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 *     following disclaimer. 
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 *     following disclaimer in the documentation and/or other 
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 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
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 */

using NUnit.Framework;
using XenAdmin;
using System.Diagnostics;
using System.Threading;


namespace XenAdminTests.UnitTests
{
    [TestFixture, Category(TestCategories.Unit)]
    public class UpdateManagerTests
    {
        private const int Delay = 1000;
        private const int Leeway = 500;
        private UpdateManager _um;

        [SetUp]
        public void SetUp()
        {
            _um = new UpdateManager();
        }

        [TearDown]
        public void TearDown()
        {
            _um.Dispose();
            _um = null;
        }

        private static void AccurateSleep(int milliseconds)
        {
            Stopwatch sw = Stopwatch.StartNew();
            while (sw.ElapsedMilliseconds < milliseconds)
            {
                Thread.Sleep(1);
            }
        }

        [Test]
        public void TestDispose()
        {
            _um.Update += delegate
            {
                Assert.Fail("Dispose didn't work");
            };
            _um.Dispose();
            _um.RequestUpdate();
        }

        [Test]
        public void TestUpdateIsOnDifferentThread()
        {
            int id = Thread.CurrentThread.ManagedThreadId;
            bool finished = false;

            _um.Update += delegate
            {
                Assert.AreNotEqual(id, Thread.CurrentThread.ManagedThreadId, "Update wasn't on different thread.");
                finished = true;
            };
            _um.RequestUpdate();

            AccurateSleep(Leeway);
            Assert.IsTrue(finished, "test never finished");
        }

        [Test]
        public void TestFirstUpdateIsNearlyImmediate()
        {
            Stopwatch sw = null;
            bool finished = false;

            _um.Update += delegate
            {
                sw.Stop();
                Assert.Less(sw.ElapsedMilliseconds, 50, "Update didn't happen immediately.");
                // it won't be completely immediate because it's on another thread and a small delay will occur.
                finished = true;
            };
            sw = Stopwatch.StartNew();
            _um.RequestUpdate();

            AccurateSleep(Leeway);
            Assert.IsTrue(finished, "Test never finished.");
        }

        [Test]
        public void TestThatTwoSlowUpdateRequestsCausesTwoUpdates()
        {
            bool secondUpdateStarted = false;
            int updateCount = 0;
            const int updateTime = 100;

            _um.Update += delegate
            {
                AccurateSleep(updateTime);

                updateCount++;

                if (updateCount == 1)
                {
                    Assert.IsFalse(secondUpdateStarted);
                }
                else
                {
                    Assert.IsTrue(secondUpdateStarted);
                }
            };

            _um.RequestUpdate();
            AccurateSleep(updateTime + Leeway);

            secondUpdateStarted = true;
            _um.RequestUpdate();
        }
    }
}