// ****************************************************************
// 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.Reflection;

namespace NUnit.Framework.Constraints
{
    /// <summary>
    /// PropertyExistsConstraint tests that a named property
    /// exists on the object provided through Match.
    /// 
    /// Originally, PropertyConstraint provided this feature
    /// in addition to making optional tests on the vaue
    /// of the property. The two constraints are now separate.
    /// </summary>
    public class PropertyExistsConstraint : Constraint
    {
        private readonly string name;

        Type actualType;

        /// <summary>
        /// Initializes a new instance of the <see cref="T:PropertyExistConstraint"/> class.
        /// </summary>
        /// <param name="name">The name of the property.</param>
        public PropertyExistsConstraint(string name)
            : base(name)
        {
            this.name = name;
        }

        /// <summary>
        /// Test whether the property exists for a given object
        /// </summary>
        /// <param name="actual">The object to be tested</param>
        /// <returns>True for success, false for failure</returns>
        public override bool Matches(object actual)
        {
            this.actual = actual;

            Guard.ArgumentNotNull(actual, "actual");

            this.actualType = actual as Type;
            if (actualType == null)
                actualType = actual.GetType();

            PropertyInfo property = actualType.GetProperty(name,
                BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetProperty);

            return property != null;
        }

        /// <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.Write("property " + name);
        }

        /// <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)
        {
            writer.WriteActualValue(actualType);
        }

        /// <summary>
        /// Returns the string representation of the constraint.
        /// </summary>
        /// <returns></returns>
        protected override string GetStringRepresentation()
        {
            return string.Format("<propertyexists {0}>", name);
        }
    }
}
