using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;

namespace AMWD.Common.Tests.Extensions
{
	[TestClass]
	public class StreamExtensionsTest
	{
		public TestContext TestContext { get; set; }

		[TestMethod]
		public void ShouldReadLineFromStreamSynchronous()
		{
			// arrange
			var sb = new StringBuilder();
			sb.AppendLine("First Line");
			sb.AppendLine("Second Line");
			byte[] buffer = Encoding.UTF8.GetBytes(sb.ToString().Trim());
			var stream = new MemoryStream(buffer);

			// act
			string line = stream.ReadLine();

			// assert
			Assert.AreEqual("First Line", line);

			stream.Dispose();
		}

		[TestMethod]
		public void ShouldReadUntilEndAsLineSynchronous()
		{
			// arrange
			byte[] buffer = Encoding.UTF8.GetBytes("Single Line");
			var stream = new MemoryStream(buffer);

			// act
			string line = stream.ReadLine();

			// assert
			Assert.AreEqual("Single Line", line);

			stream.Dispose();
		}

		[TestMethod]
		public void ShouldReturnNullWhenNotReadableSynchronous()
		{
			// arrange
			var stream = new WriteOnlyStream();

			// act
			string line = stream.ReadLine();

			// assert
			Assert.IsNull(line);

			stream.Dispose();
		}

		[TestMethod]
		public async Task ShouldReadLineFromStreamAsynchronous()
		{
			// arrange
			var sb = new StringBuilder();
			sb.AppendLine("First Line");
			sb.AppendLine("Second Line");
			byte[] buffer = Encoding.UTF8.GetBytes(sb.ToString().Trim());
			var stream = new MemoryStream(buffer);

			// act
			string line = await stream.ReadLineAsync(cancellationToken: TestContext.CancellationToken);

			// assert
			Assert.AreEqual("First Line", line);

			stream.Dispose();
		}

		[TestMethod]
		public async Task ShouldReadUntilEndAsLineAsynchronous()
		{
			// arrange
			byte[] buffer = Encoding.UTF8.GetBytes("Single Line");
			var stream = new MemoryStream(buffer);

			// act
			string line = await stream.ReadLineAsync(cancellationToken: TestContext.CancellationToken);

			// assert
			Assert.AreEqual("Single Line", line);

			stream.Dispose();
		}

		[TestMethod]
		public async Task ShouldReturnNullWhenNotReadableAsynchronous()
		{
			// arrange
			var stream = new WriteOnlyStream();

			// act
			string line = await stream.ReadLineAsync(cancellationToken: TestContext.CancellationToken);

			// assert
			Assert.IsNull(line);

			stream.Dispose();
		}

		private class WriteOnlyStream : Stream
		{
			public override bool CanRead => false;

			public override bool CanSeek => false;

			public override bool CanWrite => true;

			public override long Length => 0;

			public override long Position { get => 0; set => throw new NotImplementedException(); }

			public override void Flush()
			{ }

			public override int Read(byte[] buffer, int offset, int count) => 0;

			public override long Seek(long offset, SeekOrigin origin) => 0;

			public override void SetLength(long value)
			{ }

			public override void Write(byte[] buffer, int offset, int count)
			{ }
		}
	}
}