using System;
using System.Linq.Expressions;

namespace MyCode.Project.Infrastructure
{
    /// <summary>
    /// Represents that the implemented classes are specifications. For more
    /// information about the specification pattern, please refer to
    /// http://martinfowler.com/apsupp/spec.pdf.
    /// </summary>
    /// <typeparam name="T">The type of the object to which the specification
    /// is applied.</typeparam>
    public interface ISpecification<T>
    {
        /// <summary>
        /// Returns a <see cref="System.Boolean"/> value which indicates whether the specification
        /// is satisfied by the given object.
        /// </summary>
        /// <param name="obj">The object to which the specification is applied.</param>
        /// <returns>True if the specification is satisfied, otherwise false.</returns>
        bool IsSatisfiedBy(T obj);
        /// <summary>
        /// Combines the current specification instance with another specification instance
        /// and returns the combined specification which represents that both the current and
        /// the given specification must be satisfied by the given object.
        /// </summary>
        /// <param name="other">The specification instance with which the current specification
        /// is combined.</param>
        /// <returns>The combined specification instance.</returns>
        ISpecification<T> And(ISpecification<T> other);
        /// <summary>
        /// Combines the current specification instance with another specification instance
        /// and returns the combined specification which represents that either the current or
        /// the given specification should be satisfied by the given object.
        /// </summary>
        /// <param name="other">The specification instance with which the current specification
        /// is combined.</param>
        /// <returns>The combined specification instance.</returns>
        ISpecification<T> Or(ISpecification<T> other);
        /// <summary>
        /// Combines the current specification instance with another specification instance
        /// and returns the combined specification which represents that the current specification
        /// should be satisfied by the given object but the specified specification should not.
        /// </summary>
        /// <param name="other">The specification instance with which the current specification
        /// is combined.</param>
        /// <returns>The combined specification instance.</returns>
        ISpecification<T> AndNot(ISpecification<T> other);
        /// <summary>
        /// Reverses the current specification instance and returns a specification which represents
        /// the semantics opposite to the current specification.
        /// </summary>
        /// <returns>The reversed specification instance.</returns>
        ISpecification<T> Not();
        /// <summary>
        /// Gets the LINQ expression which represents the current specification.
        /// </summary>
        /// <returns>The LINQ expression.</returns>
        Expression<Func<T, bool>> GetExpression();
    }
}