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

namespace BITKit
{
    public static class FuncExtensions
    {
        public static IEnumerable<Func<T>> CastAsFunc<T>(this Func<T> self)
        {
            var value = self;
            return value is null? Array.Empty<Func<T>>() : self?.GetInvocationList().Cast<Func<T>>();
        }
        public static IEnumerable<Func<T0, T1>> CastAsFunc<T0, T1>(this Func<T0, T1> self)
        {
            return self is null ? Array.Empty<Func<T0,T1>>() : self?.GetInvocationList().Cast<Func<T0, T1>>();
        }

        public static IEnumerable<Func<T0, T1, T2>> CastAsFunc<T0, T1, T2>(this Func<T0, T1, T2> self)
        {
            if (self is null)
            {
                yield break;
            }

            Delegate[] invocationList = self.GetInvocationList();

            // 遍历委托数组，将每个委托转换为 Func<T0, T1, T2> 并返回
            foreach (var delegateItem in invocationList)
            {
                if (delegateItem is not null && delegateItem is Func<T0, T1, T2> func)
                {
                    yield return func;
                }
            }
        }

        public static IEnumerable<Func<T0, T1, T2, T3>> CastAsFunc<T0, T1, T2, T3>(this Func<T0, T1, T2, T3> self)
        {
            return self?.GetInvocationList().Cast<Func<T0, T1, T2, T3>>();
        }

        public static IEnumerable<Func<T0, T1, T2, T3, T4>> CastAsFunc<T0, T1, T2, T3, T4>(
            this Func<T0, T1, T2, T3, T4> self)
        {
            return self?.GetInvocationList().Cast<Func<T0, T1, T2, T3, T4>>();
        }

        public static IEnumerable<Func<T0, T1, T2, T3, T4, T5>> CastAsFunc<T0, T1, T2, T3, T4, T5>(
            this Func<T0, T1, T2, T3, T4, T5> self)
        {
            return self?.GetInvocationList().Cast<Func<T0, T1, T2, T3, T4, T5>>();
        }

        public static IEnumerable<Func<T0, T1, T2, T3, T4, T5, T6>> CastAsFunc<T0, T1, T2, T3, T4, T5, T6>(
            this Func<T0, T1, T2, T3, T4, T5, T6> self)
        {
            return self?.GetInvocationList().Cast<Func<T0, T1, T2, T3, T4, T5, T6>>();
        }

        public static IEnumerable<Func<T0, T1, T2, T3, T4, T5, T6, T7>> CastAsFunc<T0, T1, T2, T3, T4, T5, T6, T7>(
            this Func<T0, T1, T2, T3, T4, T5, T6, T7> self)
        {
            return self?.GetInvocationList().Cast<Func<T0, T1, T2, T3, T4, T5, T6, T7>>();
        }
    }
}