TemplateProviderBase.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Markup;

namespace SiliconStudio.Presentation.View
{
    /// <summary>
    /// An abstract implementation of the <see cref="ITemplateProvider"/> interface.
    /// </summary>
    [ContentProperty("Template")]
    public abstract class TemplateProviderBase : DependencyObject, ITemplateProvider
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="TemplateProviderBase"/> class.
        /// </summary>
        protected TemplateProviderBase()
        {
            OverriddenProviderNames = new List<string>();
            OverrideRule = OverrideRule.Some;
        }

        /// <inheritdoc/>
        public abstract string Name { get; }

        /// <inheritdoc/>
        public DataTemplate Template { get; set; }

        /// <inheritdoc/>
        public OverrideRule OverrideRule { get; set; }

        /// <inheritdoc/>
        public List<string> OverriddenProviderNames { get; private set; }

        /// <inheritdoc/>
        public abstract bool Match(object obj);

        public int CompareTo(ITemplateProvider other)
        {
            if (other == null) throw new ArgumentNullException("other");

            // Both overrides all: undeterminated.
            if (OverrideRule == OverrideRule.All && other.OverrideRule == OverrideRule.All)
                return 0;

            // This overrides all: this is first.
            if (OverrideRule == OverrideRule.All)
                return -1;

            // Other overrides all: other is first.
            if (other.OverrideRule == OverrideRule.All)
                return 1;

            // Both overrides none: undeterminated.
            if (OverrideRule == OverrideRule.None && other.OverrideRule == OverrideRule.None)
                return 0;

            // This overrides none: other is first.
            if (OverrideRule == OverrideRule.None)
                return 1;

            // Other overrides none: this is first.
            if (other.OverrideRule == OverrideRule.None)
                return -1;

            // Both overrides most: undeterminated.
            if (OverrideRule == OverrideRule.Most && other.OverrideRule == OverrideRule.Most)
                return 0;
            
            // From this point, at least one have the "Some" rule and at most one have the "Most" rule.
            bool thisOverrides = OverriddenProviderNames.Contains(other.Name);
            bool otherOverrides = other.OverriddenProviderNames.Contains(Name);

            // Both overrides each other: undeterminated
            if (thisOverrides && otherOverrides)
                return 0;

            // None overrides the other...
            if (!thisOverrides && !otherOverrides)
            {
                // ...but this overrides most: this is first.
                if (OverrideRule == OverrideRule.Most)
                    return -1;

                // ...but other overrides most: other is first.
                if (other.OverrideRule == OverrideRule.Most)
                    return 1;
            }
            // Result: whichever overrides the other is first.
            return thisOverrides ? -1 : 1;
        }
    }
}