// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNet.Http;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Routing;
using Moq;
using Xunit;

namespace Microsoft.AspNet.Mvc.Core.Test
{
    public class ViewResultTest
    {
        // The buffer size of the StreamWriter used in ViewResult.
        private const int ViewResultStreamWriterBufferSize = 1024;

        [Fact]
        public async Task ExecuteResultAsync_WritesOutputWithoutBOM()
        {
            // Arrange
            var expected = new byte[] { 97, 98, 99, 100 };
            var memoryStream = new MemoryStream();
            var response = new Mock<HttpResponse>();
            response.SetupGet(r => r.Body)
                   .Returns(memoryStream);
            var context = new Mock<HttpContext>();
            context.SetupGet(c => c.Response)
                   .Returns(response.Object);
            var routeDictionary = new Dictionary<string, object>();
            var actionContext = new ActionContext(context.Object,
                                                  new RouteData() {  Values = routeDictionary },
                                                  new ActionDescriptor());
            var view = new Mock<IView>();
            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
                 .Callback((ViewContext v) =>
                 {
                     v.Writer.Write("abcd");
                 })
                 .Returns(Task.FromResult(0));
            var serviceProvider = Mock.Of<IServiceProvider>();
            var viewEngine = new Mock<IViewEngine>();
            viewEngine.Setup(v => v.FindView(routeDictionary, It.IsAny<string>()))
                      .Returns(ViewEngineResult.Found("MyView", view.Object));
            var viewResult = new ViewResult(serviceProvider, viewEngine.Object);

            // Act
            await viewResult.ExecuteResultAsync(actionContext);

            // Assert
            Assert.Equal(expected, memoryStream.ToArray());
        }

        // The StreamWriter used by ViewResult an internal buffer and consequently anything written to this buffer
        // prior to it filling up will not be written to the underlying stream once an exception is thrown.
        [Theory]
        [InlineData(30, 0)]
        [InlineData(ViewResultStreamWriterBufferSize + 30, ViewResultStreamWriterBufferSize)]
        public async Task ExecuteResultAsync_DoesNotWriteToResponse_OnceExceptionIsThrown(int writtenLength, int expectedLength)
        {
            // Arrange
            var longString = new string('a', writtenLength);
            var memoryStream = new MemoryStream();
            var response = new Mock<HttpResponse>();
            response.SetupGet(r => r.Body)
                   .Returns(memoryStream);
            var context = new Mock<HttpContext>();
            context.SetupGet(c => c.Response)
                   .Returns(response.Object);
            var routeDictionary = new Dictionary<string, object>();
            var actionContext = new ActionContext(context.Object,
                                                  new RouteData() { Values = routeDictionary },
                                                  new ActionDescriptor());
            var view = new Mock<IView>();
            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
                 .Callback((ViewContext v) =>
                 {
                     v.Writer.Write(longString);
                     throw new Exception();
                 });
            var serviceProvider = Mock.Of<IServiceProvider>();
            var viewEngine = new Mock<IViewEngine>();
            viewEngine.Setup(v => v.FindView(routeDictionary, It.IsAny<string>()))
                      .Returns(ViewEngineResult.Found("MyView", view.Object));
            var viewResult = new ViewResult(serviceProvider, viewEngine.Object);

            // Act
            await Record.ExceptionAsync(() => viewResult.ExecuteResultAsync(actionContext));

            // Assert
            Assert.Equal(expectedLength, memoryStream.Length);
        }
    }
}