/*
 *  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 library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * $Id: EmbeddedDownload.java 223 2007-04-21 22:13:05Z dizzzz $
 */

package org.exist.protocolhandler.embedded;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Optional;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import org.exist.collections.Collection;
import org.exist.dom.persistent.BinaryDocument;
import org.exist.dom.persistent.DocumentImpl;
import org.exist.protocolhandler.xmldb.XmldbURL;
import org.exist.security.Subject;
import org.exist.storage.BrokerPool;
import org.exist.storage.DBBroker;
import org.exist.storage.lock.Lock.LockMode;
import org.exist.storage.serializers.EXistOutputKeys;
import org.exist.storage.serializers.Serializer;
import org.exist.xmldb.XmldbURI;

/**
 * Read document from an embedded database and write the data into an
 * output stream.
 *
 * @author Dannes Wessels
 */
public class EmbeddedDownload {

    private final static Logger LOG = LogManager.getLogger(EmbeddedDownload.class);

    private BrokerPool pool;

    /**
     * Set the BrokerPool for resolving the resource
     *
     * @param brokerPool A BrokerPool
     */
    public void setBrokerPool(final BrokerPool brokerPool) {
        this.pool = brokerPool;
    }

    /**
     * Write document referred by URL to an (output)stream.
     *
     * @param xmldbURL Document location in database.
     * @param os       Stream to which the document is written.
     */
    public void stream(final XmldbURL xmldbURL, final OutputStream os) throws IOException {
        stream(xmldbURL, os, null);
    }

    /**
     * Write document referred by URL to an (output)stream as specified user.
     *
     * @param user     Effective user for operation. If NULL the user information
     *                 is distilled from the URL.
     * @param xmldbURL Document location in database.
     * @param os       Stream to which the document is written.
     */
    public void stream(final XmldbURL xmldbURL, final OutputStream os, Subject user) throws IOException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Begin document download");
        }

        try {
            final XmldbURI path = XmldbURI.create(xmldbURL.getPath());

            if (pool == null) {
                pool = BrokerPool.getInstance();
            }

            if (user == null) {
                if (xmldbURL.hasUserInfo()) {
                    user = EmbeddedUser.authenticate(xmldbURL, pool);
                    if (user == null) {
                        throw new IOException("Unauthorized user " + xmldbURL.getUsername());
                    }

                } else {
                    user = EmbeddedUser.getUserGuest(pool);
                }
            }

            try (final DBBroker broker = pool.get(Optional.of(user))) {

                DocumentImpl resource = null;
                Collection collection = null;
                try {
                    resource = broker.getXMLResource(path, LockMode.READ_LOCK);
                    if (resource == null) {
                        // Test for collection
                        collection = broker.openCollection(path, LockMode.READ_LOCK);
                        if (collection == null) {
                            // No collection, no document
                            throw new IOException("Resource " + xmldbURL.getPath() + " not found.");

                        } else {
                            // Collection
                            throw new IOException("Resource " + xmldbURL.getPath() + " is a collection.");
                        }

                    } else {
                        if (resource.getResourceType() == DocumentImpl.XML_FILE) {
                            final Serializer serializer = broker.getSerializer();
                            serializer.reset();

                            // Preserve doctype
                            serializer.setProperty(EXistOutputKeys.OUTPUT_DOCTYPE, "yes");
                            try(final Writer w = new OutputStreamWriter(os, "UTF-8")) {
                                serializer.serialize(resource, w);
                            }

                        } else {
                            broker.readBinaryResource((BinaryDocument) resource, os);
                        }
                    }
                } finally {
                    if (collection != null) {
                        collection.release(LockMode.READ_LOCK);
                    }

                    if (resource != null) {
                        resource.getUpdateLock().release(LockMode.READ_LOCK);
                    }

                    if (LOG.isDebugEnabled()) {
                        LOG.debug("End document download");
                    }
                }
            }
        } catch (final IOException ex) {
            LOG.error(ex);
            throw ex;
        } catch (final Exception ex) {
            LOG.error(ex);
            throw new IOException(ex.getMessage(), ex);

        }
    }
}