namespace System.Web.Mvc.ExpressionUtil {
    using System;
    using System.Linq.Expressions;

    // Serves as the base class for all expression fingerprints. Provides a default implementation
    // of GetHashCode().

    internal abstract class ExpressionFingerprint {

        protected ExpressionFingerprint(ExpressionType nodeType, Type type) {
            NodeType = nodeType;
            Type = type;
        }

        // the type of expression node, e.g. OP_ADD, MEMBER_ACCESS, etc.
        public ExpressionType NodeType { get; private set; }

        // the CLR type resulting from this expression, e.g. int, string, etc.
        public Type Type { get; private set; }

        internal virtual void AddToHashCodeCombiner(HashCodeCombiner combiner) {
            combiner.AddInt32((int)NodeType);
            combiner.AddObject(Type);
        }

        protected bool Equals(ExpressionFingerprint other) {
            return (other != null)
                && (this.NodeType == other.NodeType)
                && Equals(this.Type, other.Type);
        }

        public override bool Equals(object obj) {
            return Equals(obj as ExpressionFingerprint);
        }

        public override int GetHashCode() {
            HashCodeCombiner combiner = new HashCodeCombiner();
            AddToHashCodeCombiner(combiner);
            return combiner.CombinedHash;
        }

    }
}