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

// Copyright 2007, 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.Collections;

#if NET_2_0

using System.Collections.Generic;

#endif



namespace NUnit.Framework.Constraints

{

    /// <summary>

    /// Abstract base class for constraints that compare values to

    /// determine if one is greater than, equal to or less than

    /// the other.

    /// </summary>

    public abstract class ComparisonConstraint : Constraint

    {

        /// <summary>

        /// The value against which a comparison is to be made

        /// </summary>

        protected object expected;

        /// <summary>

        /// If true, less than returns success

        /// </summary>

        protected bool ltOK = false;

        /// <summary>

        /// if true, equal returns success

        /// </summary>

        protected bool eqOK = false;

        /// <summary>

        /// if true, greater than returns success

        /// </summary>

        protected bool gtOK = false;

        /// <summary>

        /// The predicate used as a part of the description

        /// </summary>

        private string predicate;



        /// <summary>

        /// ComparisonAdapter to be used in making the comparison

        /// </summary>

        private ComparisonAdapter comparer = ComparisonAdapter.Default;



        /// <summary>

        /// Initializes a new instance of the <see cref="T:ComparisonConstraint"/> class.

        /// </summary>

        /// <param name="value">The value against which to make a comparison.</param>

        /// <param name="ltOK">if set to <c>true</c> less succeeds.</param>

        /// <param name="eqOK">if set to <c>true</c> equal succeeds.</param>

        /// <param name="gtOK">if set to <c>true</c> greater succeeds.</param>

        /// <param name="predicate">String used in describing the constraint.</param>

        public ComparisonConstraint(object value, bool ltOK, bool eqOK, bool gtOK, string predicate)

            : base(value)

        {

            this.expected = value;

            this.ltOK = ltOK;

            this.eqOK = eqOK;

            this.gtOK = gtOK;

            this.predicate = predicate;

        }



        /// <summary>

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

        /// </summary>

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

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

        public override bool Matches(object actual)

        {

            this.actual = actual;



            if (expected == null)

                throw new ArgumentException("Cannot compare using a null reference", "expected");



            if (actual == null)

                throw new ArgumentException("Cannot compare to null reference", "actual");



            int icomp = comparer.Compare(expected, actual);



            return icomp < 0 && gtOK || icomp == 0 && eqOK || icomp > 0 && ltOK;

        }



        /// <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)

        {

            writer.WritePredicate(predicate);

            writer.WriteExpectedValue(expected);

        }



        /// <summary>

        /// Modifies the constraint to use an IComparer and returns self

        /// </summary>

        public ComparisonConstraint Using(IComparer comparer)

        {

            this.comparer = ComparisonAdapter.For(comparer);

            return this;

        }



#if NET_2_0

        /// <summary>

        /// Modifies the constraint to use an IComparer&lt;T&gt; and returns self

        /// </summary>

        public ComparisonConstraint Using<T>(IComparer<T> comparer)

        {

            this.comparer = ComparisonAdapter.For(comparer);

            return this;

        }



        /// <summary>

        /// Modifies the constraint to use a Comparison&lt;T&gt; and returns self

        /// </summary>

        public ComparisonConstraint Using<T>(Comparison<T> comparer)

        {

            this.comparer = ComparisonAdapter.For(comparer);

            return this;

        }

#endif

    }



    /// <summary>

    /// Tests whether a value is greater than the value supplied to its constructor

    /// </summary>

    public class GreaterThanConstraint : ComparisonConstraint

    {

        /// <summary>

        /// Initializes a new instance of the <see cref="T:GreaterThanConstraint"/> class.

        /// </summary>

        /// <param name="expected">The expected value.</param>

        public GreaterThanConstraint(object expected) : base(expected, false, false, true, "greater than") { }

    }



    /// <summary>

    /// Tests whether a value is greater than or equal to the value supplied to its constructor

    /// </summary>

    public class GreaterThanOrEqualConstraint : ComparisonConstraint

    {

        /// <summary>

        /// Initializes a new instance of the <see cref="T:GreaterThanOrEqualConstraint"/> class.

        /// </summary>

        /// <param name="expected">The expected value.</param>

        public GreaterThanOrEqualConstraint(object expected) : base(expected, false, true, true, "greater than or equal to") { }

    }



    /// <summary>

    /// Tests whether a value is less than the value supplied to its constructor

    /// </summary>

    public class LessThanConstraint : ComparisonConstraint

    {

        /// <summary>

        /// Initializes a new instance of the <see cref="T:LessThanConstraint"/> class.

        /// </summary>

        /// <param name="expected">The expected value.</param>

        public LessThanConstraint(object expected) : base(expected, true, false, false, "less than") { }

    }



    /// <summary>

    /// Tests whether a value is less than or equal to the value supplied to its constructor

    /// </summary>

    public class LessThanOrEqualConstraint : ComparisonConstraint

    {

        /// <summary>

        /// Initializes a new instance of the <see cref="T:LessThanOrEqualConstraint"/> class.

        /// </summary>

        /// <param name="expected">The expected value.</param>

        public LessThanOrEqualConstraint(object expected) : base(expected, true, true, false, "less than or equal to") { }

    }

}