/* ============================================================
    * JRobin : Pure java implementation of RRDTool's functionality
    * ============================================================
    *
    * Project Info:  http://www.jrobin.org
    * Project Lead:  Sasa Markovic (saxon@jrobin.org);
    *
    * (C) Copyright 2003-2005, by Sasa Markovic.
    *
   * This library 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 2.1 of the License, or (at your option) any later version.
   *
   * Developers:    Sasa Markovic (saxon@jrobin.org)
   *
   *
   * This library 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., 59 Temple Place, Suite 330,
   * Boston, MA 02111-1307, USA.
   */
  
  package org.jrobin.core;
  
  import java.io.IOException;
  
  /**
   * Class to represent RRD header. Header information is mainly static (once set, it
   * cannot be changed), with the exception of last update time (this value is changed whenever
   * RRD gets updated).<p>
   * <p/>
   * Normally, you don't need to manipulate the Header object directly - JRobin framework
   * does it for you.<p>
   *
   * @author <a href="mailto:saxon@jrobin.org">Sasa Markovic</a>*
   */
  public class Header implements RrdUpdater {
  	static final int SIGNATURE_LENGTH = 2;
  	static final String SIGNATURE = "JR";
  
  	static final String DEFAULT_SIGNATURE = "JRobin, version 0.1";
  	static final String RRDTOOL_VERSION = "0001";
  
  	private RrdDb parentDb;
  
  	private RrdString signature;
  	private RrdLong step;
  	private RrdInt dsCount, arcCount;
  	private RrdLong lastUpdateTime;
  
  	Header(RrdDb parentDb, RrdDef rrdDef) throws IOException {
  		boolean shouldInitialize = rrdDef != null;
  		this.parentDb = parentDb;
  		signature = new RrdString(this);			 // NOT constant, may be cached
  		step = new RrdLong(this, true);			 // constant, may be cached
  		dsCount = new RrdInt(this, true);			 // constant, may be cached
  		arcCount = new RrdInt(this, true);			 // constant, may be cached
  		lastUpdateTime = new RrdLong(this);
  		if (shouldInitialize) {
  			signature.set(DEFAULT_SIGNATURE);
  			step.set(rrdDef.getStep());
  			dsCount.set(rrdDef.getDsCount());
  			arcCount.set(rrdDef.getArcCount());
  			lastUpdateTime.set(rrdDef.getStartTime());
  		}
  	}
  
  	Header(RrdDb parentDb, DataImporter reader) throws IOException, RrdException {
  		this(parentDb, (RrdDef) null);
  		String version = reader.getVersion();
  		if (!version.equals(RRDTOOL_VERSION)) {
  			throw new RrdException("Could not unserilalize xml version " + version);
  		}
  		signature.set(DEFAULT_SIGNATURE);
  		step.set(reader.getStep());
  		dsCount.set(reader.getDsCount());
  		arcCount.set(reader.getArcCount());
  		lastUpdateTime.set(reader.getLastUpdateTime());
  	}
  
  	/**
  	 * Returns RRD signature. Initially, the returned string will be
  	 * of the form <b><i>JRobin, version x.x</i></b>. Note: RRD format did not
  	 * change since Jrobin 1.0.0 release (and probably never will).
  	 *
  	 * @return RRD signature
  	 * @throws IOException Thrown in case of I/O error
  	 */
  	public String getSignature() throws IOException {
  		return signature.get();
  	}
  
  	public String getInfo() throws IOException {
  		return getSignature().substring(SIGNATURE_LENGTH);
  	}
  
 	public void setInfo(String info) throws IOException {
 		if (info != null && info.length() > 0) {
 			signature.set(SIGNATURE + info);
 		}
 		else {
 			signature.set(SIGNATURE);
 		}
 	}
 
 	/**
 	 * Returns the last update time of the RRD.
 	 *
 	 * @return Timestamp (Unix epoch, no milliseconds) corresponding to the last update time.
 	 * @throws IOException Thrown in case of I/O error
 	 */
 	public long getLastUpdateTime() throws IOException {
 		return lastUpdateTime.get();
 	}
 
 	/**
 	 * Returns primary RRD time step.
 	 *
 	 * @return Primary time step in seconds
 	 * @throws IOException Thrown in case of I/O error
 	 */
 	public long getStep() throws IOException {
 		return step.get();
 	}
 
 	/**
 	 * Returns the number of datasources defined in the RRD.
 	 *
 	 * @return Number of datasources defined
 	 * @throws IOException Thrown in case of I/O error
 	 */
 	public int getDsCount() throws IOException {
 		return dsCount.get();
 	}
 
 	/**
 	 * Returns the number of archives defined in the RRD.
 	 *
 	 * @return Number of archives defined
 	 * @throws IOException Thrown in case of I/O error
 	 */
 	public int getArcCount() throws IOException {
 		return arcCount.get();
 	}
 
 	void setLastUpdateTime(long lastUpdateTime) throws IOException {
 		this.lastUpdateTime.set(lastUpdateTime);
 	}
 
 	String dump() throws IOException {
 		return "== HEADER ==\n" +
 				"signature:" + getSignature() +
 				" lastUpdateTime:" + getLastUpdateTime() +
 				" step:" + getStep() +
 				" dsCount:" + getDsCount() +
 				" arcCount:" + getArcCount() + "\n";
 	}
 
 	void appendXml(XmlWriter writer) throws IOException {
 		writer.writeComment(signature.get());
 		writer.writeTag("version", RRDTOOL_VERSION);
 		writer.writeComment("Seconds");
 		writer.writeTag("step", step.get());
 		writer.writeComment(Util.getDate(lastUpdateTime.get()));
 		writer.writeTag("lastupdate", lastUpdateTime.get());
 	}
 
 	/**
 	 * Copies object's internal state to another Header object.
 	 *
 	 * @param other New Header object to copy state to
 	 * @throws IOException  Thrown in case of I/O error
 	 * @throws RrdException Thrown if supplied argument is not a Header object
 	 */
 	public void copyStateTo(RrdUpdater other) throws IOException, RrdException {
 		if (!(other instanceof Header)) {
 			throw new RrdException(
 					"Cannot copy Header object to " + other.getClass().getName());
 		}
 		Header header = (Header) other;
 		header.signature.set(signature.get());
 		header.lastUpdateTime.set(lastUpdateTime.get());
 	}
 
 	/**
 	 * Returns the underlying storage (backend) object which actually performs all
 	 * I/O operations.
 	 *
 	 * @return I/O backend object
 	 */
 	public RrdBackend getRrdBackend() {
 		return parentDb.getRrdBackend();
 	}
 
 	boolean isJRobinHeader() throws IOException {
 		return signature.get().startsWith(SIGNATURE);
 	}
 
 	void validateHeader() throws IOException, RrdException {
 		if (!isJRobinHeader()) {
 			String msg = "Invalid file header. File [" + parentDb.getCanonicalPath() + "] is not a JRobin RRD file";
 			throw new RrdException(msg);
 		}
 	}
 
 	/**
 	 * Required to implement RrdUpdater interface. You should never call this method directly.
 	 *
 	 * @return Allocator object
 	 */
 	public RrdAllocator getRrdAllocator() {
 		return parentDb.getRrdAllocator();
 	}
 }