001/*
002 * Copyright 2015 DuraSpace, Inc.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.fcrepo.migration.foxml;
017
018import java.io.File;
019import java.io.FileFilter;
020import java.io.FileNotFoundException;
021import java.util.ArrayList;
022import java.util.Arrays;
023import java.util.Iterator;
024import java.util.List;
025import java.util.Stack;
026
027import javax.xml.stream.XMLStreamException;
028
029import org.fcrepo.migration.FedoraObjectProcessor;
030
031/**
032 * A depth-first-search iteration over a tree of files that exposes them as FedoraObjectProcessors.
033 * Each file in the tree is expected to be a FOXML file.   This implementation likely minimizes
034 * memory usage for the expected organization of FOXML files on disk.
035 * @author mdurbin
036 */
037public class FoxmlDirectoryDFSIterator implements Iterator<FedoraObjectProcessor> {
038
039    private List<File> current;
040    private Stack<List<File>> stack;
041
042    private InternalIDResolver resolver;
043    private URLFetcher fetcher;
044
045    private String localFedoraServer;
046
047    private FileFilter fileFilter;
048
049    /**
050     * foxml directory DFS iterator.
051     * @param root the root file
052     * @param fetcher the fetcher
053     * @param localFedoraServer uri to local fedora server
054     * @param fileFilter a FileFilter that defined which files should be included
055     *        in this Iterator.
056     */
057    public FoxmlDirectoryDFSIterator(final File root, final URLFetcher fetcher, final String localFedoraServer,
058            final FileFilter fileFilter) {
059        stack = new Stack<List<File>>();
060        current = new ArrayList<File>(Arrays.asList(root.listFiles()));
061        this.fetcher = fetcher;
062        this.localFedoraServer = localFedoraServer;
063        this.fileFilter = fileFilter;
064    }
065
066    /**
067     * foxml directory DFS iterator with three parameters
068     * @param root the root file
069     * @param resolver the resolver
070     * @param fetcher the fetcher
071     * @param localFedoraServer the domain and port for the server that hosted the fedora objects in the format
072     *                          "localhost:8080".
073     * @param fileFilter a FileFilter that defined which files should be included
074     *        in this Iterator.
075     */
076    public FoxmlDirectoryDFSIterator(final File root, final InternalIDResolver resolver, final URLFetcher fetcher,
077                                     final String localFedoraServer, final FileFilter fileFilter) {
078        this(root, fetcher, localFedoraServer, fileFilter);
079        this.resolver = resolver;
080    }
081
082    private boolean advanceToNext() {
083        while (current.size() > 0 || stack.size() > 0) {
084            if (current.isEmpty()) {
085                current = stack.pop();
086            } else {
087                final File first = current.get(0);
088                if (first.isFile()) {
089                    if (this.fileFilter.accept(first)) {
090                        return true;
091                    } else {
092                        // exclude the current file and get the next one...
093                        current.remove(0);
094                        return advanceToNext();
095                    }
096                } else {
097                    final File directory = current.remove(0);
098                    stack.push(current);
099                    current = new ArrayList<File>(Arrays.asList(directory.listFiles()));
100                }
101            }
102        }
103        return false;
104    }
105
106    @Override
107    public boolean hasNext() {
108        return advanceToNext();
109    }
110
111    @Override
112    public FedoraObjectProcessor next() {
113        if (!advanceToNext()) {
114            throw new IllegalStateException();
115        } else {
116            final File currentFile = current.remove(0);
117            try {
118                return new FoxmlInputStreamFedoraObjectProcessor(
119                        currentFile, fetcher, resolver, localFedoraServer);
120            } catch (final XMLStreamException e) {
121                throw new RuntimeException(currentFile.getPath() + " doesn't appear to be an XML file."
122                        + (e.getMessage() != null ? "  (" + e.getMessage() + ")" : ""));
123            } catch (final FileNotFoundException e) {
124                throw new RuntimeException(e);
125            }
126        }
127    }
128
129    @Override
130    public void remove() {
131        throw new UnsupportedOperationException();
132    }
133
134}