package de.intevation.gnv.exports;

import au.com.bytecode.opencsv.CSVWriter;

import de.intevation.gnv.geobackend.base.Result;

import de.intevation.gnv.state.exception.StateException;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;

import java.util.Collection;
import java.util.Iterator;

import org.apache.log4j.Logger;

/**
 * This class is the default implementation of {@link Export}.
 *
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class DefaultExport
implements   Export
{
    /**
     * Logger used for logging via log4j.
     */
    private static Logger log = Logger.getLogger(DefaultExport.class);

    /**
     * DataCollector used to extract data from <code>Result</code> objects.
     */
    protected Export.DataCollector collector;

    /**
     * Constructor
     *
     * @param collector See {@link #collector}
     */
    public DefaultExport(Export.DataCollector collector) {
        this.collector = collector;
    }

    /**
     * This method writes data stored in <code>result</code> into a CSV document
     * using <code>writer</code>.
     *
     * @param profile <code>Profile</code> used to specify the format and columns.
     * @param result Collection storing the required data.
     * @param writer CSVWriter to write the csv document.
     *
     * @throws StateException
     */
    protected void writeData(
        Profile    profile,
        Collection result,
        CSVWriter  writer
    )
    throws StateException {
        log.debug("create content for export.");
        Iterator<Result> it = result.iterator();

        String[] header = profile.getHeader();
        if (header != null)
            writer.writeNext(header);

        while (it.hasNext()) {
            Result res = it.next();

            writer.writeNext(collector.getData(res));
        }
    }

    /**
     * This method takes a data Collection and writes it to
     * <code>outputStream</code> using the the format specified by
     * <code>profile</code>.
     *
     * @param profile used to specify the format and columns.
     * @param outputStream OutputStream which is used for writing the export
     * document to.
     * @param result Collection storing the data.
     *
     * @throws IOException if writing to OutputStream failed.
     * @throws UnsupportedEncodingException if the encoding was not accepted.
     * @throws StateException if result is null.
     */
    public void create(
        Profile      profile,
        OutputStream outputStream,
        Collection   result
    )
    throws
        IOException,
        UnsupportedEncodingException,
        StateException
    {
        if (result == null) {
            String msg = "No data given for generation of " +
                profile.getType() + " file.";
            log.error(msg);
            throw new StateException(msg);
        }

        CSVWriter writer = new CSVWriter(
            new OutputStreamWriter(
                outputStream,
                profile.getEncoding()),
            profile.getSeparator(),
            profile.getQuoteCharacter(),
            profile.getEscapeCharacter());

        writeData(profile, result, writer);

        writer.close();
    }
}
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