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Stanford CoreNLP provides a set of natural language analysis tools which can take raw English language text input and give the base forms of words, their parts of speech, whether they are names of companies, people, etc., normalize dates, times, and numeric quantities, mark up the structure of sentences in terms of phrases and word dependencies, and indicate which noun phrases refer to the same entities. It provides the foundational building blocks for higher level text understanding applications.

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package edu.stanford.nlp.trees.tregex.tsurgeon;

import java.util.List;
import java.util.Map;

import edu.stanford.nlp.trees.Tree;
import edu.stanford.nlp.trees.tregex.TregexMatcher;
import edu.stanford.nlp.util.Generics;

/**
 * Given the start and end children of a particular node, takes all
 * children between start and end (including the endpoints) and
 * combines them in a new node with the given label.
 *
 * @author John Bauer
 */
public class CreateSubtreeNode extends TsurgeonPattern {
  private AuxiliaryTree auxTree;

  public CreateSubtreeNode(TsurgeonPattern start, AuxiliaryTree tree) {
    this(start, null, tree);
  }

  public CreateSubtreeNode(TsurgeonPattern start, TsurgeonPattern end, AuxiliaryTree tree) {
    super("combineSubtrees",
      (end == null) ? new TsurgeonPattern[] { start } : new TsurgeonPattern[] { start, end });

    this.auxTree = tree;
    findFoot();
  }

  /**
   * We want to support a command syntax where a simple node label can
   * be given (i.e., without using a tree literal).
   *
   * Check if this syntax is being used, and simulate a foot if so.
   */
  private void findFoot() {
    if (auxTree.foot == null) {
      if (!auxTree.tree.isLeaf())
        throw new TsurgeonParseException("No foot node found for " + auxTree);

      // Pretend this leaf is a foot node
      auxTree.foot = auxTree.tree;
    }
  }

  @Override
  public TsurgeonMatcher matcher(Map newNodeNames, CoindexationGenerator coindexer) {
    return new Matcher(newNodeNames, coindexer);
  }

  private class Matcher extends TsurgeonMatcher {
    public Matcher(Map newNodeNames, CoindexationGenerator coindexer) {
      super(CreateSubtreeNode.this, newNodeNames, coindexer);
    }

    /**
     * Combines all nodes between start and end into one subtree, then
     * replaces those nodes with the new subtree in the corresponding
     * location under parent
     */
    @Override
    public Tree evaluate(Tree tree, TregexMatcher tregex) {
      Tree startChild = childMatcher[0].evaluate(tree, tregex);
      Tree endChild = (childMatcher.length == 2) ? childMatcher[1].evaluate(tree, tregex) : startChild;

      Tree parent = startChild.parent(tree);

      // sanity check
      if (parent != endChild.parent(tree)) {
        throw new TsurgeonRuntimeException("Parents did not match for trees when applied to " + this);
      }
      
      AuxiliaryTree treeCopy = auxTree.copy(this, tree.treeFactory(), tree.label().labelFactory());

      // Collect all the children of the parent of the node we care
      // about.  If the child is one of the nodes we care about, or
      // between those two nodes, we add it to a list of inner children.
      // When we reach the second endpoint, we turn that list of inner
      // children into a new node using the newly created label.  All
      // other children are kept in an outer list, with the new node
      // added at the appropriate location.
      List children = Generics.newArrayList();
      List innerChildren = Generics.newArrayList();
      boolean insideSpan = false;
      for (Tree child : parent.children()) {
        if (child == startChild || child == endChild) {
          if (!insideSpan && startChild != endChild) {
            insideSpan = true;
            innerChildren.add(child);
          } else {
            insideSpan = false;
            innerChildren.add(child);

            // All children have been collected; place these beneath the foot of the auxiliary tree
            treeCopy.foot.setChildren(innerChildren);
            children.add(treeCopy.tree);
          }
        } else if (insideSpan) {
          innerChildren.add(child);
        } else {
          children.add(child);
        }
      }

      parent.setChildren(children);

      return tree;
    }
  }
}