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namespace Pithos.ShellExtensions
{
    using System;
    using System.ComponentModel.Composition;
    using System.ComponentModel.Composition.Hosting;
    using System.Diagnostics;
    using System.Reflection;
    
    /// <summary>
    /// The IoC class initializes MEF DI and acts as a service locator.
    /// A singleton instance of IoC is provided by Instance
    /// </summary>
    public class IoC
    {
        private static readonly log4net.ILog Log = log4net.LogManager.GetLogger("Pithos.Extensions.IoC");

        /// <summary>
        /// The MEF Container
        /// </summary>
        public CompositionContainer Container;
        
        /// <summary>
        /// Layily initialized singleton instance of IoC
        /// </summary>
        static readonly Lazy<IoC> Instance=new Lazy<IoC>();

        /// <summary>
        /// Gets the singleton instance of IoC
        /// </summary>
        public static IoC Current
        {
            get { return Instance.Value; }
        }

        /// <summary>
        /// Initializes a new instance of the IoC from types exported from the executing assembly
        /// </summary>
        public IoC()
        {
            var catalog = new AggregateCatalog();
            catalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));            
            
            Container=new CompositionContainer(catalog);
        }
        
        /// <summary>
        /// Initializes all imported properties of the target object
        /// </summary>
        /// <typeparam name="T">Type of the target object</typeparam>
        /// <param name="target">The target object</param>
        /// <returns>The object with all imported properties initialized</returns>
        public T Compose<T>(T target)
        {
            try
            {
                Container.ComposeParts(target);
                return target;
            }
            catch (Exception exc)
            {
                Log.ErrorFormat("Composition Error: {0}",exc);
                throw;
            }
        }
    }
}