using System.Collections.Generic;
using System.Linq;
using System.Windows.Controls;
using System.Windows.Data;

namespace DTS.Common.Controls
{
    public class AutoSizedGridView : GridView
    {
        HashSet<int> _allColumns;
        HashSet<int> _autoWidthColumns;
        Dictionary<int, BindingExpression> _widthBoundColumns;

        protected override void PrepareItem(ListViewItem item)
        {
            if (null == _allColumns || !Columns.Select(col => col.GetHashCode()).SequenceEqual(_allColumns))
            {
                _allColumns = new HashSet<int>();
                _autoWidthColumns = new HashSet<int>();
                _widthBoundColumns = new Dictionary<int, BindingExpression>();

                foreach (var column in Columns)
                {
                    _allColumns.Add(column.GetHashCode());
                    if (double.IsNaN(column.Width) && //Width == "Auto"
                        null == BindingOperations.GetBindingExpression(column, GridViewColumn.WidthProperty)) //Width isn't bound
                    {
                        _autoWidthColumns.Add(column.GetHashCode());
                    }
                    else if (null != BindingOperations.GetBindingExpression(column, GridViewColumn.WidthProperty))
                    {
                        _widthBoundColumns.Add(column.GetHashCode(), BindingOperations.GetBindingExpression(column, GridViewColumn.WidthProperty));
                    }
                }
            }

            foreach (var column in Columns)
            {
                if (_autoWidthColumns.Contains(column.GetHashCode()))
                {
                    //force remeasure
                    if (double.IsNaN(column.Width))
                    {
                        column.Width = column.ActualWidth;
                    }
                    column.Width = double.NaN;
                }
                else if (_widthBoundColumns.ContainsKey(column.GetHashCode()))
                {
                    //check if binding lost, re-bind
                    if (null == BindingOperations.GetBindingExpression(column, GridViewColumn.WidthProperty))
                    {
                        BindingOperations.SetBinding(column, GridViewColumn.WidthProperty, _widthBoundColumns[column.GetHashCode()].ParentBindingBase);
                    }
                }
            }

            base.PrepareItem(item);
        }
    }
}