if chain_length > 0 {
                         // fill all opposite colors with this color
@@ -91,18 +109,20 @@ impl Board {
                         for &(i_o, j_o) in history {
                             self.place_and_prop_unchecked(i_o, j_o, starting_color);
                         }
+                        return true;
                     }
                     // either the other pieces were replaced, or this was an invalid chain,
                     // in both cases, the loop needs to be breaked
-                    break;
+                    return false;
                 }
             }
         }
+        false
     }
 
-    fn place_and_prop_unchecked(&mut self, i: usize, j: usize, piece: Piece) {
+    fn place_and_prop_unchecked(&mut self, i: usize, j: usize, piece: Piece) -> bool {
         self.place_unchecked(i, j, piece);
-        self.propegate_from(i, j);
+        self.propegate_from(i, j)
     }
 
     /// Place a piece on the [`Board`]