// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
namespace System.Windows.Automation.Peers
{
    ///
    public class FrameworkElementAutomationPeer : UIElementAutomationPeer
    {
        ///
        public FrameworkElementAutomationPeer(FrameworkElement owner)
            : base(owner)
        { }
 
        ///
        protected override string GetAutomationIdCore()
        {
            //  1. fetch AutomationProperties.AutomationIdProperty
            string result = base.GetAutomationIdCore();
 
            if (string.IsNullOrEmpty(result))
            {
                //  2. fetch x:Uid
                FrameworkElement owner = (FrameworkElement)Owner;
                result = Owner.Uid;
 
                if (string.IsNullOrEmpty(result))
                {
                    //  3. fetch FrameworkElement.NameProperty
                    result = owner.Name;
                }
            }
 
            return result ?? string.Empty;
        }
 
        ///
        override protected string GetNameCore()
        {
            string result = base.GetNameCore();
            if (string.IsNullOrEmpty(result))
            {
                AutomationPeer labelAutomationPeer = GetLabeledByCore();
                if (labelAutomationPeer != null)
                    result = labelAutomationPeer.GetName();
 
                if (string.IsNullOrEmpty(result))
                    result = ((FrameworkElement)Owner).GetPlainText();
            }
 
            return result ?? string.Empty;
        }
 
        ///
        protected override string GetHelpTextCore()
        {
            string result = base.GetHelpTextCore();
            if (string.IsNullOrEmpty(result))
            {
                object toolTip = ((FrameworkElement)Owner).ToolTip;
                if (toolTip != null)
                {
                    result = toolTip as string;
                    if (string.IsNullOrEmpty(result))
                    {
                        FrameworkElement toolTipElement = toolTip as FrameworkElement;
                        if (toolTipElement != null)
                            result = toolTipElement.GetPlainText();
                    }
                }
            }
            return result ?? String.Empty;
        }
 
        ///
        override internal bool IgnoreUpdatePeer()
        {
            // Ignore UpdatePeer if the peer's owner has been removed from the
            // visual tree.  There's no need to update such a peer, as it no longer
            // participates in automation.  And UpdatePeer actually throws exceptions
            // in some cases.
 
            // There's no general-purpose efficient test for "belongs to the visual tree",
            // but we can test for elements that belong to data templates corresponding
            // to items that have been virtualized or removed from the underlying
            // collection, and that's enough to avoid the ElementNotAvailable exceptions.
            DependencyObject owner = Owner;
            if (owner == null ||
                owner.GetValue(FrameworkElement.DataContextProperty) ==
                    System.Windows.Data.BindingOperations.DisconnectedSource)
            {
                return true;
            }
 
            return base.IgnoreUpdatePeer();
        }
    }
}