Catel - Part 4 of n: Unit testing with Catel

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using Catel.Windows.Properties;

namespace Catel.Windows.Data.Converters
{
    /// <summary>
    /// A base class that makes it easier to create values to visibility converters.
    /// </summary>
    public abstract class VisibilityConverterBase : IValueConverter
    {
        #region Constructor & destructor
        /// <summary>
        /// Initializes a new instance of the <see cref="VisibilityConverterBase"/> class.
        /// </summary>
        /// <param name="notVisibleVisibility">The <see cref="Visibility"/> state when not visibible should be returned.</param>
        /// <exception cref="ArgumentException">when <paramref name="notVisibleVisibility"/> is <see cref="Visibility.Visible"/>.</exception>
        protected VisibilityConverterBase(Visibility notVisibleVisibility)
        {
            if (notVisibleVisibility == Visibility.Visible)
            {
                throw new ArgumentException(Exceptions.VisibilityIsNotAllowedForConverter, "notVisibleVisibility");
            }

            NotVisibleVisibility = notVisibleVisibility;
        }
        #endregion

        #region Properties
        /// <summary>
        /// Gets the <see cref="Visibility"/> state when not visibible should be returned.
        /// </summary>
        /// <value>The not visible visibility.</value>
        public Visibility NotVisibleVisibility { get; private set; }
        #endregion

        #region Methods

        /// <summary>
        /// Determines what value this converter should return.
        /// </summary>
        /// <param name="value">The value produced by the binding source.</param>
        /// <param name="targetType">The type of the binding target property.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        /// <returns>
        /// 	<c>true</c> if the specified value is visible; otherwise, <c>false</c>.
        /// </returns>
        public abstract bool IsVisible(object value, Type targetType, object parameter, CultureInfo culture);

        /// <summary>
        /// Converts a value.
        /// </summary>
        /// <param name="value">The value produced by the binding source.</param>
        /// <param name="targetType">The type of the binding target property.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return IsVisible(value, targetType, parameter, culture) ? Visibility.Visible : NotVisibleVisibility;
        }

        /// <summary>
        /// Converts a value.
        /// </summary>
        /// <param name="value">The value that is produced by the binding target.</param>
        /// <param name="targetType">The type to convert to.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        /// <remarks>
        /// By default, this method does nothing.
        /// </remarks>
        public virtual object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return ConverterHelper.DoNothingBindingValue;
        }
        #endregion
    }

    /// <summary>
    /// A base class that makes it easier to create values to visibility converters.
    /// <para />
    /// This converter returns <see cref="Visibility.Collapsed"/> when a non-visible state should be returned.
    /// </summary>
    public abstract class CollapsingVisibilityConverterBase : VisibilityConverterBase
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="CollapsingVisibilityConverterBase"/> class.
        /// </summary>
        protected CollapsingVisibilityConverterBase()
            : base(Visibility.Collapsed) { }   
    }

#if !SILVERLIGHT
    /// <summary>
    /// A base class that makes it easier to create values to visibility converters.
    /// <para />
    /// This converter returns <see cref="Visibility.Hidden"/> when a non-visible state should be returned.
    /// </summary>
    public abstract class HidingVisibilityConverterBase : VisibilityConverterBase
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="HidingVisibilityConverterBase"/> class.
        /// </summary>
        protected HidingVisibilityConverterBase()
            : base(Visibility.Hidden) { }
    }
#endif
}