card playing 1/2

src/grid.rs

@@ -12,7 +12,7 @@ impl Plugin for GridPlugin {
 }
 
 #[derive(Component)]
-struct Grid {
+pub struct Grid {
     bounds: Rect,
     columns: usize,
     rows: usize,
@@ -42,9 +42,43 @@ impl Grid {
             .extend(0.)
     }
 
+    pub fn is_in_grid(&self, position: Vec2) -> bool {
+        self.bounds.contains(position)
+    }
+
+    pub fn is_occupied(&self, position: Vec2) -> bool {
+        if self.is_in_grid(position) == false {
+            return true;
+        }
+
+        match self.elements[self.indexify_position(position)] {
+            Some(_) => true,
+            None => false,
+        }
+    }
+
+    pub fn is_free(&self, position: Vec2) -> bool {
+        self.is_occupied(position) == false
+    }
+
+    pub fn try_set(&mut self, position: Vec2, entity: Entity) -> bool {
+        if self.is_occupied(position) {
+            return false;
+        }
+        let index = self.indexify_position(position);
+
+        self.elements[index] = Some(entity);
+        true
+    }
+
     fn cell_size(&self) -> Vec2 {
         self.bounds.size() / vec2(self.columns as f32, -(self.rows as f32))
     }
+
+    fn indexify_position(&self, position: Vec2) -> usize {
+        let indexified_position = (position / self.cell_size()).floor();
+        indexified_position.x as usize + indexified_position.y as usize * self.columns
+    }
 }
 
 fn setup_grid(mut commands: Commands) {