context: //
  // EnumerableTest.cs
  //
  // Author:
  //   Jb Evain (jbevain@novell.com)
  //
  // (C) 2007 Novell, Inc. (http://www.novell.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  //
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  using System;
  using System.IO;
  using System.Collections;
  using System.Collections.Generic;
  using System.Linq;
  using System.Linq.Expressions;
  
  using NUnit.Framework;
  
  namespace MonoTests.System.Linq {
  
  	[TestFixture]
  	public class EnumerableTest {
  
  		[Test]
  		public void TestSimpleExcept ()
  		{
  			int [] first = {0, 1, 2, 3, 4, 5};
  			int [] second = {2, 4, 6};
  			int [] result = {0, 1, 3, 5};
  
  			AssertAreSame (result, first.Except (second));
  		}
  
  		[Test]
  		public void TestSimpleIntersect ()
  		{
  			int [] first = {0, 1, 2, 3, 4, 5};
  			int [] second = {2, 4, 6};
  			int [] result = {2, 4};
  
  			AssertAreSame (result, first.Intersect (second));
  		}
  
  		[Test]
  		public void TestSimpleUnion ()
  		{
  			int [] first = {0, 1, 2, 3, 4, 5};
  			int [] second = {2, 4, 6};
  			int [] result = {0, 1, 2, 3, 4, 5, 6};
  
  			AssertAreSame (result, first.Union (second));
  		}
  
  		class Foo {}
  		class Bar : Foo {}
  
  		[Test]
  		public void TestCast ()
  		{
  			Bar a = new Bar ();
  			Bar b = new Bar ();
  			Bar c = new Bar ();
  
  			Foo [] foos = new Foo [] {a, b, c};
  			Bar [] result = new Bar [] {a, b, c};
  
  			AssertAreSame (result, foos.Cast<Bar> ());
  		}
  
  		class Bingo : IEnumerable<int>, IEnumerable<string> {
  
  			IEnumerator<int> IEnumerable<int>.GetEnumerator ()
  			{
  				yield return 42;
  				yield return 12;
  			}
  
  			IEnumerator<string> IEnumerable<string>.GetEnumerator ()
  			{
  				yield return "foo";
  				yield return "bar";
  			}
  
  			public IEnumerator GetEnumerator ()
  			{
  				return (this as IEnumerable<int>).GetEnumerator ();
  			}
  		}
  
  		[Test]
  		public void TestCastToImplementedType ()
  		{
  			var ints = new int [] { 42, 12 };
  			var strs = new string [] { "foo", "bar" };
  
  			var bingo = new Bingo ();
  
  			AssertAreSame (ints, bingo.Cast<int> ());
  			AssertAreSame (strs, bingo.Cast<string> ());
  		}
  
  		[Test]
  		public void TestLast ()
  		{
  			int [] data = {1, 2, 3};
  
  			Assert.AreEqual (3, data.Last ());
  		}
  
  		[Test]
  		public void TestLastOrDefault ()
  		{
  			int [] data = {};
  
  			Assert.AreEqual (default (int), data.LastOrDefault ());
  		}
  
  		[Test]
  		public void TestFirst ()
  		{
  			int [] data = {1, 2, 3};
  
  			Assert.AreEqual (1, data.First ());
  		}
  
  		[Test]
  		public void TestFirstOrDefault ()
  		{
  			int [] data = {};
  
  			Assert.AreEqual (default (int), data.FirstOrDefault ());
  		}
  
  		[Test]
  		public void TestSequenceEqual ()
  		{
  			int [] first = {0, 1, 2, 3, 4, 5};
  			int [] second = {0, 1, 2};
  			int [] third = {0, 1, 2, 3, 4, 5};
  
  			Assert.IsFalse (first.SequenceEqual (second));
  			Assert.IsTrue (first.SequenceEqual (third));
  		}
  
  		[Test]
  		public void TestSkip ()
  		{
  			int [] data = {0, 1, 2, 3, 4, 5};
  			int [] result = {3, 4, 5};
  
  			AssertAreSame (result, data.Skip (3));
  		}
  
  		[Test]
  		public void TestSkipWhile ()
  		{
  			int [] data = {0, 1, 2, 3, 4, 5};
  			int [] result = {3, 4, 5};
  
  			AssertAreSame (result, data.SkipWhile (i => i < 3));
  		}
  
  		[Test]
  		public void TestTake ()
  		{
  			int [] data = {0, 1, 2, 3, 4, 5};
  			int [] result = {0, 1, 2};
  
  			AssertAreSame (result, data.Take (3));
  		}
  
  		[Test]
  		public void TestTakeWhile ()
  		{
  			int [] data = {0, 1, 2, 3, 4, 5};
  			int [] result = {0, 1, 2};
  
  			AssertAreSame (result, data.TakeWhile (i => i < 3));
  		}
  
  		[Test]
  		public void TestSelect ()
  		{
  			int [] data = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
  			int [] result = {1, 3, 5, 7, 9};
  
  			AssertAreSame (result, data.Where (i => i % 2 != 0));
  		}
  
  		[Test]
  		public void TestReverse ()
  		{
  			int [] data = {0, 1, 2, 3, 4};
  			int [] result = {4, 3, 2, 1, 0};
  
  			AssertAreSame (result, data.Reverse ());
  			AssertAreSame (result, Enumerable.Range (0, 5).Reverse ());
  		}
  
  		[Test]
  		public void ReverseArrays ()
  		{
  			int[] source = { 1, 2, 3 };
  
  			var query = source.Reverse ();
  			using (var enumerator = query.GetEnumerator ()) {
  				enumerator.MoveNext ();
  				Assert.AreEqual (3, enumerator.Current);
  
  				source [1] = 42;
  				enumerator.MoveNext ();
  				Assert.AreEqual (2, enumerator.Current);
  
  				enumerator.MoveNext ();
  				Assert.AreEqual (1, enumerator.Current);
  			}
  		}
  
  		[Test]
  		public void TestSum ()
  		{
  			int [] data = {1, 2, 3, 4};
  
  			Assert.AreEqual (10, data.Sum ());
  		}
  
  		[Test]
  		public void SumOnEmpty ()
  		{
  			int [] data = {};
  
  			Assert.AreEqual (0, data.Sum ());
  		}
  
  		[Test]
  		public void TestMax ()
  		{
  			int [] data = {1, 3, 5, 2};
  
  			Assert.AreEqual (5, data.Max ());
  		}
  
  		[Test]
  		public void TestMaxNullableInt32 ()
  		{
  			int? [] data = { null, null, null };
  
  			Assert.IsNull (data.Max (x => -x));
  
  			data = new int? [] { null, 1, 2 };
  
  			Assert.AreEqual (-1, data.Max (x => -x));
  		}
  
  		[Test]
  		public void TestMin ()
  		{
  			int [] data = {3, 5, 2, 6, 1, 7};
  
  			Assert.AreEqual (1, data.Min ());
  		}
  
  		[Test]
  		public void TestMinNullableInt32 ()
  		{
  			int? [] data = { null, null, null };
  
  			Assert.IsNull (data.Min(x => -x));
  
  			data = new int? [] { null, 1, 2 };
  
  			Assert.AreEqual (-2, data.Min (x => -x));
  		}
  
  		[Test]
  		public void TestMinStringEmpty ()
  		{
  			Assert.IsNull ((new string [0]).Min ());
  		}
  
  		[Test]
  		public void TestMaxStringEmpty ()
  		{
  			Assert.IsNull ((new string [0]).Max ());
  		}
  
  		[Test]
  		public void TestToList ()
  		{
  			int [] data = {3, 5, 2};
  
  			var list = data.ToList ();
  
  			AssertAreSame (data, list);
  
  			Assert.AreEqual (typeof (List<int>), list.GetType ());
  		}
  
  		[Test]
  		public void TestToArray ()
  		{
  			ICollection<int> coll = new List<int> ();
  			coll.Add (0);
  			coll.Add (1);
  			coll.Add (2);
  
  			int [] result = {0, 1, 2};
  
  			var array = coll.ToArray ();
  
  			AssertAreSame (result, array);
  
  			Assert.AreEqual (typeof (int []), array.GetType ());
  		}
  
  		[Test]
  		public void TestIntersect ()
  		{
  			int [] left = { 1, 1 }, right = { 1, 1 };
  			int [] result = { 1 };
  
  			AssertAreSame (result, left.Intersect (right));
  		}
  
  		[Test]
  		public void TestAverageOnInt32 ()
  		{
  			Assert.AreEqual (23.25, (new int [] { 24, 7, 28, 34 }).Average ());
  		}
  
  		[Test]
  		public void TestAverageOnInt64 ()
  		{
  			Assert.AreEqual (23.25, (new long [] { 24, 7, 28, 34 }).Average ());
  		}
  
  		[Test]
  		public void TestAverageInt32 ()
  		{
  			// This does not overflow, computation is done with longs
  			var x = new int [] { Int32.MaxValue, Int32.MaxValue };
  			Assert.AreEqual ((double) Int32.MaxValue, x.Average ());
  		}
  		
  		[Test]
  		public void TestAverageOverflowOnInt64 ()
  		{
  			try {
  				var x = new long [] { Int64.MaxValue, Int64.MaxValue };
  				x.Average ();
  				Assert.Fail ("#1");
  			} catch (OverflowException) {
  			}
  		}
  
  		[Test]
  		public void TestAverageOnLongNullable ()
  		{
  			List<long?> list = new List<long?> ();
  			list.Add (2);
  			list.Add (3);
  			Assert.AreEqual (2.5d, list.Average ());
  		}
  
  		[Test]
  		public void TestRange ()
  		{
  			AssertAreSame (new [] {1, 2, 3, 4}, Enumerable.Range (1, 4));
  			AssertAreSame (new [] {0, 1, 2, 3}, Enumerable.Range (0, 4));
  		}
  
  		[Test]
  		public void SingleValueOfMaxInt32 ()
  		{
  			AssertAreSame (new [] { int.MaxValue }, Enumerable.Range(int.MaxValue, 1));
  		}
  
  		[Test]
  		public void EmptyRangeStartingAtMinInt32 ()
  		{
  			AssertAreSame (new int [0], Enumerable.Range(int.MinValue, 0));
  		}
  
  		static void AssertThrows<T> (Action action) where T : Exception
  		{
  			try {
  				action ();
  				Assert.Fail ();
  			} catch (T) {
  			} catch {
  				Assert.Fail ();
  			}
  		}
  
  		[Test]
  		public void TestTakeTakesProperNumberOfItems ()
  		{
  			var stream = new MemoryStream (new byte [] { 1, 2, 3, 4, 0 });
  
  			Assert.AreEqual (0, stream.Position);
  
  			foreach (byte b in AsEnumerable (stream).Take (2))
  				;
  
  			Assert.AreEqual (2, stream.Position);
  		}
  
  		static IEnumerable<byte> AsEnumerable (Stream stream)
  		{
  			byte b;
  			while ((b = (byte) stream.ReadByte ()) >= 0)
  				yield return b;
  		}
  
  		[Test]
  		public void TestOrderBy ()
  		{
  				int [] array = { 14, 53, 3, 9, 11, 14, 5, 32, 2 };
  				var q = from i in array
  						orderby i
  						select i;
  				AssertIsOrdered (q);
  		}
  
  		class Baz {
  			string name;
  			int age;
  
  			public string Name
  			{
  				get {
  					if (string.IsNullOrEmpty (name))
  						return Age.ToString ();
  
  					return name + " (" + Age + ")";
  				}
  			}
  
  			public int Age
  			{
  				get { return age + 1; }
  			}
  
  			public Baz (string name, int age)
  			{
  				this.name = name;
  				this.age = age;
  			}
  
  			public override int GetHashCode ()
  			{
  				return this.Age ^ this.Name.GetHashCode ();
  			}
  
  			public override bool Equals (object obj)
  			{
  				Baz b = obj as Baz;
  				if (b == null)
  					return false;
  
  				return b.Age == this.Age && b.Name == this.Name;
  			}
  
  			public override string ToString ()
  			{
  				return this.Name;
  			}
  		}
  
  		static IEnumerable<Baz> CreateBazCollection ()
  		{
  			return new [] {
  				new Baz ("jb", 25),
  				new Baz ("ana", 20),
  				new Baz ("reg", 28),
  				new Baz ("ro", 25),
  				new Baz ("jb", 7),
  			};
  		}
  
  		[Test]
  		public void TestOrderByAgeAscendingTheByNameDescending ()
  		{
  			var q = from b in CreateBazCollection ()
  					orderby b.Age ascending, b.Name descending
  					select b;
  
  			var expected = new [] {
  				new Baz ("jb", 7),
  				new Baz ("ana", 20),
  				new Baz ("ro", 25),
  				new Baz ("jb", 25),
  				new Baz ("reg", 28),
  			};
  
  			AssertAreSame (expected, q);
  		}
  
  		class Data {
  			public int ID { get; set; }
  			public string Name { get; set; }
  
  			public override string ToString ()
  			{
  				return ID + " " + Name;
  			}
  		}
  
  		IEnumerable<Data> CreateData ()
  		{
  			return new [] {
  				new Data { ID = 10, Name = "bcd" },
  				new Data { ID = 20, Name = "Abcd" },
  				new Data { ID = 20, Name = "Ab" },
  				new Data { ID = 10, Name = "Zyx" },
  			};
  		}
  
  		[Test]
  		public void TestOrderByIdDescendingThenByNameAscending ()
  		{
  			var q = from d in CreateData ()
  					orderby d.ID descending, d.Name ascending
  					select d;
  
  			var list = new List<Data> (q);
  
  			Assert.AreEqual ("Ab", list [0].Name);
  			Assert.AreEqual ("Abcd", list [1].Name);
  			Assert.AreEqual ("bcd", list [2].Name);
  			Assert.AreEqual ("Zyx", list [3].Name);
  		}
  
  		[Test]
  		public void TestOrderByDescendingStability ()
  		{
  			var data = new [] {
  				new { Key = true, Value = 1 },
  				new { Key = false, Value = 2},
  				new { Key = true, Value = 3},
  				new { Key = false, Value = 4},
  				new { Key = true, Value = 5},
  				new { Key = false, Value = 6},
  				new { Key = true, Value = 7},
  				new { Key = false, Value = 8},
  				new { Key = true, Value = 9},
  				new { Key = false, Value = 10},
  			};
  
  			var expected = new [] {
  				new { Key = true, Value = 1 },
  				new { Key = true, Value = 3},
  				new { Key = true, Value = 5},
  				new { Key = true, Value = 7},
  				new { Key = true, Value = 9},
  				new { Key = false, Value = 2},
  				new { Key = false, Value = 4},
  				new { Key = false, Value = 6},
  				new { Key = false, Value = 8},
  				new { Key = false, Value = 10},
  			};
  
  			AssertAreSame (expected, data.OrderByDescending (x => x.Key));
  		}
  
  		static void AssertIsOrdered (IEnumerable<int> e)
  		{
  				int f = int.MinValue;
  				foreach(int i in e) {
  						Assert.IsTrue (f <= i);
  						f = i;
  				}
  		}
  
  		static void AssertAreSame<T> (IEnumerable<T> expected, IEnumerable<T> actual)
  		{
  			if (expected == null) {
  				Assert.IsNull (actual);
  				return;
  			}
  
  			Assert.IsNotNull (actual);
  
  			IEnumerator<T> ee = expected.GetEnumerator ();
  			IEnumerator<T> ea = actual.GetEnumerator ();
  
  			while (ee.MoveNext ()) {
  				Assert.IsTrue (ea.MoveNext (), "'" + ee.Current + "' expected.");
  				Assert.AreEqual (ee.Current, ea.Current);
  			}
  
  
gt: 			if (ea.MoveNext ())