namespace System.Collections.Generic
{
	/// <summary>
	/// Provides extension methods for generic <see cref="ICollection{T}"/> implementations.
	/// </summary>
	public static class CollectionExtensions
	{
		/// <summary>
		/// Add the <paramref name="item"/> to the <paramref name="collection"/> if it is not <see langword="null"/>.
		/// </summary>
		/// <typeparam name="T">The type of the elements in the collection</typeparam>
		/// <param name="collection">The collection.</param>
		/// <param name="item">The item to add if not <see langword="null"/>.</param>
		public static void AddIfNotNull<T>(this ICollection<T> collection, T item)
		{
#if NET8_0_OR_GREATER
			ArgumentNullException.ThrowIfNull(collection);
#else
			if (collection == null)
				throw new ArgumentNullException(nameof(collection));
#endif

			if (item == null)
				return;

			collection.Add(item);
		}

		/// <summary>
		/// Adds a <see cref="AddRange{T}(ICollection{T}, IEnumerable{T})"/> functionallity to <see cref="ICollection{T}"/>.
		/// </summary>
		/// <typeparam name="T">The type of the elements in the collection.</typeparam>
		/// <param name="collection">The collection.</param>
		/// <param name="items">The items to add.</param>
		public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> items)
		{
#if NET8_0_OR_GREATER
			ArgumentNullException.ThrowIfNull(collection);
			ArgumentNullException.ThrowIfNull(items);
#else
			if (collection == null)
				throw new ArgumentNullException(nameof(collection));

			if (items == null)
				throw new ArgumentNullException(nameof(items));
#endif

			if (collection == items)
				return;

			foreach (var item in items)
				collection.Add(item);
		}
	}
}