PublishedContent - implement a model factory

src/Umbraco.Core/Models/PublishedContent/PublishedContentModel.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Umbraco.Core.Models.PublishedContent
+{
+    /// <summary>
+    /// Represents a strongly-typed published content.
+    /// </summary>
+    /// <remarks>Every strongly-typed published content class should inherit from <c>PublishedContentModel</c>
+    /// (or inherit from a class that inherits from... etc.) so they are picked by the factory.</remarks>
+    public abstract class PublishedContentModel : PublishedContentExtended
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PublishedContentModel"/> class with
+        /// an original <see cref="IPublishedContent"/> instance.
+        /// </summary>
+        /// <param name="content">The original content.</param>
+        protected PublishedContentModel(IPublishedContent content)
+            : base(content)
+        { }
+    }
+}

src/Umbraco.Core/Models/PublishedContent/PublishedContentModelAttribute.cs

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+using System;
+
+namespace Umbraco.Core.Models.PublishedContent
+{
+    /// <summary>
+    /// Indicates that the class is a published content model for a specified content type.
+    /// </summary>
+    /// <remarks>By default, the name of the class is assumed to be the content type alias. The
+    /// <c>PublishedContentModelAttribute</c> can be used to indicate a different alias.</remarks>
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
+    public sealed class PublishedContentModelAttribute : Attribute
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PublishedContentModelAttribute"/> class with a content type alias.
+        /// </summary>
+        /// <param name="contentTypeAlias">The content type alias.</param>
+        public PublishedContentModelAttribute(string contentTypeAlias)
+        {
+            if (string.IsNullOrWhiteSpace(contentTypeAlias))
+                throw new ArgumentException("Argument cannot be null nor empty.", "contentTypeAlias");
+            ContentTypeAlias = contentTypeAlias;
+        }
+
+        /// <summary>
+        /// Gets or sets the content type alias.
+        /// </summary>
+        public string ContentTypeAlias { get; private set; }
+    }
+}

src/Umbraco.Core/Models/PublishedContent/PublishedContentModelFactoryImpl.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+
+namespace Umbraco.Core.Models.PublishedContent
+{
+    /// <summary>
+    /// Implements a strongly typed content model factory
+    /// </summary>
+    internal class PublishedContentModelFactoryImpl : IPublishedContentModelFactory
+    {
+        //private readonly Dictionary<string, ConstructorInfo> _constructors
+        //    = new Dictionary<string, ConstructorInfo>();
+
+        private readonly Dictionary<string, Func<IPublishedContent, IPublishedContent>> _constructors
+             = new Dictionary<string, Func<IPublishedContent, IPublishedContent>>();
+
+        public PublishedContentModelFactoryImpl()
+        {
+            var types = PluginManager.Current.ResolveTypes<PublishedContentModel>();
+            var ctorArgTypes = new[] { typeof(IPublishedContent) };
+
+            foreach (var type in types)
+            {
+                if (type.Inherits<PublishedContentModel>() == false)
+                    throw new InvalidOperationException(string.Format("Type {0} is marked with PublishedContentModel attribute but does not inherit from PublishedContentExtended.", type.FullName));
+                var constructor = type.GetConstructor(ctorArgTypes);
+                if (constructor == null)
+                    throw new InvalidOperationException(string.Format("Type {0} is missing a public constructor with one argument of type IPublishedContent.", type.FullName));
+                var attribute = type.GetCustomAttribute<PublishedContentModelAttribute>(false);
+                var typeName = attribute == null ? type.Name : attribute.ContentTypeAlias;
+                typeName = typeName.ToLowerInvariant();
+
+                if (_constructors.ContainsKey(typeName))
+                    throw new InvalidOperationException(string.Format("More that one type want to be a model for content type {0}.", typeName));
+
+                // should work everywhere, potentially slow?
+                //_constructors[typeName] = constructor;
+
+                // note: would it be even faster with a dynamic method?
+                // here http://stackoverflow.com/questions/16363838/how-do-you-call-a-constructor-via-an-expression-tree-on-an-existing-object
+                // but MediumTrust issue?
+
+                // fixme - must make sure that works in medium trust
+                // read http://boxbinary.com/2011/10/how-to-run-a-unit-test-in-medium-trust-with-nunitpart-three-umbraco-framework-testing/
+                var exprArg = Expression.Parameter(typeof(IPublishedContent), "content");
+                var exprNew = Expression.New(constructor, exprArg);
+                var expr = Expression.Lambda<Func<IPublishedContent, IPublishedContent>>(exprNew, exprArg);
+                var func = expr.Compile();
+                _constructors[typeName] = func;
+            }
+        }
+
+        public IPublishedContent CreateModel(IPublishedContent content)
+        {
+            // be case-insensitive
+            var contentTypeAlias = content.DocumentTypeAlias.ToLowerInvariant();
+
+            //ConstructorInfo constructor;
+            //return _constructors.TryGetValue(contentTypeAlias, out constructor)
+            //    ? (IPublishedContent) constructor.Invoke(new object[] { content })
+            //    : content;
+
+            Func<IPublishedContent, IPublishedContent> constructor;
+            return _constructors.TryGetValue(contentTypeAlias, out constructor)
+                ? constructor(content)
+                : content;
+        }
+    }
+}