/src/Caliburn.MEF/ComponentPart.cs

namespace Caliburn.MEF

{

	using System;

	using System.Collections.Generic;

	using System.ComponentModel.Composition;

	using System.ComponentModel.Composition.Hosting;

	using System.ComponentModel.Composition.Primitives;

	using System.ComponentModel.Composition.ReflectionModel;

	using System.Linq;

	using System.Reflection;

	using Core.InversionOfControl;



	/// <summary>

	/// A <see cref="ComposablePart"/> used to configure MEF with Caliburn's required services.

	/// </summary>

	public class ComponentPart : ComposablePart

	{

		readonly ComponentRegistrationBase registration;

		readonly List<ImportDefinition> imports = new List<ImportDefinition>();

		ExportDefinition[] exports;



		readonly Dictionary<ImportDefinition, Export> satisfiedImports =

			new Dictionary<ImportDefinition, Export>();



		object cachedInstance;

		readonly ConstructorInfo greedyConstructor;



		/// <summary>

		/// Initializes a new instance of the <see cref="ComponentPart"/> class.

		/// </summary>

		/// <param name="registration">The registration.</param>

		public ComponentPart(ComponentRegistrationBase registration)

		{

			this.registration = registration;



			var implementation = GetImplementation(registration);

			

			var instanceReg = registration as Instance;

			if (instanceReg != null)

			{

				cachedInstance = instanceReg.Implementation;

			}

			else

			{

				greedyConstructor = implementation

					.SelectEligibleConstructor();

				ConfigureImportDefinitions();

			}



			ConfigureExportDefinitions(implementation, registration.Service);

		}



		private void ConfigureExportDefinitions(Type implementationType, Type contractType)

		{

			var lazyMember = new LazyMemberInfo(implementationType);

			var contractName = !registration.HasName()

								  ? AttributedModelServices.GetContractName(registration.Service)

								  : registration.Name;



			var metadata = new Lazy<IDictionary<string, object>>(() =>

			{

				var md = new Dictionary<string, object>();

				md.Add(CompositionConstants.ExportTypeIdentityMetadataName,

					   AttributedModelServices.GetTypeIdentity(contractType));

				return md;

			});



			exports = new[] { ReflectionModelServices.CreateExportDefinition(lazyMember, contractName, metadata, null) };

		}



		private void ConfigureImportDefinitions()

		{

			foreach (var param in greedyConstructor.GetParameters())

			{

				var cardinality = GetCardinality(param.ParameterType);

				var importType = cardinality == ImportCardinality.ZeroOrMore

									 ? GetCollectionContractType(param.ParameterType)

									 : param.ParameterType;



				imports.Add(

					ReflectionModelServices.CreateImportDefinition(

						new Lazy<ParameterInfo>(() => param),

						AttributedModelServices.GetContractName(importType),

						AttributedModelServices.GetTypeIdentity(importType),

						Enumerable.Empty<KeyValuePair<string, Type>>(),

						cardinality,

						CreationPolicy.Any,

						null

						)

					);

			}

		}



		private static Type GetCollectionContractType(Type collectionType)

		{

			return collectionType.GetElementType();

		}



		private static ImportCardinality GetCardinality(Type targetType)

		{

			if (targetType.IsArray)

				return ImportCardinality.ZeroOrMore;

			return ImportCardinality.ExactlyOne;

		}



		/// <summary>

		/// Gets the exported object described by the specified definition.

		/// </summary>

		/// <param name="definition">One of the <see cref="T:System.ComponentModel.Composition.Primitives.ExportDefinition"/> objects from the

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePart.ExportDefinitions"/> property describing the exported object

		/// to return.</param>

		/// <returns>

		/// The exported <see cref="T:System.Object"/> described by <paramref name="definition"/>.

		/// </returns>

		/// <exception cref="T:System.ArgumentNullException">

		/// 	<paramref name="definition"/> is <see langword="null"/>.

		/// </exception>

		/// <exception cref="T:System.ArgumentException">

		/// 	<paramref name="definition"/> did not originate from the <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePart.ExportDefinitions"/>

		/// property on the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/>.

		/// </exception>

		/// <exception cref="T:System.InvalidOperationException">

		/// One or more pre-requisite imports, indicated by <see cref="P:System.ComponentModel.Composition.Primitives.ImportDefinition.IsPrerequisite"/>,

		/// have not been set.

		/// </exception>

		/// <exception cref="T:System.ObjectDisposedException">

		/// The <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> has been disposed of.

		/// </exception>

		/// <exception cref="T:System.ComponentModel.Composition.Primitives.ComposablePartException">

		/// An error occurred getting the exported object described by the <see cref="T:System.ComponentModel.Composition.Primitives.ExportDefinition"/>.

		/// </exception>

		public override object GetExportedValue(ExportDefinition definition)

		{

		    if (registration is PerRequest)

				return CreateInstance(definition);



		    return cachedInstance ?? (cachedInstance = CreateInstance(definition));

		}



	    /// <summary>

		/// Creates the instance.

		/// </summary>

		/// <param name="definition">The definition.</param>

		/// <returns></returns>

		private object CreateInstance(ExportDefinition definition)

		{

			var args = new List<object>();



			foreach (var parameterInfo in greedyConstructor.GetParameters())

			{

				var arg = (from export in satisfiedImports.Values

						   where export.Definition.ContractName ==

								 AttributedModelServices.GetContractName(parameterInfo.ParameterType)

						   select export).FirstOrDefault();



				args.Add(arg.Value);

			}



			var instance = args.Count > 0

					   ? Activator.CreateInstance(GetImplementation(registration), args.ToArray())

					   : Activator.CreateInstance(GetImplementation(registration));



			IoC.Get<CompositionContainer>().SatisfyImportsOnce(instance);



			return instance;

		}



		/// <summary>

		/// Sets the import described by the specified definition with the specified exports.

		/// </summary>

		/// <param name="definition">One of the <see cref="T:System.ComponentModel.Composition.Primitives.ImportDefinition"/> objects from the

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePart.ImportDefinitions"/> property describing the import to be set.</param>

		/// <param name="exports">An <see cref="T:System.Collections.Generic.IEnumerable`1"/> of <see cref="T:System.ComponentModel.Composition.Primitives.Export"/> objects of which

		/// to set the import described by <paramref name="definition"/>.</param>

		/// <exception cref="T:System.ArgumentNullException">

		/// 	<paramref name="definition"/> is <see langword="null"/>.

		/// <para>

		/// -or-

		/// </para>

		/// 	<paramref name="exports"/> is <see langword="null"/>.

		/// </exception>

		/// <exception cref="T:System.ArgumentException">

		/// 	<paramref name="definition"/> did not originate from the <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePart.ImportDefinitions"/>

		/// property on the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/>.

		/// <para>

		/// -or-

		/// </para>

		/// 	<paramref name="exports"/> contains an element that is <see langword="null"/>.

		/// <para>

		/// -or-

		/// </para>

		/// 	<paramref name="exports"/> is empty and <see cref="P:System.ComponentModel.Composition.Primitives.ImportDefinition.Cardinality"/> is

		/// <see cref="F:System.ComponentModel.Composition.Primitives.ImportCardinality.ExactlyOne"/>.

		/// <para>

		/// -or-

		/// </para>

		/// 	<paramref name="exports"/> contains more than one element and

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ImportDefinition.Cardinality"/> is <see cref="F:System.ComponentModel.Composition.Primitives.ImportCardinality.ZeroOrOne"/> or

		/// <see cref="F:System.ComponentModel.Composition.Primitives.ImportCardinality.ExactlyOne"/>.

		/// </exception>

		/// <exception cref="T:System.InvalidOperationException">

		/// 	<see cref="M:System.ComponentModel.Composition.Primitives.ComposablePart.OnComposed"/> has been previously called and

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ImportDefinition.IsRecomposable"/> is <see langword="false"/>.

		/// </exception>

		/// <exception cref="T:System.ObjectDisposedException">

		/// The <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> has been disposed of.

		/// </exception>

		/// <exception cref="T:System.ComponentModel.Composition.Primitives.ComposablePartException">

		/// An error occurred setting the import described by the <see cref="T:System.ComponentModel.Composition.Primitives.ImportDefinition"/>.

		/// </exception>

		public override void SetImport(ImportDefinition definition, IEnumerable<Export> exports)

		{

			if (definition == null) throw new ArgumentNullException("definition");

			if (exports == null) throw new ArgumentNullException("exports");



			satisfiedImports[definition] = exports.FirstOrDefault();

		}



		/// <summary>

		/// Gets the export definitions that describe the exported objects provided by the part.

		/// </summary>

		/// <value>

		/// An <see cref="T:System.Collections.Generic.IEnumerable`1"/> of <see cref="T:System.ComponentModel.Composition.Primitives.ExportDefinition"/> objects describing

		/// the exported objects provided by the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/>.

		/// </value>

		/// <exception cref="T:System.ObjectDisposedException">

		/// The <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> has been disposed of.

		/// </exception>

		/// <remarks>

		/// 	<para>

		/// 		<note type="inheritinfo">

		/// If the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> was created from a

		/// <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePartDefinition"/>, this property should return the result of

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePartDefinition.ExportDefinitions"/>.

		/// </note>

		/// 	</para>

		/// 	<para>

		/// 		<note type="inheritinfo">

		/// Overriders of this property should never return <see langword="null"/>.

		/// If the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> does not have exports, return an empty

		/// <see cref="T:System.Collections.Generic.IEnumerable`1"/> instead.

		/// </note>

		/// 	</para>

		/// </remarks>

		public override IEnumerable<ExportDefinition> ExportDefinitions

		{

			get { return exports; }

		}



		/// <summary>

		/// Gets the import definitions that describe the imports required by the part.

		/// </summary>

		/// <value>

		/// An <see cref="T:System.Collections.Generic.IEnumerable`1"/> of <see cref="T:System.ComponentModel.Composition.Primitives.ImportDefinition"/> objects describing

		/// the imports required by the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/>.

		/// </value>

		/// <exception cref="T:System.ObjectDisposedException">

		/// The <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> has been disposed of.

		/// </exception>

		/// <remarks>

		/// 	<para>

		/// 		<note type="inheritinfo">

		/// If the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> was created from a

		/// <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePartDefinition"/>, this property should return the result of

		/// <see cref="P:System.ComponentModel.Composition.Primitives.ComposablePartDefinition.ImportDefinitions"/>.

		/// </note>

		/// 	</para>

		/// 	<para>

		/// 		<note type="inheritinfo">

		/// Overrides of this property should never return <see langword="null"/>.

		/// If the <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePart"/> does not have imports, return an empty

		/// <see cref="T:System.Collections.Generic.IEnumerable`1"/> instead.

		/// </note>

		/// 	</para>

		/// </remarks>

		public override IEnumerable<ImportDefinition> ImportDefinitions

		{

			get { return imports; }

		}



		private static Type GetImplementation(IComponentRegistration registration)

		{

			var singleton = registration as Singleton;

			if (singleton != null) return singleton.Implementation;



			var perRequest = registration as PerRequest;

			if (perRequest != null) return perRequest.Implementation;



			var instance = registration as Instance;

			if (instance != null && instance.Implementation != null) return instance.Implementation.GetType();

			

			throw new NotSupportedException();

		}

	}

}