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ElementTraversal.scala
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ElementTraversal.scala
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/*
* Copyright 2012-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package laika.ast
import scala.collection.mutable.ListBuffer
/** Provides means to traverse and select elements of a document tree.
* This trait can get mixed in by any element node, not just the root Document class,
* therefore providing traversal for any kind of sub-tree, too.
*
* @author Jens Halm
*/
trait ElementTraversal { this: Element =>
/** Invokes the specified function for each child of this element
* container, including children of children, and this element itself,
* in depth-first traversal.
*/
def foreach(f: Element => Unit): Unit = {
def foreachInElement(element: Element, f: Element => Unit): Unit = {
foreachInIterable(element.productIterator.toSeq, f)
f(element)
}
def foreachInIterable(t: Iterable[_], f: Element => Unit): Unit = {
t.foreach {
case e: Element => foreachInElement(e, f)
case t: Iterable[_] => foreachInIterable(t, f)
case _ => ()
}
}
foreachInElement(this, f)
}
/** Selects all elements satisfying the specified predicate, collecting
* in depth-first traversal, including this element itself.
*/
def select(p: Element => Boolean): List[Element] = {
val buffer = new ListBuffer[Element]
foreach { e =>
if (p(e)) buffer += e
}
buffer.toList
}
/** Collects elements by applying the partial function to all elements
* it is defined for, in depth-first traversal, including this element
* itself.
*/
def collect[B](pf: PartialFunction[Element, B]): List[B] = {
val buffer = new ListBuffer[B]
foreach { e =>
if (pf.isDefinedAt(e)) buffer += pf(e)
}
buffer.toList
}
}