/*******************************************************************************
 *  Copyright (c) 2000, 2009 IBM Corporation and others.
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  which accompanies this distribution, and is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 * 
 *  Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.resources;

import org.eclipse.core.runtime.IPath;

/**
 * A context for workspace <code>save</code> operations.
 * <p>
 * Note that <code>IWorkspace.save</code> uses a different save context for each registered
 * participant, allowing each to declare whether they have actively participated and decide whether
 * to receive a resource delta on reactivation.
 * </p>
 * 
 * @see IWorkspace#save(boolean, org.eclipse.core.runtime.IProgressMonitor)
 * @noimplement This interface is not intended to be implemented by clients.
 * @noextend This interface is not intended to be extended by clients.
 */
public interface ISaveContext {

	/*====================================================================
	 * Constants related to save kind
	 *====================================================================*/

	/**
	 * Type constant which identifies a full save.
	 * 
	 * @see ISaveContext#getKind()
	 */
	public static final int FULL_SAVE= 1;

	/**
	 * Type constant which identifies a snapshot.
	 * 
	 * @see ISaveContext#getKind()
	 */
	public static final int SNAPSHOT= 2;

	/**
	 * Type constant which identifies a project save.
	 * 
	 * @see ISaveContext#getKind()
	 */
	public static final int PROJECT_SAVE= 3;

	/**
	 * Returns current files mapped with the <code>ISaveContext.map</code> facility or an empty
	 * array if there are no mapped files.
	 * 
	 * @return the files currently mapped by the participant
	 * 
	 * @see #map(IPath, IPath)
	 */
	public IPath[] getFiles();

	/**
	 * Returns the type of this save. The types can be:
	 * <ul>
	 * <li> <code>ISaveContext.FULL_SAVE</code></li>
	 * <li> <code>ISaveContext.SNAPSHOT</code></li>
	 * <li> <code>ISaveContext.PROJECT_SAVE</code></li>
	 * </ul>
	 * 
	 * @return the type of the current save
	 */
	public int getKind();

	/**
	 * Returns the number for the previous save in which the plug-in actively participated, or
	 * <code>0</code> if the plug-in has never actively participated in a save before.
	 * <p>
	 * In the event of an unsuccessful save, this is the value to <code>rollback</code> to.
	 * </p>
	 * 
	 * @return the previous save number if positive, or <code>0</code> if never saved before
	 * @see ISaveParticipant#rollback(ISaveContext)
	 */
	public int getPreviousSaveNumber();

	/**
	 * If the current save is a project save, this method returns the project being saved.
	 * 
	 * @return the project being saved or <code>null</code> if this is not project save
	 * 
	 * @see #getKind()
	 */
	public IProject getProject();

	/**
	 * Returns the number for this save. This number is guaranteed to be <code>1</code> more than
	 * the previous save number.
	 * <p>
	 * This is the value to use when, for example, creating files in which a participant will save
	 * its data.
	 * </p>
	 * 
	 * @return the save number
	 * @see ISaveParticipant#saving(ISaveContext)
	 */
	public int getSaveNumber();

	/**
	 * Returns the current location for the given file or <code>null</code> if none.
	 * 
	 * @return the location of a given file or <code>null</code>
	 * @see #map(IPath, IPath)
	 * @see ISavedState#lookup(IPath)
	 */
	public IPath lookup(IPath file);

	/**
	 * Maps the given plug-in file to its real location. This method is intended to be used with
	 * <code>ISaveContext.getSaveNumber()</code> to map plug-in configuration file names to real
	 * locations.
	 * <p>
	 * For example, assume a plug-in has a configuration file named "config.properties". The map
	 * facility can be used to map that logical name onto a real name which is specific to a
	 * particular save (e.g., 10.config.properties, where 10 is the current save number). The paths
	 * specified here should always be relative to the plug-in state location for the plug-in saving
	 * the state.
	 * </p>
	 * <p>
	 * Each save participant must manage the deletion of its old state files. Old state files can be
	 * discovered using <code>getPreviousSaveNumber</code> or by using <code>getFiles</code> to
	 * discover the current files and comparing that to the list of files on disk.
	 * </p>
	 * 
	 * @param file the logical name of the participant's data file
	 * @param location the real (i.e., filesystem) name by which the file should be known for this
	 *            save, or <code>null</code> to remove the entry
	 * @see #lookup(IPath)
	 * @see #getSaveNumber()
	 * @see #needSaveNumber()
	 * @see ISavedState#lookup(IPath)
	 */
	public void map(IPath file, IPath location);

	/**
	 * Indicates that the saved workspace tree should be remembered so that a delta will be
	 * available in a subsequent session when the plug-in re-registers to participate in saves. If
	 * this method is not called, no resource delta will be made available. This facility is not
	 * available for marker deltas. Plug-ins must assume that all markers may have changed when they
	 * are activated.
	 * <p>
	 * Note that this is orthogonal to <code>needSaveNumber</code>. That is, one can ask for a delta
	 * regardless of whether or not one is an active participant.
	 * </p>
	 * <p>
	 * Note that deltas are not guaranteed to be saved even if saving is requested. Deltas cannot be
	 * supplied where the previous state is too old or has become invalid.
	 * </p>
	 * <p>
	 * This method is only valid for full saves. It is ignored during snapshots or project saves.
	 * </p>
	 * 
	 * @see IWorkspace#addSaveParticipant(org.eclipse.core.runtime.Plugin, ISaveParticipant)
	 * @see ISavedState#processResourceChangeEvents(IResourceChangeListener)
	 */
	public void needDelta();

	/**
	 * Indicates that this participant has actively participated in this save. If the save is
	 * successful, the current save number will be remembered; this save number will be the previous
	 * save number for subsequent saves until the participant again actively participates.
	 * <p>
	 * If this method is not called, the plug-in is not deemed to be an active participant in this
	 * save.
	 * </p>
	 * <p>
	 * Note that this is orthogonal to <code>needDelta</code>. That is, one can be an active
	 * participant whether or not one asks for a delta.
	 * </p>
	 * 
	 * @see IWorkspace#addSaveParticipant(org.eclipse.core.runtime.Plugin, ISaveParticipant)
	 * @see ISavedState#getSaveNumber()
	 */
	public void needSaveNumber();
}