package org.vamsas.client.simpleclient;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Hashtable;
import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.vamsas.client.object;
import org.vamsas.objects.core.ApplicationData;
import org.vamsas.objects.core.VAMSAS;
import org.vamsas.objects.core.VamsasDocument;

/**
 * Class for creating a vamsas archive
 * (with backups)
 * Writes to a temporary file and then swaps new file for backup.
 * uses the sessionFile locking mechanism for safe I/O
 * @author jimp
 *
 */
public class VamsasArchive {
  private static Log log = LogFactory.getLog(VamsasArchive.class);
  /**
   * destination of new archive data
   */
  java.io.File archive=null;
  /**
   * locked IO handler for new archive file
   */
  SessionFile rchive=null; 
  /**
   * original archive file that is to be updated
   */
  java.io.File original=null;
  /**
   * original archive IO handler
   */
  SessionFile odoclock = null;
  /**
   * Original archive reader class
   */
  VamsasArchiveReader odoc = null;
  /**
   * true if a real vamsas document is being written.
   */
  boolean vamsasdocument=true;
  /**
   * Output stream for archived data
   */
  JarOutputStream newarchive=null;
  /**
   * JarEntries written to archive
   */
  Hashtable entries = null;
  /**
   * true if we aren't just updating an archive
   */
  private boolean virginArchive=false;
  /**
   * Create a new vamsas archive
   * nb. No file locks are made until open() is called.
   * @param archive - file spec for new vamsas archive
   * @param vamsasdocument true if archive is to be a fully fledged vamsas document archive
   */
  public VamsasArchive(File archive, boolean vamsasdocument) {
    super();
    if (archive==null || (archive!=null && archive.canWrite())) {
      log.fatal("Invalid parameters for VamsasArchive constructor:"+((archive!=null) 
          ? "File cannot be overwritten." : "Null Object not valid constructor parameter"));
    }
    this.vamsasdocument = vamsasdocument;
    if (archive.exists()) {
      this.original = archive;
      this.archive = null;       // archive will be a temp file when the open method is called
      virginArchive=false;
    } else {
      this.original = null;
      this.archive = archive; // archive is written in place.
      virginArchive = true;
    }
  }
  /**
   * name of backup of existing archive that has been updated/overwritten.
   */
  File originalBackup = null;
  
  private void makeBackup() {
    if (!virginArchive) {
      if (originalBackup==null && original!=null && original.exists()) {
        try {
          accessOriginal();
          originalBackup = odoclock.backupSessionFile(null, original.getName(), ".bak", original.getParentFile());
        }
        catch (IOException e) {
          log.warn("Problem whilst making a backup of original archive.",e);
        }
      }
    }
  }
  /**
   * called after archive is written to put file in its final place
   * TODO: FINISH original should have sessionFile, and archive should also have sessionFile
   */
  private void updateOriginal() {
    if (original!=null) {
      if (!virginArchive) {
        if (odoc!=null) {
          odoc.close();
          odoc=null;
        }
        if (!archive.getAbsolutePath().equals(original)) {
          if (originalBackup==null) 
            makeBackup();
          try {
            odoclock.updateFrom(null, rchive);
          }
          catch (IOException e) {
            log.error("Problem updating archive from temporary file!",e);
          }
        } else {
          log.warn("archive and original are the same file! ("+archive.getAbsolutePath()+")");
        }
      } // else virginArchive are put in correct place from the beginning
      
    }
  }
  /**
   * called by app to get name of backup if it was made.
   * @return null or a valid file object
   */
  public File backupFile() {
    
    if (!virginArchive) {
      makeBackup();
      return ((original==null) ? originalBackup : null);
    
    }
    return null;
  }
  
  protected String getDocumentJarEntry() {
    if (vamsasdocument)
      return VamsasArchiveReader.VAMSASDOC;
    return VamsasArchiveReader.VAMSASXML;
  }
  
  /**
   * @return true if Vamsas Document has been written to archive
   */
  protected boolean isDocumentWritten() {
    if (newarchive==null)
      log.warn("isDocumentWritten called for unopened archive.");
    if (entries!=null) {
      if (entries.containsKey(getDocumentJarEntry()))
          return true;
    }
    return false;
  }
  /**
   * Add unique entry strings to internal JarEntries list.
   * @param entry
   * @return true if entry was unique and was added.
   */
  private boolean addEntry(String entry) {
    if (entries!=null)
      entries=new Hashtable();
    if (entries.containsKey(entry))
      return false;
    entries.put(entry, new Integer(entries.size()));
    return true;
  }
  /**
   * adds named entry to newarchive or returns false.
   * @param entry
   * @return true if entry was unique and could be added
   * @throws IOException if entry name was invalid or a new entry could not be made on newarchive
   */
  private boolean addValidEntry(String entry) throws IOException {
    JarEntry je = new JarEntry(entry);
    if (!addEntry(entry))
      return false;
    newarchive.putNextEntry(je);
    return true;
  }
  
  /**
   * opens the new archive ready for writing. If the new archive is replacing an existing one, 
   * then the existing archive will be locked, and the new archive written to a temporary file. 
   * The new archive will be put in place once close() is called.
   * @throws IOException
   */
  private void openArchive() throws IOException {
    
    if (newarchive!=null) {
      log.warn("openArchive() called multiple times.");
      throw new IOException("Vamsas Archive '"+archive.getAbsolutePath()+"' is already open.");
    }
    
    if (archive==null) {
      if (original==null) {
        log.warn("openArchive called on uninitialised VamsasArchive object.");
        throw new IOException("Badly initialised VamsasArchive object - no archive file specified.");
      }
      // lock the original
      accessOriginal();
      // make a temporary file to write to
      archive = File.createTempFile(original.getName(), "new",original.getParentFile());
    }
    
    rchive = new SessionFile(archive);
    rchive.lockFile();
    newarchive = new JarOutputStream(new BufferedOutputStream(new java.io.FileOutputStream(archive)));  
    entries = new Hashtable();
  }
  /**
   * Safely initializes the VAMSAS XML document Jar Entry. 
   * @return Writer to pass to the marshalling function.
   * @throws IOException if a document entry has already been written. 
   */
  public PrintWriter getDocumentOutputStream() throws IOException {
    if (newarchive==null)
      openArchive();
    if (!isDocumentWritten()) {
      try {
        if (addValidEntry(getDocumentJarEntry())) 
          return new PrintWriter(new java.io.OutputStreamWriter(newarchive, "UTF-8"));
      } catch (Exception e) {
        log.warn("Problems opening XML document JarEntry stream",e);
      }
    } else {
      throw new IOException("Vamsas Document output stream is already written.");
    }
    return null;
  }
  /**
   * Opens and returns the applicationData output stream for the appdataReference string.
   * @param appdataReference
   * @return Output stream to write to
   * @throws IOException
   */
  public AppDataOutputStream getAppDataStream(String appdataReference) throws IOException {
    if (newarchive!=null)
      openArchive();
    if (addValidEntry(appdataReference)) {
      return new AppDataOutputStream(newarchive);
    }
    return null;
  }
  
  /**
   * Stops any current write to archive, and reverts to the backup if it exists.
   * All existing locks on the original will be released.
   */
  public boolean cancelArchive() {
    if (newarchive!=null) {
      try { 
        newarchive.close();
      } catch (Exception e) {};
      if (!virginArchive) {
        // then there is something to recover.
        if (originalBackup!=null) {
          // backup has been made.
          // revert from backup and delete it (changing backup filename)
          if (rchive==null) {
            rchive = new SessionFile(original);
          }
          SessionFile bckup = new SessionFile(originalBackup);
          
            try {
              rchive.updateFrom(null,bckup); // recover from backup file.
              bckup.unlockFile();
              bckup=null;
              originalBackup.delete();
            }
            catch (Exception e) {
              log.warn("Problems when trying to cancel Archive "+archive.getAbsolutePath(), e);
              return false;
            }
        }
        // original is untouched
        // just delete temp files
        
        }
    } else {
      log.info("cancelArchive called before archive("+original.getAbsolutePath()+") has been opened!");
    }
    closeAndReset();
    return true;
  }
  
  /**
   * only do this if you want to destroy the current file output stream
   *
   */
  private void closeAndReset() {
    rchive.unlockFile();
    rchive = null;
    if (original!=null) {
      if (odoc!=null) {
        odoc.close();
        odoc=null;
      }
      archive.delete();
      if (odoclock!=null) {
        odoclock.unlockFile();
        odoclock = null;
      }
    }
    newarchive=null;
    original=null;
    entries=null;
  }

  private final int _TRANSFER_BUFFER=4096*4;
  /**
   * open backup for exclusive (locked) reading.
   * @throws IOException
   */
  private void accessOriginal() throws IOException {
    if (original!=null && original.exists()) {
      if (odoclock==null) 
        odoclock = new SessionFile(original);
      odoclock.lockFile();
      if (odoc == null) 
        odoc = new VamsasArchiveReader(original);
    }
  }

  /**
   * Convenience method to copy over the referred entry from the backup to the new version.
   * Warning messages are raised if no backup exists or the 
   * entry doesn't exist in the backed-up original.
   * Duplicate writes return true - but a warning message will also be raised.
   * @param AppDataReference
   * @return true if AppDataReference now exists in the new document
   * @throws IOException
   */
  public boolean transferAppDataEntry(String AppDataReference) throws IOException {
    return transferAppDataEntry(AppDataReference, AppDataReference);
  }
  /**
   * Transfers an AppDataReference from old to new vamsas archive, with a name change.
   * @see transferAppDataEntry(String AppDataReference)
   * @param AppDataReference
   * @param NewAppDataReference - AppDataReference in new Archive
   * @return
   * @throws IOException
   */
  public boolean transferAppDataEntry(String AppDataReference, String NewAppDataReference) throws IOException {
    // TODO: Specify valid AppDataReference form in all VamsasArchive handlers
    if (AppDataReference==null)
      throw new IOException("null AppDataReference!");
    if (original==null || !original.exists()) {
      log.warn("No backup archive exists.");
      return false;
    }
    if (entries.containsKey(NewAppDataReference)) {
      log.warn("Attempt to write '"+NewAppDataReference+"' twice! - IGNORED");
      return true;
    }
    
    accessOriginal();
    
    java.io.InputStream adstream = odoc.getAppdataStream(AppDataReference);
    
    if (adstream==null) {
      log.warn("AppDataReference '"+AppDataReference+"' doesn't exist in backup archive.");
      return false;
    }
    
    java.io.OutputStream adout = getAppDataStream(NewAppDataReference);
    // copy over the bytes
    int written=-1;
    long count=0;
    byte[] buffer = new byte[_TRANSFER_BUFFER]; // conservative estimate of a sensible buffer
    do {
      if ((written = adstream.read(buffer))>-1) {
        adout.write(buffer, 0, written);
        log.debug("Transferring "+written+".");
        count+=written;
      }
    } while (written>-1);
    log.debug("Sucessfully transferred AppData for '"
        +AppDataReference+"' as '"+NewAppDataReference+"' ("+count+" bytes)");
    return true;
  }
  /**
   * Tidies up and closes archive, removing any backups that were created.
   * NOTE: It is up to the caller to delete the original archive backup obtained from backupFile()
   */
  public void closeArchive() throws IOException {
    if (newarchive!=null) {
      newarchive.closeEntry();
      if (!isDocumentWritten())
        log.warn("Premature closure of archive '"+archive.getAbsolutePath()+"': No document has been written.");
      newarchive.close();
      updateOriginal();
      closeAndReset();
    } else {
      log.warn("Attempt to close archive that has not been opened for writing.");
    }
  }
  /**
   * Access original archive if it exists, pass the reader to the client
   * Note: this is NOT thread safe and a call to closeArchive() will by necessity 
   * close and invalidate the VamsasArchiveReader object.
   * @return null if no original archive exists.
   */
  public VamsasArchiveReader getOriginalArchiveReader() throws IOException {
    if (!virginArchive) {
      accessOriginal();
      return odoc;
    }
    return null;
  }
  /**
   * returns original document's root vamsas elements.
   * @return
   * @throws IOException
   * @throws org.exolab.castor.xml.MarshalException
   * @throws org.exolab.castor.xml.ValidationException
   */
  public object[] getOriginalRoots() throws IOException, 
  org.exolab.castor.xml.MarshalException, org.exolab.castor.xml.ValidationException  {
    return VamsasArchive.getOriginalRoots(this);
  }
  /**
   * Access original document if it exists, and get VAMSAS root objects.
   * @return vector of vamsas roots from original document
   * @throws IOException
   */
  public static object[] getOriginalRoots(VamsasArchive ths) throws IOException, 
    org.exolab.castor.xml.MarshalException, org.exolab.castor.xml.ValidationException {
    VamsasArchiveReader oReader = ths.getOriginalArchiveReader();
    if (oReader!=null) {
      
      if (oReader.isValid()) {
        InputStreamReader vdoc = new InputStreamReader(oReader.getVamsasDocumentStream());
        VamsasDocument doc = VamsasDocument.unmarshal(vdoc);
        if (doc!=null) 
          return doc.getVAMSAS();
        // TODO ensure embedded appDatas are garbage collected 
      } else {
        InputStream vxmlis = oReader.getVamsasXmlStream();
        if (vxmlis!=null) { // Might be an old vamsas file.
          BufferedInputStream ixml = new BufferedInputStream(oReader.getVamsasXmlStream());
          InputStreamReader vxml = new InputStreamReader(ixml);
          VAMSAS root[] = new VAMSAS[1];
          root[0] = VAMSAS.unmarshal(vxml);
          if (root[0]!=null)
            return root;
        }
      }
    }
    return null;
  }
  

}