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

namespace Capnp.Net.Runtime.Tests
{
    [TestClass]
    public class General
    {
        [TestMethod]
        public void AwaitOrderTest()
        {
            // This test verifies an execution order assumption about the .NET environment:
            // When I register multiple continuations on the same Task, using the await
            // keyword, I expect all continuations be executed in the same order they were
            // registered. Despite I could not find any official statement on this behavior,
            // the Capnp.Net.Runtime implementation relies on that assumption. Should that
            // assumption turn out to be wrong, you might observe RPCs which are executed in
            // a different order than they were requested.

            int returnCounter = 0;

            async Task ExpectCount(Task task, int count)
            {
                await task;
                Assert.AreEqual(count, returnCounter++);
            }

            var tcs = new TaskCompletionSource<int>();

            var tasks =
                from i in Enumerable.Range(0, 100)
                select ExpectCount(tcs.Task, i);

            tcs.SetResult(0);

            Task.WhenAll(tasks).Wait();
        }

        [TestMethod]
        public void AwaitOrderTest2()
        {
            int returnCounter = 0;

            async Task ExpectCount(Task task, int count)
            {
                await task;
                Assert.AreEqual(count, returnCounter++);
            }

            var tcs = new TaskCompletionSource<int>();
            var cts = new CancellationTokenSource();

            var tasks =
                from i in Enumerable.Range(0, 100)
                select ExpectCount(tcs.Task.ContinueWith(
                    t => t, 
                    cts.Token,
                    TaskContinuationOptions.ExecuteSynchronously,
                    TaskScheduler.Current), i);

            tcs.SetResult(0);

            Task.WhenAll(tasks).Wait();
        }
    }
}