// ****************************************************************
// 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.IO;
using System.Collections;
#if CLR_2_0 || CLR_4_0
using System.Collections.Generic;
#endif

namespace NUnit.Framework.Constraints
{
    /// <summary>
    /// EqualConstraint is able to compare an actual value with the
    /// expected value provided in its constructor. Two objects are 
    /// considered equal if both are null, or if both have the same 
    /// value. NUnit has special semantics for some object types.
    /// </summary>
    public class EqualConstraint : Constraint
    {
        #region Static and Instance Fields

		private readonly object expected;

        private Tolerance tolerance = Tolerance.Empty;

        /// <summary>
        /// If true, strings in error messages will be clipped
        /// </summary>
        private bool clipStrings = true;

        /// <summary>
        /// NUnitEqualityComparer used to test equality.
        /// </summary>
        private NUnitEqualityComparer comparer = new NUnitEqualityComparer();

        #region Message Strings
        private static readonly string StringsDiffer_1 =
			"String lengths are both {0}. Strings differ at index {1}.";
		private static readonly string StringsDiffer_2 =
			"Expected string length {0} but was {1}. Strings differ at index {2}.";
		private static readonly string StreamsDiffer_1 =
			"Stream lengths are both {0}. Streams differ at offset {1}.";
		private static readonly string StreamsDiffer_2 =
			"Expected Stream length {0} but was {1}.";// Streams differ at offset {2}.";
		private static readonly string CollectionType_1 =
			"Expected and actual are both {0}";
		private static readonly string CollectionType_2 =
			"Expected is {0}, actual is {1}";
		private static readonly string ValuesDiffer_1 =
			"Values differ at index {0}";
		private static readonly string ValuesDiffer_2 =
			"Values differ at expected index {0}, actual index {1}";
		
        #endregion

        #endregion

        #region Constructor
        /// <summary>
        /// Initializes a new instance of the <see cref="EqualConstraint"/> class.
        /// </summary>
        /// <param name="expected">The expected value.</param>
        public EqualConstraint(object expected) : base(expected)
        {
            this.expected = expected;
        }
        #endregion

        #region Constraint Modifiers
        /// <summary>
        /// Flag the constraint to ignore case and return self.
        /// </summary>
        public EqualConstraint IgnoreCase
        {
            get
            {
                comparer.IgnoreCase = true;
                return this;
            }
        }

        /// <summary>
        /// Flag the constraint to suppress string clipping 
        /// and return self.
        /// </summary>
        public EqualConstraint NoClip
        {
            get
            {
                clipStrings = false;
                return this;
            }
        }

        /// <summary>
        /// Flag the constraint to compare arrays as collections
        /// and return self.
        /// </summary>
        public EqualConstraint AsCollection
        {
            get
            {
                comparer.CompareAsCollection = true;
                return this;
            }
        }

        /// <summary>
        /// Flag the constraint to use a tolerance when determining equality.
        /// </summary>
        /// <param name="amount">Tolerance value to be used</param>
        /// <returns>Self.</returns>
        public EqualConstraint Within(object amount)
        {
            if (!tolerance.IsEmpty)
                throw new InvalidOperationException("Within modifier may appear only once in a constraint expression");

            tolerance = new Tolerance(amount);
            return this;
        }

        /// <summary>
        /// Switches the .Within() modifier to interpret its tolerance as
        /// a distance in representable values (see remarks).
        /// </summary>
        /// <returns>Self.</returns>
        /// <remarks>
        /// Ulp stands for "unit in the last place" and describes the minimum
        /// amount a given value can change. For any integers, an ulp is 1 whole
        /// digit. For floating point values, the accuracy of which is better
        /// for smaller numbers and worse for larger numbers, an ulp depends
        /// on the size of the number. Using ulps for comparison of floating
        /// point results instead of fixed tolerances is safer because it will
        /// automatically compensate for the added inaccuracy of larger numbers.
        /// </remarks>
        public EqualConstraint Ulps
        {
            get
            {
                tolerance = tolerance.Ulps;
                return this;
            }
        }

        /// <summary>
        /// Switches the .Within() modifier to interpret its tolerance as
        /// a percentage that the actual values is allowed to deviate from
        /// the expected value.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Percent
        {
            get
            {
                tolerance = tolerance.Percent;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in days.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Days
        {
            get
            {
                tolerance = tolerance.Days;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in hours.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Hours
        {
            get
            {
                tolerance = tolerance.Hours;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in minutes.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Minutes
        {
            get
            {
                tolerance = tolerance.Minutes;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in seconds.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Seconds
        {
            get
            {
                tolerance = tolerance.Seconds;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in milliseconds.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Milliseconds
        {
            get
            {
                tolerance = tolerance.Milliseconds;
                return this;
            }
        }

        /// <summary>
        /// Causes the tolerance to be interpreted as a TimeSpan in clock ticks.
        /// </summary>
        /// <returns>Self</returns>
        public EqualConstraint Ticks
        {
            get
            {
                tolerance = tolerance.Ticks;
                return this;
            }
        }

        /// <summary>
        /// Flag the constraint to use the supplied IComparer object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        [Obsolete("Replace with 'Using'")]
        public EqualConstraint Comparer(IComparer comparer)
        {
            return Using(comparer);
        }

        /// <summary>
        /// Flag the constraint to use the supplied IComparer object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        public EqualConstraint Using(IComparer comparer)
        {
            this.comparer.ExternalComparers.Add(EqualityAdapter.For(comparer));
            return this;
        }

#if CLR_2_0 || CLR_4_0
        /// <summary>
        /// Flag the constraint to use the supplied IComparer object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        public EqualConstraint Using<T>(IComparer<T> comparer)
        {
            this.comparer.ExternalComparers.Add(EqualityAdapter.For( comparer ));
            return this;
        }

                /// <summary>
        /// Flag the constraint to use the supplied Comparison object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        public EqualConstraint Using<T>(Comparison<T> comparer)
        {
            this.comparer.ExternalComparers.Add(EqualityAdapter.For( comparer ));
            return this;
        }

        /// <summary>
        /// Flag the constraint to use the supplied IEqualityComparer object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        public EqualConstraint Using(IEqualityComparer comparer)
        {
            this.comparer.ExternalComparers.Add(EqualityAdapter.For(comparer));
            return this;
        }

        /// <summary>
        /// Flag the constraint to use the supplied IEqualityComparer object.
        /// </summary>
        /// <param name="comparer">The IComparer object to use.</param>
        /// <returns>Self.</returns>
        public EqualConstraint Using<T>(IEqualityComparer<T> comparer)
        {
            this.comparer.ExternalComparers.Add(EqualityAdapter.For(comparer));
            return this;
        }
#endif
        #endregion

        #region Public Methods
        /// <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;

            return comparer.AreEqual(expected, actual, ref tolerance);
        }

        /// <summary>
        /// Write a failure message. Overridden to provide custom 
        /// failure messages for EqualConstraint.
        /// </summary>
        /// <param name="writer">The MessageWriter to write to</param>
        public override void WriteMessageTo(MessageWriter writer)
        {
            DisplayDifferences(writer, expected, actual, 0);
        }


        /// <summary>
        /// Write description of this constraint
        /// </summary>
        /// <param name="writer">The MessageWriter to write to</param>
        public override void WriteDescriptionTo(MessageWriter writer)
        {
			writer.WriteExpectedValue( expected );

            if (tolerance != null && !tolerance.IsEmpty)
			{
				writer.WriteConnector("+/-");
                writer.WriteExpectedValue(tolerance.Value);
                if (tolerance.Mode != ToleranceMode.Linear)
                    writer.Write(" {0}", tolerance.Mode);
			}

			if ( comparer.IgnoreCase )
				writer.WriteModifier("ignoring case");
        }

        private void DisplayDifferences(MessageWriter writer, object expected, object actual, int depth)
        {
            if (expected is string && actual is string)
                DisplayStringDifferences(writer, (string)expected, (string)actual);
            else if (expected is ICollection && actual is ICollection)
                DisplayCollectionDifferences(writer, (ICollection)expected, (ICollection)actual, depth);
            else if (expected is IEnumerable && actual is IEnumerable)
                DisplayEnumerableDifferences(writer, (IEnumerable)expected, (IEnumerable)actual, depth);
            else if (expected is Stream && actual is Stream)
				DisplayStreamDifferences(writer, (Stream)expected, (Stream)actual, depth);
            else if (tolerance != null)
                writer.DisplayDifferences(expected, actual, tolerance);
            else
                writer.DisplayDifferences(expected, actual);
        }
        #endregion

        #region DisplayStringDifferences
        private void DisplayStringDifferences(MessageWriter writer, string expected, string actual)
        {
            int mismatch = MsgUtils.FindMismatchPosition(expected, actual, 0, comparer.IgnoreCase);

            if (expected.Length == actual.Length)
				writer.WriteMessageLine(StringsDiffer_1, expected.Length, mismatch);
			else
				writer.WriteMessageLine(StringsDiffer_2, expected.Length, actual.Length, mismatch);

            writer.DisplayStringDifferences(expected, actual, mismatch, comparer.IgnoreCase, clipStrings);
        }
        #endregion

		#region DisplayStreamDifferences
		private void DisplayStreamDifferences(MessageWriter writer, Stream expected, Stream actual, int depth)
		{
			if ( expected.Length == actual.Length )
			{
				FailurePoint fp = (FailurePoint)comparer.FailurePoints[depth];
                long offset = fp.Position;
				writer.WriteMessageLine(StreamsDiffer_1, expected.Length, offset);
			}
			else
				writer.WriteMessageLine(StreamsDiffer_2, expected.Length, actual.Length);
		}
		#endregion

        #region DisplayCollectionDifferences
        /// <summary>
        /// Display the failure information for two collections that did not match.
        /// </summary>
        /// <param name="writer">The MessageWriter on which to display</param>
        /// <param name="expected">The expected collection.</param>
        /// <param name="actual">The actual collection</param>
        /// <param name="depth">The depth of this failure in a set of nested collections</param>
        private void DisplayCollectionDifferences(MessageWriter writer, ICollection expected, ICollection actual, int depth)
        {
            DisplayTypesAndSizes(writer, expected, actual, depth);

            if (comparer.FailurePoints.Count > depth)
            {
                FailurePoint failurePoint = (FailurePoint)comparer.FailurePoints[depth];

                DisplayFailurePoint(writer, expected, actual, failurePoint, depth);

                if (failurePoint.ExpectedHasData && failurePoint.ActualHasData)
                    DisplayDifferences(
                        writer,
                        failurePoint.ExpectedValue,
                        failurePoint.ActualValue,
                        ++depth);
                else if (failurePoint.ActualHasData)
                {
                    writer.Write("  Extra:    ");
                    writer.WriteCollectionElements(actual, failurePoint.Position, 3);
                }
                else
                {
                    writer.Write("  Missing:  ");
                    writer.WriteCollectionElements(expected, failurePoint.Position, 3);
                }
            }
        }

        /// <summary>
        /// Displays a single line showing the types and sizes of the expected
        /// and actual enumerations, collections or arrays. If both are identical, 
        /// the value is only shown once.
        /// </summary>
        /// <param name="writer">The MessageWriter on which to display</param>
        /// <param name="expected">The expected collection or array</param>
        /// <param name="actual">The actual collection or array</param>
        /// <param name="indent">The indentation level for the message line</param>
        private void DisplayTypesAndSizes(MessageWriter writer, IEnumerable expected, IEnumerable actual, int indent)
        {
            string sExpected = MsgUtils.GetTypeRepresentation(expected);
            if (expected is ICollection && !(expected is Array))
                sExpected += string.Format(" with {0} elements", ((ICollection)expected).Count);

            string sActual = MsgUtils.GetTypeRepresentation(actual);
            if (actual is ICollection && !(actual is Array))
                sActual += string.Format(" with {0} elements", ((ICollection)actual).Count);

            if (sExpected == sActual)
                writer.WriteMessageLine(indent, CollectionType_1, sExpected);
            else
                writer.WriteMessageLine(indent, CollectionType_2, sExpected, sActual);
        }

        /// <summary>
        /// Displays a single line showing the point in the expected and actual
        /// arrays at which the comparison failed. If the arrays have different
        /// structures or dimensions, both values are shown.
        /// </summary>
        /// <param name="writer">The MessageWriter on which to display</param>
        /// <param name="expected">The expected array</param>
        /// <param name="actual">The actual array</param>
        /// <param name="failurePoint">Index of the failure point in the underlying collections</param>
        /// <param name="indent">The indentation level for the message line</param>
        private void DisplayFailurePoint(MessageWriter writer, IEnumerable expected, IEnumerable actual, FailurePoint failurePoint, int indent)
        {
            Array expectedArray = expected as Array;
            Array actualArray = actual as Array;

            int expectedRank = expectedArray != null ? expectedArray.Rank : 1;
            int actualRank = actualArray != null ? actualArray.Rank : 1;

            bool useOneIndex = expectedRank == actualRank;

            if (expectedArray != null && actualArray != null)
                for (int r = 1; r < expectedRank && useOneIndex; r++)
                    if (expectedArray.GetLength(r) != actualArray.GetLength(r))
                        useOneIndex = false;

            int[] expectedIndices = MsgUtils.GetArrayIndicesFromCollectionIndex(expected, failurePoint.Position);
            if (useOneIndex)
            {
                writer.WriteMessageLine(indent, ValuesDiffer_1, MsgUtils.GetArrayIndicesAsString(expectedIndices));
            }
            else
            {
                int[] actualIndices = MsgUtils.GetArrayIndicesFromCollectionIndex(actual, failurePoint.Position);
                writer.WriteMessageLine(indent, ValuesDiffer_2,
                    MsgUtils.GetArrayIndicesAsString(expectedIndices), MsgUtils.GetArrayIndicesAsString(actualIndices));
            }
        }

        private static object GetValueFromCollection(ICollection collection, int index)
        {
            Array array = collection as Array;

            if (array != null && array.Rank > 1)
                return array.GetValue(MsgUtils.GetArrayIndicesFromCollectionIndex(array, index));

            if (collection is IList)
                return ((IList)collection)[index];

            foreach (object obj in collection)
                if (--index < 0)
                    return obj;

            return null;
        }
        #endregion

        #region DisplayEnumerableDifferences
        /// <summary>
        /// Display the failure information for two IEnumerables that did not match.
        /// </summary>
        /// <param name="writer">The MessageWriter on which to display</param>
        /// <param name="expected">The expected enumeration.</param>
        /// <param name="actual">The actual enumeration</param>
        /// <param name="depth">The depth of this failure in a set of nested collections</param>
        private void DisplayEnumerableDifferences(MessageWriter writer, IEnumerable expected, IEnumerable actual, int depth)
        {
            DisplayTypesAndSizes(writer, expected, actual, depth);

            if (comparer.FailurePoints.Count > depth)
            {
                FailurePoint failurePoint = (FailurePoint)comparer.FailurePoints[depth];

                DisplayFailurePoint(writer, expected, actual, failurePoint, depth);

                if (failurePoint.ExpectedHasData && failurePoint.ActualHasData)
                    DisplayDifferences(
                        writer,
                        failurePoint.ExpectedValue,
                        failurePoint.ActualValue,
                        ++depth);
                //else if (failurePoint.ActualHasData)
                //{
                //    writer.Write("  Extra:    ");
                //    writer.WriteCollectionElements(actual, failurePoint.Position, 3);
                //}
                //else
                //{
                //    writer.Write("  Missing:  ");
                //    writer.WriteCollectionElements(expected, failurePoint.Position, 3);
                //}
            }
        }

        #endregion
    }
}
