using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Media;
using System.Windows.Input;
using AIStudio.Wpf.DiagramDesigner.Helpers;
using System.Diagnostics;

namespace AIStudio.Wpf.DiagramDesigner
{
    public class ZoomBox : Control
    {
        private Thumb zoomThumb;
        private Canvas zoomCanvas;
        private Slider zoomSlider;

        #region DPs

        #region ScrollViewer
        public ScrollViewer ScrollViewer
        {
            get
            {
                return (ScrollViewer)GetValue(ScrollViewerProperty);
            }
            set
            {
                SetValue(ScrollViewerProperty, value);
            }
        }

        public static readonly DependencyProperty ScrollViewerProperty =
            DependencyProperty.Register(nameof(ScrollViewer), typeof(ScrollViewer), typeof(ZoomBox));
        #endregion

        #region FrameworkElement


        public static readonly DependencyProperty DesignerCanvasProperty =
            DependencyProperty.Register(nameof(DesignerCanvas), typeof(FrameworkElement), typeof(ZoomBox),
                new FrameworkPropertyMetadata(null,
                    new PropertyChangedCallback(OnDesignerCanvasChanged)));

        public FrameworkElement DesignerCanvas
        {
            get
            {
                return (FrameworkElement)GetValue(DesignerCanvasProperty);
            }
            set
            {
                SetValue(DesignerCanvasProperty, value);
            }
        }

        private static void OnDesignerCanvasChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ZoomBox target = (ZoomBox)d;
            FrameworkElement oldDesignerCanvas = (FrameworkElement)e.OldValue;
            FrameworkElement newDesignerCanvas = (FrameworkElement)e.NewValue;
            target.OnDesignerCanvasChanged(oldDesignerCanvas, newDesignerCanvas);
        }

        protected virtual void OnDesignerCanvasChanged(FrameworkElement oldDesignerCanvas, FrameworkElement newDesignerCanvas)
        {
            if (oldDesignerCanvas != null)
            {
                oldDesignerCanvas.LayoutUpdated -= this.DesignerCanvas_LayoutUpdated;
                oldDesignerCanvas.MouseDown -= this.DesignerCanvas_MouseRightButtonDown;
                oldDesignerCanvas.MouseUp -= this.DesignerCanvas_MouseRightButtonUp;
                oldDesignerCanvas.MouseMove -= this.DesignerCanvas_MouseMove;
            }

            if (newDesignerCanvas != null)
            {
                newDesignerCanvas.LayoutUpdated += this.DesignerCanvas_LayoutUpdated;
                newDesignerCanvas.MouseRightButtonDown += this.DesignerCanvas_MouseRightButtonDown;
                newDesignerCanvas.MouseRightButtonUp += this.DesignerCanvas_MouseRightButtonUp;
                newDesignerCanvas.MouseMove += this.DesignerCanvas_MouseMove;
            }
        }
        #endregion

        public static readonly DependencyProperty OffSetProperty =
           DependencyProperty.Register(nameof(OffSet), typeof(bool), typeof(ZoomBox), new UIPropertyMetadata(false));
        public bool OffSet
        {
            get
            {
                return (bool)GetValue(OffSetProperty);
            }
            set
            {
                SetValue(OffSetProperty, value);
            }
        }

        public static readonly DependencyProperty ZoomValueProperty =
            DependencyProperty.Register(nameof(ZoomValue), typeof(double), typeof(ZoomBox), new UIPropertyMetadata(1d));
        public double ZoomValue
        {
            get
            {
                return (double)GetValue(ZoomValueProperty);
            }
            set
            {
                SetValue(ZoomValueProperty, value);
            }
        }

        public static readonly DependencyProperty MaximumZoomValueProperty =
           DependencyProperty.Register(nameof(MaximumZoomValue), typeof(double), typeof(ZoomBox), new UIPropertyMetadata(3d));
        public double MaximumZoomValue
        {
            get
            {
                return (double)GetValue(MaximumZoomValueProperty);
            }
            set
            {
                SetValue(MaximumZoomValueProperty, value);
            }
        }

        public static readonly DependencyProperty MinimumZoomValueProperty =
           DependencyProperty.Register(nameof(MinimumZoomValue), typeof(double), typeof(ZoomBox), new UIPropertyMetadata(0.5d));
        public double MinimumZoomValue
        {
            get
            {
                return (double)GetValue(MinimumZoomValueProperty);
            }
            set
            {
                SetValue(MinimumZoomValueProperty, value);
            }
        }

        public static readonly DependencyProperty FitViewModelProperty =
           DependencyProperty.Register(nameof(FitViewModel), typeof(FitViewModel), typeof(ZoomBox),
               new FrameworkPropertyMetadata(null,
                   new PropertyChangedCallback(OnFitViewModelChanged)));

        public FitViewModel FitViewModel
        {
            get
            {
                return (FitViewModel)GetValue(FitViewModelProperty);
            }
            set
            {
                SetValue(FitViewModelProperty, value);
            }
        }

        private static void OnFitViewModelChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ZoomBox target = (ZoomBox)d;
            var fitviewmodel = e.NewValue as FitViewModel;
            if (fitviewmodel != null)
            {
                target.OnFitViewModelChanged(fitviewmodel);
            }
        }

        private void OnFitViewModelChanged(FitViewModel fitViewModel)
        {
            if (IsLoaded && fitViewModel != null)
            {
                if (fitViewModel.FitMode == FitMode.None)
                {

                }
                else if (fitViewModel.FitMode == FitMode.FitWidth)
                {
                    ZoomValue = (this.ScrollViewer.ViewportWidth * fitViewModel.PaddingRate) / fitViewModel.BoundingRect.Width;
                }
                else if (fitViewModel.FitMode == FitMode.FitHeight)
                {
                    ZoomValue = (this.ScrollViewer.ViewportHeight * fitViewModel.PaddingRate) / fitViewModel.BoundingRect.Height;
                }
                else if (fitViewModel.FitMode == FitMode.FitAuto)
                {
                    ZoomValue = Math.Min(
                        (this.ScrollViewer.ViewportWidth * fitViewModel.PaddingRate) / fitViewModel.BoundingRect.Width,
                        (this.ScrollViewer.ViewportHeight * fitViewModel.PaddingRate) / fitViewModel.BoundingRect.Height
                        );
                }
              
                double xOffset, yOffset;
                xOffset = fitViewModel.BoundingRect.Left * ZoomValue - (this.ScrollViewer.ViewportWidth - fitViewModel.BoundingRect.Width * ZoomValue) / 2;
                yOffset = fitViewModel.BoundingRect.Top * ZoomValue - (this.ScrollViewer.ViewportHeight - fitViewModel.BoundingRect.Height * ZoomValue) / 2;
                if (OffSet)
                {
                    Vector vector = System.Windows.Media.VisualTreeHelper.GetOffset(DesignerCanvas);
                    xOffset += vector.X;
                    yOffset += vector.Y;
                }
                this.ScrollViewer.ScrollToHorizontalOffset(xOffset);
                this.ScrollViewer.ScrollToVerticalOffset(yOffset);
            }
        }
        #endregion

        public ZoomBox()
        {
            this.Loaded += ZoomBox_Loaded;
        }

        private void ZoomBox_Loaded(object sender, RoutedEventArgs e)
        {
            OnFitViewModelChanged(FitViewModel);
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            this.ScrollViewer = VisualHelper.TryFindParent<ScrollViewer>(this.DesignerCanvas);
            if (this.ScrollViewer == null)
                return;

            this.zoomThumb = Template.FindName("PART_ZoomThumb", this) as Thumb;
            if (this.zoomThumb == null)
                throw new Exception("PART_ZoomThumb template is missing!");

            this.zoomCanvas = Template.FindName("PART_ZoomCanvas", this) as Canvas;
            if (this.zoomCanvas == null)
                throw new Exception("PART_ZoomCanvas template is missing!");

            this.zoomSlider = Template.FindName("PART_ZoomSlider", this) as Slider;
            if (this.zoomSlider == null)
                throw new Exception("PART_ZoomSlider template is missing!");

            this.zoomThumb.DragDelta += new DragDeltaEventHandler(this.Thumb_DragDelta);
            this.zoomSlider.ValueChanged += new RoutedPropertyChangedEventHandler<double>(this.ZoomSlider_ValueChanged);


        }

        private void ZoomSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
        {
            double scale = e.NewValue / e.OldValue;
            double halfViewportHeight = this.ScrollViewer.ViewportHeight / 2;
            double newVerticalOffset = ((this.ScrollViewer.VerticalOffset + halfViewportHeight) * scale - halfViewportHeight);
            double halfViewportWidth = this.ScrollViewer.ViewportWidth / 2;
            double newHorizontalOffset = ((this.ScrollViewer.HorizontalOffset + halfViewportWidth) * scale - halfViewportWidth);
            this.ScrollViewer.ScrollToHorizontalOffset(newHorizontalOffset);
            this.ScrollViewer.ScrollToVerticalOffset(newVerticalOffset);
        }

        private void Thumb_DragDelta(object sender, DragDeltaEventArgs e)
        {
            double scale, xOffset, yOffset;
            this.InvalidateScale(out scale, out xOffset, out yOffset);
            this.ScrollViewer.ScrollToHorizontalOffset(this.ScrollViewer.HorizontalOffset + e.HorizontalChange / scale);
            this.ScrollViewer.ScrollToVerticalOffset(this.ScrollViewer.VerticalOffset + e.VerticalChange / scale);
        }

        private void DesignerCanvas_LayoutUpdated(object sender, EventArgs e)
        {
            try
            {

                double scale, xOffset, yOffset;
                this.InvalidateScale(out scale, out xOffset, out yOffset);
                this.zoomThumb.Width = (this.ScrollViewer.ViewportWidth) * scale;
                this.zoomThumb.Height = (this.ScrollViewer.ViewportHeight) * scale;
                Canvas.SetLeft(this.zoomThumb, xOffset + this.ScrollViewer.HorizontalOffset * scale);
                Canvas.SetTop(this.zoomThumb, yOffset + this.ScrollViewer.VerticalOffset * scale);
            }
            catch { }
        }

        /// <summary>
        /// 用于记录鼠标按下的点
        /// </summary>
        private Point _clickPoint = new Point(0, 0);

        private void DesignerCanvas_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
        {
            _clickPoint = e.GetPosition((FrameworkElement)sender);
            DesignerCanvas.Cursor = Cursors.Hand;
        }

        private void DesignerCanvas_MouseRightButtonUp(object sender, MouseButtonEventArgs e)
        {
            DesignerCanvas.Cursor = Cursors.Arrow;
        }

        private void DesignerCanvas_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.RightButton == MouseButtonState.Pressed)
            {
                FrameworkElement cabSender = (FrameworkElement)sender;
                double x;
                double y;
                Point p = e.MouseDevice.GetPosition(cabSender);

                x = _clickPoint.X - p.X;
                y = _clickPoint.Y - p.Y;

                ScrollViewer?.ScrollToHorizontalOffset(ScrollViewer.HorizontalOffset + x);
                ScrollViewer?.ScrollToVerticalOffset(ScrollViewer.VerticalOffset + y);
            }
        }

        private void InvalidateScale(out double scale, out double xOffset, out double yOffset)
        {
            if (OffSet)
            {
                Vector vector = System.Windows.Media.VisualTreeHelper.GetOffset(DesignerCanvas);
                double w = DesignerCanvas.ActualWidth + vector.X * 2;
                double h = DesignerCanvas.ActualHeight + vector.Y * 2;

                // zoom canvas size
                double x = this.zoomCanvas.ActualWidth;
                double y = this.zoomCanvas.ActualHeight;
                double scaleX = x / w;
                double scaleY = y / h;
                scale = (scaleX < scaleY) ? scaleX : scaleY;
                xOffset = (x - scale * w) / 2;
                yOffset = (y - scale * h) / 2;
            }
            else
            {
                double w = DesignerCanvas.ActualWidth;
                double h = DesignerCanvas.ActualHeight;

                // zoom canvas size
                double x = this.zoomCanvas.ActualWidth;
                double y = this.zoomCanvas.ActualHeight;
                double scaleX = x / w;
                double scaleY = y / h;
                scale = (scaleX < scaleY) ? scaleX : scaleY;
                xOffset = (x - scale * w) / 2;
                yOffset = (y - scale * h) / 2;
            }

        }
    }

    public class FitViewModel
    {
        public Rect BoundingRect
        {
            get; set;
        }

        public FitMode FitMode
        {
            get; set;
        }

        public double PaddingRate
        {
            get; set;
        } = 0.9;
    }

    public enum FitMode
    {
        None,
        FitAuto,
        FitWidth,
        FitHeight,
    }
}