NHibernate CustomHasManyToManyStep

NHibernate CustomHasManyToManyStep

public class CustomHasManyToManyStep : IAutomappingStep
    {
        private readonly IAutomappingConfiguration cfg;
        public CustomHasManyToManyStep(IAutomappingConfiguration cfg)
        {
            this.cfg = cfg;
        }
        public bool ShouldMap(Member member)
        {
            var type = member.PropertyType;
            if (type.Namespace != "Iesi.Collections.Generic" &&
                type.Namespace != "System.Collections.Generic")
                return false;
            if (type.HasInterface(typeof(IDictionary)) || type.ClosesInterface(typeof(IDictionary<,>)) || type.Closes(typeof(System.Collections.Generic.IDictionary<,>)))
                return false;
            //SamerA: Tweak to allow unidirectional ManyToMany mapping along with the Bidirectional            
            return (IsBidirectionalManyToMany(member) || IsUnidirectionalManyToMany(member));
        }
        static Member GetInverseCollectionProperty(Member member)
        {
            var type = member.PropertyType;
            var expectedInversePropertyType = type.GetGenericTypeDefinition()
                .MakeGenericType(member.DeclaringType);
            var argument = type.GetGenericArguments()[0];
            return argument.GetProperties()
                .Select(x => x.ToMember())
                .Where(x => x.PropertyType == expectedInversePropertyType && x != member)
                .FirstOrDefault();
        }
        static bool IsBidirectionalManyToMany(Member member)
        {
            var type = member.PropertyType;
            var expectedInversePropertyType = type.GetGenericTypeDefinition()
                .MakeGenericType(member.DeclaringType);
            var argument = type.GetGenericArguments()[0];
            return argument.GetProperties()
                .Select(x => x.ToMember())
                .Any(x => x.PropertyType == expectedInversePropertyType && x != member);
        }
        static bool IsUnidirectionalManyToMany(Member member)
        {
            var type = member.PropertyType;
            var argument = type.GetGenericArguments()[0];
            return argument.GetProperties()
                .Select(x => x.ToMember()).All(x => x.PropertyType != member.DeclaringType && x != member);
        }
        public void Map(ClassMappingBase classMap, Member member)
        {
            var inverseProperty = GetInverseCollectionProperty(member);
            var parentSide = inverseProperty == null ? member.DeclaringType : cfg.GetParentSideForManyToMany(member.DeclaringType, inverseProperty.DeclaringType);
            var mapping = GetCollection(member);
            ConfigureModel(member, mapping, classMap, parentSide);
            classMap.AddCollection(mapping);
        }
        static CollectionMapping GetCollection(Member property)
        {
            var collectionType = CollectionTypeResolver.Resolve(property);
            return CollectionMapping.For(collectionType);
        }
        void ConfigureModel(Member member, CollectionMapping mapping, ClassMappingBase classMap, Type parentSide)
        {
            // TODO: Make the child type safer
            mapping.SetDefaultValue(x => x.Name, member.Name);
            mapping.Relationship = CreateManyToMany(member, member.PropertyType.GetGenericArguments()[0], classMap.Type);
            mapping.ContainingEntityType = classMap.Type;
            mapping.ChildType = member.PropertyType.GetGenericArguments()[0];
            mapping.Member = member;
            SetDefaultAccess(member, mapping);
            SetKey(member, classMap, mapping);
            if (parentSide != member.DeclaringType)
                mapping.Inverse = true;
        }
        void SetDefaultAccess(Member member, CollectionMapping mapping)
        {
            var resolvedAccess = MemberAccessResolver.Resolve(member);
            if (resolvedAccess != Access.Property && resolvedAccess != Access.Unset)
            {
                // if it's a property or unset then we'll just let NH deal with it, otherwise
                // set the access to be whatever we determined it might be
                mapping.SetDefaultValue(x => x.Access, resolvedAccess.ToString());
            }
            if (member.IsProperty && !member.CanWrite)
                mapping.SetDefaultValue(x => x.Access, cfg.GetAccessStrategyForReadOnlyProperty(member).ToString());
        }
        ICollectionRelationshipMapping CreateManyToMany(Member property, Type child, Type parent)
        {
            var mapping = new ManyToManyMapping
            {
                Class = new TypeReference(property.PropertyType.GetGenericArguments()[0]),
                ContainingEntityType = parent
            };
            mapping.AddDefaultColumn(new ColumnMapping { Name = child.Name + "_id" });
            return mapping;
        }
        void SetKey(Member property, ClassMappingBase classMap, CollectionMapping mapping)
        {
            var columnName = property.DeclaringType.Name + "_id";
            var key = new KeyMapping();
            key.ContainingEntityType = classMap.Type;
            key.AddDefaultColumn(new ColumnMapping { Name = columnName });
            mapping.SetDefaultValue(x => x.Key, key);
        }
    }