riversong-code-showcase/Source/Riversong/Game/UI/Framework/UIRoot.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using Cysharp.Threading.Tasks;
using UnityEngine;
using UnityEngine.UIElements;

namespace DanieleMarotta.RiversongCodeShowcase
{
    [RequireComponent(typeof(UIDocument))]
    public class UIRoot : MonoBehaviour, IUIRoot
    {
        private UIDocument _document;

        private Dictionary<Type, UIView> _views = new();

        public VisualElement RootVisualElement { get; private set; }

        public event Action<ClickEvent> ElementClicked;

        private void Awake()
        {
            _document = GetComponent<UIDocument>();
        }

        public async UniTask Initialize(UIService uiService)
        {
            RootVisualElement = _document.rootVisualElement;

            await DiscoverViewsAsync(uiService);

            InitializeDragging();

            RootVisualElement.RegisterCallback<ClickEvent>(OnClick);
        }

        public void Dispose()
        {
            foreach (var view in _views.Values) view.Dispose();

            RootVisualElement.UnregisterCallback<ClickEvent>(OnClick);
        }

        private void OnClick(ClickEvent evt)
        {
            ElementClicked?.Invoke(evt);
        }

        private async UniTask DiscoverViewsAsync(UIService uiService)
        {
            var assemblies = AppDomain.CurrentDomain.GetAssemblies();

            foreach (var assembly in assemblies)
            foreach (var type in assembly.GetTypes())
            {
                var viewAttribute = type.GetCustomAttribute<UIViewAttribute>();
                if (viewAttribute == null) continue;

                var element = RootVisualElement.Q(className: viewAttribute.UssClassName);
                var view = await uiService.CreateView(type, element);

                _views.Add(type, view);
            }
        }

        private void InitializeDragging()
        {
            var targets = RootVisualElement.Query<VisualElement>(className: "drag-target").ToList();
            foreach (var target in targets) MakeDraggable(target);
        }

        public void MakeDraggable(VisualElement target)
        {
            var handle = target.Q<VisualElement>(className: "drag-handle") ?? target;
            handle.AddManipulator(new DraggableManipulator(target));
        }

        public T GetView<T>() where T : UIView
        {
            return _views.TryGetValue(typeof(T), out var view) ? (T)view : null;
        }
    }
}