/*
 * [The "BSD license"]
 * Copyright (c) 2013 Terence Parr
 * Copyright (c) 2013 Sam Harwell
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.antlr.v4.runtime.tree.pattern;

import org.antlr.v4.runtime.misc.MultiMap;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;
import org.antlr.v4.runtime.tree.ParseTree;

import java.util.Collections;
import java.util.List;

/**
 * Represents the result of matching a {@link ParseTree} against a tree pattern.
 */
public class ParseTreeMatch {
	/**
	 * This is the backing field for {@link #getTree()}.
	 */
	private final ParseTree tree;

	/**
	 * This is the backing field for {@link #getPattern()}.
	 */
	private final ParseTreePattern pattern;

	/**
	 * This is the backing field for {@link #getLabels()}.
	 */
	private final MultiMap<String, ParseTree> labels;

	/**
	 * This is the backing field for {@link #getMismatchedNode()}.
	 */
	private final ParseTree mismatchedNode;

	/**
	 * Constructs a new instance of {@link ParseTreeMatch} from the specified
	 * parse tree and pattern.
	 *
	 * @param tree The parse tree to match against the pattern.
	 * @param pattern The parse tree pattern.
	 * @param labels A mapping from label names to collections of
	 * {@link ParseTree} objects located by the tree pattern matching process.
	 * @param mismatchedNode The first node which failed to match the tree
	 * pattern during the matching process.
	 *
	 * @exception IllegalArgumentException if {@code tree} is {@code null}
	 * @exception IllegalArgumentException if {@code pattern} is {@code null}
	 * @exception IllegalArgumentException if {@code labels} is {@code null}
	 */
	public ParseTreeMatch(@NotNull ParseTree tree, @NotNull ParseTreePattern pattern, @NotNull MultiMap<String, ParseTree> labels, @Nullable ParseTree mismatchedNode) {
		if (tree == null) {
			throw new IllegalArgumentException("tree cannot be null");
		}

		if (pattern == null) {
			throw new IllegalArgumentException("pattern cannot be null");
		}

		if (labels == null) {
			throw new IllegalArgumentException("labels cannot be null");
		}

		this.tree = tree;
		this.pattern = pattern;
		this.labels = labels;
		this.mismatchedNode = mismatchedNode;
	}

	/**
	 * Get the last node associated with a specific {@code label}.
	 * <p/>
	 * For example, for pattern {@code <id:ID>}, {@code get("id")} returns the
	 * node matched for that {@code ID}. If more than one node
	 * matched the specified label, only the last is returned. If there is
	 * no node associated with the label, this returns {@code null}.
	 * <p/>
	 * Pattern tags like {@code <ID>} and {@code <expr>} without labels are
	 * considered to be labeled with {@code ID} and {@code expr}, respectively.
	 *
	 * @param label The label to check.
	 *
	 * @return The last {@link ParseTree} to match a tag with the specified
	 * label, or {@code null} if no parse tree matched a tag with the label.
	 */
	@Nullable
	public ParseTree get(String label) {
		List<ParseTree> parseTrees = labels.get(label);
		if ( parseTrees==null ) {
			return null;
		}

		return parseTrees.get( parseTrees.size()-1 ); // return last if multiple
	}

	/**
	 * Return all nodes matching a rule or token tag with the specified label.
	 * <p/>
	 * If the {@code label} is the name of a parser rule or token in the
	 * grammar, the resulting list will contain both the parse trees matching
	 * rule or tags explicitly labeled with the label and the complete set of
	 * parse trees matching the labeled and unlabeled tags in the pattern for
	 * the parser rule or token. For example, if {@code label} is {@code "foo"},
	 * the result will contain <em>all</em> of the following.
	 *
	 * <ul>
	 * <li>Parse tree nodes matching tags of the form {@code <foo:anyRuleName>} and
	 * {@code <foo:AnyTokenName>}.</li>
	 * <li>Parse tree nodes matching tags of the form {@code <anyLabel:foo>}.</li>
	 * <li>Parse tree nodes matching tags of the form {@code <foo>}.</li>
	 * </ul>
	 *
	 * @param label The label.
	 *
	 * @return A collection of all {@link ParseTree} nodes matching tags with
	 * the specified {@code label}. If no nodes matched the label, an empty list
	 * is returned.
	 */
	@NotNull
	public List<ParseTree> getAll(@NotNull String label) {
		List<ParseTree> nodes = labels.get(label);
		if ( nodes==null ) {
			return Collections.emptyList();
		}

		return nodes;
	}

	/**
	 * Return a mapping from label &rarr; [list of nodes].
	 * <p/>
	 * The map includes special entries corresponding to the names of rules and
	 * tokens referenced in tags in the original pattern. For additional
	 * information, see the description of {@link #getAll(String)}.
	 *
	 * @return A mapping from labels to parse tree nodes. If the parse tree
	 * pattern did not contain any rule or token tags, this map will be empty.
	 */
	@NotNull
	public MultiMap<String, ParseTree> getLabels() {
		return labels;
	}

	/**
	 * Get the node at which we first detected a mismatch.
	 *
	 * @return the node at which we first detected a mismatch, or {@code null}
	 * if the match was successful.
	 */
	@Nullable
	public ParseTree getMismatchedNode() {
		return mismatchedNode;
	}

	/**
	 * Gets a value indicating whether the match operation succeeded.
	 *
	 * @return {@code true} if the match operation succeeded; otherwise,
	 * {@code false}.
	 */
	public boolean succeeded() {
		return mismatchedNode == null;
	}

	/**
	 * Get the tree pattern we are matching against.
	 *
	 * @return The tree pattern we are matching against.
	 */
	@NotNull
	public ParseTreePattern getPattern() {
		return pattern;
	}

	/**
	 * Get the parse tree we are trying to match to a pattern.
	 *
	 * @return The {@link ParseTree} we are trying to match to a pattern.
	 */
	@NotNull
	public ParseTree getTree() {
		return tree;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String toString() {
		return String.format(
			"Match %s; found %d labels",
			succeeded() ? "succeeded" : "failed",
			getLabels().size());
	}
}

@@ -4429,32 +4429,56 @@
 arseTrees==null 
+%7C%7C parseTrees.size()==0 
 ) %7B%0A%09%09%09return nu

check for empty tree list.