using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;



namespace Microsoft.Research.DynamicDataDisplay.Common.Auxiliary

{

	/// <summary>

	/// Contains extension methods for IEnumerable.

	/// </summary>

	public static class IEnumerableExtensions

	{

		/// <summary>

		/// Gets the value indicating wheter count of elements in a given sequence is greater or equal than specified value.

		/// </summary>

		/// <typeparam name="T"></typeparam>

		/// <param name="enumerable">The enumerable.</param>

		/// <param name="count">The count.</param>

		/// <returns></returns>

		public static bool CountGreaterOrEqual<T>(this IEnumerable<T> enumerable, int count)

		{

			int counter = 0;

			using (var enumerator = enumerable.GetEnumerator())

			{

				while (counter < count && enumerator.MoveNext())

				{

					counter++;

				}

			}



			return counter == count;

		}



		/// <summary>

		/// Splits the specified source sequnce into a sequence of sequences, with the length of inner sequence not longer than 

		/// specified maximal count.

		/// </summary>

		/// <typeparam name="T"></typeparam>

		/// <param name="source">The source.</param>

		/// <param name="maxCount">The max count.</param>

		/// <returns></returns>

		public static IEnumerable<IEnumerable<T>> Split<T>(this IEnumerable<T> source, int maxCount)

		{

			using (var enumerator = new FixedEnumeratorWrapper<T>(source.GetEnumerator()))

			{

				do

				{

					var enumerable = new FixedEnumerable<T>(enumerator);

					yield return enumerable.Take(maxCount);

				}

				while (enumerator.CanMoveNext);

			}

		}



		private sealed class FixedEnumeratorWrapper<T> : IEnumerator<T>

		{

			private readonly IEnumerator<T> enumerator;



			public FixedEnumeratorWrapper(IEnumerator<T> enumerator)

			{

				this.enumerator = enumerator;

			}



			#region IEnumerator<T> Members



			public T Current

			{

				get { return enumerator.Current; }

			}



			#endregion



			#region IDisposable Members



			public void Dispose()

			{

				//enumerator.Dispose();

			}



			#endregion



			#region IEnumerator Members



			object IEnumerator.Current

			{

				get { return enumerator.Current; }

			}



			private bool canMoveNext = false;

			public bool CanMoveNext

			{

				get { return canMoveNext; }

			}



			public bool MoveNext()

			{

				canMoveNext = enumerator.MoveNext();

				return canMoveNext;

			}



			public void Reset()

			{

				enumerator.Reset();

			}



			#endregion

		}



		private sealed class FixedEnumerable<T> : IEnumerable<T>

		{

			private readonly IEnumerator<T> enumerator;

			public FixedEnumerable(IEnumerator<T> enumerator)

			{

				this.enumerator = enumerator;

			}



			#region IEnumerable<T> Members



			public IEnumerator<T> GetEnumerator()

			{

				return enumerator;

			}



			#endregion



			#region IEnumerable Members



			IEnumerator IEnumerable.GetEnumerator()

			{

				return enumerator;

			}



			#endregion

		}

	}

}