using System.Collections.Generic;
using Chernobyl.Values;
using NUnit.Framework;
using System.Utility;

namespace Chernobyl.DesignPatterns.Extension
{
    [TestFixture, Description("Tests for the Attach<T> type.")]
    public class AttachTests
    {
        [Test, Description("Ensures AttachExtensions.Attach<T>(IValue<T>, IValue<IExtension<T>>) " +
                           "attaches the IExtension<T> to the IExtendable immediately.")]
        public void AttachAttachesImmediately()
        {
            IContainer<IExtendable> extendable = new DynamicContainer<IExtendable>(new Extendable());
            IContainer<IExtension<IExtendable>> extension = new DynamicContainer<IExtension<IExtendable>>(new Extension());

            extendable.Attach(extension);

            extension.Value.Extended.IsEqualTo(extendable.Value, 
                                               "IExtension<IExtendable>.Extended.");
        }

        [Test, Description("Ensures AttachExtensions.Attach<T>(IValue<T>, IValue<IExtension<T>>) " +
                           "attaches/detaches the IExtension<T> to/from the IExtendable if the " +
                           "IExtendable changes.")]
        public void AttachAttachesAndDetachesIfExtendableChanges()
        {
            IExtendable previousExtendable = new Extendable();
            IDynamicContainer<IExtendable> extendable = new DynamicContainer<IExtendable>(previousExtendable);
            IContainer<IExtension<IExtendable>> extension = new DynamicContainer<IExtension<IExtendable>>(new Extension());

            extendable.Attach(extension);
            extension.Value.Extended.IsEqualTo(extendable.Value,
                                               "IExtension<IExtendable>.Extended.");
            
            IExtendable newExtendable = new Extendable();
            extendable.Value = newExtendable;

            extension.Value.Extended.IsEqualTo(newExtendable,
                                               "IExtension<IExtendable>.Extended.");
        }

        [Test, Description("Ensures AttachExtensions.Attach<T>(IValue<T>, IValue<IExtension<T>>) " +
                           "attaches/detaches the IExtension<T> to/from the IExtendable if the " +
                           "IExtension<T> changes.")]
        public void AttachAttachesAndDetachesIfExtensionChanges()
        {
            IExtension<IExtendable> previousExtension = new Extension();
            IContainer<IExtendable> extendable = new DynamicContainer<IExtendable>(new Extendable());
            IDynamicContainer<IExtension<IExtendable>> extension = new DynamicContainer<IExtension<IExtendable>>(previousExtension);

            extendable.Attach(extension);
            previousExtension.Extended.IsEqualTo(extendable.Value,
                                                 "IExtension<IExtendable>.Extended.");

            IExtension<IExtendable> newExtension = new Extension();
            extension.Value = newExtension;

            previousExtension.Extended.IsEqualTo(null, "IExtension<IExtendable>.Extended.");
            newExtension.Extended.IsEqualTo(extendable.Value,
                                            "IExtension<IExtendable>.Extended.");
        }

        /// <summary>
        /// A helper type used for testing purposes.
        /// </summary>
        public class Extendable : IExtendable
        {
            public IList<IExtension> Extensions
            {
                get { return _extensions; }
            }

            IList<IExtension> _extensions = new List<IExtension>();
        }

        /// <summary>
        /// A helper type used for testing purposes.
        /// </summary>
        public class Extension : Extension<IExtendable>
        {
            protected override void AttachTo(IExtendable extended)
            {
                extended.Extensions.Add(this);
            }

            protected override void DetachFrom(IExtendable extended)
            {
                extended.Extensions.Remove(this);
            }
        }
    }
}