#if XUNIT_NULLABLE
#nullable enable
#endif

using System;
using System.Linq;

namespace Xunit.Sdk
{
	/// <summary>
	/// Exception thrown when Assert.Collection fails.
	/// </summary>
#if XUNIT_VISIBILITY_INTERNAL
	internal
#else
	public
#endif
	class CollectionException : XunitException
	{
#if XUNIT_NULLABLE
		readonly string? innerException;
		readonly string? innerStackTrace;
#else
		readonly string innerException;
		readonly string innerStackTrace;
#endif

		/// <summary>
		/// Creates a new instance of the <see cref="CollectionException"/> class.
		/// </summary>
		/// <param name="collection">The collection that failed the test.</param>
		/// <param name="expectedCount">The expected number of items in the collection.</param>
		/// <param name="actualCount">The actual number of items in the collection.</param>
		/// <param name="indexFailurePoint">The index of the position where the first comparison failure occurred.</param>
		/// <param name="innerException">The exception that was thrown during the comparison failure.</param>
		public CollectionException(
#if XUNIT_NULLABLE
			object? collection,
			int expectedCount,
			int actualCount,
			int indexFailurePoint = -1,
			Exception? innerException = null) :
#else
			object collection,
			int expectedCount,
			int actualCount,
			int indexFailurePoint = -1,
			Exception innerException = null) :
#endif
				base("Assert.Collection() Failure")
		{
			Collection = collection;
			ExpectedCount = expectedCount;
			ActualCount = actualCount;
			IndexFailurePoint = indexFailurePoint;
			this.innerException = FormatInnerException(innerException);
			innerStackTrace = innerException == null ? null : innerException.StackTrace;
		}

		/// <summary>
		/// The collection that failed the test.
		/// </summary>
#if XUNIT_NULLABLE
		public object? Collection { get; set; }
#else
		public object Collection { get; set; }
#endif

		/// <summary>
		/// The actual number of items in the collection.
		/// </summary>
		public int ActualCount { get; set; }

		/// <summary>
		/// The expected number of items in the collection.
		/// </summary>
		public int ExpectedCount { get; set; }

		/// <summary>
		/// The index of the position where the first comparison failure occurred, or -1 if
		/// comparisions did not occur (because the actual and expected counts differed).
		/// </summary>
		public int IndexFailurePoint { get; set; }

		/// <inheritdoc/>
		public override string Message
		{
			get
			{
				if (IndexFailurePoint >= 0)
					return $"{base.Message}{Environment.NewLine}Collection: {ArgumentFormatter.Format(Collection)}{Environment.NewLine}Error during comparison of item at index {IndexFailurePoint}{Environment.NewLine}Inner exception: {innerException}";

				return $"{base.Message}{Environment.NewLine}Collection: {ArgumentFormatter.Format(Collection)}{Environment.NewLine}Expected item count: {ExpectedCount}{Environment.NewLine}Actual item count:   {ActualCount}";
			}
		}

		/// <inheritdoc/>
#if XUNIT_NULLABLE
		public override string? StackTrace
#else
		public override string StackTrace
#endif
		{
			get
			{
				if (innerStackTrace == null)
					return base.StackTrace;

				return innerStackTrace + Environment.NewLine + base.StackTrace;
			}
		}

#if XUNIT_NULLABLE
		static string? FormatInnerException(Exception? innerException)
#else
		static string FormatInnerException(Exception innerException)
#endif
		{
			if (innerException == null)
				return null;

			var lines =
				innerException
					.Message
					.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries)
					.Select((value, idx) => idx > 0 ? "        " + value : value);

			return string.Join(Environment.NewLine, lines);
		}
	}
}