// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
#nullable disable
 
using System.ComponentModel;
using System.Globalization;
 
namespace System.Xaml.Schema
{
    public class XamlTypeTypeConverter : TypeConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return sourceType == typeof(string);
        }
 
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (context is not null && value is string typeName)
            {
                XamlType result = ConvertStringToXamlType(context, typeName);
                if (result is not null)
                {
                    return result;
                }
            }
 
            return base.ConvertFrom(context, culture, value);
        }
 
        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return destinationType == typeof(string);
        }
 
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            XamlType xamlType = value as XamlType;
 
            if (context is not null && xamlType is not null && destinationType == typeof(string))
            {
                string result = ConvertXamlTypeToString(context, xamlType);
                if (result is not null)
                {
                    return result;
                }
            }
 
            return base.ConvertTo(context, culture, value, destinationType);
        }
 
        internal static string ConvertXamlTypeToString(ITypeDescriptorContext context, XamlType xamlType)
        {
            var prefixLookup = GetService<INamespacePrefixLookup>(context);
            if (prefixLookup is null)
            {
                return null;
            }
 
            XamlTypeName typeName = new XamlTypeName(xamlType);
            return typeName.ToString(prefixLookup);
        }
 
        private static XamlType ConvertStringToXamlType(ITypeDescriptorContext context, string typeName)
        {
            var namespaceResolver = GetService<IXamlNamespaceResolver>(context);
            if (namespaceResolver is null)
            {
                return null;
            }
 
            XamlTypeName xamlTypeName = XamlTypeName.Parse(typeName, namespaceResolver);
            var schemaContextProvider = GetService<IXamlSchemaContextProvider>(context);
            if (schemaContextProvider is null)
            {
                return null;
            }
 
            if (schemaContextProvider.SchemaContext is null)
            {
                return null;
            }
 
            return GetXamlTypeOrUnknown(schemaContextProvider.SchemaContext, xamlTypeName);
        }
 
        private static TService GetService<TService>(ITypeDescriptorContext context) where TService : class
        {
            return context.GetService(typeof(TService)) as TService;
        }
 
        private static XamlType GetXamlTypeOrUnknown(XamlSchemaContext schemaContext, XamlTypeName typeName)
        {
            XamlType result = schemaContext.GetXamlType(typeName);
            if (result is not null)
            {
                return result;
            }
 
            XamlType[] typeArgs = null;
            if (typeName.HasTypeArgs)
            {
                typeArgs = new XamlType[typeName.TypeArguments.Count];
                for (int i = 0; i < typeName.TypeArguments.Count; i++)
                {
                    typeArgs[i] = GetXamlTypeOrUnknown(schemaContext, typeName.TypeArguments[i]);
                }
            }
 
            result = new XamlType(typeName.Namespace, typeName.Name, typeArgs, schemaContext);
            return result;
        }
    }
}