/*
 * eXist Open Source Native XML Database
 * Copyright (C) 2009 The eXist Project
 * http://exist-db.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *  
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *  
 *  $Id$
 */
package org.exist.backup.xquery;

import org.exist.xquery.BasicFunction;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.Cardinality;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.XPathException;
import org.exist.xquery.Variable;
import org.exist.xquery.functions.response.ResponseModule;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.JavaObjectValue;
import org.exist.dom.QName;
import org.exist.storage.BrokerPool;
import org.exist.http.servlets.ResponseWrapper;
import org.exist.backup.ZipArchiveBackupDescriptor;

import java.io.File;
import java.io.OutputStream;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

public class RetrieveBackup extends BasicFunction {

    public final static FunctionSignature signature =
        new FunctionSignature(
                new QName("retrieve", BackupModule.NAMESPACE_URI, BackupModule.PREFIX),
                "Retrieves a zipped backup archive, $name, and directly streams it to the HTTP response. " +
                "For security reasons, the function will only read .zip files in the specified directory, $directory.",
                new SequenceType[] {
                        new FunctionParameterSequenceType("directory", Type.STRING, Cardinality.EXACTLY_ONE, "The path to the directory where the backup file is located."),
                        new FunctionParameterSequenceType("name", Type.STRING, Cardinality.EXACTLY_ONE, "The name of the file to retrieve.")
                },
                new SequenceType(Type.ITEM, Cardinality.EMPTY)
        );

    public RetrieveBackup(XQueryContext context) {
        super(context, signature);
    }

    public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
        String exportDir = args[0].getStringValue();
        File dir = new File(exportDir);
        if (!dir.isAbsolute())
            dir = new File((String)context.getBroker().getConfiguration()
                    .getProperty(BrokerPool.PROPERTY_DATA_DIR), exportDir);
        String name = args[1].getStringValue();
        File backupFile = new File(dir, name);
        if (!backupFile.canRead())
            return Sequence.EMPTY_SEQUENCE;
        if (!name.endsWith(".zip"))
            throw new XPathException(this, "for security reasons, the function only allows " +
                    "reading zipped backup archives");
        try {
            ZipArchiveBackupDescriptor descriptor = new ZipArchiveBackupDescriptor(backupFile);
            Properties properties = descriptor.getProperties();
            if (properties == null || properties.size() == 0)
                throw new XPathException(this, "the file does not see to be a valid backup archive");
        } catch (IOException e) {
            throw new XPathException(this, "the file does not see to be a valid backup archive");
        }

        // directly stream the backup contents to the HTTP response
        ResponseModule myModule = (ResponseModule)context.getModule(ResponseModule.NAMESPACE_URI);
        // response object is read from global variable $response
        Variable respVar = myModule.resolveVariable(ResponseModule.RESPONSE_VAR);
        if(respVar == null)
            throw new XPathException(this, "No response object found in the current XQuery context.");
        if(respVar.getValue().getItemType() != Type.JAVA_OBJECT)
            throw new XPathException(this, "Variable $response is not bound to an Java object.");
        JavaObjectValue respValue = (JavaObjectValue)
                respVar.getValue().itemAt(0);
        if (!"org.exist.http.servlets.HttpResponseWrapper".equals(respValue.getObject().getClass().getName()))
            throw new XPathException(this, signature.toString() +
                    " can only be used within the EXistServlet or XQueryServlet");
        ResponseWrapper response = (ResponseWrapper) respValue.getObject();

        response.setContentType("application/zip");
        try {
            InputStream is = new FileInputStream(backupFile);
            OutputStream os = response.getOutputStream();
            byte[] buf = new byte[4096];
            int c;
            while ((c = is.read(buf)) > -1) {
                os.write(buf, 0, c);
            }
            is.close();
            os.close();
            response.flushBuffer();
        } catch (IOException e) {
            throw new XPathException(this, "An IO error occurred while reading the backup archive");
        }
        return Sequence.EMPTY_SEQUENCE;
    }
}