/* ======================================================================
   Parts Copyright 2006 University of Leeds, Oxford University, University of the Highlands and Islands.

   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.

====================================================================== */

package org.bodington.util;

import java.io.IOException;
import java.io.Writer;
import java.util.regex.Pattern;

/**
 * A CSV file writer. This escapes all the passed content so it can be written
 * safely to a CSV file.
 * Implementation created as we can't reuse an existing GPL CSV project.
 * Guidance from:
 * http://www.creativyst.com/Doc/Articles/CSV/CSV01.htm
 * @author buckett
 */
public class CSVWriter
{
    // Starts of ends with a blank, or contains a double quote, comma or newline
    private static final Pattern shouldQuote = Pattern.compile("(^\\p{Blank})|\"|,|\\n|\\r|(\\p{Blank}$)");
    private static final Pattern doubleQuote = Pattern.compile("\""); 
    private static final String separator = ",";
    
    private Writer out;
    private boolean firstColumn = true;
    private String lineEnding = "\n";

    
    /**
     * Create the writer wrapping up an existing writer.
     * @param out The output to send the CSV file to.
     */
    public CSVWriter (Writer out)
    {
        this.out = out;
    }

    /**
     * Write a single data value to the CSV file.
     * @param data The data to write to the CSV file
     */
    public void write(String data) throws IOException
    {
        if (firstColumn)
            firstColumn = false;
        else
            out.write(separator);
        out.write(formatData(data));
    }
    
    /**
     * Terminates the current CSV row.
     */
    public void writeln() throws IOException
    {
        out.write(lineEnding);
        firstColumn = true;
    }
    
    /**
     * Outputs a complete CSV row.
     * @param columns The data to write out to row. 
     */
    public void writeln(String[] columns) throws IOException
    {
        for (int column = 0; column < columns.length; column++)
            write(columns[column]);
        writeln();
    }
    
    
    private String formatData(String data)
    {
        if (shouldQuote.matcher(data).find())
        {
            data = "\""+ doubleQuote.matcher(data).replaceAll("\"\"")+ "\"";
        }
        return data;
    }

}