// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Runtime.CompilerServices;
 
namespace System.Windows.Markup
{
    /// <summary>
    /// XmlnsDefinitionAttribute keeps a mapping between Xml namespace and CLR namespace in an Assembly.
    /// The Xml namespace can be used in a Xaml Markup file.
    ///
    ///
    /// To find the appropriate types for element and attribute in xaml file, xaml processors MUST
    /// search each referenced assembly for XmlnsDefinitionAttribute. If the xmlns for element tag
    /// or attribute matches with the XmlNamespace in this XmlnsDefinitionAttibute, the Xaml processor
    /// then takes use of the ClrNamespace and AssemblyName stored in this Attibute instance to check
    /// if the element or attribute matches any type inside this namespace in the Assembly.
    ///
    /// For a WinFX assembly, it can set this attibute like below:
    ///
    /// [assembly:XmlnsDefinition("http://schemas.fabrikam.com/mynamespace", "fabrikam.myproduct.mycategory1")]
    /// [assembly:XmlnsDefinition("http://schemas.fabrikam.com/mynamespace", "fabrikam.myproduct.mycategory2")]
    ///
    /// [assembly:XmlnsDefinition("xmlnamsspace", "clrnamespace", AssemblyName="myassembly or full assemblyname")]
    ///
    /// If fabrikam.myproduct.mycategory namespace in this assembly contains a UIElement such as "MyButton", the
    /// xaml file could use it like below:
    ///
    ///   Page xmlns:myns="http://schemas.fabrikam.com/mynamespace" ....
    ///      myns:MyButton ...../myns:MyButton
    ///   /Page
    /// </summary>
    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
    [TypeForwardedFrom("WindowsBase, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")]
    public sealed class XmlnsDefinitionAttribute : Attribute
    {
        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="xmlNamespace">
        /// XmlNamespace used by Markup file
        /// </param>
        /// <param name="clrNamespace">
        /// Clr namespace which contains known types that are used by Markup File.
        /// </param>
        public XmlnsDefinitionAttribute(string xmlNamespace, string clrNamespace)
        {
            XmlNamespace = xmlNamespace ?? throw new ArgumentNullException(nameof(xmlNamespace));
            ClrNamespace = clrNamespace ?? throw new ArgumentNullException(nameof(clrNamespace));
        }
 
        /// <summary>
        /// XmlNamespace which can be used in Markup file.
        /// such as XmlNamespace is set to
        /// "http://schemas.fabrikam.com/mynamespace".
        ///
        /// The markup file can have definition like
        /// xmlns:myns="http://schemas.fabrikam.com/mynamespace"
        /// </summary>
        public string XmlNamespace { get; }
 
        /// <summary>
        /// ClrNamespace which map to XmlNamespace.
        /// This ClrNamespace should contain some types which are used
        /// by Xaml markup file.
        /// </summary>
        public string ClrNamespace { get; }
 
        /// <summary>
        /// The name of Assembly that contains some types inside CLRNamespace.
        /// If the assemblyName is not set, the code should take the assembly
        /// for which the instance of this attribute is created.
        /// </summary>
        public string? AssemblyName { get; set; }
   }
}