using System;
using System.Collections.Generic;
using System.Linq;

using NUnit.Framework;
using System.IO;
using System.Threading.Tasks;
using System.Threading;

namespace Xamarin.Forms.Core.UnitTests
{
	[TestFixture]
	public class ImageTests : BaseTestFixture
	{
		[SetUp]
		public override void Setup ()
		{
			base.Setup ();
			Device.PlatformServices = new MockPlatformServices (getStreamAsync: GetStreamAsync);
		}

		[TearDown]
		public override void TearDown()
		{
			base.TearDown ();
			Device.PlatformServices = null;
		}

		[Test]
		public void TestSizing ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			var result = image.GetSizeRequest (double.PositiveInfinity, double.PositiveInfinity);

			Assert.AreEqual (100, result.Request.Width);
			Assert.AreEqual (20, result.Request.Height);
		}

		[Test]
		public void TestAspectSizingWithConstrainedHeight ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			var result = image.GetSizeRequest (double.PositiveInfinity, 10);

			Assert.AreEqual (50, result.Request.Width);
			Assert.AreEqual (10, result.Request.Height);
		}

		[Test]
		public void TestAspectSizingWithConstrainedWidth ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			var result = image.GetSizeRequest (25, double.PositiveInfinity);

			Assert.AreEqual (25, result.Request.Width);
			Assert.AreEqual (5, result.Request.Height);
		}

		[Test]
		public void TestAspectFillSizingWithConstrainedHeight ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			image.Aspect = Aspect.AspectFill;
			var result = image.GetSizeRequest (double.PositiveInfinity, 10);

			Assert.AreEqual (50, result.Request.Width);
			Assert.AreEqual (10, result.Request.Height);
		}

		[Test]
		public void TestAspectFillSizingWithConstrainedWidth ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			image.Aspect = Aspect.AspectFill;
			var result = image.GetSizeRequest (25, double.PositiveInfinity);

			Assert.AreEqual (25, result.Request.Width);
			Assert.AreEqual (5, result.Request.Height);
		}

		[Test]
		public void TestFillSizingWithConstrainedHeight ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			image.Aspect = Aspect.AspectFill;
			var result = image.GetSizeRequest (double.PositiveInfinity, 10);

			Assert.AreEqual (50, result.Request.Width);
			Assert.AreEqual (10, result.Request.Height);
		}

		[Test]
		public void TestFillSizingWithConstrainedWidth ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png"), Platform = new UnitPlatform (), IsPlatformEnabled = true};

			image.Aspect = Aspect.AspectFill;
			var result = image.GetSizeRequest (25, double.PositiveInfinity);

			Assert.AreEqual (25, result.Request.Width);
			Assert.AreEqual (5, result.Request.Height);
		}

		[Test]
		public void TestSizeChanged ()
		{
			var image = new Image { Source = "File0.png" };
			Assert.AreEqual ("File0.png", ((FileImageSource)image.Source).File);

			var preferredSizeChanged = false;
			image.MeasureInvalidated += (sender, args) => preferredSizeChanged = true;

			image.Source = "File1.png";
			Assert.AreEqual ("File1.png", ((FileImageSource)image.Source).File);
			Assert.True (preferredSizeChanged);
		}

		[Test]
		public void TestSource ()
		{
			var image = new Image ();

			Assert.IsNull (image.Source);

			bool signaled = false;
			image.PropertyChanged += (sender, e) => {
				if (e.PropertyName == "Source")
					signaled = true;
			};

			var source = ImageSource.FromFile ("File.png");
			image.Source = source;

			Assert.AreEqual (source, image.Source);
			Assert.True (signaled);
		}

		[Test]
		public void TestSourceDoubleSet ()
		{
			var image = new Image {Source = ImageSource.FromFile ("File.png")};

			bool signaled = false;
			image.PropertyChanged += (sender, e) => {
				if (e.PropertyName == "Source")
					signaled = true;
			};

			image.Source = image.Source;

			Assert.False (signaled);
		}

		[Test]
		public void TestFileImageSourceChanged ()
		{
			var source = (FileImageSource)ImageSource.FromFile ("File.png");

			bool signaled = false;
			source.SourceChanged += (sender, e) => {
				signaled = true;
			};

			source.File = "Other.png";
			Assert.AreEqual ("Other.png", source.File);

			Assert.True (signaled);
		}

		[Test]
		public void TestFileImageSourcePropertiesChangedTriggerResize ()
		{
			var source = new FileImageSource ();
			var image = new Image { Source = source };
			bool fired = false;
			image.MeasureInvalidated += (sender, e) => fired = true;
			Assert.Null (source.File);
			source.File = "foo.png";
			Assert.NotNull (source.File);
			Assert.True (fired);
		}
				
		[Test]
		public void TestStreamImageSourcePropertiesChangedTriggerResize ()
		{
			var source = new StreamImageSource ();
			var image = new Image { Source = source };
			bool fired = false;
			image.MeasureInvalidated += (sender, e) => fired = true;
			Assert.Null (source.Stream);
			source.Stream = token => Task.FromResult<Stream> (null);
			Assert.NotNull (source.Stream);
			Assert.True (fired);
		}

		[Test]
		public void TestImageSourceToNullCancelsLoading ()
		{
			var image = new Image ();
			var mockImageRenderer = new MockImageRenderer (image);
			var loader = new UriImageSource { Uri = new Uri ("http://www.public-domain-image.com/free-images/miscellaneous/big-high-border-fence.jpg") };
			image.Source = loader;
			Assert.IsTrue (image.IsLoading);
			image.Source = null;
			Assert.IsFalse (image.IsLoading);
			Assert.IsTrue (cancelled);
		}

		static bool cancelled;

		static async Task<Stream> GetStreamAsync (Uri uri, CancellationToken cancellationToken)
		{
			try {
				await Task.Delay (5000, cancellationToken);
			} catch (TaskCanceledException ex) {
				cancelled = true;
				throw ex;
			}

			if (cancellationToken.IsCancellationRequested) {
				cancelled = true;
				throw new TaskCanceledException ();
			}

			var stream = typeof(ImageTests).Assembly.GetManifestResourceStream (uri.LocalPath.Substring (1));
			return stream;
		}

		class MockImageRenderer
		{
			public MockImageRenderer (Image element)
			{
				Element = element;
				Element.PropertyChanged += ( sender, e) => {
					if (e.PropertyName == nameof (Image.Source))
						Load ();
				};
			}

			public Image Element { get; set; }

			public async void Load ()
			{
				if (initialLoad && Element.Source != null) {
					initialLoad = false;
					Element.SetIsLoading(true);
					await (Element.Source as UriImageSource).GetStreamAsync ();
					Element.SetIsLoading(false);
				}
			}

			bool initialLoad = true;
		}
	}
}