/src/MefContrib/Hosting/Conventions/ConventionPartCreator.cs

namespace MefContrib.Hosting.Conventions

{

    using System;

    using System.Collections.Generic;

    using System.ComponentModel.Composition.Hosting;

    using System.ComponentModel.Composition.Primitives;

    using System.ComponentModel.Composition.ReflectionModel;

    using System.Linq;

    using System.Reflection;

    using MefContrib.Hosting.Conventions.Configuration;



    /// <summary>

    /// 

    /// </summary>

    public class ConventionPartCreator

    {

        /// <summary>

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

        /// </summary>

        /// <param name="registry">The <see cref="IPartRegistry{T}"/> instance that should be used by the part creator.</param>

        /// <exception cref="ArgumentNullException">The provided <paramref name="registry"/> was <see langword="null"/>.</exception>

        public ConventionPartCreator(IPartRegistry<IContractService> registry)

        {

            if (registry == null)

            {

                throw new ArgumentNullException("registry", "The registry cannot be null.");

            }



            this.Registry = registry;

        }



        /// <summary>

        /// Gets the <see cref="IPartRegistry{T}"/> instance used by the part creator.

        /// </summary>

        /// <value>An <see cref="IPartRegistry{T}"/> instance.</value>

        public IPartRegistry<IContractService> Registry { get; private set; }



        /// <summary>

        /// Gets the <see cref="ITypeScanner"/> used by the <see cref="Registry"/>.

        /// </summary>

        /// <value>An <see cref="ITypeScanner"/> instance.</value>

        private ITypeScanner Scanner

        {

            get { return this.Registry.TypeScanner; }

        }



        /// <summary>

        /// Gets the <see cref="IContractService"/> used by the <see cref="Registry"/>.

        /// </summary>

        /// <value>An <see cref="IContractService"/> instance.</value>

        private IContractService ContractService

        {

            get { return this.Registry.ContractService; }

        }



        /// <summary>

        /// Creates <see cref="ComposablePartDefinition"/> instances from the <see cref="IPartConvention"/> and types.

        /// </summary>

        /// <returns>An <see cref="IEnumerable{T}"/>, containing <see cref="ComposablePartDefinition"/> instances.</returns>

        public IEnumerable<ComposablePartDefinition> CreateParts()

        {

            if (this.Scanner == null)

            {

                return Enumerable.Empty<ComposablePartDefinition>();

            }



            var definitionsFromConventions =

               from convention in this.Registry.GetConventions()

               from type in this.Scanner.GetTypes(convention.Condition)

               select CreatePartDefinition(convention, type);



            return definitionsFromConventions.ToList();

        }



        /// <summary>

        /// Creates <see cref="ExportDefinition"/> instance from the provided <see cref="IExportConvention"/> instances and type.

        /// </summary>

        /// <param name="exportConventions">An <see cref="IEnumerable{T}"/> of <see cref="IExportConvention"/> instances that should be used to create the <see cref="ExportDefinition"/> instances.</param>

        /// <param name="type">The <see cref="Type"/> for which the <see cref="ExportDefinition"/> instances should be created.</param>

        /// <returns>An <see cref="IEnumerable{T}"/> of <see cref="ExportDefinition"/> instances.</returns>

        private IEnumerable<ExportDefinition> CreateExportDefinitions(IEnumerable<IExportConvention> exportConventions, Type type)

        {

            var exportDefinitionsFromConvention =

                from exportConvention in exportConventions

                from member in exportConvention.Members.Invoke(type)

                select ReflectionModelServices.CreateExportDefinition(

                    member.ToLazyMemberInfo(),

                    this.ContractService.GetExportContractName(exportConvention, member),

                    new Lazy<IDictionary<string, object>>(() => GetExportDefinitionMetadata(exportConvention, member)),

                    null);



            return exportDefinitionsFromConvention.ToList();

        }



        /// <summary>

        /// Creates <see cref="ImportDefinition"/> instance from the provided <see cref="IImportConvention"/> instances and type.

        /// </summary>

        /// <param name="importConventions">An <see cref="IEnumerable{T}"/> of <see cref="IImportConvention"/> instances that should be used to create the <see cref="ImportDefinition"/> instances.</param>

        /// <param name="type">The <see cref="Type"/> for which the <see cref="ImportDefinition"/> instances should be created.</param>

        /// <returns>An <see cref="IEnumerable{T}"/> of <see cref="ImportDefinition"/> instances.</returns>

        private IEnumerable<ImportDefinition> CreateImportDefinitions(IEnumerable<IImportConvention> importConventions, Type type)

        {

            var importDefinitionsFromConvention = new List<ImportDefinition>();



            foreach (var importConvention in importConventions)

            {

                foreach (var member in importConvention.Members.Invoke(type))

                {

                    if (member is ConstructorInfo)

                    {

                        importDefinitionsFromConvention.AddRange(((ConstructorInfo)member).GetParameters().Select(parameter => GetImportParameterDefinition(importConvention, parameter)));

                    }

                    else

                    {

                        importDefinitionsFromConvention.Add(GetImportDefinition(importConvention, member));

                    }

                }

            }



            return importDefinitionsFromConvention.ToList();

        }



        /// <summary>

        /// Gets an <see cref="ImportDefinition"/> for a <see cref="ParameterInfo"/> instance using the provided <see cref="IImportConvention"/> instance.

        /// </summary>

        /// <param name="importConvention"><see cref="IImportConvention"/> instances that should be used to create the <see cref="ImportDefinition"/> instances.</param>

        /// <param name="parameter">The <see cref="ParameterInfo"/> for which the <see cref="ImportDefinition"/> instances should be created.</param>

        /// <returns>An <see cref="ImportDefinition"/> instance.</returns>

        private ImportDefinition GetImportParameterDefinition(IImportConvention importConvention, ParameterInfo parameter)

        {

            var actualType =

                parameter.ParameterType.GetActualType();



            return ReflectionModelServices.CreateImportDefinition(

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

                this.ContractService.GetImportContractName(importConvention, actualType),

                this.ContractService.GetImportTypeIdentity(importConvention, actualType),

                null,

                parameter.ParameterType.GetCardinality(importConvention.AllowDefaultValue),

                importConvention.CreationPolicy,

                null);

        }



        /// <summary>

        /// Gets an <see cref="ImportDefinition"/> for a <see cref="MemberInfo"/> instance using the provided <see cref="IImportConvention"/> instance.

        /// </summary>

        /// <param name="importConvention"><see cref="IImportConvention"/> instances that should be used to create the <see cref="ImportDefinition"/> instances.</param>

        /// <param name="member">The <see cref="MemberInfo"/> for which the <see cref="ImportDefinition"/> instances should be created.</param>

        /// <returns>An <see cref="ImportDefinition"/> instance.</returns>

        private ImportDefinition GetImportDefinition(IImportConvention importConvention, MemberInfo member)

        {

            return ReflectionModelServices.CreateImportDefinition(

                member.ToLazyMemberInfo(),

                this.ContractService.GetImportContractName(importConvention, member),

                this.ContractService.GetImportTypeIdentity(importConvention, member),

                importConvention.RequiredMetadata.Select(x => new KeyValuePair<string, Type>(x.Name, x.Type)),

                member.GetCardinality(importConvention.AllowDefaultValue),

                importConvention.Recomposable,

                importConvention.CreationPolicy,

                null);

        }



        /// <summary>

        /// Create a <see cref="ComposablePartDefinition"/> for a specified type using the provided <see cref="IPartConvention"/>.

        /// </summary>

        /// <param name="convention">The <see cref="IPartConvention"/> instance which is used to create the <see cref="ComposablePartDefinition"/>.</param>

        /// <param name="type">The <see cref="Type"/> for which the <see cref="ComposablePartDefinition"/> should be created.</param>

        /// <returns>A <see cref="ComposablePartDefinition"/> instance.</returns>

        private ComposablePartDefinition CreatePartDefinition(IPartConvention convention, Type type)

        {

            return ReflectionModelServices.CreatePartDefinition(

                    new Lazy<Type>(() => type),

                    false,

                    new Lazy<IEnumerable<ImportDefinition>>(() => CreateImportDefinitions(convention.Imports, type)),

                    new Lazy<IEnumerable<ExportDefinition>>(() => CreateExportDefinitions(convention.Exports, type)),

                    new Lazy<IDictionary<string, object>>(() => GetPartDefinitionMetadata(convention)),

                    null);

        }



        /// <summary>

        /// Gets the metadata for the provided <see cref="IExportConvention"/>.

        /// </summary>

        /// <param name="exportConvention">The <see cref="IExportConvention"/> that the metadata should be retrieved for.</param>

        /// <param name="member">The <see cref="MemberInfo"/> that is being exported.</param>

        /// <returns>An <see cref="IDictionary{TKey,TValue}"/> containing the metadata for the export.</returns>

        private IDictionary<string, object> GetExportDefinitionMetadata(IExportConvention exportConvention, MemberInfo member)

        {

            var exportDefinitionMetadata =

                exportConvention.Metadata.ToMetadataDictionary();



            exportDefinitionMetadata.Add(

                CompositionConstants.ExportTypeIdentityMetadataName,

                this.ContractService.GetExportTypeIdentity(exportConvention, member));



            return exportDefinitionMetadata;

        }



        /// <summary>

        /// Gets the metadata for the provided <see cref="IPartConvention"/>.

        /// </summary>

        /// <param name="partConvention">The <see cref="IPartConvention"/> that the metadata should be retrieved for.</param>

        /// <returns>An <see cref="IDictionary{TKey,TValue}"/> containing the metadata for the part.</returns>

        private static IDictionary<string, object> GetPartDefinitionMetadata(IPartConvention partConvention)

        {

            var partDefinitionMetadata =

                partConvention.Metadata.ToMetadataDictionary();



            partDefinitionMetadata.Add(CompositionConstants.PartCreationPolicyMetadataName, partConvention.CreationPolicy);



            return partDefinitionMetadata;

        }

    }

}