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package org.apache.james.mailbox.jcr;

import javax.jcr.Node;
import javax.jcr.RepositoryException;
import javax.jcr.Session;

import org.apache.jackrabbit.commons.JcrUtils;
import org.apache.james.mailbox.MailboxSession;
import org.apache.james.mailbox.exception.MailboxException;
import org.apache.james.mailbox.store.transaction.TransactionalMapper;

/**
 * Abstract base class for Mapper's which support scaling. This supports Level 1 Implementations of JCR. So no real transaction management is used. 
 * 
 * The Session.save() will get called on commit() method,  session.refresh(false) on rollback, and session.refresh(true) on begin()
 *
 */
public abstract class AbstractJCRScalingMapper extends TransactionalMapper implements JCRImapConstants {
    public static final String MAILBOXES_PATH =  "mailboxes";

    private final MailboxSessionJCRRepository repository;
    private final int scaling;

    private final MailboxSession mSession;
    private static final char PAD = '_';
    
    public AbstractJCRScalingMapper(MailboxSessionJCRRepository repository, MailboxSession mSession, int scaling) {
        this.scaling = scaling;
        
        this.mSession = mSession;
        this.repository = repository;
    }
    
    /**
     * Return the JCR Session
     * 
     * @return session
     */
    protected Session getSession() throws RepositoryException {
        return repository.login(mSession);
    }

    /**
     * Begin is not supported by level 1 JCR implementations, however we refresh the session
     */
    @Override
    protected void begin() throws MailboxException {
        try {
            getSession().refresh(true);
        } catch (RepositoryException e) {
            // do nothin on refresh
        }
        // Do nothing
    }

    /**
     * Just call save on the underlying JCR Session, because level 1 JCR implementation does not offer Transactions
     */
    @Override
    protected void commit() throws MailboxException {
        try {
            if (getSession().hasPendingChanges()) {
                getSession().save();
            }
        } catch (RepositoryException e) {
            throw new MailboxException("Unable to commit", e);
        }
    }

    /**
     * Rollback is not supported by level 1 JCR implementations, so just do nothing
     */
    @Override
    protected void rollback() throws MailboxException {
        try {
            // just refresh session and discard all pending changes
            getSession().refresh(false);
        } catch (RepositoryException e) {
            // just catch on rollback by now
        }
    }

    /**
     * Logout from open JCR Session
     */
    @Override
    public void endRequest() {
       repository.logout(mSession);
    }
    
    /**
     * Construct the user node path part, using the specified scaling factor.
     * If the username is not long enough it will fill it with {@link #PAD}
     * 
     * So if you use a scaling of 2 it will look like:
     * 
     * foo:
     *     f/fo/foo
     *     
     * fo:
     *     f/fo/fo
     * 
     * f: 
     *    f/f_/f
     * 
     * @param username
     * @return path
     */
    protected String constructUserPathPart(String username) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < scaling; i++) {
            if (username.length() > i) {
                sb.append(username.substring(0,i + 1));
            } else {
                sb.append(username);
                int a = i - username.length();
                for (int b = 0; b < a; b++) {
                    sb.append(PAD);
                }
            }
            sb.append(NODE_DELIMITER);
        }
        sb.append(username);
        return sb.toString();

    }

    /**
     * Create the needed Node structure for the given username using the given Node as parent.
     * 
     * The method will use {@link #constructUserPathPart(String)} for create the needed node path and split
     * it when a NODE_DELIMITER was found
     * 
     * @param parent
     * @param username
     * @return userNode
     * @throws RepositoryException
     */
    protected Node createUserPathStructure(Node parent, String username)
            throws RepositoryException {
        String userpath = constructUserPathPart(username);

        String[] userPathParts = userpath.split(NODE_DELIMITER);
        for (int a = 0; a < userPathParts.length; a++) {
            parent = JcrUtils.getOrAddNode(parent, userPathParts[a],
                    "nt:unstructured");

            // thats the last user node so add the right mixin type
            if (a + 1 == userPathParts.length) {
                parent.addMixin("jamesMailbox:user");
            }
        }

        return parent;

    }
}




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