// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Diagnostics;
using System.Linq;

using ICSharpCode.AvalonEdit.Document;

namespace ICSharpCode.AvalonEdit.Xml
{
	static class ExtensionMethods
	{
		// Copied from ICSharpCode.SharpDevelop.Dom.ExtensionMethods
		/// <summary>
		/// Converts a recursive data structure into a flat list.
		/// </summary>
		/// <param name="input">The root elements of the recursive data structure.</param>
		/// <param name="recursion">The function that gets the children of an element.</param>
		/// <returns>Iterator that enumerates the tree structure in preorder.</returns>
		public static IEnumerable<T> Flatten<T>(this IEnumerable<T> input, Func<T, IEnumerable<T>> recursion)
		{
			Stack<IEnumerator<T>> stack = new Stack<IEnumerator<T>>();
			try {
				stack.Push(input.GetEnumerator());
				while (stack.Count > 0) {
					while (stack.Peek().MoveNext()) {
						T element = stack.Peek().Current;
						yield return element;
						IEnumerable<T> children = recursion(element);
						if (children != null) {
							stack.Push(children.GetEnumerator());
						}
					}
					stack.Pop().Dispose();
				}
			} finally {
				while (stack.Count > 0) {
					stack.Pop().Dispose();
				}
			}
		}
	}
}
