/Source/Bifrost/Events/EventMigrationHierarchyManager.cs

#region License

//

// Copyright (c) 2008-2012, DoLittle Studios and Komplett ASA

//

// Licensed under the Microsoft Permissive License (Ms-PL), Version 1.1 (the "License")

// With one exception :

//   Commercial libraries that is based partly or fully on Bifrost and is sold commercially,

//   must obtain a commercial license.

//

// You may not use this file except in compliance with the License.

// You may obtain a copy of the license at

//

//   http://bifrost.codeplex.com/license

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

#endregion

using System;

using System.Collections.Generic;

using System.Linq;

using Bifrost.Execution;



namespace Bifrost.Events

{

    /// <summary>

    /// Represents a <see cref="IEventMigrationHierarchyManager">IEventMigrationHierarchyManager</see>

    /// </summary>

    /// <remarks>

    /// The manager will automatically build an <see cref="EventMigrationHierarchy">EventMigrationHierarchy</see> for all events and

    /// allow clients to query for the current migration level for a specific logical event or the concrete type of a particular link

    /// in the migration chain for a logical event.

    /// </remarks>

    [Singleton]

    public class EventMigrationHierarchyManager : IEventMigrationHierarchyManager

    {

        private readonly IEventMigrationHierarchyDiscoverer _eventMigrationHierarchyDiscoverer;

        private readonly IEnumerable<EventMigrationHierarchy> _hierarchies;



        /// <summary>

        /// Initializes an instance of <see cref="EventMigrationHierarchyManager">EventMigrationHierarchyManager</see>

        /// </summary>

        /// <param name="eventMigrationHierarchyDiscoverer">IEventMigrationHierarchyDiscoverer</param>

        public EventMigrationHierarchyManager(IEventMigrationHierarchyDiscoverer eventMigrationHierarchyDiscoverer)

        {

            _eventMigrationHierarchyDiscoverer = eventMigrationHierarchyDiscoverer;

            _hierarchies = _eventMigrationHierarchyDiscoverer.GetMigrationHierarchies();

        }



#pragma warning disable 1591 // Xml Comments

        public int GetCurrentMigrationLevelForLogicalEvent(Type logicalEvent)

        {

            var hierarchy = GetHierarchyForLogicalType(logicalEvent);

            return hierarchy.MigrationLevel;

        }



        public Type GetConcreteTypeForLogicalEventMigrationLevel(Type logicalEvent, int level)

        {

            if(level < 0)

                throw new MigrationLevelOutOfRangeException(string.Format("The lowest possible migration level is 0.  You asked for {0}",level));





            var hierarchy = GetHierarchyForLogicalType(logicalEvent);

            Type type;

            try

            {

                 type = hierarchy.GetConcreteTypeForLevel(level);

            }

            catch (Exception ex)

            {

                throw new MigrationLevelOutOfRangeException(string.Format(

                                        "The maximum migration level for the logical event {0} is {1}.  Does not have a migration level of {2}",

                                        logicalEvent.FullName, hierarchy.MigrationLevel, level

                                        ),ex);

            }



            return type;

        }



        public Type GetLogicalTypeForEvent(Type @event)

        {

            var hierarchy = _hierarchies.Where(h => h.MigratedTypes.Contains(@event)).FirstOrDefault();



            if(hierarchy == null)

                throw new UnregisteredEventException(string.Format("Cannot find an event migration hierarchy that contains '{0}' event type", @event.AssemblyQualifiedName));



            return hierarchy.LogicalEvent;

        }



        public Type GetLogicalTypeFromName(string typeName)

        {

            var hierarchy = _hierarchies.Where(h => h.LogicalEvent.Name == typeName).FirstOrDefault();



            if (hierarchy == null)

                throw new UnregisteredEventException(string.Format("Cannot find an event migration hierarchy with the logical event named '{0}'.", typeName));



            return hierarchy.LogicalEvent;

        }



#pragma warning restore 1591 // Xml Comments



        private EventMigrationHierarchy GetHierarchyForLogicalType(Type logicalEvent)

        {

            var hierarchy = _hierarchies.Where(hal => hal.LogicalEvent == logicalEvent).FirstOrDefault();



            if(hierarchy == null)

                throw new UnregisteredEventException(string.Format("Cannot find the logical event '{0}' in the migration hierarchies.", logicalEvent.AssemblyQualifiedName));



            return hierarchy;

        }

    }

}