using System;
using System.Collections.Generic;

namespace OpenMacroBoard.SDK.Utils
{
    /// <summary>
    /// Some LINQ extensions we use internally.
    /// </summary>
    public static class LinqExtensions
    {
        /// <summary>
        /// <para>
        /// A useful combination of LINQs Select() and Where().
        /// Prevents invalid object states between those two calls by combining them.
        /// </para>
        /// <para>
        /// If the <paramref name="selector"/> returns <c>(true, value)</c> the value will be yielded.
        /// If the <paramref name="selector"/> returns <c>(false, value)</c> it will not be present in
        /// the ouput enumerble.
        /// </para>
        /// </summary>
        /// <typeparam name="TIn">Input type.</typeparam>
        /// <typeparam name="TOut">Output type.</typeparam>
        /// <param name="source">Incomming source enumerable</param>
        /// <param name="selector">Filter/Selector</param>
        public static IEnumerable<TOut> SelectWhere<TIn, TOut>(
            this IEnumerable<TIn> source,
            Func<TIn, (bool Success, TOut Output)> selector
        )
        {
            foreach (var item in source)
            {
                var (success, output) = selector(item);

                if (success)
                {
                    yield return output;
                }
            }
        }
    }
}