// 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.
 
//
//
// Description: DataTemplate describes how to display a single data item.
//
// Specs:       http://avalon/coreui/Specs%20%20Property%20Engine/Styling%20Revisited.doc
//
 
using System.ComponentModel;
using System.Windows.Controls;
using System.Windows.Markup;
 
namespace System.Windows
{
    /// <summary>
    ///     DataTemplate describes how to display a single data item.
    /// </summary>
    [DictionaryKeyProperty("DataTemplateKey")]
    public class DataTemplate : FrameworkTemplate
    {
        #region Constructors
 
        //-------------------------------------------------------------------
        //
        //  Constructors
        //
        //-------------------------------------------------------------------
 
        /// <summary>
        ///     DataTemplate Constructor
        /// </summary>
        public DataTemplate()
        {
        }
 
        /// <summary>
        ///     DataTemplate Constructor
        /// </summary>
        public DataTemplate(object dataType)
        {
            Exception ex = TemplateKey.ValidateDataType(dataType, "dataType");
            if (ex != null)
                throw ex;
 
            _dataType = dataType;
        }
 
        #endregion Constructors
 
        #region Public Properties
 
        //-------------------------------------------------------------------
        //
        //  Public Properties
        //
        //-------------------------------------------------------------------
 
        /// <summary>
        ///     DataType for this DataTemplate.  If the template is intended
        ///     for object data, this is the Type of the data.  If the
        ///     template is intended for XML data, this is the tag name
        ///     of the data (i.e. a string).
        /// </summary>
        [DefaultValue(null)]
        [Ambient]
        public object DataType
        {
            get {  return _dataType; }
            set
            {
                Exception ex = TemplateKey.ValidateDataType(value, "value");
                if (ex != null)
                    throw ex;
 
                CheckSealed();
                _dataType = value;
            }
        }
 
        /// <summary>
        ///     Collection of Triggers
        /// </summary>
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        [DependsOn("VisualTree")]
        [DependsOn("Template")]
        public TriggerCollection Triggers
        {
            get
            {
                if (_triggers == null)
                {
                    _triggers = new TriggerCollection();
 
                    // If the template has been sealed prior to this the newly
                    // created TriggerCollection also needs to be sealed
                    if (IsSealed)
                    {
                        _triggers.Seal();
                    }
                }
                return _triggers;
            }
        }
 
        /// <summary>
        ///     The key that will be used if the DataTemplate is added to a
        ///     ResourceDictionary in Xaml without a specified Key (x:Key).
        /// </summary>
        public object DataTemplateKey
        {
            get
            {
                return (DataType != null) ? new DataTemplateKey(DataType) : null;
            }
        }
 
        #endregion PublicProperties
 
        #region Internal Properties
 
        //-------------------------------------------------------------------
        //
        //  Internal Properties
        //
        //-------------------------------------------------------------------
 
        //
        //  TargetType for DataTemplate. This is override is
        //  so FrameworkTemplate can see this property.
        //
        internal override Type TargetTypeInternal
        {
            get {  return DefaultTargetType; }
        }
 
        // Subclasses must provide a way for the parser to directly set the
        // target type.  For DataTemplate, this is not allowed.
        internal override void SetTargetTypeInternal(Type targetType)
        {
            throw new InvalidOperationException(SR.TemplateNotTargetType);
        }
 
        //
        //  DataType for DataTemplate. This is override is
        //  so FrameworkTemplate can see this property.
        //
        internal override object DataTypeInternal
        {
            get {  return DataType; }
        }
 
        //
        //  Collection of Triggers for a DataTemplate. This is
        //  override is so FrameworkTemplate can see this property.
        //
        internal override TriggerCollection TriggersInternal
        {
            get { return Triggers; }
        }
 
        // Target type of DataTrigger is ContentPresenter
        static internal Type DefaultTargetType
        {
            get { return typeof(ContentPresenter); }
        }
 
        #endregion Internal Properties
 
        #region Protected Methods
 
        //-------------------------------------------------------------------
        //
        //  Protected Methods
        //
        //-------------------------------------------------------------------
 
        /// <summary>
        ///     Validate against the following rules
        ///     1. Must have a non-null feTemplatedParent
        ///     2. A DataTemplate must be applied to a ContentPresenter
        /// </summary>
        protected override void ValidateTemplatedParent(FrameworkElement templatedParent)
        {
            // Must have a non-null feTemplatedParent
            ArgumentNullException.ThrowIfNull(templatedParent);
 
            // A DataTemplate must be applied to a ContentPresenter
            if (!(templatedParent is ContentPresenter))
            {
                throw new ArgumentException(SR.Format(SR.TemplateTargetTypeMismatch, "ContentPresenter", templatedParent.GetType().Name));
            }
        }
 
        #endregion Protected Methods
 
        #region Data
 
        private object                  _dataType;
        private TriggerCollection       _triggers;
 
        #endregion Data
    }
}