Calcium: A modular application toolset leveraging PRISM – Part 1

//===================================================================================
// Microsoft patterns & practices
// Composite Application Guidance for Windows Presentation Foundation and Silverlight
//===================================================================================
// Copyright (c) Microsoft Corporation.  All rights reserved.
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE.
//===================================================================================
// The example companies, organizations, products, domain names,
// e-mail addresses, logos, people, places, and events depicted
// herein are fictitious.  No association with any real company,
// organization, product, domain name, email address, logo, person,
// places, or events is intended or should be inferred.
//===================================================================================
using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading;
using Microsoft.Practices.Composite.Presentation.Properties;
using Microsoft.Practices.Composite.Regions;
using Microsoft.Practices.ServiceLocation;

namespace Microsoft.Practices.Composite.Presentation.Regions
{
    /// <summary>
    /// Defines a factory that allows the registration of the default set of <see cref="IRegionBehavior"/>, that will
    /// be added to the <see cref="IRegionBehaviorCollection"/> of all <see cref="IRegion"/>s, unless overridden on a 'per-region' basis. 
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix", Justification = "It is more of a factory than a collection")]
    public class RegionBehaviorFactory : IRegionBehaviorFactory
    {
        private readonly IServiceLocator serviceLocator;
        private readonly Dictionary<string, Type> registeredBehaviors = new Dictionary<string, Type>();

        /// <summary>
        /// Initializes a new instance of <see cref="RegionBehaviorFactory"/>.
        /// </summary>
        /// <param name="serviceLocator"><see cref="IServiceLocator"/> used to create the instance of the behavior from its <see cref="Type"/>.</param>
        public RegionBehaviorFactory(IServiceLocator serviceLocator)
        {
            this.serviceLocator = serviceLocator;
        }

        /// <summary>
        /// Adds a particular type of RegionBehavior if it was not already registered. The <paramref name="behaviorKey"/> string is used to check if the behavior is already present
        /// </summary>
        /// <param name="behaviorKey">The behavior key that's used to find if a certain behavior is already added.</param>
        /// <param name="behaviorType">Type of the behavior to add.</param>
        public void AddIfMissing(string behaviorKey, Type behaviorType)
        {
            if (behaviorKey == null)
            {
                throw new ArgumentNullException("behaviorKey");
            }

            if (behaviorType == null)
            {
                throw new ArgumentNullException("behaviorType");
            }

            // Check if the type is a IRegionBehavior
            if (!typeof(IRegionBehavior).IsAssignableFrom(behaviorType))
            {
                throw new ArgumentException(
                    string.Format(Thread.CurrentThread.CurrentCulture, Resources.CanOnlyAddTypesThatInheritIFromRegionBehavior, behaviorType.Name), "behaviorType");
            }

            // Only add the behaviorKey if it doesn't already exists. 
            if (this.registeredBehaviors.ContainsKey(behaviorKey))
            {
                return;
            }

            this.registeredBehaviors.Add(behaviorKey, behaviorType);
        }

        /// <summary>
        /// Creates an instance of the the behavior <see cref="Type"/> that is registered using the specified key.
        /// </summary>
        /// <param name="key">The key that is used to register a behavior type.</param>
        /// <returns>A new instance of the behavior. </returns>
        public IRegionBehavior CreateFromKey(string key)
        {
            if (!this.ContainsKey(key))
            {
                throw new ArgumentException(
                    string.Format(Thread.CurrentThread.CurrentCulture, Resources.TypeWithKeyNotRegistered, key), "key");
            }
                
            return (IRegionBehavior)this.serviceLocator.GetInstance(this.registeredBehaviors[key]);
        }


        /// <summary>
        /// Returns an enumerator that iterates through the collection.
        /// </summary>
        /// <returns>
        /// A <see cref="T:System.Collections.Generic.IEnumerator`1" /> that can be used to iterate through the collection.
        /// </returns>
        /// <filterpriority>1</filterpriority>
        public IEnumerator<string> GetEnumerator()
        {
            return this.registeredBehaviors.Keys.GetEnumerator();
        }

        /// <summary>
        /// Returns an enumerator that iterates through a collection.
        /// </summary>
        /// <returns>
        /// An <see cref="T:System.Collections.IEnumerator" /> object that can be used to iterate through the collection.
        /// </returns>
        /// <filterpriority>2</filterpriority>
        IEnumerator IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator();
        }

        /// <summary>
        /// Determines whether a behavior with the specified key already exists.
        /// </summary>
        /// <param name="behaviorKey">The behavior key.</param>
        /// <returns>
        /// <see langword="true"/> if a behavior with the specified key is present; otherwise, <see langword="false"/>.
        /// </returns>
        public bool ContainsKey(string behaviorKey)
        {
            return this.registeredBehaviors.ContainsKey(behaviorKey);
        }
    }
}