// Copyright (c) 2012-2024 Wojciech Figat. All rights reserved.

using System;
using FlaxEngine;
using FlaxEngine.GUI;

namespace FlaxEditor.GUI.Docking
{
    /// <summary>
    /// Helper class used to handle docking windows dragging and docking.
    /// </summary>
    public class DockHintWindow
    {
        private FloatWindowDockPanel _toMove;

        private Float2 _dragOffset;
        private Float2 _defaultWindowSize;
        private Rectangle _rectDock;
        private Rectangle _rectWindow;
        private Float2 _mouse;
        private DockState _toSet;
        private DockPanel _toDock;
        private bool _lateDragOffsetUpdate;
        private float _lateDragStartTimer;
        private bool _moveWindow;
        private Window _dragSourceWindow;

        private Rectangle _rLeft, _rRight, _rBottom, _rUpper, _rCenter;

        private DockHintWindow(FloatWindowDockPanel toMove, Window dragSourceWindow)
        {
            _toMove = toMove;
            _toSet = DockState.Float;
            var window = toMove.Window.Window;

            // Remove focus from drag target
            //_toMove.Focus();
            //_toMove.Defocus();

            // Focus window
            //window.Focus();

            // Check if window is maximized and restore window.
            if (window.IsMaximized)
            {
                // Restore window and set position to mouse.
                var mousePos = window.MousePosition;
                var previousSize = window.Size;
                window.Restore();
                window.Position = Platform.MousePosition - mousePos * window.Size / previousSize;
            }
            
            // If the _toMove window was not focused when initializing this window, the result vector only contains zeros
            // and to prevent a failure, we need to perform an update for the drag offset at later time which will be done in the OnMouseMove event handler.
            //if (mouseScreenPosition != Float2.Zero)
            //    CalculateDragOffset(mouseScreenPosition);
            //else
            //    _lateDragOffsetUpdate = true;
            
            

            // Get initial size
            _defaultWindowSize = window.Size;

            // Init proxy window
            /*Proxy.Init(ref _defaultWindowSize);

            // Bind events
            */
            
            //FlaxEngine.Input.MouseMove += OnMouseMove;
            FlaxEngine.Scripting.Update += OnUpdate;
            _toMove.Window.Window.MouseUp += OnMouseUp;
            /*
            Proxy.Window.MouseUp += OnMouseUp;
            Proxy.Window.MouseMove += OnMouseMove;
            Proxy.Window.LostFocus += OnLostFocus;
            _toMove.Window.Window.MouseUp += OnMouseUp; // Intercept the drag release mouse event from source window
*/
            // Update window GUI
            //Proxy.Window.GUI.PerformLayout();

            // Update rectangles
            UpdateRects();

            // Enable hit window presentation
            /*Proxy.Window.RenderingEnabled = true;
            Proxy.Window.Show();
            Proxy.Window.Focus();*/

            // Hide base window
            //window.Hide();

            // window.Show();
            _dragSourceWindow = dragSourceWindow;
            _moveWindow = _dragSourceWindow != null;
            if (_dragSourceWindow != null) // Detaching a tab from existing window
            {
                _dragOffset = new Float2(window.Size.X / 2, 10.0f);

                // TODO: when detaching tab in floating window (not main window), the drag source window is still main window?
                var dragSourceWindowWayland = toMove.MasterPanel?.RootWindow.Window ?? Editor.Instance.Windows.MainWindow;
                window.DoDragDrop("", _dragOffset, dragSourceWindowWayland);

                _dragSourceWindow.MouseUp += OnMouseUp; // The mouse up event is sent to the source window on Windows
            }
            else
            {
                var mouseClientPosition = Platform.MousePosition;
                CalculateDragOffset(mouseClientPosition);

                window.DoDragDrop("", _dragOffset, window);
            }

            //window.Show();
            //window.BringToFront();
            //window.Focus();
            //toMove.OnShow();

            // Perform layout again
            //windowGUI.PerformLayout();
            
            
            // Start tracking mouse
            //Proxy.Window.StartTrackingMouse(false);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        public void Dispose()
        {
            // End tracking mouse
            /*Proxy.Window.EndTrackingMouse();

            // Disable rendering
            Proxy.Window.RenderingEnabled = false;

            // Unbind events
            Proxy.Window.MouseUp -= OnMouseUp;
            Proxy.Window.MouseMove -= OnMouseMove;
            Proxy.Window.LostFocus -= OnLostFocus;
            if (_toMove?.Window?.Window)
                _toMove.Window.Window.MouseUp -= OnMouseUp;

            // Hide the proxy
            Proxy.Hide();*/
            
            RemoveDockHints();
            
            //FlaxEngine.Input.MouseMove -= OnMouseMove;
            FlaxEngine.Scripting.Update -= OnUpdate;
            if (_toMove?.Window?.Window)
                _toMove.Window.Window.MouseUp -= OnMouseUp;

            if (_dragSourceWindow != null)
                _dragSourceWindow.MouseUp -= OnMouseUp; // The mouse up event is sent to the source window on Windows

            if (_toMove == null)
                return;

            _toMove.Window.Window.Opacity = 1.0f;

            // Check if window won't be docked
            if (_toSet == DockState.Float)
            {
                var window = _toMove.Window?.Window;
                if (window == null)
                    return;
                var mouse = Platform.MousePosition;

                // Move base window
                //window.Position = mouse - _dragOffset;

                // Show base window
                window.Show();
            }
            else
            {
                bool hasNoChildPanels = _toMove.ChildPanelsCount == 0;

                // Check if window has only single tab
                if (hasNoChildPanels && _toMove.TabsCount == 1)
                {
                    // Dock window
                    _toMove.GetTab(0).Show(_toSet, _toDock);
                }
                // Check if dock as tab and has no child panels
                else if (hasNoChildPanels && _toSet == DockState.DockFill)
                {
                    // Dock all tabs
                    while (_toMove.TabsCount > 0)
                    {
                        _toMove.GetTab(0).Show(DockState.DockFill, _toDock);
                    }
                }
                else
                {
                    var selectedTab = _toMove.SelectedTab;

                    // Dock the first tab into the target location
                    if (_toMove.TabsCount > 0)
                    {
                        var firstTab = _toMove.GetTab(0);
                        firstTab.Show(_toSet, _toDock);

                        // Dock rest of the tabs
                        while (_toMove.TabsCount > 0)
                        {
                            _toMove.GetTab(0).Show(DockState.DockFill, firstTab);
                        }
                    }

                    // Keep selected tab being selected
                    selectedTab?.SelectTab();
                }

                // Focus target window
                _toDock.Root.Focus();
            }

            _toMove = null;
        }

        /// <summary>
        /// Creates the new dragging hit window.
        /// </summary>
        /// <param name="toMove">Floating dock panel to move.</param>
        /// <returns>The dock hint window object.</returns>
        public static DockHintWindow Create(FloatWindowDockPanel toMove)
        {
            if (toMove == null)
                throw new ArgumentNullException();

            return new DockHintWindow(toMove, null);
        }

        /// <summary>
        /// Creates the new dragging hit window.
        /// </summary>
        /// <param name="toMove">Dock window to move.</param>
        /// <returns>The dock hint window object.</returns>
        public static DockHintWindow Create(DockWindow toMove, Window dragSourceWindow)
        {
            if (toMove == null)
                throw new ArgumentNullException();

            // Show floating
            toMove.CreateFloating();

            // Move window to the mouse position (with some offset for caption bar)
            var window = (WindowRootControl)toMove.Root;
            /*var mouse = Platform.MousePosition;
            window.Window.Position = mouse - new Float2(8, 8);*/

            // Get floating panel
            var floatingPanelToMove = window.GetChild(0) as FloatWindowDockPanel;

            return new DockHintWindow(floatingPanelToMove, dragSourceWindow);
        }

        /// <summary>
        /// Calculates window rectangle in the dock window.
        /// </summary>
        /// <param name="state">Window dock state.</param>
        /// <param name="rect">Dock panel rectangle.</param>
        /// <returns>Calculated window rectangle.</returns>
        public static Rectangle CalculateDockRect(DockState state, ref Rectangle rect)
        {
            Rectangle result = rect;
            switch (state)
            {
            case DockState.DockFill:
                result.Location.Y += DockPanel.DefaultHeaderHeight;
                result.Size.Y -= DockPanel.DefaultHeaderHeight;
                break;
            case DockState.DockTop:
                result.Size.Y *= DockPanel.DefaultSplitterValue;
                break;
            case DockState.DockLeft:
                result.Size.X *= DockPanel.DefaultSplitterValue;
                break;
            case DockState.DockBottom:
                result.Location.Y += result.Size.Y * (1 - DockPanel.DefaultSplitterValue);
                result.Size.Y *= DockPanel.DefaultSplitterValue;
                break;
            case DockState.DockRight:
                result.Location.X += result.Size.X * (1 - DockPanel.DefaultSplitterValue);
                result.Size.X *= DockPanel.DefaultSplitterValue;
                break;
            }
            return result;
        }

        private void CalculateDragOffset(Float2 mouseScreenPosition)
        {
            var baseWinPos = _toMove.Window.Window.Position;
            //_dragOffset = mouseScreenPosition - baseWinPos;

            //Editor.Log($"_dragOffset: {_dragOffset}, mouse: {mouseScreenPosition}, basewinpos: {baseWinPos}");
        }

        DockHintControl _dockHintDown;
        DockHintControl _dockHintUp;
        DockHintControl _dockHintLeft;
        DockHintControl _dockHintRight;
        DockHintControl _dockHintCenter;
        private void AddDockHints()
        {
            if (_toDock == null)
                return;

            if (_toDock.RootWindow.Window != _dragSourceWindow)
                _toDock.RootWindow.Window.MouseUp += OnMouseUp;

            _dockHintDown = AddHintControl(new Float2(0.5f, 1));
            _dockHintUp = AddHintControl(new Float2(0.5f, 0));
            _dockHintLeft = AddHintControl(new Float2(0, 0.5f));
            _dockHintRight = AddHintControl(new Float2(1, 0.5f));
            _dockHintCenter = AddHintControl(new Float2(0.5f, 0.5f));

            DockHintControl AddHintControl(Float2 pivot)
            {
                DockHintControl hintControl = _toDock.AddChild<DockHintControl>();
                hintControl.Size = new Float2(Proxy.HintWindowsSize);
                hintControl.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                hintControl.Pivot = pivot;
                hintControl.PivotRelative = true;
                //.SetAnchorPreset(AnchorPresets.StretchAll, true);
                return hintControl;
            }
        }
        
        private void RemoveDockHints()
        {
            if (_toDock == null)
                return;

            if (_toDock.RootWindow.Window != _dragSourceWindow)
                _toDock.RootWindow.Window.MouseUp -= OnMouseUp;

            _dockHintDown?.Parent.RemoveChild(_dockHintDown);
            _dockHintUp?.Parent.RemoveChild(_dockHintUp);
            _dockHintLeft?.Parent.RemoveChild(_dockHintLeft);
            _dockHintRight?.Parent.RemoveChild(_dockHintRight);
            _dockHintCenter?.Parent.RemoveChild(_dockHintCenter);
            _dockHintDown = _dockHintUp = _dockHintLeft = _dockHintRight = _dockHintCenter = null;
        }

        private void UpdateRects()
        {
            // Cache mouse position
            _mouse = Platform.MousePosition;

            // Check intersection with any dock panel
            var uiMouse = _mouse;
            DockPanel dockPanel = null;
            if (_toMove.MasterPanel.HitTest(ref uiMouse, _toMove, out var hitResults))
            {
                dockPanel = hitResults[0];

                // Prefer panel which currently has focus
                foreach (var hit in hitResults)
                {
                    if (hit.RootWindow.Window.IsFocused)
                    {
                        dockPanel = hit;
                        break;
                    }
                }

                // Prefer panel in the same window we hit earlier
                if (dockPanel?.RootWindow != _toDock?.RootWindow)
                {
                    foreach (var hit in hitResults)
                    {
                        if (hit.RootWindow == _toDock?.RootWindow)
                        {
                            dockPanel = _toDock;
                            break;
                        }
                    }
                }
            }
            
            if (dockPanel != _toDock)
            {
                RemoveDockHints();
                _toDock = dockPanel;
                AddDockHints();

                // Make sure the all the dock hint areas are not under other windows
                _toDock?.RootWindow.Window.BringToFront();
                _toMove.RootWindow.Window.BringToFront();

                // Make the dragged window transparent when dock hints are visible
                _toMove.Window.Window.Opacity = _toDock == null ? 1.0f : 0.4f;
            }
            
            // Check dock state to use
            bool showProxyHints = _toDock != null;
            bool showBorderHints = showProxyHints;
            bool showCenterHint = showProxyHints;
            DockHintControl hoveredHintControl = null;
            Float2 hoveredSizeOverride = Float2.Zero;
            if (showProxyHints)
            {
                // If moved window has not only tabs but also child panels disable docking as tab
                if (_toMove.ChildPanelsCount > 0)
                    showCenterHint = false;

                // Disable docking windows with one or more dock panels inside
                if (_toMove.ChildPanelsCount > 0)
                    showBorderHints = false;

                // Get dock area
                _rectDock = _toDock.DockAreaBounds;

                // Cache dock rectangles
                var size = _rectDock.Size / Platform.DpiScale;
                var offset = _toDock.PointFromScreen(_rectDock.Location);
                var borderMargin = 4.0f;
                var hintWindowsSize = Proxy.HintWindowsSize;
                var hintWindowsSize2 = hintWindowsSize * 0.5f;
                var hintPreviewSize = new Float2(Math.Max(Proxy.HintWindowsSize * 2, size.X * 0.5f), Math.Max(Proxy.HintWindowsSize * 2, size.Y * 0.5f));
                var centerX = size.X * 0.5f;
                var centerY = size.Y * 0.5f;
                _rUpper = new Rectangle(centerX - hintWindowsSize2, borderMargin, hintWindowsSize, hintWindowsSize) + offset;
                _rBottom = new Rectangle(centerX - hintWindowsSize2, size.Y - hintWindowsSize - borderMargin, hintWindowsSize, hintWindowsSize) + offset;
                _rLeft = new Rectangle(borderMargin, centerY - hintWindowsSize2, hintWindowsSize, hintWindowsSize) + offset;
                _rRight = new Rectangle(size.X - hintWindowsSize - borderMargin, centerY - hintWindowsSize2, hintWindowsSize, hintWindowsSize) + offset;
                _rCenter = new Rectangle(centerX - hintWindowsSize2, centerY - hintWindowsSize2, hintWindowsSize, hintWindowsSize) + offset;

                // Hit test
                DockState toSet = DockState.Float;
                if (showBorderHints)
                {
                    if (_rUpper.Contains(_toDock.PointFromScreen(_mouse)))
                    {
                        toSet = DockState.DockTop;
                        hoveredHintControl = _dockHintUp;
                        hoveredSizeOverride = new Float2(size.X, hintPreviewSize.Y);
                    }
                    else if (_rBottom.Contains(_toDock.PointFromScreen(_mouse)))
                    {
                        toSet = DockState.DockBottom;
                        hoveredHintControl = _dockHintDown;
                        hoveredSizeOverride = new Float2(size.X, hintPreviewSize.Y);
                    }
                    else if (_rLeft.Contains(_toDock.PointFromScreen(_mouse)))
                    {
                        toSet = DockState.DockLeft;
                        hoveredHintControl = _dockHintLeft;
                        hoveredSizeOverride = new Float2(hintPreviewSize.X, size.Y);
                    }
                    else if (_rRight.Contains(_toDock.PointFromScreen(_mouse)))
                    {
                        toSet = DockState.DockRight;
                        hoveredHintControl = _dockHintRight;
                        hoveredSizeOverride = new Float2(hintPreviewSize.X, size.Y);
                    }
                }
                if (showCenterHint && _rCenter.Contains(_toDock.PointFromScreen(_mouse)))
                {
                    toSet = DockState.DockFill;
                    hoveredHintControl = _dockHintCenter;
                    hoveredSizeOverride = new Float2(size.X, size.Y);
                }

                //if (toSet != DockState.Float)
                    
                
                _toSet = toSet;
            }
            else
            {
                _toSet = DockState.Float;
            }
            
            Editor.Log($"docking: {_toSet}, pos: {_mouse}");

            // Calculate proxy/dock/window rectangles
            if (_toDock == null)
            {
                // Floating window over nothing
                //_rectWindow = new Rectangle(_mouse - _dragOffset, _defaultWindowSize);
                if (hoveredHintControl != null)
                    hoveredHintControl.BackgroundColor = Color.Green;
            }
            else
            {
                if (hoveredHintControl != _dockHintDown)
                {
                    _dockHintDown.Size = new Float2(Proxy.HintWindowsSize);
                    _dockHintDown.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                }
                if (hoveredHintControl != _dockHintLeft)
                {
                    _dockHintLeft.Size = new Float2(Proxy.HintWindowsSize);
                    _dockHintLeft.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                }
                if (hoveredHintControl != _dockHintRight)
                {
                    _dockHintRight.Size = new Float2(Proxy.HintWindowsSize);
                    _dockHintRight.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                }
                if (hoveredHintControl != _dockHintUp)
                {
                    _dockHintUp.Size = new Float2(Proxy.HintWindowsSize);
                    _dockHintUp.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                }
                if (hoveredHintControl != _dockHintCenter)
                {
                    _dockHintCenter.Size = new Float2(Proxy.HintWindowsSize);
                    _dockHintCenter.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(0.6f);
                }
                if (_toSet == DockState.Float)
                {
                    // Floating window over dock panel
                    if (hoveredHintControl != null)
                        hoveredHintControl.BackgroundColor = Color.Red;
                }
                else
                {
                    // Use only part of the dock panel to show hint
                    if (hoveredHintControl != null)
                    {
                        hoveredHintControl.BackgroundColor = Style.Current.DragWindow.AlphaMultiplied(1.0f);
                        hoveredHintControl.Size = hoveredSizeOverride;
                    }
                }
            }
            
            if (showProxyHints)
            {
                if (hoveredHintControl != _dockHintDown)
                    _dockHintDown.Location = _rBottom.Location;
                if (hoveredHintControl != _dockHintLeft)
                    _dockHintLeft.Location = _rLeft.Location;
                if (hoveredHintControl != _dockHintRight)
                    _dockHintRight.Location = _rRight.Location;
                if (hoveredHintControl != _dockHintUp)
                    _dockHintUp.Location = _rUpper.Location;
                if (hoveredHintControl != _dockHintCenter)
                    _dockHintCenter.Location = _rCenter.Location;
                
                // Update proxy hint windows visibility
                _dockHintDown.Visible = showProxyHints & showBorderHints;
                _dockHintLeft.Visible = showProxyHints & showBorderHints;
                _dockHintRight.Visible = showProxyHints & showBorderHints;
                _dockHintUp.Visible = showProxyHints & showBorderHints;
                _dockHintCenter.Visible = showProxyHints & showCenterHint;
            }

            // Update proxy window
            //Proxy.Window.ClientBounds = _rectWindow;
        }

        private void OnMouseUp(ref Float2 location, MouseButton button, ref bool handled)
        {
            Editor.Log("DockHintWindow.OnMouseUp");
            if (button == MouseButton.Left)
            {
                Dispose();
            }
        }

        private void OnUpdate()
        {
            //Editor.Log("OnUpdate");
            var mousePos = Platform.MousePosition;
            if (_mouse != mousePos)
            {
                //Editor.Log($"mouse pos {_mouse} -> {mousePos}");
                OnMouseMove(mousePos);
            }
        }
        
        private void OnMouseMove(Float2 mousePos)
        {
            if (_moveWindow)
            {
                _toMove.Window.Window.Position = mousePos - _dragOffset;
            }
            //Editor.Log("OnMouseMove");
            // Recalculate the drag offset because the current mouse screen position was invalid when we initialized the window
            if (_lateDragOffsetUpdate)
            {
                // Calculate dragging offset and move window to the destination position
                CalculateDragOffset(mousePos);

                // Reset state
                _lateDragOffsetUpdate = false;
            }

            UpdateRects();
        }

        private void OnLostFocus()
        {
            Dispose();
        }
        
        public class DockHintControl : Control
        {
            public DockHintControl()
            {
                AnchorPreset = AnchorPresets.StretchAll;
                Offsets = Margin.Zero;
            }
        }

        /// <summary>
        /// Contains helper proxy windows shared across docking panels. They are used to visualize docking window locations.
        /// </summary>
        public static class Proxy
        {
            /// <summary>
            /// The drag proxy window.
            /// </summary>
            public static Window Window;

            /// <summary>
            /// The left hint proxy window.
            /// </summary>
            public static Window Left;

            /// <summary>
            /// The right hint proxy window.
            /// </summary>
            public static Window Right;

            /// <summary>
            /// The up hint proxy window.
            /// </summary>
            public static Window Up;

            /// <summary>
            /// The down hint proxy window.
            /// </summary>
            public static Window Down;

            /// <summary>
            /// The center hint proxy window.
            /// </summary>
            public static Window Center;

            /// <summary>
            /// The hint windows size.
            /// </summary>
            public const float HintWindowsSize = 32.0f;

            /// <summary>
            /// Initializes the hit proxy windows. Those windows are used to indicate drag target areas (left, right, top, bottom, etc.).
            /// </summary>
            public static void InitHitProxy()
            {
                CreateProxy(ref Left, "DockHint.Left");
                CreateProxy(ref Right, "DockHint.Right");
                CreateProxy(ref Up, "DockHint.Up");
                CreateProxy(ref Down, "DockHint.Down");
                CreateProxy(ref Center, "DockHint.Center");
            }

            /// <summary>
            /// Initializes the hint window.
            /// </summary>
            /// <param name="initSize">Initial size of the proxy window.</param>
            public static void Init(ref Float2 initSize)
            {
                if (Window == null)
                {
                    var settings = CreateWindowSettings.Default;
                    settings.Title = "DockHint.Window";
                    settings.Size = initSize;
                    settings.AllowInput = true;
                    settings.AllowMaximize = false;
                    settings.AllowMinimize = false;
                    settings.HasBorder = false;
                    settings.HasSizingFrame = false;
                    settings.Type = WindowType.Utility;
                    settings.SupportsTransparency = true;
                    settings.ShowInTaskbar = false;
                    settings.ShowAfterFirstPaint = false;
                    settings.IsTopmost = true;

                    Window = Platform.CreateWindow(ref settings);
                    Window.Opacity = 0.6f;
                    Window.GUI.BackgroundColor = Style.Current.DragWindow;
                }
                else
                {
                    // Resize proxy
                    Window.ClientSize = initSize;
                }

                InitHitProxy();
            }

            private static void CreateProxy(ref Window win, string name)
            {
                if (win != null)
                    return;

                var settings = CreateWindowSettings.Default;
                settings.Title = name;
                settings.Size = new Float2(HintWindowsSize * Platform.DpiScale);
                settings.AllowInput = false;
                settings.AllowMaximize = false;
                settings.AllowMinimize = false;
                settings.HasBorder = false;
                settings.HasSizingFrame = false;
                settings.Type = WindowType.Utility;
                settings.SupportsTransparency = true;
                settings.ShowInTaskbar = false;
                settings.ActivateWhenFirstShown = false;
                settings.IsTopmost = true;
                settings.ShowAfterFirstPaint = false;

                win = Platform.CreateWindow(ref settings);
                win.Opacity = 0.6f;
                win.GUI.BackgroundColor = Style.Current.DragWindow;
            }

            /// <summary>
            /// Hides proxy windows.
            /// </summary>
            public static void Hide()
            {
                HideProxy(ref Window);
                HideProxy(ref Left);
                HideProxy(ref Right);
                HideProxy(ref Up);
                HideProxy(ref Down);
                HideProxy(ref Center);
            }

            private static void HideProxy(ref Window win)
            {
                if (win)
                {
                    win.Hide();
                }
            }

            /// <summary>
            /// Releases proxy data and windows.
            /// </summary>
            public static void Dispose()
            {
                DisposeProxy(ref Window);
                DisposeProxy(ref Left);
                DisposeProxy(ref Right);
                DisposeProxy(ref Up);
                DisposeProxy(ref Down);
                DisposeProxy(ref Center);
            }

            private static void DisposeProxy(ref Window win)
            {
                if (win)
                {
                    win.Close(ClosingReason.User);
                    win = null;
                }
            }
        }
    }
}