using System;

using System.Collections.Generic;

using System.Linq;

namespace Simple.Data.Extensions

{

public static class EnumerableExtensions

{

public static IDictionary<TKey,TValue> ToDictionary<TKey,TValue>(this IEnumerable<KeyValuePair<TKey,TValue>> source)

{

var dict = source as IDictionary<TKey, TValue>;

if (dict != null) return new Dictionary<TKey, TValue>(dict);

return source.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

}

public static IDictionary<TKey,TValue> ToDictionary<TKey,TValue>(this IEnumerable<KeyValuePair<TKey,TValue>> source, IEqualityComparer<TKey> equalityComparer)

{

var dict = source as IDictionary<TKey, TValue>;

if (dict != null) return new Dictionary<TKey, TValue>(dict);

return source.ToDictionary(kvp => kvp.Key, kvp => kvp.Value, equalityComparer);

}

public static IEnumerable<T> SkipLast<T>(this IEnumerable<T> source)

{

var buffer = default(T);

var enumerator = source.GetEnumerator();

if (enumerator.MoveNext())

{

buffer = enumerator.Current;

}

while (enumerator.MoveNext())

{

yield return buffer;

buffer = enumerator.Current;

}

}

public static IEnumerable<Tuple<T,T>> ToTuplePairs<T>(this IEnumerable<T> source)

{

var buffer = default(T);

var enumerator = source.GetEnumerator();

if (enumerator.MoveNext())

{

buffer = enumerator.Current;

}

while (enumerator.MoveNext())

{

yield return Tuple.Create(buffer, enumerator.Current);

buffer = enumerator.Current;

}

}

public static IEnumerable<T> ExtendInfinite<T>(this IEnumerable<T> source)

{

foreach (var item in source)

{

yield return item;

}

while (true)

{

yield return default(T);

}

}

public static IEnumerable<T> Replace<T>(this IEnumerable<T> source, T toReplace, T replaceWith)

{

return source.Select(item => Equals(item, toReplace) ? replaceWith : item);

}

public static IEnumerable<T> Append<T>(this IEnumerable<T> source, T item)

{

return source.Concat(Return(item));

}

public static IEnumerable<T> Return<T>(T item)

{

yield return item;

}

}

}