#if XUNIT_NULLABLE
#nullable enable
#endif

using System;

namespace Xunit.Sdk
{
	/// <summary>
	/// The base assert exception class
	/// </summary>
#if XUNIT_VISIBILITY_INTERNAL
	internal
#else
	public
#endif
	class XunitException : Exception, IAssertionException
	{
#if XUNIT_NULLABLE
		readonly string? stackTrace;
#else
		readonly string stackTrace;
#endif

		/// <summary>
		/// Initializes a new instance of the <see cref="XunitException"/> class.
		/// </summary>
		public XunitException()
		{ }

		/// <summary>
		/// Initializes a new instance of the <see cref="XunitException"/> class.
		/// </summary>
		/// <param name="userMessage">The user message to be displayed</param>
#if XUNIT_NULLABLE
		public XunitException(string? userMessage) :
			this(userMessage, (Exception?)null)
#else
		public XunitException(string userMessage) :
			this(userMessage, (Exception)null)
#endif
		{ }

		/// <summary>
		/// Initializes a new instance of the <see cref="XunitException"/> class.
		/// </summary>
		/// <param name="userMessage">The user message to be displayed</param>
		/// <param name="innerException">The inner exception</param>
		public XunitException(
#if XUNIT_NULLABLE
			string? userMessage,
			Exception? innerException) :
#else
			string userMessage,
			Exception innerException) :
#endif
				base(userMessage, innerException)
		{
			UserMessage = userMessage;
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="XunitException"/> class.
		/// </summary>
		/// <param name="userMessage">The user message to be displayed</param>
		/// <param name="stackTrace">The stack trace to be displayed</param>
		protected XunitException(
#if XUNIT_NULLABLE
			string? userMessage,
			string? stackTrace) :
#else
			string userMessage,
			string stackTrace) :
#endif
				this(userMessage)
		{
			this.stackTrace = stackTrace;
		}

		/// <summary>
		/// Gets a string representation of the frames on the call stack at the time the current exception was thrown.
		/// </summary>
		/// <returns>A string that describes the contents of the call stack, with the most recent method call appearing first.</returns>
#if XUNIT_NULLABLE
		public override string? StackTrace =>
#else
		public override string StackTrace =>
#endif
			stackTrace ?? base.StackTrace;

		/// <summary>
		/// Gets the user message
		/// </summary>
#if XUNIT_NULLABLE
		public string? UserMessage { get; protected set; }
#else
		public string UserMessage { get; protected set; }
#endif

		/// <inheritdoc/>
		public override string ToString()
		{
			var className = GetType().ToString();
			var message = Message;
			string result;

			if (message == null || message.Length <= 0)
				result = className;
			else
				result = $"{className}: {message}";

			var stackTrace = StackTrace;
			if (stackTrace != null)
				result = $"{result}{Environment.NewLine}{stackTrace}";

			return result;
		}
	}
}