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

namespace Sony.Filtr.Utility.Extensions
{
    public static class DictionaryExtensions
    {
        public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key)
        {
            TValue value;
            return dictionary.TryGetValue(key, out value) ? value : default(TValue);
        }

        public static TEnum? GetValueOrNull<TKey, TEnum>(this IDictionary<TKey, TEnum> dictionary, TKey key) where TEnum : struct, Enum
        {
            if (key == null)
            {
                return null;
            }
            return dictionary.TryGetValue(key, out var value) ? value : (TEnum?)null;
        }

        public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue)
        {
            TValue value;
            return dictionary.TryGetValue(key, out value) ? value : defaultValue;
        }

        public static Dictionary<K, List<T>> ToDictionaryWithListValues<T, K>(this IEnumerable<T> source, Func<T, K> getSelector)
        {
            return source
                .GroupBy(getSelector)
                .ToDictionary(g => g.Key, g => g.ToList());
        }
    }
}