using System;

using System.Collections.Generic;

using NUnit.Framework;



namespace Delta.Utilities.Collections

{

	/// <summary>

	/// Extensions to <see cref="IEnumerable{T}"/>, make sure to use this

	/// namespace when using this extensions. Includes ForEach, TryDo, Do and

	/// EnumerateAll methods for IEnumerable items.

	/// </summary>

	public static class EnumerableExtensions

	{

		#region ForEach (Static)

		/// <summary>

		/// Iterates the <paramref name="source"/> and applies the

		/// <paramref name="action"/> to each item.

		/// </summary>

		/// <typeparam name="TItem">TItem</typeparam>

		/// <param name="action">Action</param>

		/// <param name="source">Source</param>

		public static void ForEach<TItem>(this IEnumerable<TItem> source,

			Action<TItem> action)

		{

			foreach (var item in source)

			{

				action(item);

			}

		}

		#endregion



		#region TryDo (Static)

		/// <summary>

		/// Allows chaining actions on a set of items for later processing,

		/// filtering or projection (transformation), ignoring exceptions that

		/// might happen in the action.

		/// </summary>

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

		/// <param name="action">Action</param>

		/// <param name="source">Source</param>

		/// <returns>An enumeration with the same items as the source.</returns>

		public static IEnumerable<T> TryDo<T>(this IEnumerable<T> source,

			Action<T> action)

		{

			foreach (var item in source)

			{

				try

				{

					action(item);

				}

				catch

				{

				}



				yield return item;

			}

		}

		#endregion



		#region Do (Static)

		/// <summary>

		/// Allows chaining actions on a set of items for later processing,

		/// filtering or projection (transformation).

		/// </summary>

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

		/// <param name="action">Action</param>

		/// <param name="source">Source</param>

		/// <returns>An enumeration with the same items as the source.</returns>

		public static IEnumerable<T> Do<T>(this IEnumerable<T> source,

			Action<T> action)

		{

			foreach (var item in source)

			{

				action(item);

				yield return item;

			}

		}

		#endregion



		#region EnumerateAll (Static)

		/// <summary>

		/// Enumerates all elements in the source, so that any intermediate 

		/// action or side-effect from it is performed eagerly.

		/// Note: Does nothing inside the enumeration!

		/// </summary>

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

		/// <param name="source">Source</param>

		public static void EnumerateAll<T>(this IEnumerable<T> source)

		{

			foreach (var item in source)

			{

			}

		}

		#endregion



		/// <summary>

		/// Tests for EnumerableExtensions. Not really useful, we just use some

		/// numbers to test the functionality, but in order to use this class for

		/// real a state machine (e.g. for AI) should be used.

		/// </summary>

		internal class EnumerableExtensionsTests

		{

			#region TestForEach

			[Test]

			public void TestForEach()

			{

				List<int> someNumbers = new List<int>();

				someNumbers.Add(1);

				someNumbers.Add(2);

				someNumbers.Add(5);

				someNumbers.Add(10);



				// And add all numbers

				int allNumbers = 0;

				someNumbers.ForEach(delegate(int number)

				{

					allNumbers += number;

				});

				Assert.Equal(allNumbers, 1 + 2 + 5 + 10);

			}

			#endregion



			#region TestDo

			[Test, Category("LongRunning")]

			public void TestDo()

			{

				List<int> someNumbers = new List<int>();

				someNumbers.Add(1);

				someNumbers.Add(2);

				someNumbers.Add(5);

				someNumbers.Add(10);



				// Define action what to do when calling the Do method below

				Action<int> printNumberAndSquare = delegate(int number)

				{

					Console.WriteLine(

						"Number: " + number + ", Square: " + number * number);

				};



				// And print them all out, calling them one by one

				// Note: This is obviously not very useful code, it just shows how

				// to use the Do method. You need more useful state machine code!

				foreach (int number in someNumbers.Do(printNumberAndSquare))

				{

					Console.WriteLine("Processed number: " + number);

				}

			}

			#endregion

		}

	}

}