using System;

namespace BLToolkit.Patterns
{
    [AttributeUsage(AttributeTargets.Interface | AttributeTargets.Method | AttributeTargets.Property)]
    public sealed class MustImplementAttribute : Attribute
    {
        public MustImplementAttribute(bool implement, bool throwException, string exceptionMessage)
        {
            _implement        = implement;
            _throwException   = throwException;
            _exceptionMessage = exceptionMessage;
        }

        public MustImplementAttribute(bool implement, bool throwException)
            : this(implement, throwException, null)
        {
        }

        public MustImplementAttribute(bool implement, string exceptionMessage)
            : this(implement, true, exceptionMessage)
        {
        }

        public MustImplementAttribute(bool implement)
            : this(implement, true, null)
        {
        }

        public MustImplementAttribute()
            : this(true, true, null)
        {
        }

        private readonly bool _implement;
        public           bool  Implement
        {
            get { return _implement;  }
        }

        private bool _throwException;
        public  bool  ThrowException
        {
            get { return _throwException;  }
            set { _throwException = value; }
        }

        private string _exceptionMessage;
        public  string  ExceptionMessage
        {
            get { return _exceptionMessage;  }
            set { _exceptionMessage = value; }
        }

        /// <summary>
        /// All methods are optional and throws <see cref="NotImplementedException"/> at run tune.
        /// </summary>
        public static readonly MustImplementAttribute Default   = new MustImplementAttribute(false, true, null);

        /// <summary>
        /// All methods are optional and does nothing at run tune.
        /// Return value and all output parameters will be set to appropriate default values.
        /// </summary>
        public static readonly MustImplementAttribute Aggregate = new MustImplementAttribute(false, false, null);
    }
}