using System;
using System.Collections.Generic;
using System.Reflection;
using System.Threading.Tasks;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace UnitTests.Common.Utilities
{
	[TestClass]
	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
	public class AsyncQueueTests
	{
		private Queue<TestElement> internalQueue;

		private TestElement queueElement1;
		private TestElement queueElement2;
		private TestElement queueElement3;

		[TestInitialize]
		public void InitializeTest()
		{
			queueElement1 = new TestElement
			{
				Number = 111,
				Text = "one"
			};
			queueElement2 = new TestElement
			{
				Number = 222,
				Text = "two"
			};
			queueElement3 = new TestElement
			{
				Number = 333,
				Text = "three"
			};

			internalQueue = new Queue<TestElement>();
			internalQueue.Enqueue(queueElement1);
			internalQueue.Enqueue(queueElement2);
			internalQueue.Enqueue(queueElement3);
		}

		[TestMethod]
		public void ShouldEnqueueItem()
		{
			// arrange
			var element = new TestElement { Number = 1, Text = "Hello" };

			internalQueue.Clear();
			var queue = GetQueue();

			// act
			queue.Enqueue(element);

			// assert
			Assert.AreEqual(1, internalQueue.Count);
			Assert.AreEqual(internalQueue.Count, queue.Count);
		}

		[TestMethod]
		public void ShouldEnqueueItemAndResetAvailableToken()
		{
			// arrange
			var element = new TestElement { Number = 1, Text = "Hello" };
			bool available = false;

			internalQueue.Clear();
			var queue = GetQueue();

			// act
			var task = Task.Run(async () =>
			{
				await queue.WaitAsync();
				available = true;
			});
			queue.Enqueue(element);
			task.Wait();

			// assert
			Assert.IsTrue(available);
		}

		[TestMethod]
		public void ShouldEnqueueItemAndResetDequeueToken()
		{
			// arrange
			var element = new TestElement { Number = 1, Text = "Hello" };
			TestElement callback = null;

			internalQueue.Clear();
			var queue = GetQueue();

			// act
			var task = Task.Run(async () =>
			{
				callback = await queue.DequeueAsync();
			});
			queue.Enqueue(element);
			task.Wait();

			// assert
			Assert.IsNotNull(callback);
			Assert.AreEqual(element, callback);
		}

		[TestMethod]
		public void ShouldEnqueueMultipleItems()
		{
			// arrange
			var elements = new TestElement[]
			{
				new TestElement { Number = 1, Text = "Hello" },
				new TestElement { Number = 2, Text = "World" },
			};
			internalQueue.Clear();
			var queue = GetQueue();

			// act
			queue.Enqueue(elements);

			// assert
			Assert.AreEqual(2, internalQueue.Count);
			Assert.AreEqual(queue.Count, internalQueue.Count);
		}

		[TestMethod]
		public void ShouldPeekAValue()
		{
			// arrange
			var queue = GetQueue();

			// act
			bool isSuccess = queue.TryPeek(out var item);

			// assert
			Assert.IsTrue(isSuccess);
			Assert.IsNotNull(item);
			Assert.AreEqual(queueElement1, item);
			Assert.AreEqual(3, queue.Count);
		}

		[TestMethod]
		public void ShouldNotPeekAValue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			// act
			bool isSuccess = queue.TryPeek(out var item);

			// assert
			Assert.IsFalse(isSuccess);
			Assert.IsNull(item);
		}

		[TestMethod]
		public void ShouldDequeueAValue()
		{
			// arrange
			var queue = GetQueue();

			// act
			bool isSuccess = queue.TryDequeue(out var item);

			// assert
			Assert.IsTrue(isSuccess);
			Assert.IsNotNull(item);
			Assert.AreEqual(queueElement1, item);
			Assert.AreEqual(2, queue.Count);
		}

		[TestMethod]
		public void ShouldNotDequeueAValue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			// act
			bool isSuccess = queue.TryDequeue(out var item);

			// assert
			Assert.IsFalse(isSuccess);
			Assert.IsNull(item);
		}

		[TestMethod]
		public void ShouldRemoveAValue()
		{
			// arrange
			var queue = GetQueue();

			// act
			queue.Remove(queueElement2);
			var item1 = queue.Dequeue();
			var item2 = queue.Dequeue();

			// assert
			Assert.AreEqual(0, queue.Count);
			Assert.AreEqual(queueElement1, item1);
			Assert.AreEqual(queueElement3, item2);
		}

		[TestMethod]
		public void ShouldNotRemoveAValue()
		{
			// arrange
			var queue = GetQueue();

			// act
			queue.Remove(null);
			var item1 = queue.Dequeue();
			var item2 = queue.Dequeue();
			var item3 = queue.Dequeue();

			// assert
			Assert.AreEqual(0, queue.Count);
			Assert.AreEqual(queueElement1, item1);
			Assert.AreEqual(queueElement2, item2);
			Assert.AreEqual(queueElement3, item3);
		}

		[TestMethod]
		public async Task ShouldAwaitOneDequeue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			var task = Task.Run(async () =>
			{
				await Task.Delay(1000);
				queue.Enqueue(new[] { queueElement1, queueElement2, queueElement3 });
			});

			// act
			var item = await queue.DequeueAsync();

			// assert
			Assert.AreEqual(2, queue.Count);
			Assert.IsNotNull(item);
			Assert.AreEqual(queueElement1, item);
		}

		[TestMethod]
		public async Task ShouldAwaitManyDequeue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			var task = Task.Run(async () =>
			{
				await Task.Delay(1000);
				queue.Enqueue(new[] { queueElement1, queueElement2, queueElement3 });
			});

			// act
			var items = await queue.DequeueManyAsync(2);

			// assert
			Assert.AreEqual(1, queue.Count);
			Assert.IsNotNull(items);
			Assert.AreEqual(2, items.Length);
			Assert.AreEqual(queueElement1, items[0]);
			Assert.AreEqual(queueElement2, items[1]);
		}

		[TestMethod]
		public async Task ShouldAwaitAllDequeue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			var task = Task.Run(async () =>
			{
				await Task.Delay(1000);
				queue.Enqueue(new[] { queueElement1, queueElement2, queueElement3 });
			});

			// act
			var items = await queue.DequeueAvailableAsync();

			// assert
			Assert.AreEqual(0, queue.Count);
			Assert.IsNotNull(items);
			Assert.AreEqual(3, items.Length);
			Assert.AreEqual(queueElement1, items[0]);
			Assert.AreEqual(queueElement2, items[1]);
			Assert.AreEqual(queueElement3, items[2]);
		}

		[TestMethod]
		public async Task ShouldAwaitAvailableDequeue()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			var task = Task.Run(async () =>
			{
				await Task.Delay(1000);
				queue.Enqueue(new[] { queueElement1, queueElement2, queueElement3 });
			});

			// act
			var items = await queue.DequeueAvailableAsync(2);

			// assert
			Assert.AreEqual(1, queue.Count);
			Assert.IsNotNull(items);
			Assert.AreEqual(2, items.Length);
			Assert.AreEqual(queueElement1, items[0]);
			Assert.AreEqual(queueElement2, items[1]);
		}

		[TestMethod]
		[ExpectedException(typeof(ArgumentOutOfRangeException))]
		public async Task ShouldThrowArumentOutOfRangeException()
		{
			// arrange
			internalQueue.Clear();
			var queue = GetQueue();

			// act
			await queue.DequeueManyAsync(-2);

			// assert - ArgumentOutOfRangeException expected
			Assert.Fail();
		}

		private AsyncQueue<TestElement> GetQueue()
		{
			var asyncQueue = new AsyncQueue<TestElement>();

			var field = asyncQueue.GetType().GetField("queue", BindingFlags.Instance | BindingFlags.NonPublic);
			field.SetValue(asyncQueue, internalQueue);

			return asyncQueue;
		}

		private class TestElement
		{
			public int Number { get; set; }

			public string Text { get; set; }
		}
	}
}