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

namespace Ips.Library.Basic
{
    public static class EnumerableExtensions
    {
        public static bool IsNullOrEmpty<T>(this IEnumerable<T> @this)
        {
            return @this == null || !@this.Any();
        }

        public static bool IsNotNullOrEmpty<T>(this IEnumerable<T> @this)
        {
            return @this != null && @this.Any();
        }

        public static string JoinAsString(this IEnumerable<string> source, string separator)
        {
            return source.Any() ? string.Join(separator, source) : "";
        }

        public static string JoinAsString<T>(this IEnumerable<T> source, string separator)
        {
            return source.Any() ? string.Join(separator, source) : "";
        }

        public static IEnumerable<T> WhereIf<T>(this IEnumerable<T> source, bool condition, Func<T, bool> predicate)
        {
            return condition
                ? source.Where(predicate)
                : source;
        }

        public static IEnumerable<T> WhereIf<T>(this IEnumerable<T> source, bool condition, Func<T, int, bool> predicate)
        {
            return condition
                ? source.Where(predicate)
                : source;
        }

        public static IEnumerable<T> ForEach<T>(this IEnumerable<T> array, Action<T> act)
        {
            foreach (var i in array)
                act(i);
            return array;
        }

        public static IEnumerable<T> ForEach<T>(this IEnumerable arr, Action<T> act)
        {
            return arr.Cast<T>().ForEach<T>(act);
        }

        public static IEnumerable<RT> ForEach<T, RT>(this IEnumerable<T> array, Func<T, RT> func)
        {
            var list = new List<RT>();
            foreach (var i in array)
            {
                var obj = func(i);
                if (obj != null)
                    list.Add(obj);
            }
            return list;
        }

        public static Dictionary<TKey, List<TValue>> ToDictionary<TKey, TValue>(this IEnumerable<IGrouping<TKey, TValue>> groupings)
        {
            return groupings.ToDictionary(group => group.Key, group => group.ToList());
        }
    }
}