spectre.console/src/Spectre.Console/Extensions/EnumerableExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Spectre.Console.Internal
{
    internal static class EnumerableExtensions
    {
        public static int IndexOf<T>(this IEnumerable<T> source, T item)
            where T : class
        {
            var index = 0;
            foreach (var candidate in source)
            {
                if (candidate == item)
                {
                    return index;
                }

                index++;
            }

            return -1;
        }

        public static int GetCount<T>(this IEnumerable<T> source)
        {
            if (source is IList<T> list)
            {
                return list.Count;
            }

            if (source is T[] array)
            {
                return array.Length;
            }

            return source.Count();
        }

        public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
        {
            foreach (var item in source)
            {
                action(item);
            }
        }

        public static bool AnyTrue(this IEnumerable<bool> source)
        {
            return source.Any(b => b);
        }

        public static IEnumerable<(int Index, bool First, bool Last, T Item)> Enumerate<T>(this IEnumerable<T> source)
        {
            if (source is null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            return Enumerate(source.GetEnumerator());
        }

        public static IEnumerable<(int Index, bool First, bool Last, T Item)> Enumerate<T>(this IEnumerator<T> source)
        {
            if (source is null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            var first = true;
            var last = !source.MoveNext();
            T current;

            for (var index = 0; !last; index++)
            {
                current = source.Current;
                last = !source.MoveNext();
                yield return (index, first, last, current);
                first = false;
            }
        }

        public static IEnumerable<TResult> SelectIndex<T, TResult>(this IEnumerable<T> source, Func<T, int, TResult> func)
        {
            return source.Select((value, index) => func(value, index));
        }

#if !NET5_0
        public static IEnumerable<(TFirst First, TSecond Second)> Zip<TFirst, TSecond>(
            this IEnumerable<TFirst> source, IEnumerable<TSecond> first)
        {
            return source.Zip(first, (first, second) => (first, second));
        }
#endif

        public static IEnumerable<(TFirst First, TSecond Second, TThird Third)> Zip<TFirst, TSecond, TThird>(
            this IEnumerable<TFirst> first, IEnumerable<TSecond> second, IEnumerable<TThird> third)
        {
            return first.Zip(second, (a, b) => (a, b))
                .Zip(third, (a, b) => (a.a, a.b, b));
        }
    }
}