Implement make_move function on engine

rs/src/board.rs

@@ -205,19 +205,25 @@ pub struct Board {
 }
 
 impl Board {
-    pub fn get_at(&self, position: &Position) -> Option<&Piece> {
+    fn get_at(&self, position: &Position) -> Option<&Piece> {
         self.state.get(position)
     }
-    pub fn set_at(
-        &mut self,
-        position: Position,
-        piece_or_empty: Option<Piece>,
-    ) {
+    fn set_at(&mut self, position: Position, piece_or_empty: Option<Piece>) {
         match piece_or_empty {
             Some(piece) => self.state.insert(position, piece),
             None => self.state.remove(&position),
         };
     }
+    fn move_from_to(
+        &mut self,
+        source: &Position,
+        target: Position,
+    ) -> Result<(), ()> {
+        let (_, piece) = self.state.remove_entry(source).ok_or(())?;
+        self.set_at(target, Some(piece));
+        Ok(())
+    }
+
     pub fn new() -> Board {
         Board {
             state: Default::default(),
@@ -255,4 +261,16 @@ impl Board {
             });
         Some(valid_moves.chain(valid_captures).collect())
     }
+    pub fn make_move(
+        &mut self,
+        source: &Position,
+        target: Position,
+    ) -> Result<(), ()> {
+        if !self.get_legal_moves(source).ok_or(())?.contains(&target) {
+            Err(())
+        } else {
+            // We checked that there is a piece at source in get_legal_moves
+            self.move_from_to(source, target)
+        }
+    }
 }