// 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.Data;
 
namespace System.Windows.Controls
{
    /// <summary>
    ///     A column definition that allows a developer to specify specific
    ///     editing and non-editing templates.
    /// </summary>
    public class DataGridTemplateColumn : DataGridColumn
    {
        #region Constructors
 
        static DataGridTemplateColumn()
        {
            CanUserSortProperty.OverrideMetadata(
                typeof(DataGridTemplateColumn),
                new FrameworkPropertyMetadata(null, new CoerceValueCallback(OnCoerceTemplateColumnCanUserSort)));
            SortMemberPathProperty.OverrideMetadata(
                typeof(DataGridTemplateColumn),
                new FrameworkPropertyMetadata(new PropertyChangedCallback(OnTemplateColumnSortMemberPathChanged)));
        }
 
        #endregion
 
        #region Auto Sort
 
        private static void OnTemplateColumnSortMemberPathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            DataGridTemplateColumn column = (DataGridTemplateColumn)d;
            column.CoerceValue(CanUserSortProperty);
        }
 
        private static object OnCoerceTemplateColumnCanUserSort(DependencyObject d, object baseValue)
        {
            DataGridTemplateColumn templateColumn = (DataGridTemplateColumn)d;
            if (string.IsNullOrEmpty(templateColumn.SortMemberPath))
            {
                return false;
            }
 
            return DataGridColumn.OnCoerceCanUserSort(d, baseValue);
        }
 
        #endregion
 
        #region Templates
 
        /// <summary>
        ///     A template describing how to display data for a cell in this column.
        /// </summary>
        public DataTemplate CellTemplate
        {
            get { return (DataTemplate)GetValue(CellTemplateProperty); }
            set { SetValue(CellTemplateProperty, value); }
        }
 
        /// <summary>
        ///     The DependencyProperty representing the CellTemplate property.
        /// </summary>
        public static readonly DependencyProperty CellTemplateProperty = DependencyProperty.Register(
                                                                            "CellTemplate", 
                                                                            typeof(DataTemplate), 
                                                                            typeof(DataGridTemplateColumn),
                                                                            new FrameworkPropertyMetadata(null, new PropertyChangedCallback(DataGridColumn.NotifyPropertyChangeForRefreshContent)));
 
        /// <summary>
        ///     A template selector describing how to display data for a cell in this column.
        /// </summary>
        public DataTemplateSelector CellTemplateSelector
        {
            get { return (DataTemplateSelector)GetValue(CellTemplateSelectorProperty); }
            set { SetValue(CellTemplateSelectorProperty, value); }
        }
 
        /// <summary>
        ///     The DependencyProperty representing the CellTemplateSelector property.
        /// </summary>
        public static readonly DependencyProperty CellTemplateSelectorProperty = DependencyProperty.Register(
                                                                                    "CellTemplateSelector", 
                                                                                    typeof(DataTemplateSelector), 
                                                                                    typeof(DataGridTemplateColumn),
                                                                                    new FrameworkPropertyMetadata(null, new PropertyChangedCallback(DataGridColumn.NotifyPropertyChangeForRefreshContent)));
 
        /// <summary>
        ///     A template describing how to display data for a cell 
        ///     that is being edited in this column.
        /// </summary>
        public DataTemplate CellEditingTemplate
        {
            get { return (DataTemplate)GetValue(CellEditingTemplateProperty); }
            set { SetValue(CellEditingTemplateProperty, value); }
        }
 
        /// <summary>
        ///     The DependencyProperty representing the CellEditingTemplate
        /// </summary>
        public static readonly DependencyProperty CellEditingTemplateProperty = DependencyProperty.Register(
                                                                                    "CellEditingTemplate", 
                                                                                    typeof(DataTemplate), 
                                                                                    typeof(DataGridTemplateColumn),
                                                                                    new FrameworkPropertyMetadata(null, new PropertyChangedCallback(DataGridColumn.NotifyPropertyChangeForRefreshContent)));
 
        /// <summary>
        ///     A template selector describing how to display data for a cell 
        ///     that is being edited in this column.
        /// </summary>
        public DataTemplateSelector CellEditingTemplateSelector
        {
            get { return (DataTemplateSelector)GetValue(CellEditingTemplateSelectorProperty); }
            set { SetValue(CellEditingTemplateSelectorProperty, value); }
        }
 
        /// <summary>
        ///     The DependencyProperty representing the CellEditingTemplateSelector
        /// </summary>
        public static readonly DependencyProperty CellEditingTemplateSelectorProperty = DependencyProperty.Register(
                                                                                            "CellEditingTemplateSelector", 
                                                                                            typeof(DataTemplateSelector), 
                                                                                            typeof(DataGridTemplateColumn), 
                                                                                            new FrameworkPropertyMetadata(null, new PropertyChangedCallback(DataGridColumn.NotifyPropertyChangeForRefreshContent)));
 
        /// <summary>
        ///     Returns either the specified CellTemplate[Selector] or CellEditingTemplate[Selector].
        ///     CellTemplate[Selector] is the fallack if CellEditingTemplate[Selector] is null.
        /// </summary>
        /// <param name="isEditing">Whether the editing template is requested.</param>
        private void ChooseCellTemplateAndSelector(bool isEditing, out DataTemplate template, out DataTemplateSelector templateSelector)
        {
            template = null;
            templateSelector = null;
 
            if (isEditing)
            {
                template = CellEditingTemplate;
                templateSelector = CellEditingTemplateSelector;
            }
 
            if (template == null && templateSelector == null)
            {
                template = CellTemplate;
                templateSelector = CellTemplateSelector;
            }
        }
 
        #endregion
 
        #region Visual Tree Generation
 
        /// <summary>
        ///     Creates the visual tree that will become the content of a cell.
        /// </summary>
        /// <param name="isEditing">Whether the editing version is being requested.</param>
        /// <param name="dataItem">The data item for the cell.</param>
        /// <param name="cell">The cell container that will receive the tree.</param>
        private FrameworkElement LoadTemplateContent(bool isEditing, object dataItem, DataGridCell cell)
        {
            DataTemplate template;
            DataTemplateSelector templateSelector;
            ChooseCellTemplateAndSelector(isEditing, out template, out templateSelector);
            if (template != null || templateSelector != null)
            {
                ContentPresenter contentPresenter = new ContentPresenter();
                BindingOperations.SetBinding(contentPresenter, ContentPresenter.ContentProperty, new Binding());
                contentPresenter.ContentTemplate = template;
                contentPresenter.ContentTemplateSelector = templateSelector;
                return contentPresenter;
            }
 
            return null;
        }
 
        /// <summary>
        ///     Creates the visual tree that will become the content of a cell.
        /// </summary>
        protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
        {
            return LoadTemplateContent(/* isEditing = */ false, dataItem, cell);
        }
 
        /// <summary>
        ///     Creates the visual tree that will become the content of a cell.
        /// </summary>
        protected override FrameworkElement GenerateEditingElement(DataGridCell cell, object dataItem)
        {
            return LoadTemplateContent(/* isEditing = */ true, dataItem, cell);
        }
 
        #endregion
 
        #region Property Changed Handler
 
        /// <summary>
        /// Override which handles property
        /// change for template properties
        /// </summary>
        /// <param name="element"></param>
        /// <param name="propertyName"></param>
        protected internal override void RefreshCellContent(FrameworkElement element, string propertyName)
        {
            if (element is DataGridCell cell)
            {
                bool isCellEditing = cell.IsEditing;
 
                if ((!isCellEditing &&
                        (string.Equals(propertyName, "CellTemplate", StringComparison.Ordinal) ||
                        string.Equals(propertyName, "CellTemplateSelector", StringComparison.Ordinal))) ||
                    (isCellEditing &&
                        (string.Equals(propertyName, "CellEditingTemplate", StringComparison.Ordinal) ||
                        string.Equals(propertyName, "CellEditingTemplateSelector", StringComparison.Ordinal))))
                {
                    cell.BuildVisualTree();
                    return;
                }
            }
 
            base.RefreshCellContent(element, propertyName);
        }
 
        #endregion
    }
}