/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
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package com.sun.enterprise.cli.framework;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;



/**
 * Pager.java
 *
 * @author <a href="mailto:toby.h.ferguson@sun.com">Toby H Ferguson</a>
 * @version $Revision: 1.4 $
 */

class Pager {
    private BufferedReader in;
    private BufferedWriter out;
    private int pageLength;
    private String line;

	  /**
	   * Construct an object which will copy one pages worth of lines
	   * at a time from the input to the
	   * the output.
	   *
	   * No attempt is made under any circumstances to close the input
	   * or output.
	   *
	   * @param lines the number of lines in a page. A number less
	   * than 0 means copy all the input to the output.
	   * @param in the source of the copy operation
	   * @param out the destination of the copy operation
	   * @throws IOException if there's a problem reading from, or
	   * writing to, the source or destination
	   */
    
    Pager (int lines, Reader in, Writer out) throws IOException {
        this.in = new BufferedReader(in);
        this.out = new BufferedWriter(out);
        pageLength = lines;
        nextLine();
    }

	  /**
	   * Copy the next page worth of lines from input to output
	   */
    void nextPage() throws IOException {
        for (int i = 0; (pageLength < 0 || i < pageLength) && hasNext(); i++){
            out.write(line);
            out.newLine();
            nextLine();
        }
        out.flush();
    }

	  /**
	   * Indicate if there are lines left to be copied
	   * @return true iff there is at least one line left to be copied
	   */
    boolean hasNext() {
        return line != null;
    }

	  /**
	   * Get the next line and copy it inot the internal buffer so's
	   * we can answer the hasNext() question
	   */
    private void nextLine() throws IOException {
        line = in.readLine();
    }
    
}