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

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq.Expressions;

#pragma warning disable 659 // overrides AddToHashCodeCombiner instead

namespace Microsoft.Web.Mvc.ExpressionUtil
{
    // ParameterExpression fingerprint class
    // Can represent the model parameter or an inner parameter in an open lambda expression

    [SuppressMessage("Microsoft.Usage", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification = "Overrides AddToHashCodeCombiner() instead.")]
    internal sealed class ParameterExpressionFingerprint : ExpressionFingerprint
    {
        public ParameterExpressionFingerprint(ExpressionType nodeType, Type type, int parameterIndex)
            : base(nodeType, type)
        {
            ParameterIndex = parameterIndex;
        }

        // Parameter position within the overall expression, used to maintain alpha equivalence.
        public int ParameterIndex { get; private set; }

        public override bool Equals(object obj)
        {
            ParameterExpressionFingerprint other = obj as ParameterExpressionFingerprint;
            return (other != null)
                   && (this.ParameterIndex == other.ParameterIndex)
                   && this.Equals(other);
        }

        internal override void AddToHashCodeCombiner(HashCodeCombiner combiner)
        {
            combiner.AddInt32(ParameterIndex);
            base.AddToHashCodeCombiner(combiner);
        }
    }
}
