001package org.jsoup.select;
002
003import org.jsoup.nodes.Element;
004import org.jsoup.nodes.Node;
005
006import static org.jsoup.select.NodeFilter.FilterResult.CONTINUE;
007import static org.jsoup.select.NodeFilter.FilterResult.STOP;
008
009/**
010 * Collects a list of elements that match the supplied criteria.
011 *
012 * @author Jonathan Hedley
013 */
014public class Collector {
015
016    private Collector() {
017    }
018
019    /**
020     Build a list of elements, by visiting root and every descendant of root, and testing it against the evaluator.
021     @param eval Evaluator to test elements against
022     @param root root of tree to descend
023     @return list of matches; empty if none
024     */
025    public static Elements collect (Evaluator eval, Element root) {
026        Elements elements = new Elements();
027        NodeTraversor.traverse(new Accumulator(root, elements, eval), root);
028        return elements;
029    }
030
031    private static class Accumulator implements NodeVisitor {
032        private final Element root;
033        private final Elements elements;
034        private final Evaluator eval;
035
036        Accumulator(Element root, Elements elements, Evaluator eval) {
037            this.root = root;
038            this.elements = elements;
039            this.eval = eval;
040        }
041
042        public void head(Node node, int depth) {
043            if (node instanceof Element) {
044                Element el = (Element) node;
045                if (eval.matches(root, el))
046                    elements.add(el);
047            }
048        }
049
050        public void tail(Node node, int depth) {
051            // void
052        }
053    }
054
055    public static Element findFirst(Evaluator eval, Element root) {
056        FirstFinder finder = new FirstFinder(root, eval);
057        NodeTraversor.filter(finder, root);
058        return finder.match;
059    }
060
061    private static class FirstFinder implements NodeFilter {
062        private final Element root;
063        private Element match = null;
064        private final Evaluator eval;
065
066        FirstFinder(Element root, Evaluator eval) {
067            this.root = root;
068            this.eval = eval;
069        }
070
071        @Override
072        public FilterResult head(Node node, int depth) {
073            if (node instanceof Element) {
074                Element el = (Element) node;
075                if (eval.matches(root, el)) {
076                    match = el;
077                    return STOP;
078                }
079            }
080            return CONTINUE;
081        }
082
083        @Override
084        public FilterResult tail(Node node, int depth) {
085            return CONTINUE;
086        }
087    }
088
089}