using System;
using System.Linq.Expressions;

namespace Abp.Specifications
{
    /// <summary>
    /// Represents the combined specification which indicates that the first specification
    /// can be satisifed by the given object whereas the second one cannot.
    /// </summary>
    /// <typeparam name="T">The type of the object to which the specification is applied.</typeparam>
    public class AndNotSpecification<T> : CompositeSpecification<T>
    {
        /// <summary>
        /// Constructs a new instance of <see cref="AndNotSpecification{T}"/> class.
        /// </summary>
        /// <param name="left">The first specification.</param>
        /// <param name="right">The second specification.</param>
        public AndNotSpecification(ISpecification<T> left, ISpecification<T> right) : base(left, right) { }

        /// <summary>
        /// Gets the LINQ expression which represents the current specification.
        /// </summary>
        /// <returns>The LINQ expression.</returns>
        public override Expression<Func<T, bool>> ToExpression()
        {
            var rightExpression = Right.ToExpression();

            var bodyNot = Expression.Not(rightExpression.Body);
            var bodyNotExpression = Expression.Lambda<Func<T, bool>>(bodyNot, rightExpression.Parameters);

            return Left.ToExpression().And(bodyNotExpression);
        }
    }
}