feat: Implemented basic item drag-and-drop

- Added bundle names
- Added system to update bundle names with entity name

src/inventory/ui.rs

@@ -1,6 +1,6 @@
 use std::f32::consts::FRAC_PI_2;
 
-use bevy::{ecs::component::{ComponentId, ComponentIdFor}, prelude::*};
+use bevy::prelude::*;
 
 use crate::{inventory::{ActiveInventory, Inventory, item::Item}, ui::{UiRoot, WindowSize}};
 
@@ -9,7 +9,7 @@ const TEMP_ITEM_PATH: &'static str = "sprites/items/choco_bar.png";
 
 #[derive(Component, Reflect)]
 #[require(Node)]
-pub struct UiInventory;
+pub struct UiInventory(Entity);
 
 #[derive(Component, Reflect)]
 #[require(Node, ImageNode)]
@@ -20,25 +20,48 @@ pub struct UiInventorySlot(UVec2);
 pub struct UiItem(Entity);
 
 fn on_item_drag_drop(
-    event: On<Pointer<DragDrop>>,
-    ui_item_query: Query<&UiItem>,
-    slot_query: Query<(&UiInventorySlot, Option<&Children>)>,
+    mut event: On<Pointer<DragDrop>>,
+    mut commands: Commands,
+    ui_item_query: Query<(Entity, &UiItem)>,
+    ui_inventory_query: Query<&UiInventory>,
+    mut item_query: Query<&mut Item>,
+    slot_query: Query<(&ChildOf, &UiInventorySlot, Option<&Children>)>,
+    inventory_query: Query<(&Inventory, Option<&Children>)>,
 ) {
-    info!("dragdrop {} {}", event.dropped, event.event_target());
-    let Ok(ui_item) = ui_item_query.get(event.dropped) else {
+    let Ok((ui_item_entity, UiItem(item_entity))) = ui_item_query.get(event.dropped) else {
         return;
     };
-    let Ok((slot, _)) = slot_query.get(event.event_target()) else {
+    let Ok((slot_parent, UiInventorySlot(new_position), slot_children)) = slot_query.get(event.event_target()) else {
+        return;
+    };
+    if slot_children.is_some() {
+        return;
+    }
+    let Ok(UiInventory(inventory_id)) = ui_inventory_query.get(slot_parent.0) else {
+        return;
+    };
+    let Ok((inventory, inventory_children)) = inventory_query.get(*inventory_id) else {
         return;
     };
 
-    info!("Item {:?} dropped on {:?}", ui_item.0, slot.0);
+    let items = match inventory_children {
+        Some(children) => &children[..],
+        None => &[],
+    };
+    
+    if inventory.can_move(item_query.as_readonly(), items, *item_entity, *new_position) {
+        let mut item = item_query.get_mut(*item_entity).unwrap();
+        item.position = Some(*new_position);
+        commands.entity(ui_item_entity).insert(ChildOf(event.event_target()));
+    }
+
+    event.propagate(false);
 }
 
 fn ui_inventory_bundle(
     inventory: &Inventory,
+    inventory_entity: Entity,
     window_size: &Res<WindowSize>,
-    _slot_id: ComponentId,
 ) -> impl Bundle {
     let window_ratio = window_size.aspect_ratio();
     let (width, height) = {
@@ -49,7 +72,7 @@ fn ui_inventory_bundle(
         }
     };
     (
-        UiInventory,
+        UiInventory(inventory_entity),
         Node {
             align_self: AlignSelf::Center,
             align_content: AlignContent::Center,
@@ -63,8 +86,8 @@ fn ui_inventory_bundle(
         },
         Pickable::IGNORE,
         GlobalZIndex::default(),
-        Observer::new(on_item_drag_drop)
-//            .with_component(slot_id),
+        Observer::new(on_item_drag_drop),
+        Name::new(format!("UiInventory ({}x{})", inventory.size.x, inventory.size.y)),
     )
 }
 
@@ -88,6 +111,7 @@ fn inventory_slot_bundle(x: u32, y: u32, image: Handle<Image>) -> impl Bundle {
             should_block_lower: true,
             is_hoverable: true,
         },
+        Name::new(format!("UiInventorySlot({x},{y})")),
     )
 }
 
@@ -129,16 +153,19 @@ fn ui_item_bundle(item: &Item, item_entity: Entity, image: Handle<Image>) -> imp
             should_block_lower: false,
             is_hoverable: true,
         },
+        Name::new(format!("UiItem ({},{})",
+            item.position.unwrap_or_default().x,
+            item.position.unwrap_or_default().y,
+        )),
     )
 }
 
 pub fn setup_ui_inventory(
     mut commands: Commands,
     asset_server: Res<AssetServer>,
-    inventory_query: Query<(&Inventory, Option<&Children>), With<ActiveInventory>>,
+    inventory_query: Query<(Entity, &Inventory, Option<&Children>), With<ActiveInventory>>,
     item_query: Query<&Item>,
     root_query: Query<Entity, With<UiRoot>>,
-    slot_id: ComponentIdFor<UiInventorySlot>,
     window_size: Res<WindowSize>,
 ) {
     let Ok(root) = root_query.single() else {
@@ -147,7 +174,7 @@ pub fn setup_ui_inventory(
     };
     let ui_slot_image: Handle<Image> = asset_server.load(UI_SLOT_ASSET_PATH);
     let temp_item_image: Handle<Image> = asset_server.load(TEMP_ITEM_PATH);
-    for (inventory, children) in inventory_query {
+    for (inventory_entity, inventory, children) in inventory_query {
         let items = match children {
             Some(children) => {
                 children.iter().filter_map(|item_entity| {
@@ -162,7 +189,7 @@ pub fn setup_ui_inventory(
             }
             None => Vec::new(),
         };
-        let inventory_entity = commands.spawn(ui_inventory_bundle(inventory, &window_size, slot_id.get()))
+        let inventory_entity = commands.spawn(ui_inventory_bundle(inventory, inventory_entity, &window_size))
             .with_children(|commands| {
                 for x in 0..inventory.size.x { for y in 0..inventory.size.y {
                     let mut slot_commands = commands.spawn(inventory_slot_bundle(x, y, ui_slot_image.clone()));