Refactor project structure and improve performance

Changed the `ProjectRepository` class to be static for easier usage.
Changed `ProjectService` constants to public properties for accessibility.
Changed `App.xaml` to consolidate theme resources into `Override.xaml`.
Changed `App.xaml.cs` to implement an `AppStateMachine` for better state management.
Changed `ConsolePage` and `HierarchyPage` to utilize the new ViewModel structure.
Changed `ProjectPage` to use the `ExplorerItem` model for asset display.
Changed `Entity` and `EntityManager` to enhance component management with a new `IComponentData` interface.
Changed the `Logger` class to introduce structured logging functionality.
Changed the system architecture to support dependency management for better organization.
Changed the `QueryEnumerable` class to allow for more flexible entity queries.
Changed the `TypeHandle` class to improve efficiency in retrieving type handles.
Changed the `World` class to support robust world management and multiple worlds.
Updated the `Test` class to demonstrate the new entity and component management system.

Ghost.Editor/Infrastructures/AppState/AppStateMachine.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Ghost.Editor.Infrastructures.AppState;
+
+internal class AppStateMachine
+{
+    private Dictionary<StateKey, Lazy<IAppState>> s_states = new();
+    private IAppState? s_current;
+
+    public void RegisterState(StateKey key, Func<IAppState> stateFactory)
+    {
+        s_states[key] = new(stateFactory);
+    }
+
+    public async Task TransitionToAsync(StateKey stateKey, object? parameter = null)
+    {
+        var previous = s_current;
+        var next = s_states[stateKey].Value;
+
+        if (previous != null)
+        {
+            await previous.OnExitingAsync();
+        }
+
+        await next.OnEnteringAsync(parameter);
+
+        if (previous != null)
+        {
+            await previous.OnExitedAsync();
+        }
+
+        await next.OnEnteredAsync(parameter);
+
+        s_current = next;
+    }
+}

Ghost.Editor/Infrastructures/AppState/EditorState.cs

@@ -0,0 +1,61 @@
+using Ghost.Data.Models;
+using Ghost.Data.Services;
+using Ghost.Editor.View.Windows;
+using Ghost.Engine;
+using System.Threading.Tasks;
+
+namespace Ghost.Editor.Infrastructures.AppState;
+
+internal class EditorState : IAppState
+{
+    private EngineEditorWindow? _window;
+    private EngineCore? _engineCore;
+
+    public Task OnExitingAsync()
+    {
+        if (App.Window == _window)
+        {
+            App.Window = null;
+        }
+        return Task.CompletedTask;
+    }
+
+    public async Task OnEnteringAsync(object? parameter)
+    {
+        if (parameter is not ProjectMetadataInfo metadataInfo)
+        {
+            throw new System.ArgumentException("Parameter must be of type ProjectMetadata.", nameof(parameter));
+        }
+
+        ProjectService.CurrentProject = metadataInfo;
+
+        _engineCore = App.GetService<EngineCore>();
+        await _engineCore.StartAsync(new Engine.Models.LaunchArgument());
+
+        _window = App.GetService<EngineEditorWindow>();
+        _window.Activate();
+
+        App.Window = _window;
+    }
+
+    public async Task OnExitedAsync()
+    {
+        if (_engineCore != null)
+        {
+            await _engineCore.ShutDownAsync();
+        }
+
+        if (App.Window == _window)
+        {
+            App.Window = null;
+        }
+
+        _window?.Close();
+        _window = null;
+    }
+
+    public Task OnEnteredAsync(object? parameter)
+    {
+        return Task.CompletedTask;
+    }
+}

Ghost.Editor/Infrastructures/AppState/IAppState.cs

@@ -0,0 +1,28 @@
+using System.Threading.Tasks;
+
+namespace Ghost.Editor.Infrastructures.AppState;
+
+internal interface IAppState
+{
+    /// <summary>
+    /// Called when exiting the state.
+    /// </summary>
+    public Task OnExitingAsync();
+
+    /// <summary>
+    /// Called when entering the state, right after OnEnteringAsync.
+    /// <paramref name="parameter">can be used to pass data into the state, such as a project to load.</summary>
+    /// </summary>
+    public Task OnEnteringAsync(object? parameter);
+
+    /// <summary>
+    /// Called when exiting the state, specifically for pose transitions.
+    /// </summary>
+    public Task OnExitedAsync();
+
+    /// <summary>
+    /// Called when entered the state, specifically after the state has been fully initialized and is ready for interaction.
+    /// </summary>
+    /// <param name="parameter">can be used to pass data into the state, such as a project to load.</param>
+    public Task OnEnteredAsync(object? parameter);
+}

Ghost.Editor/Infrastructures/AppState/LandingState.cs

@@ -0,0 +1,44 @@
+using Ghost.Editor.View.Windows;
+using System.Threading.Tasks;
+
+namespace Ghost.Editor.Infrastructures.AppState;
+
+internal class LandingState : IAppState
+{
+    private LandingWindow? _window;
+
+    public Task OnExitingAsync()
+    {
+        if (App.Window == _window)
+        {
+            App.Window = null;
+        }
+        return Task.CompletedTask;
+    }
+
+    public Task OnEnteringAsync(object? parameter)
+    {
+        _window = App.GetService<LandingWindow>();
+        App.Window = _window;
+
+        _window.Activate();
+        return Task.CompletedTask;
+    }
+
+    public Task OnExitedAsync()
+    {
+        if (App.Window == _window)
+        {
+            App.Window = null;
+        }
+
+        _window?.Close();
+        _window = null;
+        return Task.CompletedTask;
+    }
+
+    public Task OnEnteredAsync(object? parameter)
+    {
+        return Task.CompletedTask;
+    }
+}

Ghost.Editor/Infrastructures/AppState/StateKey.cs

@@ -0,0 +1,8 @@
+namespace Ghost.Editor.Infrastructures.AppState;
+
+internal enum StateKey
+{
+    None,
+    Landing,
+    EngineEditor,
+}

Ghost.Editor/Infrastructures/SceneGraph/EntityNode.cs

@@ -0,0 +1,17 @@
+using Ghost.Entities;
+
+namespace Ghost.Editor.Infrastructures.SceneGraph;
+
+public partial class EntityNode : SceneGraphNode
+{
+    private readonly Entity _entity;
+
+    public Entity Entity => _entity;
+    public override NodeType Type => NodeType.Entity;
+
+    public EntityNode(Entity entity, string name)
+    {
+        _entity = entity;
+        Name = name;
+    }
+}

Ghost.Editor/Infrastructures/SceneGraph/SceneGraphHelpers.cs

@@ -0,0 +1,112 @@
+using Ghost.Engine.Components;
+using Ghost.Entities;
+
+namespace Ghost.Editor.Infrastructures.SceneGraph;
+
+internal class SceneGraphHelpers
+{
+    /// <summary>
+    /// Creates a new <see cref="EntityNode"/> entity with default components.
+    /// </summary>
+    /// <param name="world">The world context where the entity will be created.</param>
+    /// <param name="entity">The entity to be wrapped in the <see cref="EntityNode"/>.</param>
+    public static EntityNode CreateEntityNode(World world, Entity entity, string name)
+    {
+        world.EntityManager.AddComponent(entity, LocalToWorld.Identity);
+        world.EntityManager.AddComponent(entity, Hierarchy.Root);
+        return new EntityNode(entity, name);
+    }
+
+    /// <summary>
+    /// Creates a new <see cref="Entity"/> and <see cref="EntityNode"/> entity with default components.
+    /// </summary>
+    /// <param name="world">The world context where the entity will be created.</param>
+    public static EntityNode CreateEntityNode(World world, string name)
+    {
+        var entity = world.EntityManager.CreateEntity();
+        return CreateEntityNode(world, entity, name);
+    }
+
+    /// <summary>
+    /// Attaches childEntity to parentEntity in the scene graph.
+    /// </summary>
+    /// <param name="world">The world context where the entities exist.</param>
+    /// <param name="parentNode">The parent entity to which the child will be attached.</param>
+    /// <param name="childNode">The child entity to be attached.</param>
+    public static void AttachChild(SceneNode scene, EntityNode parentNode, EntityNode childNode)
+    {
+        // 1) If the child already has a parent, detach it first
+        var childHierarchy = scene.World.EntityManager.GetComponent<Hierarchy>(childNode.Entity);
+        if (childHierarchy.ValueRO.parent != Entity.Invalid)
+        {
+            DetachFromParent(scene, childNode);
+        }
+
+        // 2) Link child to new parent
+        childHierarchy.ValueRW.parent = parentNode.Entity;
+
+        // 3) Insert child at the head of parent's child list
+        var parentHierarchy = scene.World.EntityManager.GetComponent<Hierarchy>(parentNode.Entity);
+
+        childHierarchy.ValueRW.nextSibling = parentHierarchy.ValueRO.firstChild;
+        parentHierarchy.ValueRW.firstChild = childNode.Entity;
+
+        // 4) Write back
+        scene.World.EntityManager.SetComponent(parentNode.Entity, in parentHierarchy.ValueRO);
+        scene.World.EntityManager.SetComponent(childNode.Entity, in childHierarchy.ValueRO);
+
+        // 5) Update children list in parent node
+        parentNode.Children.Add(childNode);
+    }
+
+    /// <summary>
+    /// Detaches the specified entity from its parent in the scene graph.
+    /// </summary>
+    /// <param name="world">The world context where the entities exist.</param>
+    /// <param name="node">The entity to detach from its parent.</param>
+    public static void DetachFromParent(SceneNode scene, EntityNode node)
+    {
+        var hierarchy = scene.World.EntityManager.GetComponent<Hierarchy>(node.Entity);
+        var parent = hierarchy.ValueRO.parent;
+        if (parent == Entity.Invalid)
+        {
+            return; // already root
+        }
+
+        var parentHierarchy = scene.World.EntityManager.GetComponent<Hierarchy>(parent);
+
+        // If entity is the first child, simply move head
+        if (parentHierarchy.ValueRO.firstChild == node.Entity)
+        {
+            parentHierarchy.ValueRW.firstChild = hierarchy.ValueRO.nextSibling;
+        }
+        else
+        {
+            // Otherwise, find the previous sibling in the linked list
+            var prevSibling = parentHierarchy.ValueRO.firstChild;
+            while (prevSibling != Entity.Invalid)
+            {
+                var prevHierarchy = scene.World.EntityManager.GetComponent<Hierarchy>(prevSibling);
+                if (prevHierarchy.ValueRW.nextSibling == node.Entity)
+                {
+                    prevHierarchy.ValueRW.nextSibling = hierarchy.ValueRO.nextSibling;
+                    scene.World.EntityManager.SetComponent(prevSibling, in prevHierarchy.ValueRO);
+                    break;
+                }
+
+                prevSibling = prevHierarchy.ValueRO.nextSibling;
+            }
+        }
+
+        // Clear child's references
+        hierarchy.ValueRW.parent = Entity.Invalid;
+        hierarchy.ValueRW.nextSibling = Entity.Invalid;
+
+        // Write back
+        scene.World.EntityManager.SetComponent(parent, in parentHierarchy.ValueRO);
+        scene.World.EntityManager.SetComponent(node.Entity, in hierarchy.ValueRO);
+
+        // Remove from parent's children list
+        scene.EntityNodeLookup[parent].Children.Remove(node);
+    }
+}

Ghost.Editor/Infrastructures/SceneGraph/SceneGraphNode.cs

@@ -0,0 +1,32 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using System.Collections.ObjectModel;
+
+namespace Ghost.Editor.Infrastructures.SceneGraph;
+
+public abstract partial class SceneGraphNode : ObservableObject
+{
+    public enum NodeType
+    {
+        Scene,
+        Entity,
+    }
+
+    public abstract NodeType Type
+    {
+        get;
+    }
+
+    [ObservableProperty]
+    public partial string Name
+    {
+        get;
+        set;
+    }
+
+    // Will the new collection allocated if ui bind to this property?
+    private ObservableCollection<EntityNode>? _children;
+    public ObservableCollection<EntityNode> Children
+    {
+        get => _children ??= new();
+    }
+}

Ghost.Editor/Infrastructures/SceneGraph/SceneNode.cs

@@ -0,0 +1,58 @@
+using Ghost.Engine.Components;
+using Ghost.Entities;
+using System.Collections.Generic;
+
+namespace Ghost.Editor.Infrastructures.SceneGraph;
+
+public partial class SceneNode : SceneGraphNode
+{
+    private readonly World _world;
+    private Dictionary<Entity, EntityNode> _entityNodeLookup = new();
+
+    public World World => _world;
+    public Dictionary<Entity, EntityNode> EntityNodeLookup => _entityNodeLookup;
+
+    public override NodeType Type => NodeType.Scene;
+
+    public SceneNode(World world, string name)
+    {
+        _world = world;
+        Name = name;
+    }
+
+    private EntityNode BuildNodeRecursive(Entity entity, World world)
+    {
+        // TODO: Node serialization.
+        var node = new EntityNode(entity, "New Entity");
+        _entityNodeLookup[entity] = node;
+
+        var hc = world.EntityManager.GetComponent<Hierarchy>(entity);
+        var child = hc.ValueRO.firstChild;
+
+        while (child != Entity.Invalid)
+        {
+            node.Children.Add(BuildNodeRecursive(child, world));
+            var childHC = world.EntityManager.GetComponent<Hierarchy>(child);
+            child = childHC.ValueRO.nextSibling;
+        }
+
+        return node;
+    }
+
+    private void BuildGraph()
+    {
+        foreach (var (entity, hierarchy) in _world.Query<Hierarchy>())
+        {
+            if (hierarchy.ValueRO.parent == Entity.Invalid)
+            {
+                var node = BuildNodeRecursive(entity, _world);
+                Children.Add(node);
+            }
+        }
+    }
+
+    public void Load()
+    {
+        BuildGraph();
+    }
+}