using System;
using System.Collections.Generic;

namespace Chernobyl.Reflection
{
    /// <summary>
    /// A class that holds utility methods specifically for reflection.
    /// </summary>
    public static class Utility
    {
        /// <summary>
        /// Get all of the base types and interfaces that the passed in 
        /// <see cref="Type"/> inherits from. Note that this method does not 
        /// return the types in any specific order.
        /// </summary>
        /// <typeparam name="T">The type whose base types and interfaces are to 
        /// be retrieved for.</typeparam>
        /// <returns>A collection of types the passed in <typeparamref name="T"/> 
        /// inherits from. If the <see cref="Type"/> passed in is an 
        /// <see cref="Object"/>, the type <see cref="Object"/> will be returned.</returns>
        public static IEnumerable<Type> GetBaseTypes<T>()
        {
            return GetBaseTypes(typeof (T));
        }

        /// <summary>
        /// Get all of the base types and interfaces that the passed in 
        /// <see cref="Type"/> inherits from. Note that this method does not 
        /// return the types in any specific order.
        /// </summary>
        /// <param name="type">The <see cref="Type"/> whose base types and 
        /// interfaces are to be retrieved for.</param>
        /// <returns>A collection of types the passed in <paramref name="type"/> 
        /// inherits from. If the <see cref="Type"/> passed in is an 
        /// <see cref="Object"/>, the type <see cref="Object"/> will be returned.</returns>
        public static IEnumerable<Type> GetBaseTypes(Type type)
        {
            // yield the interfaces
            foreach (Type @interface in type.GetInterfaces())
                yield return @interface;

            // yield the base types
            Type nextType = type.BaseType ?? type;
            do
            {
                yield return nextType;
                nextType = nextType.BaseType;
            } while (nextType != null);
        }
    }
}