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

namespace System.Data.Entity.Config
{
    using System.Collections.Concurrent;
    using System.Linq;
    using Moq;
    using Xunit;

    public class CachingDependencyResolverTests : TestBase
    {
        public interface IPilkington
        {
        }

        public interface IGervais
        {
        }

        [Fact]
        public void GetService_caches_the_result_from_the_underlying_resolver_for_a_given_type_name_pair()
        {
            var mockResolver = new Mock<IDbDependencyResolver>();
            var cachingResolver = new CachingDependencyResolver(mockResolver.Object);

            VerifyServiceIsCached(new Mock<IPilkington>().Object, cachingResolver, mockResolver, "Foo");
            VerifyServiceIsCached(new Mock<IPilkington>().Object, cachingResolver, mockResolver, "Bar");
            VerifyServiceIsCached(new Mock<IPilkington>().Object, cachingResolver, mockResolver, null);

            VerifyServiceIsCached(new Mock<IGervais>().Object, cachingResolver, mockResolver, "Foo");
            VerifyServiceIsCached(new Mock<IGervais>().Object, cachingResolver, mockResolver, "Bar");
            VerifyServiceIsCached(new Mock<IGervais>().Object, cachingResolver, mockResolver, null);
        }

        private static void VerifyServiceIsCached<T>(
            T service,
            CachingDependencyResolver cachingResolver,
            Mock<IDbDependencyResolver> mockResolver,
            string name)
        {
            mockResolver.Setup(m => m.GetService(typeof(T), name)).Returns(service);

            Assert.Same(service, cachingResolver.GetService<T>(name));
            mockResolver.Verify(m => m.GetService(typeof(T), name), Times.Once());
            Assert.Same(service, cachingResolver.GetService<T>(name));
            mockResolver.Verify(m => m.GetService(typeof(T), name), Times.Once()); // Underlying resolver not called again
        }

        [Fact]
        public void A_service_that_resolves_to_null_is_still_cached()
        {
            var mockResolver = new Mock<IDbDependencyResolver>();

            VerifyServiceIsCached<IPilkington>(null, new CachingDependencyResolver(mockResolver.Object), mockResolver, null);
        }

        /// <summary>
        ///     This test makes calls from multiple threads such that we have at least some chance of finding threading
        ///     issues. As with any test of this type just because the test passes does not mean that the code is
        ///     correct. On the other hand if this test ever fails (EVEN ONCE) then we know there is a problem to
        ///     be investigated. DON'T just re-run and think things are okay if the test then passes.
        /// </summary>
        [Fact]
        public void GetService_can_be_accessed_from_multiple_threads_concurrently()
        {
            for (var i = 0; i < 30; i++)
            {
                var bag = new ConcurrentBag<IPilkington>();
                var karl = new Mock<IPilkington>().Object;
                var resolver = new CachingDependencyResolver(new SingletonDependencyResolver<IPilkington>(karl));

                ExecuteInParallel(() => bag.Add(resolver.GetService<IPilkington>()));

                Assert.Equal(20, bag.Count);
                Assert.True(bag.All(c => karl == c));
            }
        }
    }
}