namespace Example
{
	using System;
	using System.Collections.Generic;
	using System.IO;
	using System.Reflection;
	using UnityEngine;
	using UnityEngine.UIElements;
	using UnityEditor;
	using UnityEditor.SceneManagement;

	[InitializeOnLoad]
	public static partial class ToolbarUtility
	{
		// PRIVATE MEMBERS

		private static ScriptableObject _mainToolbar;
		private static int              _mainToolbarInstanceID;
		private static VisualElement    _leftToolbar;
		private static VisualElement    _rightToolbar;
		private static string           _currentScene;
		private static string[]         _scenePaths;
		private static string[]         _sceneNames;

		// CONSTRUCTORS

		static ToolbarUtility()
		{
			EditorApplication.update -= Update;
			EditorApplication.update += Update;
		}

		// PUBLIC METHODS

		public static void InvalidateToolbar()
		{
			_mainToolbarInstanceID += 1;
		}

		// PARTIAL METHODS

		static partial void OnUpdate();
		static partial void OnLeftToolbarAttached(VisualElement toolbar);
		static partial void OnRightToolbarAttached(VisualElement toolbar);

		// PRIVATE METHODS

		private static void Update()
		{
			if (_scenePaths == null || _scenePaths.Length != EditorBuildSettings.scenes.Length)
			{
				List<string> scenePaths = new List<string>();
				List<string> sceneNames = new List<string>();

				foreach (EditorBuildSettingsScene scene in EditorBuildSettings.scenes)
				{
					if (scene.path == null || scene.path.StartsWith("Assets") == false)
						continue;

					string scenePath = Application.dataPath + scene.path.Substring(6);

					scenePaths.Add(scenePath);
					sceneNames.Add(Path.GetFileNameWithoutExtension(scenePath));
				}

				_scenePaths = scenePaths.ToArray();
				_sceneNames = sceneNames.ToArray();

				InvalidateToolbar();
			}

			string currentScene = EditorSceneManager.GetActiveScene().name;
			if (_currentScene != currentScene)
			{
				_currentScene = currentScene;

				InvalidateToolbar();
			}

			if (_mainToolbar == null)
			{
				UnityEngine.Object[] toolbars = Resources.FindObjectsOfTypeAll(typeof(Editor).Assembly.GetType("UnityEditor.Toolbar"));
				_mainToolbar = toolbars.Length > 0 ? (ScriptableObject)toolbars[0] : null;
			}

			if (_mainToolbar != null)
			{
				int mainToolbarInstanceID = _mainToolbar.GetInstanceID();
				if (mainToolbarInstanceID != _mainToolbarInstanceID)
				{
					_mainToolbarInstanceID = mainToolbarInstanceID;

					RefreshToolbar(ref _leftToolbar,  "ToolbarZoneLeftAlign",  FlexDirection.Row,        LeftToolbarAttached);
					RefreshToolbar(ref _rightToolbar, "ToolbarZoneRightAlign", FlexDirection.RowReverse, RightToolbarAttached);
				}
			}

			OnUpdate();
		}

		private static void RefreshToolbar(ref VisualElement toolbar, string toolbarID, FlexDirection direction, Action<VisualElement> onAttachToMainToolbar)
		{
			if (toolbar != null)
			{
				toolbar.RemoveFromHierarchy();
				toolbar = null;
			}

			FieldInfo root = _mainToolbar.GetType().GetField("m_Root", BindingFlags.NonPublic | BindingFlags.Instance);
			if (root != null)
			{
				object rawRoot = root.GetValue(_mainToolbar);
				if (rawRoot != null)
				{
					VisualElement toolbarRoot = rawRoot as VisualElement;
					VisualElement toolbarZone = toolbarRoot.Q(toolbarID);

					toolbar = new VisualElement()
					{
						style =
						{
							flexGrow = 1,
							flexDirection = direction,
						}
					};

					toolbar.Add(new VisualElement()
					{
						style =
						{
							flexGrow = 1,
						}
					});

					toolbarZone.Add(toolbar);

					onAttachToMainToolbar(toolbar);
				}
			}
		}

		private static void LeftToolbarAttached(VisualElement toolbar)
		{
			OnLeftToolbarAttached(toolbar);
		}

		private static void RightToolbarAttached(VisualElement toolbar)
		{
			OnRightToolbarAttached(toolbar);

			toolbar.Add(CreateToolbarButton(ShowPackageManager, "Package Manager", "Packages"));
			toolbar.Add(CreateToolbarButton(ShowSettings, "Settings", "Settings"));
//			toolbar.Add(CreateToolbarButton(ShowRunnerControls, "d_SceneViewCamera@2x", "Fusion Controls"));
			toolbar.Add(CreateToolbarButton(ShowFusionConfig, "ScriptableObject Icon", "Fusion Config"));
			toolbar.Add(CreateToolbarButton(ShowScenes, "BuildSettings.Editor", string.IsNullOrEmpty(_currentScene) == false ? _currentScene : "Scene"));
		}

		private static void ShowScenes()
		{
			GenericMenu menu = new GenericMenu();

			string currentPrefix = default;

			for (int i = 0; i < _sceneNames.Length; ++i)
			{
				string scenePath = _scenePaths[i];
				if (scenePath != null)
				{
					int prefixIndex = scenePath.IndexOf("/Assets/Example/");
					if (prefixIndex >= 0)
					{
						string prefix = scenePath.Substring(prefixIndex, 18);
						if (currentPrefix != default && currentPrefix != prefix)
						{
							menu.AddSeparator("");
						}

						currentPrefix = prefix;
					}
				}

				string sceenName = _sceneNames[i];

				menu.AddItem(new GUIContent(sceenName), sceenName == _currentScene, (sceneIndex) =>
				{
					if (EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo() == true)
					{
						EditorSceneManager.OpenScene(_scenePaths[(int)sceneIndex], OpenSceneMode.Single);
						InvalidateToolbar();
					}
				}, i);
			}

			menu.ShowAsContext();
		}

		private static void ShowFusionConfig()
		{
			EditorApplication.ExecuteMenuItem("Tools/Fusion/Network Project Config");
		}

		private static void ShowRunnerControls()
		{
			EditorApplication.ExecuteMenuItem("Tools/Fusion/Windows/Network Runner Controls");
		}

		private static void ShowSettings()
		{
			GenericMenu menu = new GenericMenu();
			menu.AddItem(new GUIContent("Project"),                false, () => EditorApplication.ExecuteMenuItem("Edit/Project Settings..."));
			menu.AddItem(new GUIContent("Preferences"),            false, () => EditorApplication.ExecuteMenuItem("Edit/Preferences..."));
			menu.AddSeparator("");
			menu.AddItem(new GUIContent("Realtime Settings"),      false, () => EditorApplication.ExecuteMenuItem("Tools/Fusion/Realtime Settings"));
			menu.AddItem(new GUIContent("Network Project Config"), false, () => EditorApplication.ExecuteMenuItem("Tools/Fusion/Network Project Config"));
			menu.ShowAsContext();
		}

		private static void ShowPackageManager()
		{
			UnityEditor.PackageManager.UI.Window.Open("");
		}

		private static VisualElement CreateToolbarButton(Action onClick, string icon = null, string text = null, Color color = default)
		{
			Button buttonElement = new Button(onClick);
			buttonElement.AddToClassList("unity-toolbar-button");
			buttonElement.AddToClassList("unity-editor-toolbar-element");
			buttonElement.RemoveFromClassList("unity-button");
			buttonElement.style.marginRight = 2;
			buttonElement.style.marginLeft = 2;

			if (color != default)
			{
				buttonElement.style.color = color;
			}

			if (string.IsNullOrEmpty(icon) == false)
			{
				VisualElement iconElement = new VisualElement();
				iconElement.AddToClassList("unity-editor-toolbar-element__icon");
				iconElement.style.backgroundImage = Background.FromTexture2D(EditorGUIUtility.IconContent(icon).image as Texture2D);
				buttonElement.Add(iconElement);
			}

			if (string.IsNullOrEmpty(text) == false)
			{
				TextElement textElement = new TextElement();
				textElement.text = text;
				textElement.style.marginLeft = 4;
				textElement.style.marginRight = 4;
				textElement.style.unityTextAlign = TextAnchor.MiddleCenter;
				buttonElement.Add(textElement);
			}

			return buttonElement;
		}
	}
}