/*******************************************************************************
 * Copyright (c) 1998, 2013 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the 
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
 ******************************************************************************/  
package org.eclipse.persistence.sequencing;

import java.util.Vector;
import org.eclipse.persistence.internal.databaseaccess.Accessor;
import org.eclipse.persistence.internal.sessions.AbstractSession;

/**
 * <p>
 * <b>Purpose</b>: Reference to the default sequence.
 * <p>
 * <b>Description</b>
 * This sequence can be used to provide a sequence using the session's
 * default sequencing mechanism but override the pre-allocation size.
 */
public class DefaultSequence extends Sequence {
    protected Sequence defaultSequence;

    public DefaultSequence() {
        super();
    }

    /**
     * Create a new sequence with the name.
     */
    public DefaultSequence(String name) {
        super(name, 0);
    }
    
    /**
     * Create a new sequence with the name and sequence pre-allocation size.
     */
    public DefaultSequence(String name, int size) {
        super(name, size);
    }

    public DefaultSequence(String name, int size, int initialValue) {
        super(name, size, initialValue);
    }
    
    /**
     * INTERNAL:
     * Return the platform's default sequence.
     */
    public Sequence getDefaultSequence() {
        return getDatasourcePlatform().getDefaultSequence();
    }

    public boolean hasPreallocationSize() {
        return size != 0;
    }

    public int getPreallocationSize() {
        if ((size != 0) || (getDefaultSequence() == null)) {
            return size;
        } else {
            return getDefaultSequence().getPreallocationSize();
        }
    }

    public int getInitialValue() {
        if ((initialValue != 0) || (getDefaultSequence() == null)) {
            return initialValue;
        } else {
            return getDefaultSequence().getInitialValue();
        }
    }

    public boolean equals(Object obj) {
        if (obj instanceof DefaultSequence) {
            return equalNameAndSize(this, (DefaultSequence)obj);
        } else {
            return false;
        }
    }

    /**
     * INTERNAL:
     * Indicates whether sequencing value should be acquired after INSERT.
     * Note that preallocation could be used only in case sequencing values
     * should be acquired before insert (this method returns false).
     * In default implementation, it is true for table sequencing and native
     * sequencing on Oracle platform, false for native sequencing on other platforms.
     */
    public boolean shouldAcquireValueAfterInsert() {
        return getDefaultSequence().shouldAcquireValueAfterInsert();
    }

    /**
     * INTERNAL:
     * Indicates whether the existing pk value should always be overridden by the sequence.
     */
    public boolean shouldAlwaysOverrideExistingValue(String seqName) {
        return this.shouldAlwaysOverrideExistingValue || getDefaultSequence().shouldAlwaysOverrideExistingValue(seqName);
    }
    
    /**
     * INTERNAL:
     * Indicates whether several sequencing values should be acquired at a time
     * and be kept by TopLink. This in only possible in case sequencing numbers should
     * be acquired before insert (shouldAcquireValueAfterInsert()==false).
     * In default implementation, it is true for table sequencing and native
     * sequencing on Oracle platform, false for native sequencing on other platforms.
     */
    public boolean shouldUsePreallocation() {
        return getDefaultSequence().shouldUsePreallocation();
    }

    /**
     * INTERNAL:
     * Indicates whether EclipseLink should internally call beginTransaction() before
     * getGeneratedValue/Vector, and commitTransaction after.
     * In default implementation, it is true for table sequencing and
     * false for native sequencing.
     */
    public boolean shouldUseTransaction() {
        return getDefaultSequence().shouldUseTransaction();
    }

    /**
     * INTERNAL:
     * Return the newly-generated sequencing value.
     * Used only in case preallocation is not used (shouldUsePreallocation()==false).
     * Accessor may be non-null only in case shouldUseSeparateConnection()==true.
     * Even in this case accessor could be null - if SequencingControl().shouldUseSeparateConnection()==false;
     * Therefore in case shouldUseSeparateConnection()==true, implementation should handle
     * both cases: use a separate connection if provided (accessor != null), or get by
     * without it (accessor == null).
     * @param accessor Accessor is a separate sequencing accessor (may be null);
     * @param writeSession Session is a Session used for writing (either ClientSession or DatabaseSession);
     * @param seqName String is sequencing number field name
     */
    public Object getGeneratedValue(Accessor accessor, AbstractSession writeSession, String seqName) {
        return getDefaultSequence().getGeneratedValue(accessor, writeSession, seqName);
    }

    /**
     * INTERNAL:
     * Return a Vector of newly-generated sequencing values.
     * Used only in case preallocation is used (shouldUsePreallocation()==true).
     * Accessor may be non-null only in case shouldUseSeparateConnection()==true.
     * Even in this case accessor could be null - if SequencingControl().shouldUseSeparateConnection()==false;
     * Therefore in case shouldUseSeparateConnection()==true, implementation should handle
     * both cases: use a separate connection if provided (accessor != null), or get by
     * without it (accessor == null).
     * @param accessor Accessor is a separate sequencing accessor (may be null);
     * @param writeSession Session is a Session used for writing (either ClientSession or DatabaseSession);
     * @param seqName String is sequencing number field name
     * @param size int number of values to preallocate (output Vector size).
     */
    public Vector getGeneratedVector(Accessor accessor, AbstractSession writeSession, String seqName, int size) {
        return getDefaultSequence().getGeneratedVector(accessor, writeSession, seqName, size);
    }

    /**
     * INTERNAL:
     * This method is called when Sequencing object is created.
     * It's a chance to do initialization.
     */
    public void onConnect() {
        qualifier = getDefaultSequence().getQualifier();
    }

    /**
     * INTERNAL:
     * This method is called when Sequencing object is destroyed..
     * It's a chance to do deinitialization.
     */
    public void onDisconnect() {
        qualifier = "";
    }

    /**
     * PUBLIC:
     * Indicates that Sequence is connected.
     */
    public boolean isConnected() {
        return getDefaultSequence().isConnected();
    }
    
    /**
     * INTERNAL:
     * Ignored, getDefaultSequence().getQualifier() used instead.
     */
    public void setQualifier(String qualifier) {
    }
}
