Implement get_legal_moves function

rs/src/board.rs

@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 
-#[derive(Clone)]
+#[derive(Eq, PartialEq, Clone)]
 pub enum Color {
     Black,
     White,
@@ -234,4 +234,25 @@ impl Board {
     pub fn iter(&self) -> impl Iterator<Item = (&Position, &Piece)> {
         self.state.iter()
     }
+    pub fn get_legal_moves(
+        &self,
+        position: &Position,
+    ) -> Option<Vec<Position>> {
+        let piece = match self.get_at(position) {
+            None => return None,
+            Some(piece) => piece,
+        };
+        let valid_moves = piece
+            .get_moves(position)
+            .into_iter()
+            .filter(|pos| self.get_at(pos).is_none());
+        let valid_captures =
+            piece.get_captures(position).into_iter().filter(|pos| match self
+                .get_at(pos)
+            {
+                None => false,
+                Some(other_piece) => (other_piece.color != piece.color),
+            });
+        Some(valid_moves.chain(valid_captures).collect())
+    }
 }