using System;
using System.Collections.Generic;
using System.Reflection;
using Chernobyl.Reflection;

namespace Chernobyl.Attribution
{
    /// <summary>
    /// A type that is derived from by <see cref="Attribute" /> types that are
    /// capable of performing a task on the <see cref="ICustomAttributeProvider" />
    /// they are applied to.
    /// </summary>
    /// <typeparam name="TCustomAttributeProvider">The 
    /// <see cref="ICustomAttributeProvider"/> type that <see cref="Attribute" />
    /// is capable of processing.</typeparam>
    public interface IProcessAttribute<TCustomAttributeProvider>
        where TCustomAttributeProvider : ICustomAttributeProvider
    {
        /// <summary>
        /// Performs the task requested on the <see cref="ICustomAttributeProvider"/> 
        /// passed in.
        /// </summary>
        /// <param name="attributeProvider">The <see cref="ICustomAttributeProvider"/>  
        /// this <see cref="Attribute"/> was applied to and that is to be
        /// processed.</param>
        void Process(TCustomAttributeProvider attributeProvider);
    }

    /// <summary>
    /// Extensions and utility methods for the 
    /// <see cref="IProcessAttribute{TCustomAttributeProvider}"/>.
    /// </summary>
    public static class ProcessAttributeExtensions
    {
        /// <summary>
        /// Retrieves the <see cref="IProcessAttribute{TCustomAttributeProvider}"/>
        /// instances from the provided <see cref="ICustomAttributeProvider"/> 
        /// and then invokes 
        /// <see cref="IProcessAttribute{TCustomAttributeProvider}.Process(TCustomAttributeProvider)"/>
        /// on each one, providing the <paramref name="attributeProvider"/> as
        /// the argument.
        /// </summary>
        /// <typeparam name="TCustomAttributeProvider">The type of the 
        /// <see cref="ICustomAttributeProvider"/> that is to have it's
        /// <typeparamref name="TProcessAttribute"/> processed.</typeparam>
        /// <typeparam name="TProcessAttribute">The type of the <see cref="Attribute"/>
        /// and <see cref="IProcessAttribute{TCustomAttributeProvider}"/> to
        /// retrieve from the <paramref name="attributeProvider"/> for processing.</typeparam>
        /// <param name="attributeProvider">The instance to pull the 
        /// <see cref="Attribute"/> instance from for processing.</param>
        /// <param name="inherited">True if this instance should look up the 
        /// hierarchy chain of each method for <typeparamref name="TProcessAttribute"/>.</param>
        public static void Process<TCustomAttributeProvider, TProcessAttribute>(
            this TCustomAttributeProvider attributeProvider, bool inherited)
            where TCustomAttributeProvider : ICustomAttributeProvider
            where TProcessAttribute : IProcessAttribute<TCustomAttributeProvider>
        {
            foreach (TProcessAttribute processTypeAttribute in
                         attributeProvider.GetCustomAttributes<TProcessAttribute>(inherited))
                processTypeAttribute.Process(attributeProvider);
        }

        /// <summary>
        /// Performs the task requested on the <see cref="ICustomAttributeProvider" />
        /// passed in.
        /// </summary>
        /// <typeparam name="TCustomAttributeProvider">The type of the 
        /// <see cref="ICustomAttributeProvider"/> that is to be processed.</typeparam>
        /// <param name="attributeProviders">The <see cref="ICustomAttributeProvider" /> 
        /// instances that are to be processed.</param>
        /// <param name="inherited">True if this instance should look up the 
        /// hierarchy chain of each method for 
        /// <see cref="IProcessAttribute{TChildAttributeProvider}"/>.</param>
        public static void Process<TCustomAttributeProvider>(
            this IEnumerable<TCustomAttributeProvider> attributeProviders, bool inherited)
            where TCustomAttributeProvider : ICustomAttributeProvider
        {
            foreach (TCustomAttributeProvider provider in attributeProviders)
                provider.Process<TCustomAttributeProvider, IProcessAttribute<TCustomAttributeProvider>>(inherited);
        }
    }
}