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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Collections.Generic;
namespace ICSharpCode.NRefactory.Utils
{
/// <summary>
/// Static helper methods for traversing trees.
/// </summary>
public static class TreeTraversal
{
/// <summary>
/// Converts a tree data structure into a flat list by traversing it in pre-order.
/// </summary>
/// <param name="root">The root element of the tree.</param>
/// <param name="recursion">The function that gets the children of an element.</param>
/// <returns>Iterator that enumerates the tree structure in pre-order.</returns>
public static IEnumerable<T> PreOrder<T>(T root, Func<T, IEnumerable<T>> recursion)
{
return PreOrder(new T[] { root }, recursion);
}
/// <summary>
/// Converts a tree data structure into a flat list by traversing it in pre-order.
/// </summary>
/// <param name="input">The root elements of the forest.</param>
/// <param name="recursion">The function that gets the children of an element.</param>
/// <returns>Iterator that enumerates the tree structure in pre-order.</returns>
public static IEnumerable<T> PreOrder<T>(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();
}
}
}
/// <summary>
/// Converts a tree data structure into a flat list by traversing it in post-order.
/// </summary>
/// <param name="root">The root element of the tree.</param>
/// <param name="recursion">The function that gets the children of an element.</param>
/// <returns>Iterator that enumerates the tree structure in post-order.</returns>
public static IEnumerable<T> PostOrder<T>(T root, Func<T, IEnumerable<T>> recursion)
{
return PostOrder(new T[] { root }, recursion);
}
/// <summary>
/// Converts a tree data structure into a flat list by traversing it in post-order.
/// </summary>
/// <param name="input">The root elements of the forest.</param>
/// <param name="recursion">The function that gets the children of an element.</param>
/// <returns>Iterator that enumerates the tree structure in post-order.</returns>
public static IEnumerable<T> PostOrder<T>(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;
IEnumerable<T> children = recursion(element);
if (children != null) {
stack.Push(children.GetEnumerator());
} else {
yield return element;
}
}
stack.Pop().Dispose();
if (stack.Count > 0)
yield return stack.Peek().Current;
}
} finally {
while (stack.Count > 0) {
stack.Pop().Dispose();
}
}
}
}
}
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