source: josm/src/org/openstreetmap/josm/io/IncompleteDownloader.java@ 219

package org.openstreetmap.josm.io;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.util.Collection;
import java.util.ArrayList;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.osm.DataSet;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.Segment;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.data.osm.visitor.MergeVisitor;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

import javax.swing.JOptionPane;
import org.openstreetmap.josm.command.ChangeCommand;
import org.openstreetmap.josm.command.Command;
import org.openstreetmap.josm.command.SequenceCommand;

import uk.co.wilson.xml.MinML2;

/**
 * Capable of downloading ways without having to fully parse their segments.
 *
 * @author Imi
 */
public class IncompleteDownloader extends OsmServerReader {

        /**
         * The new downloaded data will be inserted here.
         */
        public final DataSet data = new DataSet();

        /**
         * The list of incomplete Ways to download. The ways will be filled and are complete after download.
         */
        private final Collection<Way> toDownload;
        private MergeVisitor merger = new MergeVisitor(data);

        public IncompleteDownloader(Collection<Way> toDownload) {
                this.toDownload = toDownload;
        }

        public void parse() throws SAXException, IOException {
                Main.pleaseWaitDlg.currentAction.setText(tr("Downloading incomplete ways..."));
                Main.pleaseWaitDlg.progress.setMaximum(toDownload.size());
                Main.pleaseWaitDlg.progress.setValue(0);
                ArrayList<Command> cmds = new ArrayList<Command>();
                int i = 0;
                try {
                        for (Way w : toDownload) {
                                // if some of the way's segments fail to download and the user
                                // decides to delete them, the download method will return an
                                // "edit way" command.
                                Command cmd = download(w); 
                                if (cmd != null)
                                        cmds.add(cmd);
                                Main.pleaseWaitDlg.progress.setValue(++i);
                        }
                } catch (IOException e) {
                        if (!cancel)
                                throw e;
                } catch (SAXException e) {
                        throw e;
                } catch (Exception e) {
                        if (!cancel)
                                throw (e instanceof RuntimeException) ? (RuntimeException)e : new RuntimeException(e);
                }
                if (cmds.size() > 0)
                        Main.main.editLayer().add(new SequenceCommand(tr("Fix data errors"), cmds));
        }

        private static class SegmentParser extends MinML2 {
                public long from, to;
                @Override public void startElement(String ns, String lname, String qname, Attributes a) {
                        if (qname.equals("segment")) {
                                from = Long.parseLong(a.getValue("from"));
                                to = Long.parseLong(a.getValue("to"));
                        }
                }
        }

        /**
         * Downloads all missing segments from the given way. If segments fail do download, 
         * offers the user a chance to delete those segments from the way.
         * 
         * @param w way to complete
         * @return an "edit way" command if the user decided to delete segments
         * @throws IOException
         * @throws SAXException
         */
        private Command download(Way w) throws IOException, SAXException {
                // get all the segments
                Way newway = null;
                for (Segment s : w.segments) {
                        if (!s.incomplete)
                                continue;
                        BufferedReader segReader;
                        try {
                                segReader = new BufferedReader(new InputStreamReader(getInputStream("segment/"+s.id, null), "UTF-8"));
                        } catch (FileNotFoundException e) {
                                Object[] options = {"Delete", "Ignore", "Abort"};
                                int n = JOptionPane.showOptionDialog(Main.parent,
                                                tr("Segment {0} is deleted but part of Way {1}",s.id, w.id),
                                                tr("Data error"),
                                                JOptionPane.YES_NO_CANCEL_OPTION,
                                                JOptionPane.ERROR_MESSAGE,
                                                null, options, options[2]);
                                if (n == 0)
                                {
                                        if( newway == null )
                                                newway = new Way(w);
                                        newway.segments.remove(s);
                                }
                                else if (n == 2)
                                {
                                        e.printStackTrace();
                                        throw new IOException(tr("Data error: Segment {0} is deleted but part of Way {1}", s.id, w.id));
                                }
                                continue;
                        }
                        StringBuilder segBuilder = new StringBuilder();
                        for (String line = segReader.readLine(); line != null; line = segReader.readLine())
                                segBuilder.append(line+"\n");
                        SegmentParser segmentParser = new SegmentParser();
                        segmentParser.parse(new StringReader(segBuilder.toString()));
                        if (segmentParser.from == 0 || segmentParser.to == 0)
                                throw new SAXException("Invalid segment response.");
                        if (!hasNode(segmentParser.from))
                                readNode(segmentParser.from, s.id).visit(merger);
                        if (!hasNode(segmentParser.to))
                                readNode(segmentParser.to, s.id).visit(merger);
                        readSegment(segBuilder.toString()).visit(merger);
                }
                if( newway != null )
                        return new ChangeCommand(w, newway);
                return null;
        }

        private boolean hasNode(long id) {
            for (Node n : Main.ds.nodes)
                if (n.id == id)
                        return true;
            return false;
    }

        private Segment readSegment(String seg) throws SAXException, IOException {
        return OsmReader.parseDataSet(new ByteArrayInputStream(seg.getBytes("UTF-8")), data, null).segments.iterator().next();
    }

        private Node readNode(long id, long segId) throws SAXException, IOException {
                try {
                return OsmReader.parseDataSet(getInputStream("node/"+id, null), data, null).nodes.iterator().next();
        } catch (FileNotFoundException e) {
                e.printStackTrace();
                throw new IOException(tr("Data error: Node {0} is deleted but part of Segment {1}", id, segId));
        }
    }
}