// Copyright (C) Microsoft Corporation. All Rights Reserved.
// This code released under the terms of the Microsoft Public License
// (Ms-PL, http://opensource.org/licenses/ms-pl.html).

using System.Diagnostics.CodeAnalysis;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace Delay
{
    /// <summary>
    /// Class containing a replacement for ToolTipService.SetToolTip that works
    /// around a Windows 8 platform bug where NullReferenceException is thrown
    /// from native code the next time a ToolTip is displayed if its Binding
    /// transitions from non-null to null while on screen.
    /// </summary>
    public static class ToolTipServiceExtensions
    {
        /// <summary>
        /// Gets the value of the ToolTipServiceExtensions.ToolTip XAML attached property for an object.
        /// </summary>
        /// <param name="obj">The object from which the property value is read.</param>
        /// <returns>The object's tooltip content.</returns>
        [SuppressMessage("Microsoft.Design", "CA1062:Validate arguments of public methods", MessageId = "0", Justification = "Underlying method will validate.")]
        public static object GetToolTip(DependencyObject obj)
        {
            return (object)obj.GetValue(ToolTipProperty);
        }

        /// <summary>
        /// Sets the value of the ToolTipServiceExtensions.ToolTip XAML attached property.
        /// </summary>
        /// <param name="obj">The object to set tooltip content on.</param>
        /// <param name="value">The value to set for tooltip content.</param>
        [SuppressMessage("Microsoft.Design", "CA1062:Validate arguments of public methods", MessageId = "0", Justification = "Underlying method will validate.")]
        public static void SetToolTip(DependencyObject obj, object value)
        {
            obj.SetValue(ToolTipProperty, value);
        }

        /// <summary>
        /// Gets or sets the object or string content of an element's ToolTip.
        /// </summary>
        [SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes", Justification = "Stardard attached property implementation.")]
        public static readonly DependencyProperty ToolTipProperty =
            DependencyProperty.RegisterAttached(
                "ToolTip",
                typeof(object),
                typeof(ToolTipServiceExtensions),
                new PropertyMetadata(null, ToolTipPropertyChangedCallback));

        /// <summary>
        /// Method called when the value of an element's ToolTipServiceExtensions.ToolTip XAML attached property changes.
        /// </summary>
        /// <param name="element">Element for which the property changed.</param>
        /// <param name="args">Event arguments.</param>
        private static void ToolTipPropertyChangedCallback(DependencyObject element, DependencyPropertyChangedEventArgs args)
        {
            // Capture the new value
            var newValue = args.NewValue;

            // Create a ToolTip instance to display the new value
            var toolTip = new ToolTip { Content = newValue };

            // Hide the ToolTip instance if the new value is null
            // (Prevents the display of a small white rectangle)
            if (null == newValue)
            {
                toolTip.Visibility = Visibility.Collapsed;
            }

            // Defer to ToolTipService.SetToolTip for the actual implementation
            ToolTipService.SetToolTip(element, toolTip);
        }
    }
}