// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

namespace System.Data.Entity.Core.Query.InternalTrees
{
    using System.Data.Entity.Core.Metadata.Edm;
    using System.Diagnostics;

    // <summary>
    // Basic Aggregates
    // </summary>
    internal sealed class AggregateOp : ScalarOp
    {
        #region private state

        private readonly EdmFunction m_aggFunc;
        private readonly bool m_distinctAgg;

        #endregion

        #region constructors

        internal AggregateOp(EdmFunction aggFunc, bool distinctAgg)
            : base(OpType.Aggregate, aggFunc.ReturnParameter.TypeUsage)
        {
            m_aggFunc = aggFunc;
            m_distinctAgg = distinctAgg;
        }

        private AggregateOp()
            : base(OpType.Aggregate)
        {
        }

        #endregion

        #region public methods

        // <summary>
        // Pattern for transformation rules
        // </summary>
        internal static readonly AggregateOp Pattern = new AggregateOp();

        // <summary>
        // The Aggregate function's metadata
        // </summary>
        internal EdmFunction AggFunc
        {
            get { return m_aggFunc; }
        }

        // <summary>
        // Is this a "distinct" aggregate
        // </summary>
        internal bool IsDistinctAggregate
        {
            get { return m_distinctAgg; }
        }

        // <summary>
        // Yes; this is an aggregate
        // </summary>
        internal override bool IsAggregateOp
        {
            get { return true; }
        }

        // <summary>
        // Visitor pattern method
        // </summary>
        // <param name="v"> The BasicOpVisitor that is visiting this Op </param>
        // <param name="n"> The Node that references this Op </param>
        [DebuggerNonUserCode]
        internal override void Accept(BasicOpVisitor v, Node n)
        {
            v.Visit(this, n);
        }

        // <summary>
        // Visitor pattern method for visitors with a return value
        // </summary>
        // <param name="v"> The visitor </param>
        // <param name="n"> The node in question </param>
        // <returns> An instance of TResultType </returns>
        [DebuggerNonUserCode]
        internal override TResultType Accept<TResultType>(BasicOpVisitorOfT<TResultType> v, Node n)
        {
            return v.Visit(this, n);
        }

        #endregion
    }
}
