package org.vamsas.client.simpleclient;

import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Timer;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.JarInputStream;
import java.util.jar.JarOutputStream;

import org.vamsas.objects.core.LockFileDescriptor;

/**
 * low level vamsas document management routines
 * This class is not thread safe.
 * @author jimp
 *
 */
public class documentHandler {
  /**
   * Vamsas client is intialised with a path to create live session directories. 
   * This path may contain a vamsas.properties file 
   * that sets additional parameters (otherwise client 
   * just uses the one on the classpath).
   * 
   * A vamsas session consists of :
   *  SessionDir - translates to urn of a live session.
   *  Contains: Vamsas Document (as a jar), Session client list file, 
   *  both of which may be locked, and additional 
   *  temporary versions of these files when write 
   *  operations are taking place.
   * 
   * Zip file entries
   *  - vamsasdocument.xml : core info
   *  one or more:
   *  - <applicationname>.version.sessionnumber.raw (string given in vamsasdocument.xml applicationData entry)
   *  
   * Lockfile
   *  - filename given in the vamsasdocument.xml. Should be checked for validity by any client and rewritten if necessary. 
   *    The lockfile can point to the jar itself.
   * Mode of operation.
   * Initially - documentHandler either:
   *  - creates a zip for a new session for the client
   *  - connect to an existing session zip 
   *   1. reads session urn file
   *   2. waits for lock
   *   3. examines session - decide whether to create new application data slice or connect to one stored in session.
   *   4. writes info into session file
   *   5. releases lock and generates local client events.
   *   6. Creates Watcher thread to generate events.
   * 
   * During the session
   *  - Update watcher checks for file change - 
   * 
   */
  private File vamsasJar;
  private Lock newVamsasJarLock;
  private File newVamsasJar; // file which client application is writing to.
  private File lockfile;
  private Lock lock;
  private File newSessionDir; // where new sessions (or copies of existing sessions) can be safely created
  private long timeout=1000; // time in milliseconds before we give up getting a lock
  private long interval=100; // time between attempts to lock
  private PrintWriter vamsasWriterStream; // non null if there is a write to a new Document in progress. 
  public documentHandler(File sessionDir) throws java.io.IOException {
      newSessionDir = File.createTempFile("vamsasSimple", "session", sessionDir);
  }
  
  public documentHandler(File lockfile, File vamsasJar) {
    this.lockfile = lockfile;
    this.vamsasJar = vamsasJar;
  }
  /**
   * gets an unlocked stream from the vamsas document.
   * @return reader for vamsasdocument.xml enrty
   */
  public java.io.Reader getDocumentReader() {
    
    try {
      JarFile session = new JarFile(vamsasJar);
      JarEntry vamsasDocument = session.getJarEntry("vamsasDocument.xml");
      return new InputStreamReader(session.getInputStream(vamsasDocument));
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    return null;
  }
  
  
}