/src/NUnit/framework/Constraints/DelayedConstraint.cs

// ****************************************************************

// Copyright 2008, Charlie Poole

// This is free software licensed under the NUnit license. You may

// obtain a copy of the license at http://nunit.org

// ****************************************************************

using System;

using System.Threading;



namespace NUnit.Framework.Constraints

{

    ///<summary>

    /// Applies a delay to the match so that a match can be evaluated in the future.

    ///</summary>

    public class DelayedConstraint : PrefixConstraint

    {

        private readonly int delayInMilliseconds;

        private readonly int pollingInterval;



        ///<summary>

        /// Creates a new DelayedConstraint

        ///</summary>

        ///<param name="baseConstraint">The inner constraint two decorate</param>

        ///<param name="delayInMilliseconds">The time interval after which the match is performed</param>

        ///<exception cref="InvalidOperationException">If the value of <paramref name="delayInMilliseconds"/> is less than 0</exception>

        public DelayedConstraint(Constraint baseConstraint, int delayInMilliseconds)

            : this(baseConstraint, delayInMilliseconds, 0) { }



        ///<summary>

        /// Creates a new DelayedConstraint

        ///</summary>

        ///<param name="baseConstraint">The inner constraint two decorate</param>

        ///<param name="delayInMilliseconds">The time interval after which the match is performed</param>

        ///<param name="pollingInterval">The time interval used for polling</param>

        ///<exception cref="InvalidOperationException">If the value of <paramref name="delayInMilliseconds"/> is less than 0</exception>

        public DelayedConstraint(Constraint baseConstraint, int delayInMilliseconds, int pollingInterval)

            : base(baseConstraint)

        {

            if (delayInMilliseconds < 0)

                throw new ArgumentException("Cannot check a condition in the past", "delayInMilliseconds");



            this.delayInMilliseconds = delayInMilliseconds;

            this.pollingInterval = pollingInterval;

        }



        /// <summary>

        /// Test whether the constraint is satisfied by a given value

        /// </summary>

        /// <param name="actual">The value to be tested</param>

        /// <returns>True for if the base constraint fails, false if it succeeds</returns>

        public override bool Matches(object actual)

        {

            Thread.Sleep(delayInMilliseconds);

            this.actual = actual;

            return baseConstraint.Matches(actual);

        }



        /// <summary>

        /// Test whether the constraint is satisfied by a delegate

        /// </summary>

        /// <param name="del">The delegate whose value is to be tested</param>

        /// <returns>True for if the base constraint fails, false if it succeeds</returns>

        public override bool Matches(ActualValueDelegate del)

        {

			int remainingDelay = delayInMilliseconds;



			while (pollingInterval > 0 && pollingInterval < remainingDelay)

			{

				remainingDelay -= pollingInterval;

				Thread.Sleep(pollingInterval);

				this.actual = del();

				if (baseConstraint.Matches(actual))

					return true;

			}



			if ( remainingDelay > 0 )

				Thread.Sleep(remainingDelay);

			this.actual = del();

			return baseConstraint.Matches(actual);

        }



#if NET_2_0

        /// <summary>

        /// Test whether the constraint is satisfied by a given reference.

        /// Overridden to wait for the specified delay period before

        /// calling the base constraint with the dereferenced value.

        /// </summary>

        /// <param name="actual">A reference to the value to be tested</param>

        /// <returns>True for success, false for failure</returns>

        public override bool Matches<T>(ref T actual)

        {

            int remainingDelay = delayInMilliseconds;



            while (pollingInterval > 0 && pollingInterval < remainingDelay)

            {

                remainingDelay -= pollingInterval;

                Thread.Sleep(pollingInterval);

                this.actual = actual;

                if (baseConstraint.Matches(actual))

                    return true;

            }



            if ( remainingDelay > 0 )

                Thread.Sleep(remainingDelay);

            this.actual = actual;

            return baseConstraint.Matches(actual);

        }

#else

		/// <summary>

		/// Test whether the constraint is satisfied by a given boolean reference.

		/// Overridden to wait for the specified delay period before

		/// calling the base constraint with the dereferenced value.

		/// </summary>

		/// <param name="actual">A reference to the value to be tested</param>

		/// <returns>True for success, false for failure</returns>

		public override bool Matches(ref bool actual)

		{

			int remainingDelay = delayInMilliseconds;



			while (pollingInterval > 0 && pollingInterval < remainingDelay)

			{

				remainingDelay -= pollingInterval;

				Thread.Sleep(pollingInterval);

				this.actual = actual;

				if (baseConstraint.Matches(actual))

					return true;

			}



			if ( remainingDelay > 0 )

				Thread.Sleep(remainingDelay);

			this.actual = actual;

			return baseConstraint.Matches(actual);

		}

#endif



        /// <summary>

        /// Write the constraint description to a MessageWriter

        /// </summary>

        /// <param name="writer">The writer on which the description is displayed</param>

        public override void WriteDescriptionTo(MessageWriter writer)

        {

            baseConstraint.WriteDescriptionTo(writer);

            writer.Write(string.Format(" after {0} millisecond delay", delayInMilliseconds));

        }



        /// <summary>

        /// Write the actual value for a failing constraint test to a MessageWriter.

        /// </summary>

        /// <param name="writer">The writer on which the actual value is displayed</param>

        public override void WriteActualValueTo(MessageWriter writer)

        {

            baseConstraint.WriteActualValueTo(writer);

        }



        /// <summary>

        /// Returns the string representation of the constraint.

        /// </summary>

        protected override string GetStringRepresentation()

        {

            return string.Format("<after {0} {1}>", delayInMilliseconds, baseConstraint);

        }

    }

}