#if XUNIT_NULLABLE
#nullable enable
using System.Diagnostics.CodeAnalysis;
#endif

using System;
using System.Reflection;
using Xunit.Sdk;

namespace Xunit
{
#if XUNIT_VISIBILITY_INTERNAL
	internal
#else
	public
#endif
	partial class Assert
	{
		/// <summary>
		/// Verifies that an object is of the given type or a derived type.
		/// </summary>
		/// <typeparam name="T">The type the object should be</typeparam>
		/// <param name="object">The object to be evaluated</param>
		/// <returns>The object, casted to type T when successful</returns>
		/// <exception cref="IsAssignableFromException">Thrown when the object is not the given type</exception>
#if XUNIT_NULLABLE
		public static T IsAssignableFrom<T>(object? @object)
#else
		public static T IsAssignableFrom<T>(object @object)
#endif
		{
			IsAssignableFrom(typeof(T), @object);
			return (T)@object;
		}

		/// <summary>
		/// Verifies that an object is of the given type or a derived type.
		/// </summary>
		/// <param name="expectedType">The type the object should be</param>
		/// <param name="object">The object to be evaluated</param>
		/// <exception cref="IsAssignableFromException">Thrown when the object is not the given type</exception>
#if XUNIT_NULLABLE
		public static void IsAssignableFrom(Type expectedType, [NotNull] object? @object)
#else
		public static void IsAssignableFrom(Type expectedType, object @object)
#endif
		{
			GuardArgumentNotNull(nameof(expectedType), expectedType);

			if (@object == null || !expectedType.GetTypeInfo().IsAssignableFrom(@object.GetType().GetTypeInfo()))
				throw new IsAssignableFromException(expectedType, @object);
		}

		/// <summary>
		/// Verifies that an object is not exactly the given type.
		/// </summary>
		/// <typeparam name="T">The type the object should not be</typeparam>
		/// <param name="object">The object to be evaluated</param>
		/// <exception cref="IsNotTypeException">Thrown when the object is the given type</exception>
#if XUNIT_NULLABLE
		public static void IsNotType<T>(object? @object)
#else
		public static void IsNotType<T>(object @object)
#endif
		{
			IsNotType(typeof(T), @object);
		}

		/// <summary>
		/// Verifies that an object is not exactly the given type.
		/// </summary>
		/// <param name="expectedType">The type the object should not be</param>
		/// <param name="object">The object to be evaluated</param>
		/// <exception cref="IsNotTypeException">Thrown when the object is the given type</exception>
#if XUNIT_NULLABLE
		public static void IsNotType(Type expectedType, object? @object)
#else
		public static void IsNotType(Type expectedType, object @object)
#endif
		{
			GuardArgumentNotNull(nameof(expectedType), expectedType);

			if (@object != null && expectedType.Equals(@object.GetType()))
				throw new IsNotTypeException(expectedType, @object);
		}

		/// <summary>
		/// Verifies that an object is exactly the given type (and not a derived type).
		/// </summary>
		/// <typeparam name="T">The type the object should be</typeparam>
		/// <param name="object">The object to be evaluated</param>
		/// <returns>The object, casted to type T when successful</returns>
		/// <exception cref="IsTypeException">Thrown when the object is not the given type</exception>
#if XUNIT_NULLABLE
		public static T IsType<T>([NotNull] object? @object)
#else
		public static T IsType<T>(object @object)
#endif
		{
			IsType(typeof(T), @object);
			return (T)@object;
		}

		/// <summary>
		/// Verifies that an object is exactly the given type (and not a derived type).
		/// </summary>
		/// <param name="expectedType">The type the object should be</param>
		/// <param name="object">The object to be evaluated</param>
		/// <exception cref="IsTypeException">Thrown when the object is not the given type</exception>
#if XUNIT_NULLABLE
		public static void IsType(Type expectedType, [NotNull] object? @object)
#else
		public static void IsType(Type expectedType, object @object)
#endif
		{
			GuardArgumentNotNull(nameof(expectedType), expectedType);

			if (@object == null)
				throw new IsTypeException(expectedType.FullName, null);

			var actualType = @object.GetType();
			if (expectedType != actualType)
			{
				var expectedTypeName = expectedType.FullName;
				var actualTypeName = actualType.FullName;

				if (expectedTypeName == actualTypeName)
				{
					expectedTypeName += string.Format(" ({0})", expectedType.GetTypeInfo().Assembly.GetName().FullName);
					actualTypeName += string.Format(" ({0})", actualType.GetTypeInfo().Assembly.GetName().FullName);
				}

				throw new IsTypeException(expectedTypeName, actualTypeName);
			}
		}
	}
}
