package uk.ac.vamsas.client.simpleclient;

import uk.ac.vamsas.client.*;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.Vector;

/**
 * Handler for the clientsFile within a vamsas session thread.
 * @author jim 
 */
public class ClientsFile extends ListFile {
  private static org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(ClientsFile.class);
  /**
   * number of my client in list - passed back when a client 
   * is added to list, and used (if valid) for quickly 
   * looking up presence of client handle in the list.
   */
  private int syncnum = 1;

  public ClientsFile(File filelist) throws IOException {
    super(filelist);
  }

  /**
   * internal method for getting clientList - ensures a lock has been made but
   * does not release it.
   * 
   * @return list of clients
   */
  private ClientHandle[] retrieveClientHandles() {
    if (lockFile()) {
      try {
        ClientHandle[] clients=null;
        if (fileLock.length()>0) {
          
          ObjectInputStream is = new ObjectInputStream(fileLock.getBufferedInputStream(true));
          Object o;
          o=is.readObject();
          if (o!=null) {
            try {
              clients = (ClientHandle[]) o;
            }
            catch (Exception e) {
              System.err.println("Garbage in the clientHandle list "+this.sessionFile);
            }
          }
        }
        return clients;
      } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace(System.err);
      } catch (Exception e) {
        e.printStackTrace(System.err);
      }
    }
    return null;
  }
  /**
   * get the clientList from the file. May return null if lock failed!
   * @return clientList
   */
  public ClientHandle[] retrieveClientList() {
    if (lockFile()) {
      ClientHandle[] clients = retrieveClientHandles();
      unlockFile();
      return clients;
    }
    return null;
  }
  /**
   * get list from the locked ClientList.
   * @param extantlock
   * @return clientList or null if lock failed (or file was empty)
   */
  public ClientHandle[] retrieveClientList(Lock extantlock) {
    if (lockFile(extantlock)) {
      ClientHandle[] clients = retrieveClientHandles();
      unlockFile();
      return clients;
    }
    return null;
  }
  /**
   * adds clientHandle me to the clientList under an existing lock extantLock.
   * @param me
   * @param extantLock
   * @return client index in list or 0 if lock was invalid or addClient operation failed.
   */
  public int addClient(ClientHandle me, Lock extantLock) {
    return addClient(me, true, extantLock);
  }
  
  /**
   * adds clientHandle me to the clientList under an existing lock.
   * @param me - clientHandle
   * @param disambig - if true then add will fail if an identical clientHandle already exists
   * @param extantLock - existing lock
   * @return client index in list or 0 if addClient (or the lock) failed.
   */
  
  public int addClient(ClientHandle me, boolean disambig, Lock extantLock) {
    if (lockFile(extantLock)) {
      syncnum = addClient(me, disambig);
      unlockFile();
      return syncnum;
    }
    return 0;
  }
  
  /**
   * adds the ClientHandle to the list - if it is not unique, then the
   * ClientHandle object is modified to make it unique in the list. returns the
   * clientNumber for the client in the session.
   * 
   * @param me
   * @return
   */

  public int addClient(ClientHandle me) {
    syncnum = addClient(me, true);
    unlockFile();
    return syncnum;
  }

  /**
   * removes 'me' from the session ClientList without complaint if 'me' isn't in the clientList already.
   * @param me client handle to be removed
   * @param clientlock existing lock passed from watcher.
   */
  public void removeClient(ClientHandle me, Lock clientlock) {
    int mynum=-1;
    if (lockFile(clientlock)) {
      ClientHandle[] clients = retrieveClientHandles();
      if (clients != null) {
        if ((syncnum<=0 || syncnum>clients.length) || clients[syncnum-1]!=me) {
          for (int i = 0, j = clients.length; i < j; i++) 
            if (clients[i].equals(me)) {
              mynum=i;
              break;
            }
        } else {
          mynum=syncnum-1;
        }
        if (mynum>-1) {
          ClientHandle[] newlist = new ClientHandle[clients.length - 1];
          for (int k=0,i = 0, j = clients.length; i < j; i++)
            if (i!=mynum)
              newlist[k++] = clients[i];
          if (!putClientList(newlist))
            throw new Error("Failed to write new clientList!"); // failed to put the clientList to disk.
        }
      }
      unlockFile();
    } else {
      throw new Error("Couldn't get lock for "+((sessionFile==null) ? "Unitialised sessionFile in ClientsFile" : sessionFile.getAbsolutePath()));
    }
  }
  /**
   * Adds a ClientHandle to the ClientList file - optionally disambiguating 
   * the ClientHandle (modifes the URN). 
   * Note: Caller is left to release the lock on the ClientList.
   * @param me
   * @param disambiguate -
   *          flag indicating if the URN for me should be disambiguated to
   *          differentiate between sessions.
   * @return index of clientHandle in new list, or -1-position of existing
   *         clientHandle (if disambiguate is true)
   */
  protected int addClient(ClientHandle me, boolean disambiguate) {
    int newclient = 0;
    int tries=5;
    while (tries-->0 && !lockFile())
      try { Thread.sleep(1); } catch (Exception e){};
    if (lockFile()) {
      ClientHandle[] clients = retrieveClientHandles();
      if (me.getClientUrn()==null) {
        // TODO: move this into ClientUrn as a standard form method.
        me.setClientUrn("vamsas://"+me.getClientName()+":"+me.getVersion()+"/");
      }
      if (clients == null) {
        clients = new ClientHandle[1];
        clients[0] = me;
        newclient = 1;
      } else {
        int k = 0;
        for (int i = 0, j = clients.length; i < j; i++) {
          if (clients[i].equals(me)) {
            if (disambiguate) {
              while (clients[i].equals(me)) {
                me.setClientUrn(me.getClientUrn() + k++); // TODO: make a better
                                                          // disambiguation of
                                                          // urn.
              }
            } else {
              // will not write the ambiguous clientHandle to disk, just return
              // its index.
              return -1 - i;
            }
          }
        }
        int i, j;
        ClientHandle[] newlist = new ClientHandle[clients.length + 1];
        for (i = 0, j = clients.length; i < j; i++)
          newlist[i] = clients[i];
        newlist[j] = me;
        clients = newlist;
        newclient = j+1;
      }
      if (!putClientList(clients))
        return 0; // failed to put the clientList to disk.
    }
    return newclient;
  }
  /**
   * when set true - get FileNotFoundExceptions on WinXP when writing to locked stream after the backup has been made (via the backupFile method)
   */
  boolean backup=false;
  /**
   * safely writes clients array to the file referred to by sessionFile.
   * 
   * @param clients
   * @return true if successful write. Throws Errors otherwise.
   */
  protected boolean putClientList(ClientHandle[] clients) {
    if (lockFile()) {
      File templist=null;
      if (backup) {
        templist = backupSessionFile();
      }
      if (!backup || (templist != null)) {
        int retries=3;
        while (retries-->0) {
          try {
            ObjectOutputStream os = 
              new ObjectOutputStream(fileLock.getBufferedOutputStream(true));
            log.debug("About to write "+clients.length+" clientHandles to output stream.");
            os.writeObject(clients);
            os.close();
          // All done - remove the backup.
          if (backup)
            templist.delete();
          templist = null;
          retries=-1;
          } catch (Exception e) {
            System.err
            .println("Serious - problems writing to sessionFile.");
            if (retries>0 && templist != null) {
              System.err.println("Recovering from Backup in "
                      + templist.getAbsolutePath());
              templist.renameTo(fileLock.target);
            }
            e.printStackTrace(System.err);
          }
        }
        if (retries>-2) {
          System.err
          .println("Serious - problems writing to sessionFile. Giving Up.");
          return false;
        }
      } else {
        throw new Error(
            "Couldn't create backup of the clientList before writing to it!");
      }
    } else {
      throw new Error("Could not lock the clientList: "
          + ((sessionFile == null) ? "Unitialized ClientsFile"
              : " failed to get lock on " + sessionFile.getAbsolutePath()));
    }
    // successful!
    return true;
  }

  public void clearList() {
    if (lockFile()) {
      try {
        FileOutputStream fout = fileLock.getFileOutputStream(true);
        fout.flush();
        fout.close();
      } catch (Exception e) {
        throw new Error("Problems trying to clear clientlist!",e);
        
      }
    }
    
  }
}