/**
 * 
 */
package uk.ac.vamsas.client.simpleclient;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Vector;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import java.util.jar.JarOutputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.vamsas.objects.utils.AppDataReference;

import uk.ac.vamsas.client.IClientAppdata;
import uk.ac.vamsas.objects.core.AppData;
import uk.ac.vamsas.objects.core.ApplicationData;
import uk.ac.vamsas.objects.core.User;

/**
 * @author jimp
 * Access interface to data chunks read from a VamsasArchiveReader stream 
 * (or byte buffer input stream) or written to a VamsasArchive stream.
 * // TODO: get VamsasArchiveReader from sclient
 */
public class SimpleClientAppdata implements IClientAppdata {
  private static Log log = LogFactory.getLog(SimpleClientAppdata.class);
  /**
   * has the session's document been accessed to get the AppData entrys?
   */
  protected boolean accessedDocument = false;
  /**
   * has the user datablock been modified ? 
   * temporary file containing new user specific application data chunk
   */
  SessionFile newUserData=null;
  JarOutputStream newUserDataStream = null;
  /**
   * has the apps global datablock been modified ?
   * temporary file containing new global application data chunk
   */
  SessionFile newAppData=null;
  JarOutputStream newAppDataStream=null;
  /**
   * set by extractAppData
   */
  protected ApplicationData appsGlobal = null;
  /**
   * set by extractAppData
   */
  protected User usersData = null;
  
  ClientDocument clientdoc;
  /**
   * state flags
   * - accessed ClientAppdata
   * - accessed UserAppdata
   * => inputStream from embedded xml or jar entry of backup has been created
   * - set ClientAppdata
   * - set UserAppdata
   * => an output stream has been created and written to - or a data chunk has been written.
   *  - need flag for switching between embedded and jar entry mode ? - always write a jar entry for a stream.
   *  - need code for rewind and overwriting if the set*Appdata methods are called more than once.
   *  - need flags for streams to except a call to set*Appdata when an output stream exists and is open.
   *  - need 
   * @param clientdoc The ClientDocument instance that this IClientAppData is accessing
   */
  protected SimpleClientAppdata(ClientDocument clientdoc) {
    if (clientdoc==null) {
      log.fatal("Implementation error - Null ClientDocument for SimpleClientAppdata construction.");
      throw new Error("Implementation error - Null ClientDocument for SimpleClientAppdata construction.");
    }
    this.clientdoc = clientdoc;
  }
  /**
   * gets appropriate app data for the application, if it exists in this dataset
   * Called by every accessor to ensure data has been retrieved from document.
   */
  private void extractAppData(uk.ac.vamsas.objects.core.VamsasDocument doc) {
    if (doc==null) {
      log.debug("extractAppData called for null document object");
      return;
    }
    if (accessedDocument) {
      return;
    }
    Vector apldataset = AppDataReference.getUserandApplicationsData(
        doc, clientdoc.sclient.getUserHandle(), clientdoc.sclient.getClientHandle());
    accessedDocument = true;
    if (apldataset!=null) {
      if (apldataset.size()>0) {
        AppData clientdat = (AppData) apldataset.get(0);
        if (clientdat instanceof ApplicationData) {
          appsGlobal = (ApplicationData) clientdat;
          if (apldataset.size()>1) {
            clientdat = (AppData) apldataset.get(1);
            if (clientdat instanceof User) {
              usersData = (User) clientdat;
            }
            if (apldataset.size()>2)
              log.info("Ignoring additional ("+(apldataset.size()-2)+") AppDatas returned by document appdata query.");
          } 
        } else {
          log.warn("Unexpected entry in AppDataReference query: id="+clientdat.getVorbaId()+" type="+clientdat.getClass().getName());
        }
        apldataset.removeAllElements(); // destroy references.
      }
    }
  }
  /**
   * LATER: generalize this for different low-level session implementations (it may not always be a Jar)
   * @param appdata
   * @param docreader
   * @return
   */
  private JarInputStream getAppDataStream(AppData appdata, VamsasArchiveReader docreader) {
    String entryRef = appdata.getDataReference();
    if (entryRef!=null) {
      log.debug("Resolving appData reference +"+entryRef);
      InputStream entry = docreader.getAppdataStream(entryRef);
      if (entry!=null) {
        if (entry instanceof JarInputStream) {
          return (JarInputStream) entry;
        }
        log.warn("Implementation problem - docreader didn't return a JarInputStream entry.");
      }
    } else {
      log.debug("GetAppDataStream called for an AppData without a data reference.");
    }
    return null;
  }
  /**
   * yuk - size of buffer used for slurping appData JarEntry into a byte array.
   */
  private final int _TRANSFER_BUFFER=4096*4;

  /**
   * Resolve AppData object to a byte array.
   * @param appdata
   * @param archiveReader
   * @return null or the application data as a byte array
   */
  private byte[] getAppDataAsByteArray(AppData appdata, VamsasArchiveReader docreader) {
    if (appdata.getData()==null) {
      if (docreader==null) {
        log.warn("Silently failing getAppDataAsByteArray with null docreader.",new Exception());
        return null;
      }
      // resolve and load data
      JarInputStream entry = getAppDataStream(appdata, docreader); 
      ByteArrayOutputStream bytes = new ByteArrayOutputStream();
      try {
        byte buff[] = new byte[_TRANSFER_BUFFER];
        int olen=0;
        while (entry.available()>0) {
          int len = entry.read(buff, olen, _TRANSFER_BUFFER);
          bytes.write(buff, 0, len);
          olen+=len;
        }
        buff=null;
      } catch (Exception e) {
        log.warn("Unexpected exception - probable truncation when accessing VamsasDocument entry "+appdata.getDataReference(), e);
      }
      if (bytes.size()>0) {
        // LATER: deal with probable OutOfMemoryErrors here
        log.debug("Got "+bytes.size()+" bytes from AppDataReference "+appdata.getDataReference());
        byte data[] = bytes.toByteArray();
        bytes = null;
        return data;
      }
      return null;
    } else {
      log.debug("Returning inline AppData block for "+appdata.getVorbaId());
      return appdata.getData();
    }
  }
  /**
   * internal method for getting a DataInputStream from an AppData object.
   * @param appdata
   * @param docreader
   * @return data in object or null if no data is accessible
   */
  private DataInput getAppDataAsDataInputStream(AppData appdata, VamsasArchiveReader docreader) {
    if (appdata!=null && docreader!=null) {
      String entryRef = appdata.getDataReference();
      if (entryRef!=null) {
        log.debug("Resolving AppData reference for "+entryRef);
        InputStream jstrm = docreader.getAppdataStream(entryRef);
        if (jstrm!=null)
          return new AppDataInputStream(jstrm);
        else {
          log.debug("Returning null input stream for unresolved reference ("+entryRef+") id="+appdata.getVorbaId());
          return null;
        }
      } else {
        // return a byteArray input stream
        byte[] data=appdata.getData();
        if (data.length>0) {
          ByteArrayInputStream stream = new ByteArrayInputStream(data);
          return new DataInputStream(stream);
        } else {
          log.debug("Returning null input stream for empty Appdata data block in id="+appdata.getVorbaId());
          return null;
        }
      }
    } else {
      log.debug("Returning null DataInputStream for appdata entry:"+appdata.getVorbaId());
    }
    return null;
  }

  /**
   * internal method for getting ByteArray from AppData object
   * @param clientOrUser - true for returning userData, otherwise return Client AppData.
   * @return null or byte array
   */
  private byte[] _getappdataByteArray(boolean clientOrUser) {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    byte[] data=null;
    String appdName;
    if (!clientOrUser) {
      appdName = "Client's Appdata";
    } else {
      appdName = "User's Appdata";
    }    
    log.debug("getting "+appdName+" as a byte array");
    extractAppData(clientdoc.getVamsasDocument());
    AppData object;
    if (!clientOrUser) {
      object = appsGlobal;
    } else {
      object = usersData;
    }
    if (object!=null) {
      log.debug("Trying to resolve "+appdName+" object to byte array.");
      data = getAppDataAsByteArray(object, clientdoc.getVamsasArchiveReader());
    }
    if (data == null)
      log.debug("Returning null for "+appdName+"ClientAppdata byte[] array");
    return data;
    
  }
  
  /**
   * common method for Client and User AppData->InputStream accessor
   * @param clientOrUser - the appData to resolve - false for client, true for user appdata.
   * @return null or the DataInputStream desired.
   */
  private DataInput _getappdataInputStream(boolean clientOrUser) {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    String appdName;
    if (!clientOrUser) {
      appdName = "Client's Appdata";
    } else {
      appdName = "User's Appdata";
    }
    if (log.isDebugEnabled())
      log.debug("getting "+appdName+" as an input stream.");
    extractAppData(clientdoc.getVamsasDocument());
    AppData object;
    if (!clientOrUser) {
      object = appsGlobal;
    } else {
      object = usersData;
    }
    if (object!=null) {
      log.debug("Trying to resolve ClientAppdata object to an input stream.");
      return getAppDataAsDataInputStream(object, clientdoc.getVamsasArchiveReader());
    }
    log.debug("getClientInputStream returning null.");
    return null;
  }
  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getClientAppdata()
   */
  public byte[] getClientAppdata() {
    return _getappdataByteArray(false);
  }
  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getClientInputStream()
   */
  public DataInput getClientInputStream() {
    return _getappdataInputStream(false);
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getUserAppdata()
   */
  public byte[] getUserAppdata() {
    return _getappdataByteArray(true);
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getUserInputStream()
   */
  public DataInput getUserInputStream() {
    return _getappdataInputStream(true);
  }
  /**
   * methods for writing new AppData entries.
   */
  private DataOutput _getAppdataOutputStream(boolean clientOrUser) {
    String apdname;
    SessionFile apdfile=null;
    if (!clientOrUser) {
      apdname = "clientAppData";
      apdfile = newAppData;
    } else {
      apdname = "userAppData";
      apdfile = newUserData;
    }
    try {
      if (apdfile==null) {
        apdfile=clientdoc.sclient._session.getTempSessionFile(apdname,".jar");
        log.debug("Successfully made temp appData file for "+apdname);
      } else {
        // truncate to remove existing data.
        apdfile.fileLock.getRaFile().setLength(0);
        log.debug("Successfully truncated existing temp appData for "+apdname);
      }
      } catch (Exception e) {
      log.error("Whilst opening temp file in directory "+clientdoc.sclient._session.sessionDir, e);
    }
    // we do not make another file for the new entry if one exists already
    if (!clientOrUser) {
      newAppData = apdfile;
    } else {
      newUserData = apdfile;
    }
    try {
      apdfile.lockFile();
      // LATER: Refactor these local AppDatastream IO stuff to their own class.
      JarOutputStream dstrm = 
        new JarOutputStream(apdfile.fileLock.getBufferedOutputStream(true));
      if (!clientOrUser) {
        newAppDataStream = dstrm;
      } else {
        newUserDataStream = dstrm;
      }
      dstrm.putNextEntry(new JarEntry("appData_entry.dat"));
      // LATER: there may be trouble ahead if an AppDataOutputStream is written to by one thread when another truncates the file. This situation should be prevented if possible
      return new AppDataOutputStream(dstrm);
    }
    catch (Exception e) {
      log.error("Whilst opening jar output stream for file "+apdfile.sessionFile);
    }
    // tidy up and return null
    apdfile.unlockFile();
    return null;
   }
  /**
   * copy data from the appData jar file to an appropriately 
   * referenced jar or Data entry for the given ApplicationData
   * Assumes the JarFile is properly closed. 
   * @param vdoc session Document handler
   * @param appd the AppData whose block is being updated
   * @param apdjar the new data in a Jar written by this class
   */
  protected void updateAnAppdataEntry(VamsasArchive vdoc, AppData appd, SessionFile apdjar) throws IOException {
    if (apdjar==null || apdjar.sessionFile==null || !apdjar.sessionFile.exists()) {
      throw new IOException("No temporary Appdata to recover and transfer.");
    }
    if (vdoc==null) {
      log.fatal("FATAL! NO DOCUMENT TO WRITE TO!");
      throw new IOException("FATAL! NO DOCUMENT TO WRITE TO!");
    }
    log.debug("Recovering AppData entry from "+apdjar.sessionFile);
    JarInputStream istrm = new JarInputStream(apdjar.getBufferedInputStream(true));
    JarEntry je=null;
    while (istrm.available()>0 && (je=istrm.getNextJarEntry())!=null && !je.getName().equals("appData_entry.dat")) {
      if (je!=null)
        log.debug("Ignoring extraneous entry "+je.getName());
    }
    if (istrm.available()>0 && je!=null) {
      log.debug("Found appData_entry.dat in Jar");
      String ref = appd.getDataReference();
      if (ref==null) {
        throw new IOException("Null AppData.DataReference passed.");
      }
      if (vdoc.writeAppdataFromStream(ref, istrm)) {
        log.debug("Entry updated successfully.");
      } else {
        throw new IOException("writeAppdataFromStream did not return true - expect future badness."); // LATER - verify why this might occur.
      }
    } else {
      throw new IOException("Couldn't find appData_entry.dat in temporary jar file "+apdjar.sessionFile.getAbsolutePath());
    }
    istrm.close();
  }
  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getClientOutputStream()
   */
  public DataOutput getClientOutputStream() {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    if (log.isDebugEnabled())
      log.debug("trying to getClientOutputStream for "+clientdoc.sclient.client.getClientUrn());   
    return _getAppdataOutputStream(false);
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#getUserOutputStream()
   */
  public DataOutput getUserOutputStream() {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    if (log.isDebugEnabled())
      log.debug("trying to getUserOutputStream for ("
          +clientdoc.sclient.getUserHandle().getFullName()+")"+clientdoc.sclient.client.getClientUrn());   
    return _getAppdataOutputStream(true);
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#hasClientAppdata()
   */
  public boolean hasClientAppdata() {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    extractAppData(clientdoc.getVamsasDocument());
    // LATER - check validity of a DataReference before we return true
    if ((appsGlobal!=null) && (appsGlobal.getDataReference()!=null || appsGlobal.getData()!=null))
      return true;
    return false;
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#hasUserAppdata()
   */
  public boolean hasUserAppdata() {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    extractAppData(clientdoc.getVamsasDocument());
    // LATER - check validity of a DataReference before we return true
    if ((appsGlobal!=null) && (appsGlobal.getDataReference()!=null || appsGlobal.getData()!=null))
      return true;
    return false;
  }
  private boolean _writeAppDataStream(JarOutputStream ostrm, byte[] data) {
    try {
      if (data!=null && data.length>0) 
        ostrm.write(data);
      ostrm.closeEntry();
      return true;
    }
    catch (Exception e) {
      log.error("Serious! - IO error when writing AppDataStream to file "+newAppData.sessionFile, e);
    }
    return false;
  }
  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#setClientAppdata(byte[])
   */
  public void setClientAppdata(byte[] data) {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    _getAppdataOutputStream(false);
    if (newAppDataStream==null) {
      // LATER: define an exception for this ? - operation may fail even if file i/o not involved
      log.error("Serious! - couldn't open new AppDataStream in session directory "+clientdoc.sclient._session.sessionDir);
    } else {
      _writeAppDataStream(newAppDataStream, data);
      // LATER: deal with error case - do we make session read only, or what ?
    }
  }

  /* (non-Javadoc)
   * @see uk.ac.vamsas.client.IClientAppdata#setUserAppdata(byte[])
   */
  public void setUserAppdata(byte[] data) {
    if (clientdoc==null)
      throw new Error("Implementation error, Improperly initialized SimpleClientAppdata.");
    _getAppdataOutputStream(true);
    if (newUserDataStream==null) {
      // LATER: define an exception for this ? - operation may fail even if file i/o not involved
      log.error("Serious! - couldn't open new UserDataStream in session directory "+clientdoc.sclient._session.sessionDir);
    } else {
      _writeAppDataStream(newUserDataStream, data);
      // LATER: deal with error case - do we make session read only, or what ?
    }
  }
  /**
   * flush and close outstanding output streams. 
   *  - do this before checking data length.
   * @throws IOException
   */
  protected void closeForWriting() throws IOException {
    if (newAppDataStream!=null) {
      newAppDataStream.flush();
      newAppDataStream.closeEntry();
      newAppDataStream.close();
    }
    if (newUserDataStream!=null) {
      newUserDataStream.flush();
      newUserDataStream.closeEntry();
      newUserDataStream.close();
    }
  }


  /**
   * 
   * @return true if any AppData blocks have to be updated in session Jar
   */
  protected boolean isModified() {
    // LATER differentiate between core xml modification and Jar Entry modification.
    if (newAppData.sessionFile.exists() || newUserData.sessionFile.exists())
      return true;
    return false;
  }
  /* (non-Javadoc)
   * @see java.lang.Object#finalize()
   */
  protected void finalize() throws Throwable {
    if (newAppDataStream!=null) {
      newAppDataStream = null;
    }
    if (newAppDataStream!=null) {
      newUserDataStream = null;
    }
    if (newAppData!=null) {
      newAppData.eraseExistence();
      newAppData = null;
    }
    if (newUserData!=null) {
      newUserData.eraseExistence();
      newUserData = null;
    }
    super.finalize();
  }

}