// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
 
using System.Windows.Controls.Primitives;
using System.Windows.Media;
 
namespace System.Windows.Controls
{
    /// <summary>
    /// The control which would be used to indicate the drag during column header drag-drop
    /// </summary>
    [TemplatePart(Name = "PART_VisualBrushCanvas", Type = typeof(Canvas))]
    internal class DataGridColumnFloatingHeader : Control
    {
        #region Constructors
 
        static DataGridColumnFloatingHeader()
        {
            DefaultStyleKeyProperty.OverrideMetadata(
                typeof(DataGridColumnFloatingHeader), 
                new FrameworkPropertyMetadata(DataGridColumnHeader.ColumnFloatingHeaderStyleKey));
 
            WidthProperty.OverrideMetadata(
                typeof(DataGridColumnFloatingHeader), 
                new FrameworkPropertyMetadata(new PropertyChangedCallback(OnWidthChanged), new CoerceValueCallback(OnCoerceWidth)));
 
            HeightProperty.OverrideMetadata(
                typeof(DataGridColumnFloatingHeader), 
                new FrameworkPropertyMetadata(new PropertyChangedCallback(OnHeightChanged), new CoerceValueCallback(OnCoerceHeight)));
        }
 
        #endregion
 
        #region Static Methods
 
        private static void OnWidthChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            DataGridColumnFloatingHeader header = (DataGridColumnFloatingHeader)d;
            double width = (double)e.NewValue;
            if (header._visualBrushCanvas != null && !double.IsNaN(width))
            {
                VisualBrush brush = header._visualBrushCanvas.Background as VisualBrush;
                if (brush != null)
                {
                    Rect viewBox = brush.Viewbox;
                    brush.Viewbox = new Rect(viewBox.X, viewBox.Y, width - header.GetVisualCanvasMarginX(), viewBox.Height);
                }
            }
        }
 
        private static object OnCoerceWidth(DependencyObject d, object baseValue)
        {
            double width = (double)baseValue;
            DataGridColumnFloatingHeader header = (DataGridColumnFloatingHeader)d;
            if (header._referenceHeader != null && double.IsNaN(width))
            {
                return header._referenceHeader.ActualWidth + header.GetVisualCanvasMarginX();
            }
 
            return baseValue;
        }
 
        private static void OnHeightChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            DataGridColumnFloatingHeader header = (DataGridColumnFloatingHeader)d;
            double height = (double)e.NewValue;
            if (header._visualBrushCanvas != null && !double.IsNaN(height))
            {
                VisualBrush brush = header._visualBrushCanvas.Background as VisualBrush;
                if (brush != null)
                {
                    Rect viewBox = brush.Viewbox;
                    brush.Viewbox = new Rect(viewBox.X, viewBox.Y, viewBox.Width, height - header.GetVisualCanvasMarginY());
                }
            }
        }
 
        private static object OnCoerceHeight(DependencyObject d, object baseValue)
        {
            double height = (double)baseValue;
            DataGridColumnFloatingHeader header = (DataGridColumnFloatingHeader)d;
            if (header._referenceHeader != null && double.IsNaN(height))
            {
                return header._referenceHeader.ActualHeight + header.GetVisualCanvasMarginY();
            }
 
            return baseValue;
        }
 
        #endregion
 
        #region Methods and Properties
 
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            _visualBrushCanvas = GetTemplateChild(VisualBrushCanvasTemplateName) as Canvas;
            UpdateVisualBrush();
        }
 
        internal DataGridColumnHeader ReferenceHeader
        {
            get
            {
                return _referenceHeader;
            }
 
            set
            {
                _referenceHeader = value;
            }
        }
 
        private void UpdateVisualBrush()
        {
            if (_referenceHeader != null && _visualBrushCanvas != null)
            {
                VisualBrush visualBrush = new VisualBrush(_referenceHeader)
                {
                    ViewboxUnits = BrushMappingMode.Absolute
                };
 
                double width = Width;
                if (double.IsNaN(width))
                {
                    width = _referenceHeader.ActualWidth;
                }
                else
                {
                    width -= GetVisualCanvasMarginX();
                }
 
                double height = Height;
                if (double.IsNaN(height))
                {
                    height = _referenceHeader.ActualHeight;
                }
                else
                {
                    height -= GetVisualCanvasMarginY();
                }
 
                Vector offset = VisualTreeHelper.GetOffset(_referenceHeader);
                visualBrush.Viewbox = new Rect(offset.X, offset.Y, width, height);
 
                _visualBrushCanvas.Background = visualBrush;
            }
        }
 
        internal void ClearHeader()
        {
            _referenceHeader = null;
            _visualBrushCanvas?.Background = null;
        }
 
        private double GetVisualCanvasMarginX()
        {
            double delta = 0;
            if (_visualBrushCanvas != null)
            {
                Thickness margin = _visualBrushCanvas.Margin;
                delta += margin.Left;
                delta += margin.Right;
            }
 
            return delta;
        }
 
        private double GetVisualCanvasMarginY()
        {
            double delta = 0;
            if (_visualBrushCanvas != null)
            {
                Thickness margin = _visualBrushCanvas.Margin;
                delta += margin.Top;
                delta += margin.Bottom;
            }
 
            return delta;
        }
 
        #endregion
 
        #region Data
 
        private DataGridColumnHeader _referenceHeader;
        private const string VisualBrushCanvasTemplateName = "PART_VisualBrushCanvas";
        private Canvas _visualBrushCanvas;
 
        #endregion
    }
}