using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace System.Reflection
{
	partial class FieldInfo
	{
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private static extern FieldInfo internal_from_handle_type (IntPtr field_handle, IntPtr type_handle);

		public static FieldInfo GetFieldFromHandle (RuntimeFieldHandle handle)
		{
			if (handle.IsNullHandle ())
				throw new ArgumentException (SR.Argument_InvalidHandle);
			return internal_from_handle_type (handle.Value, IntPtr.Zero);
		}

		public static FieldInfo GetFieldFromHandle (RuntimeFieldHandle handle, RuntimeTypeHandle declaringType)
		{
			if (handle.IsNullHandle ())
				throw new ArgumentException (SR.Argument_InvalidHandle);
			FieldInfo fi = internal_from_handle_type (handle.Value, declaringType.Value);
			if (fi == null)
				throw new ArgumentException ("The field handle and the type handle are incompatible.");
			return fi;
		}

		internal virtual int GetFieldOffset ()
		{
			throw NotImplemented.ByDesign;
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern MarshalAsAttribute get_marshal_info ();

		internal object[] GetPseudoCustomAttributes ()
		{
			int count = 0;

			if (IsNotSerialized)
				count ++;

			if (DeclaringType.IsExplicitLayout)
				count ++;

			MarshalAsAttribute marshalAs = get_marshal_info ();
			if (marshalAs != null)
				count ++;

			if (count == 0)
				return null;
			object[] attrs = new object [count];
			count = 0;

			if (IsNotSerialized)
				attrs [count ++] = new NonSerializedAttribute ();
			if (DeclaringType.IsExplicitLayout)
				attrs [count ++] = new FieldOffsetAttribute (GetFieldOffset ());
			if (marshalAs != null)
				attrs [count ++] = marshalAs;

			return attrs;
		}

		internal CustomAttributeData[] GetPseudoCustomAttributesData ()
		{
			int count = 0;

			if (IsNotSerialized)
				count++;

			if (DeclaringType.IsExplicitLayout)
				count++;

			MarshalAsAttribute marshalAs = get_marshal_info ();
			if (marshalAs != null)
				count++;

			if (count == 0)
				return null;
			CustomAttributeData[] attrsData = new CustomAttributeData [count];
			count = 0;

			if (IsNotSerialized)
				attrsData [count++] = new CustomAttributeData ((typeof (NonSerializedAttribute)).GetConstructor (Type.EmptyTypes));
			if (DeclaringType.IsExplicitLayout) {
				var ctorArgs = new CustomAttributeTypedArgument[] { new CustomAttributeTypedArgument (typeof (int), GetFieldOffset ()) };
				attrsData [count++] = new CustomAttributeData (
					(typeof (FieldOffsetAttribute)).GetConstructor (new[] { typeof (int) }),
					ctorArgs,
					Array.Empty<CustomAttributeNamedArgument> ());
			}

			if (marshalAs != null) {
				var ctorArgs = new CustomAttributeTypedArgument[] { new CustomAttributeTypedArgument (typeof (UnmanagedType), marshalAs.Value) };
				attrsData [count++] = new CustomAttributeData (
					(typeof (MarshalAsAttribute)).GetConstructor (new[] { typeof (UnmanagedType) }),
					ctorArgs,
					Array.Empty<CustomAttributeNamedArgument> ());//FIXME Get named params
			}

			return attrsData;
		}
	}
}