//------------------------------------------------------------------------------
// <copyright file="CompensatingCollection.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------

namespace System.Data.Common.Internal.Materialization
{
    using System.Collections.Generic;
    using System.Linq;
    using System.Linq.Expressions;

    /// <summary>
    /// What we return from our materialization of a collection column must be
    /// exactly the type that the compilers expected when they generated the
    /// code that asked for it.  This class wraps our enumerators and derives 
    /// from all the possible options, covering all the bases.
    /// </summary>
    internal class CompensatingCollection<TElement> : IOrderedQueryable<TElement>, IOrderedEnumerable<TElement>
    {
        #region private state

        /// <summary>
        /// The thing we're compensating for
        /// </summary>
        private readonly IEnumerable<TElement> _source;

        /// <summary>
        /// An expression that returns the source as a constant
        /// </summary>
        private readonly Expression _expression;

        #endregion

        #region constructors

        public CompensatingCollection(IEnumerable<TElement> source)
        {
            _source = EntityUtil.CheckArgumentNull(source, "source");
            _expression = Expression.Constant(source);
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return _source.GetEnumerator();
        }

        #endregion

        #region IEnumerable<TElement> Members

        IEnumerator<TElement> IEnumerable<TElement>.GetEnumerator()
        {
            return _source.GetEnumerator();
        }

        #endregion

        #region IOrderedEnumerable<TElement> Members

        IOrderedEnumerable<TElement> IOrderedEnumerable<TElement>.CreateOrderedEnumerable<K>(Func<TElement, K> keySelector, IComparer<K> comparer, bool descending)
        {
            throw EntityUtil.NotSupported(System.Data.Entity.Strings.ELinq_CreateOrderedEnumerableNotSupported);
        }

        #endregion

        #region IQueryable Members

        Type IQueryable.ElementType
        {
            get { return typeof(TElement); }
        }

        Expression IQueryable.Expression
        {
            get { return _expression; }
        }

        IQueryProvider IQueryable.Provider
        {
            get
            {
                throw EntityUtil.NotSupported(System.Data.Entity.Strings.ELinq_UnsupportedQueryableMethod);
            }
        }

        #endregion

        #region IQueryable<TElement> Members
        #endregion
    }
}