using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using NHibernate.SqlTypes;
using NHibernate.UserTypes;

namespace Agendas.NHibernate
{
	[Serializable]
	public abstract class GenericWellKnownInstanceType<T, TId> : IUserType where T : class
	{
		//private static readonly SqlType[] ReturnSqlTypes = { SqlTypeFactory.Int32 };
		private Func<T, TId, bool> findPredicate;
		private Func<T, TId> idGetter;
		private IEnumerable<T> repository;

		/// <summary>
		/// Base constructor
		/// </summary>
		/// <param name="repository">The collection that represent a in-memory repository.</param>
		/// <param name="findPredicate">The predicate an instance by the persisted value.</param>
		/// <param name="idGetter">The getter of the persisted value.</param>
		protected GenericWellKnownInstanceType(IEnumerable<T> repository, Func<T, TId, bool> findPredicate, Func<T, TId> idGetter)
		{
			this.repository = repository;
			this.findPredicate = findPredicate;
			this.idGetter = idGetter;
		}

		//public SqlType[] SqlTypes
		//{
		//    get { return ReturnSqlTypes; }
		//}

		public Type ReturnedType
		{
			get { return typeof(T); }
		}

		public bool IsMutable
		{
			get { return false; }
		}

		public new bool Equals(object x, object y)
		{
			if (ReferenceEquals(x, y))
			{
				return true;
			}
			if (ReferenceEquals(null, x) || ReferenceEquals(null, y))
			{
				return false;
			}

			return x.Equals(y);
		}

		public int GetHashCode(object x)
		{
			return (x == null) ? 0 : x.GetHashCode();
		}

		public object NullSafeGet(IDataReader rs, string[] names, object owner)
		{
			int index0 = rs.GetOrdinal(names[0]);
			if (rs.IsDBNull(index0))
			{
				return null;
			}

			var value = (TId)rs.GetValue(index0);
			return repository.FirstOrDefault(x => findPredicate(x, value));
		}

		public void NullSafeSet(IDbCommand cmd, object value, int index)
		{
			if (value == null)
			{
				((IDbDataParameter)cmd.Parameters[index]).Value = DBNull.Value;
			}
			else
			{
				((IDbDataParameter)cmd.Parameters[index]).Value = idGetter((T)value);
			}
		}

		public object DeepCopy(object value)
		{
			return value;
		}

		public object Replace(object original, object target, object owner)
		{
			return original;
		}

		public object Assemble(object cached, object owner)
		{
			return cached;
		}

		public object Disassemble(object value)
		{
			return value;
		}

		/// <summary>
		/// The SQL types for the columns mapped by this type. 
		/// </summary>
		public abstract SqlType[] SqlTypes { get; }
	}
}