package uk.ac.vamsas.client.simpleclient;

import java.io.File;
import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.RandomAccessFile;
import java.io.Writer;
import java.util.Enumeration;
import java.util.Vector;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.Appender;
import org.apache.log4j.Logger;
import org.apache.log4j.FileAppender;
import org.apache.log4j.PatternLayout;

import uk.ac.vamsas.client.ClientHandle;
import uk.ac.vamsas.client.IClient;
import uk.ac.vamsas.client.UserHandle;
/**
 * Does all the IO operations for a SimpleClient instance accessing 
 * a SimpleClient vamsas session.
 * 
 * Basically, it defines the various standard names for the files 
 * in the session directory (that maps to the sessionUrn), 
 * provides constructors for the file handlers and watchers of 
 * those file entities, and some higher level methods 
 * to check and change the state flags for the session.
 * 
 * TODO: move the stuff below to the SimpleClientFactory documentation.
 * much may not be valid now :
 * 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 - 
 * 
 * Procedures for file based session message exchange
 *  - session document modification flag
 *    
 */

public class VamsasSession {
  /**
   * indicator file for informing other processes that 
   * they should finalise their vamsas datasets for 
   * storing into a vamsas archive.
   */
  public static final String CLOSEANDSAVE_FILE="stored.log";
  /**
   * session file storing the last_stored_stat data 
   */
  public static final String MODIFIEDDOC_FILE="modified";

  
  private SimpleSessionManager sessionManager = null;
  
  /**
   * called to clear update flag after a successful offline storage event
   */
  protected void clearUnsavedFlag() {
    SessionFlagFile laststored = new SessionFlagFile(new File(sessionDir, MODIFIEDDOC_FILE));
    if (!laststored.clearFlag())
      log.warn("Unsaved flag was not cleared for "+sessionDir);
  }
  /**
   * called to indicate session document has been modified.
   *
   */
  protected void setUnsavedFlag() {
    SessionFlagFile laststored = new SessionFlagFile(new File(sessionDir, MODIFIEDDOC_FILE));
    if (!laststored.setFlag())
      log.warn("Couldn't set the Unsaved flag for "+sessionDir);
  }
  /**
   * 
   * @return true if session document has been modified since last offline storage event 
   */
  protected boolean getUnsavedFlag() {
    SessionFlagFile laststored = new SessionFlagFile(new File(sessionDir, MODIFIEDDOC_FILE));
    return laststored.checkFlag();
  }
  /**
   * log file location
   */
  public static final String SESSION_LOG="Log.txt";
  private static Log log = LogFactory.getLog(VamsasSession.class);
  protected Logger slog = Logger.getLogger("uk.ac.vamsas.client.SessionLog");
  /**
   * setup the sessionLog using Log4j.
   * @throws IOException
   */
  private void initLog() throws IOException {
    // TODO: fix session event logging
    // LATER: make dedicated appender format for session log.
    /*Appender app = slog.getAppender("log4j.appender.SESSIONLOG");
    // slog.addAppender(new FileAppender(app.getLayout(), new File(sessionDir, SESSION_LOG).getAbsolutePath()));
    // slog.addAppender(new FileAppender(app.getLayout(), new File(sessionDir, SESSION_LOG).getAbsolutePath()));
    for (Enumeration e = slog.getAllAppenders() ; e.hasMoreElements() ;) {
      System.out.println(e.nextElement());

    }*/
  
    if (slog!= null ) {
      File sessionLogFile =  new File(this.sessionDir, SESSION_LOG);
      slog.addAppender(new FileAppender(new PatternLayout("%-4r [%t] %-5p %c %x - %m%n"), sessionLogFile.getAbsolutePath(), true));
    } else {
      log.info("No appender for SessionLog");
    }
  }
  
  /**
   * the sessionDir is given as the session location for new clients.
   */
  protected File sessionDir;
  /**
   * holds the list of attached clients
   */
  ClientsFile clist;
  public static final String CLIENT_LIST="Clients.obj";
  /**
   * holds the data
   */
  VamsasFile vamArchive; 
  public static final String VAMSAS_OBJ="VamDoc.jar";
  
  /**
   * sets up the vamsas session files and watchers in sessionDir
   * @param sessionDir1
   */
  protected VamsasSession(File sessionDir1) throws IOException {
    if (sessionDir1==null)
      throw new Error("Null directory for VamsasSession.");
    if (sessionDir1.exists()) {
      if (!sessionDir1.isDirectory() || !sessionDir1.canWrite() || !sessionDir1.canRead())
        throw new IOException("Cannot access '"+sessionDir1+"' as a read/writable Directory.");
      if (!checkSessionFiles(sessionDir1))
      log.warn("checkSessionFiles() returned false. Possible client implementation error");
      this.sessionDir = sessionDir1; 
      initSessionObjects();
      slog.debug("Initialising additional VamsasSession instance");
      log.debug("Attached to VamsasSession in "+sessionDir1);
      //} 
    } else {
      // start from scratch
      if (!sessionDir1.mkdir())
        throw new IOException("Failed to make VamsasSession directory in "+sessionDir1);
      createSessionFiles();
      initSessionObjects();
      slog.debug("Session directory created.");
      log.debug("Initialised VamsasSession in "+sessionDir1);
    }
  }
  /**
   * tests presence of existing sessionfiles files in dir
   * @param dir
   * @return
   */
  private boolean checkSessionFiles(File dir) throws IOException {
    File c_file = new File(dir,CLIENT_LIST);
    File v_doc = new File(dir,VAMSAS_OBJ);
    if (c_file.exists() && v_doc.exists())
      return true;
    return false;
  }
  /**
   * create new empty files in dir
   *
   */
  private void createSessionFiles() throws IOException {
    if (sessionDir==null)
      throw new IOException("Invalid call to createSessionFiles() with null sessionDir");
    File c_file = new File(sessionDir,CLIENT_LIST);
    File v_doc = new File(sessionDir,VAMSAS_OBJ);
    if (!c_file.exists() && c_file.createNewFile())
      log.debug("Created new ClientFile "+c_file); // don't care if this works or not
    if (!v_doc.exists() && v_doc.createNewFile())
      log.debug("Created new Vamsas Session Document File "+v_doc); 
  }
  /**
   * construct SessionFile objects and watchers for each
   */
  private void initSessionObjects() throws IOException {
    createSessionFiles();
    if (clist!=null || vamArchive!=null)
      throw new IOException("initSessionObjects called for initialised VamsasSession object.");
    clist = new ClientsFile(new File(sessionDir,CLIENT_LIST));
    vamArchive = new VamsasFile(new File(sessionDir,VAMSAS_OBJ));
    storedocfile=new ClientsFile(new File(sessionDir, CLOSEANDSAVE_FILE));
    initLog();
  }
  /**
   * make a new watcher object for the clientFile
   * @return new ClientFile watcher instance
   */
  public FileWatcher getClientWatcher() {
    return new FileWatcher(clist.sessionFile);
  }
  /**
   * make a new watcher object for the vamsas Document
   * @return new ClientFile watcher instance
   */
  public FileWatcher getDocWatcher() {
    return new FileWatcher(vamArchive.sessionFile);
  }
  FileWatcher store_doc_file=null;
  public ClientsFile storedocfile=null;
  /**
   * make a new watcher object for the messages file
   * @return new watcher instance
   */
  public FileWatcher getStoreWatcher() {
    return new FileWatcher(new File(sessionDir,CLOSEANDSAVE_FILE));

  }
  /**
   * write to the StoreWatcher file to indicate that a storeDocumentRequest has been made.
   * The local client's storeWatcher FileWatcher object is updated so the initial change is not registered.
   * @param client
   * @param user
   * @return
   */
  public void addStoreDocumentRequest(ClientHandle client, UserHandle user) throws IOException {
    // TODO: replace this with clientsFile mechanism
    SessionFile sfw = new SessionFile(new File(sessionDir, CLOSEANDSAVE_FILE));
    while (!sfw.lockFile())
      log.debug("Trying to get lock for "+CLOSEANDSAVE_FILE);
    RandomAccessFile sfwfile=sfw.fileLock.getRaFile();
    sfwfile.setLength(0); // wipe out any old info.
    // TODO: rationalise what gets written to this file (ie do we want other clients to read the id of the requestor?)
    sfwfile.writeUTF(client.getClientUrn()+":"+user.getFullName()+"@"+user.getOrganization());
    sfw.unlockFile();
    if (store_doc_file!=null)
      store_doc_file.setState();
    slog.info("FinalizeAppData request from "+user.getFullName()+" using "+client.getClientUrn()+"");
  }
  /**
   * create a new session with an existing vamsas Document - by copying it into the session.
   * @param archive
   */
  public void setVamsasDocument(File archive) throws IOException {
    log.debug("Transferring vamsas data from "+archive+" to session:"+vamArchive.sessionFile);
    SessionFile xtantdoc = new SessionFile(archive);
    vamArchive.updateFrom(null, xtantdoc);
    // LATER: decide if session archive provenance should be updated to reflect access.
    // TODO: soon! do a proper import objects from external file 
    log.debug("Transfer complete.");
  }
  /**
   * write session as a new vamsas Document (this will overwrite any existing file without warning)
   * TODO: test
   * TODO: verify that lock should be released for vamsas document.
   * @param destarchive
   */
  protected void writeVamsasDocument(File destarchive, Lock extlock) throws IOException {
    log.debug("Transferring vamsas data from "+vamArchive.sessionFile+" to session:"+destarchive);
    SessionFile newdoc = new SessionFile(destarchive);
    if (extlock==null && !vamArchive.lockFile())
      while (!vamArchive.lockFile())
        log.info("Trying to get lock for "+vamArchive.sessionFile);
    // TODO: LATER: decide if a provenance entry should be written in the exported document recording the export from the session
    newdoc.updateFrom(extlock, vamArchive);
    // LATER: LATER: fix use of updateFrom for file systems where locks cannot be made (because they don't have a lockManager, ie NFS/Unix, etc).
    vamArchive.unLock();
    newdoc.unlockFile();
    log.debug("Transfer complete.");
  }
  /**
	 * extant archive IO handler
	 */
  VamsasArchive _va=null;
  /**
   * Creates a VamsasArchive Vobject for accessing and updating document
   * Note: this will lock the Vamsas Document for exclusive access to the client.
   * @return session vamsas document
   * @throws IOException if locks fail or vamsas document read fails.
   */
  protected VamsasArchive getVamsasDocument() throws IOException {
    // check we haven't already done this once - probably should be done by caller
    if (_va!=null)
      return _va;
    // patiently wait for a lock on the document. (from ArchiveClient.getUpdateable())
    long tries=5000;
    while (vamArchive.getLock()==null && --tries>0) {
//       Thread.sleep(1);
        log.debug("Trying to get a document lock for the "+tries+"'th time.");
      }
    if (tries==0) 
      throw new IOException("Failed to get lock for vamsas archive.");
      
    VamsasArchive va = new VamsasArchive(vamArchive.sessionFile, false, true, vamArchive);

    return va;
  }
  /**
   * Unlocks the vamsas archive session document after it has been closed.
   * @throws IOException
   */
  protected void unlockVamsasDocument() throws IOException {
    if (_va!=null)
      _va.closeArchive();
    _va=null;
    if (vamArchive!=null)
      vamArchive.unLock();
    
  }
  /**
   * create a uniquely named uk.ac.vamsas.client.simpleclient.ClientsFile.addClient(ClientHandle)ile in the session Directory
   * @see java.io.File.createTempFile
   * @param pref Prefix for name
   * @param suff Suffix for name
   * @return SessionFile object configured for the new file (of length zero)
   * @throws IOException
   */
  protected SessionFile getTempSessionFile(String pref, String suff) throws IOException {
    File tfile = File.createTempFile(pref,suff,sessionDir);
    SessionFile tempFile = new SessionFile(tfile);
    return tempFile;
  }
  
  /**
   * add a IClient to the session
   * 
   * add the client to the client list file
   * @param client client to add to the session
   */
  protected void addClient(IClient client)
  {
    if (client == null)
      slog.error("Try to add a null client to the session ");
    else {
      log.debug("Adding client "+client.getClientHandle().getClientUrn());
      getClientWatcherElement().haltWatch();
      clist.addClient(client.getClientHandle());
      getClientWatcherElement().enableWatch();
      log.debug("Added.");
    }
  }
  
/**
 *  
 * removes a client from the current session
 *  removes the client from the session client list
 *  if the client is the last one from the session  (ClientList), the current session is removed 
 *  from active session list.
 *  
 * @param client client to remove
 */
  protected void removeClient(IClient client)
  {
    if (client == null)
      {
        log.error("Null client passed to removeClient");
        return;
      }
    SessionFileWatcherElement cwe=getClientWatcherElement();
    if (cwe!=null && cwe.isWatchEnabled()) {
      cwe.haltWatch();
    };
    clist.removeClient(client.getClientHandle(),null);
    if (this.clist.retrieveClientList() == null|| this.clist.retrieveClientList().length<1)
      {//assume it is the last client has been removed shutting down session
        slog.info("last client removed: removing session");
        log.debug("last client removed: removing session");
        this.getSessionManager().removeSession(client.getSessionHandle());
      }
    else
    {
      int active=clist.retrieveClientList().length;
      log.debug("Still "+active+" active clients");
      slog.info("Still "+active+" active clients");
    }
    if (cwe!=null) {
      cwe.enableWatch();
    }
  }
/**
 * @return the sessionManager
 */
protected SimpleSessionManager getSessionManager() {
  return sessionManager;
}
/**
 * @param sessionManager the sessionManager to set
 */
protected void setSessionManager(SimpleSessionManager sessionManager) {
  this.sessionManager = sessionManager;
}
public ClientsFile getStoreDocFile() {
  if (storedocfile==null) {
    
  }
  return storedocfile;
}
SessionFileWatcherElement clistWatchElement=null;
public SessionFileWatcherElement getClientWatcherElement() {
  if (clistWatchElement==null) {
    clistWatchElement=new SessionFileWatcherElement(clist,null);
  }
  return clistWatchElement;
}
/**
 * writes a vector of vorba Ids to the session.
 * @param modObjects 
public void setModObjectList(Vector modObjects) {
  log.debug("Writing "+modObjects.size()+" ids to ModObjectList");
  // TODO Auto-generated method stub
}
**
 * get current list of modified objects.
 * @return null or Vector of objects
 *
public Vector getModObjectList() {
  log.debug("Reading modObjectList");
  return null;
}
*/
}