/*
 * (C) Copyright 2006-2015 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Contributors:
 *     Bogdan Stefanescu
 *     Thierry Delprat
 *     Florent Guillaume
 */
package org.nuxeo.ecm.core.io.impl.plugins;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;

import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.input.CloseShieldInputStream;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;
import org.nuxeo.common.utils.Path;
import org.nuxeo.ecm.core.api.Blob;
import org.nuxeo.ecm.core.api.Blobs;
import org.nuxeo.ecm.core.api.impl.blob.ZipEntryBlob;
import org.nuxeo.ecm.core.io.ExportConstants;
import org.nuxeo.ecm.core.io.ExportedDocument;
import org.nuxeo.ecm.core.io.impl.AbstractDocumentReader;
import org.nuxeo.ecm.core.io.impl.DWord;
import org.nuxeo.ecm.core.io.impl.ExportedDocumentImpl;

/**
 * Reads nuxeo archives generated using {@link NuxeoArchiveWriter}.
 * <p>
 * If you need to read a CoreIO XML Archive that was not directly generated by {@link NuxeoArchiveWriter} or that was
 * modified you need to use the NuxeoArchiveReader(File) constructor.
 * <p>
 * This implementation holds either a {@link ZipInputStream}, in which case it is assumed to have been generated by
 * {@link NuxeoArchiveWriter} and has a special format (TODO DOCUMENT), or it holds a {@link ZipFile} that may be used
 * in a random-access manner.
 */
public class NuxeoArchiveReader extends AbstractDocumentReader {

    private ZipInputStream in;

    private boolean inMustBeClosed;

    private ZipFile zipFile;

    private List<String> zipIndex;

    private final Collection<File> filesToDelete = new ArrayList<File>();

    /**
     * Create a {@link NuxeoArchiveReader} from an {@link InputStream}.
     * <p>
     * The InputStream must point to an archive that was generated by {@link NuxeoArchiveWriter}.
     *
     * @param in InputStream pointing an archive that was generated by NuxeoArchiveWriter
     * @throws IOException
     */
    public NuxeoArchiveReader(InputStream in) throws IOException {
        this(new ZipInputStream(in), true);
    }

    /**
     * Protected constructor used by {@link ZipReader}. Must not close the stream when done.
     */
    protected NuxeoArchiveReader(ZipInputStream in, boolean checkMarker) throws IOException {
        this.in = in;
        inMustBeClosed = !checkMarker;
        if (checkMarker) {
            checkMarker();
        }
    }

    /**
     * Create a {@link NuxeoArchiveReader} from a {@link File}.
     * <p>
     * This constructor is different from others because it allows the input zip file to have been generated by an other
     * engine that {@link NuxeoArchiveWriter}.
     * <p>
     * In particular, you can use this constructor on a Zip Archive that was manually modified.
     *
     * @param file a Zip archive
     */
    public NuxeoArchiveReader(File file) throws IOException {
        this.zipFile = new ZipFile(file);
        buildOrderedZipIndex();
        checkMarker();
    }

    protected void buildOrderedZipIndex() {
        zipIndex = new ArrayList<String>();
        Enumeration<? extends ZipEntry> entries = zipFile.entries();

        while (entries.hasMoreElements()) {
            ZipEntry entry = entries.nextElement();
            zipIndex.add(entry.getName());
        }
        Collections.sort(zipIndex, new Comparator<String>() {
            @Override
            public int compare(String spath1, String spath2) {
                return spath1.compareTo(spath2);
            }
        });
    }

    @Override
    public ExportedDocument read() throws IOException {
        if (zipFile != null) {
            return readZip();
        } else {
            return readOrderedStream();
        }
    }

    protected ExportedDocument readZip() throws IOException {

        if (zipIndex.size() == 0) {
            return null;
        }
        String idxname = zipIndex.remove(0);
        ZipEntry entry = zipFile.getEntry(idxname);
        if (entry == null) {
            return null;
        }

        if (!entry.isDirectory()) {
            if (entry.getName().equals(ExportConstants.MARKER_FILE)) {
                return read();
            } else if (entry.getName().equals(ExportConstants.DOCUMENT_FILE)) {
                // the repository ROOT! TODO: how to handle root? it doesn't
                // have a dir ..
                ExportedDocument xdoc = new ExportedDocumentImpl();
                xdoc.setPath(new Path("/"));
                xdoc.setDocument(loadXML(entry));
                return xdoc;
            } else {
                throw new IOException("Invalid Nuxeo archive on entry " + entry.getName());
            }
        }

        // find the direct children entry that are part of the same document
        // since archive is modifiable we can not rely on the Extra bits thing
        List<String> childEntries = new ArrayList<String>();
        int depth = new Path(idxname).removeTrailingSeparator().segmentCount();
        for (String path : zipIndex) {
            if (path.startsWith(idxname)) {
                int subdepth = new Path(path).removeTrailingSeparator().segmentCount();
                if (subdepth != depth + 1 || zipFile.getEntry(path).isDirectory()) {
                    continue;
                }
                childEntries.add(path);
            } else {
                break;
            }
        }

        if (childEntries.size() == 0) {
            return read(); // empty dir -> try next directory
        }
        String name = entry.getName();
        ExportedDocument xdoc = new ExportedDocumentImpl();
        xdoc.setPath(new Path(name).removeTrailingSeparator());
        for (String childEntryName : childEntries) {
            int i = zipIndex.indexOf(childEntryName);
            idxname = zipIndex.remove(i);
            entry = zipFile.getEntry(idxname);
            name = entry.getName();
            if (name.endsWith(ExportConstants.DOCUMENT_FILE)) {
                xdoc.setDocument(loadXML(entry));
            } else if (name.endsWith(".xml")) { // external doc file
                xdoc.putDocument(FilenameUtils.getBaseName(entry.getName()), loadXML(entry));
            } else { // should be a blob
                xdoc.putBlob(FilenameUtils.getName(entry.getName()), createBlob(entry));
            }
        }
        return xdoc;
    }

    protected ExportedDocument readOrderedStream() throws IOException {
        ZipEntry entry = in.getNextEntry();
        if (entry == null) {
            return null;
        }
        if (!entry.isDirectory()) {
            if (entry.getName().equals(ExportConstants.MARKER_FILE)) {
                return read();
            } else if (entry.getName().equals(ExportConstants.DOCUMENT_FILE)) {
                // the repository ROOT! TODO: how to handle root? it doesn't
                // have a dir ..
                ExportedDocument xdoc = new ExportedDocumentImpl();
                xdoc.setPath(new Path("/"));
                xdoc.setDocument(loadXML(entry));
                return xdoc;
            } else {
                throw new IOException("Invalid Nuxeo archive");
            }
        }
        int count = getFilesCount(entry);
        if (count == 0) {
            return read(); // empty dir -> try next directory
        }
        String name = entry.getName();
        ExportedDocument xdoc = new ExportedDocumentImpl();
        xdoc.setPath(new Path(name).removeTrailingSeparator());
        for (int i = 0; i < count; i++) {
            entry = in.getNextEntry();
            name = entry.getName();
            if (name.endsWith(ExportConstants.DOCUMENT_FILE)) {
                xdoc.setDocument(loadXML(entry));
            } else if (name.endsWith(".xml")) { // external doc file
                xdoc.putDocument(FilenameUtils.getBaseName(entry.getName()), loadXML(entry));
            } else { // should be a blob
                xdoc.putBlob(FilenameUtils.getName(entry.getName()), createBlob(entry));
            }
        }
        return xdoc;
    }

    @Override
    public void close() {
        IOUtils.closeQuietly(zipFile);
        if (inMustBeClosed) {
            IOUtils.closeQuietly(in);
        }
        for (File file : filesToDelete) {
            file.delete();
        }
    }

    private static int getFilesCount(ZipEntry entry) throws IOException {
        byte[] bytes = entry.getExtra();
        if (bytes == null) {
            return 0;
        } else if (bytes.length != 4) {
            throw new IOException("Invalid Nuxeo Archive");
        } else {
            return new DWord(bytes).getInt();
        }
    }

    private Document loadXML(ZipEntry entry) throws IOException {
        try {
            SAXReader saxReader = new SAXReader();
            if (zipFile != null) {
                try (InputStream stream = zipFile.getInputStream(entry)) {
                    return saxReader.read(stream);
                }
            } else {
                // SAXReader.read always closes the stream, but we don't want that
                // so wrap it in a CloseShieldInputStream
                try (CloseShieldInputStream ncin = new CloseShieldInputStream(in)) {
                    return saxReader.read(ncin);
                }
            }
        } catch (DocumentException e) {
            throw new IOException("Failed to read zip entry: " + entry.getName(), e);
        }
    }

    private Blob createBlob(ZipEntry entry) throws IOException {
        if (zipFile != null) {
            return new ZipEntryBlob(zipFile, entry);
        } else {
            // should decompress since this is a generic stream
            // FileBlob always closes the stream, but we don't want that
            // so wrap it in a CloseShieldInputStream
            try (CloseShieldInputStream ncin = new CloseShieldInputStream(in)) {
                Blob blob = Blobs.createBlob(ncin);
                filesToDelete.add(blob.getFile());
                return blob;
            }
        }
    }

    private void checkMarker() throws IOException {

        if (zipFile == null) {
            ZipEntry entry = in.getNextEntry();
            if (entry == null) {
                throw new IOException("Not a valid Nuxeo Archive - no marker file found (unexpected end of zip)");
            }
            if (!isMarkerEntry(entry)) {
                throw new IOException("Not a valid Nuxeo Archive - no marker file found");
            }
        } else {
            if (!zipIndex.contains(ExportConstants.MARKER_FILE)) {
                throw new IOException("Not a valid Nuxeo Archive - no marker file found");
            }
        }
    }

    public static boolean isMarkerEntry(ZipEntry entry) {
        return entry.getName().equals(ExportConstants.MARKER_FILE);
    }

}