how to put this into engine???

src/engine/mod.rs

@@ -5,6 +5,7 @@ mod rotation_systems;
 mod systems;
 mod components;
 mod resources;
+pub mod randomizers;
 
 pub struct UBSGEngine;
 

src/engine/randomizers.rs

@@ -0,0 +1,26 @@
+use rand::seq::SliceRandom;
+use rand::thread_rng;
+
+use super::{rotation_systems::PiecesData, resources::Piece};
+
+pub trait Randomizer{
+    fn populate_next(&self, pieces_data: PiecesData) -> Vec<Piece>;
+}
+
+pub struct Bag {}
+
+impl Randomizer for Bag {
+    fn populate_next(&self, pieces_data: PiecesData) -> Vec<Piece> {
+        let mut bag = vec![];
+        let mut id: usize = 0;
+        for _ in pieces_data.pieces{
+            let final_position = (3+pieces_data.spawn_offsets[id].0, 20+pieces_data.spawn_offsets[id].1);
+            let element = Piece { id: id, position: final_position, rotation: 0 };
+            id += 1;
+            bag.insert(0, element);
+        }
+        let mut rng = thread_rng();
+        bag.shuffle(&mut rng);
+        bag
+    }
+}