/*******************************************************************************
 * Copyright (c) 2000, 2007 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.jdt.core;

import org.eclipse.core.resources.IResourceDelta;
import org.eclipse.jdt.core.dom.CompilationUnit;

/**
 * A Java element delta describes changes in Java element between two discrete
 * points in time.  Given a delta, clients can access the element that has 
 * changed, and any children that have changed.
 * <p>
 * Deltas have a different status depending on the kind of change they represent.  
 * The list below summarizes each status (as returned by {@link #getKind})
 * and its meaning (see individual constants for a more detailled description):
 * <ul>
 * <li>{@link #ADDED} - The element described by the delta has been added.</li>
 * <li>{@link #REMOVED} - The element described by the delta has been removed.</li>
 * <li>{@link #CHANGED} - The element described by the delta has been changed in some way.  
 * Specification of the type of change is provided by {@link #getFlags} which returns the following values:
 * <ul>
 * <li>{@link #F_ADDED_TO_CLASSPATH} - A classpath entry corresponding to the element
 * has been added to the project's classpath. This flag is only valid if the element is an 
 * {@link IPackageFragmentRoot}.</li>
 * <li>{@link #F_ARCHIVE_CONTENT_CHANGED} - The contents of an archive
 * has changed in some way. This flag is only valid if the element is an {@link IPackageFragmentRoot}
 * which is an archive.</li>
 * <li>{@link #F_CHILDREN} - A child of the element has changed in some way.  This flag
 * is only valid if the element is an {@link IParent}.</li>
 * <li>{@link #F_CLASSPATH_REORDER} - A classpath entry corresponding to the element
 * has changed position in the project's classpath. This flag is only valid if the element is an 
 * {@link IPackageFragmentRoot}.</li>
 * <li>{@link #F_CLOSED} - The underlying {@link org.eclipse.core.resources.IProject}
 * has been closed. This flag is only valid if the element is an {@link IJavaProject}.</li>
 * <li>{@link #F_CONTENT} - The contents of the element have been altered.  This flag
 * is only valid for elements which correspond to files.</li>
 *<li>{@link #F_FINE_GRAINED} - The delta is a fine-grained delta, that is, an analysis down
 * to the members level was done to determine if there were structural changes to members of the element.</li>
 * <li>{@link #F_MODIFIERS} - The modifiers on the element have changed in some way. 
 * This flag is only valid if the element is an {@link IMember}.</li>
 * <li>{@link #F_OPENED} - The underlying {@link org.eclipse.core.resources.IProject}
 * has been opened. This flag is only valid if the element is an {@link IJavaProject}.</li>
 * <li>{@link #F_REMOVED_FROM_CLASSPATH} - A classpath entry corresponding to the element 
 * has been removed from the project's classpath. This flag is only valid if the element is an 
 * {@link IPackageFragmentRoot}.</li>
 * <li>{@link #F_SOURCEATTACHED} - The source attachment path or the source attachment root path
 * of a classpath entry corresponding to the element was added. This flag is only valid if the element is an 
 * {@link IPackageFragmentRoot}.</li>
 * <li>{@link #F_SOURCEDETACHED} - The source attachment path or the source attachment root path
 * of a classpath entry corresponding to the element was removed. This flag is only valid if the element is an 
 * {@link IPackageFragmentRoot}.</li>
 * <li>{@link #F_SUPER_TYPES} - One of the supertypes of an {@link IType} has changed</li>.
 * </ul>
 * </li>
 * </ul>
 * </p>
 * <p>
 * Move operations are indicated by other change flags, layered on top
 * of the change flags described above. If element A is moved to become B,
 * the delta for the  change in A will have status {@link #REMOVED},
 * with change flag {@link #F_MOVED_TO}. In this case,
 * {@link #getMovedToElement} on delta A will return the handle for B.
 * The  delta for B will have status {@link #ADDED}, with change flag
 * {@link #F_MOVED_FROM}, and {@link #getMovedFromElement} on delta
 * B will return the handle for A. (Note, the handle to A in this case represents
 * an element that no longer exists).
 * </p>
 * <p>
 * Note that the move change flags only describe the changes to a single element, they
 * do not imply anything about the parent or children of the element.
 * </p>
 * <p>
 * The {@link #F_ADDED_TO_CLASSPATH}, {@link #F_REMOVED_FROM_CLASSPATH} and
 * {@link #F_CLASSPATH_REORDER} flags are triggered by changes to a project's classpath. They do not mean that
 * the underlying resource was added, removed or changed. For example, if a project P already contains a folder src, then 
 * adding a classpath entry with the 'P/src' path to the project's classpath will result in an {@link IJavaElementDelta} 
 * with the {@link #F_ADDED_TO_CLASSPATH} flag for the {@link IPackageFragmentRoot} P/src.
 * On the contrary, if a resource is physically added, removed or changed and this resource corresponds to a classpath
 * entry of the project, then an {@link IJavaElementDelta} with the {@link #ADDED}, 
 * {@link #REMOVED}, or {@link #CHANGED} kind will be fired.
 * </p>
 * <p>
 * Note that when a source attachment path or a source attachment root path is changed, then the flags of the delta contain
 * both {@link #F_SOURCEATTACHED} and {@link #F_SOURCEDETACHED}.
 * </p>
 * <p>
 * No assumptions should be made on whether the java element delta tree is rooted at the {@link IJavaModel}
 * level or not.
 * </p>
 * <p>
 * {@link IJavaElementDelta} object are not valid outside the dynamic scope
 * of the notification.
 * </p>
 * <p>
 * This interface is not intended to be implemented by clients.
 * </p>
 */
public interface IJavaElementDelta {

	/**
	 * Status constant indicating that the element has been added.
	 * Note that an added java element delta has no children, as they are all implicitely added.
	 */
	public int ADDED = 1;

	/**
	 * Status constant indicating that the element has been removed.
	 * Note that a removed java element delta has no children, as they are all implicitely removed.
	 */
	public int REMOVED = 2;

	/**
	 * Status constant indicating that the element has been changed,
	 * as described by the change flags.
	 * 
	 * @see #getFlags()
	 */
	public int CHANGED = 4;

	/**
	 * Change flag indicating that the content of the element has changed.
	 * This flag is only valid for elements which correspond to files.
	 */
	public int F_CONTENT = 0x000001;

	/**
	 * Change flag indicating that the modifiers of the element have changed.
	 * This flag is only valid if the element is an {@link IMember}. 
	 */
	public int F_MODIFIERS = 0x000002;

	/**
	 * Change flag indicating that there are changes to the children of the element.
	 * This flag is only valid if the element is an {@link IParent}. 
	 */
	public int F_CHILDREN = 0x000008;

	/**
	 * Change flag indicating that the element was moved from another location.
	 * The location of the old element can be retrieved using {@link #getMovedFromElement}.
	 */
	public int F_MOVED_FROM = 0x000010;

	/**
	 * Change flag indicating that the element was moved to another location.
	 * The location of the new element can be retrieved using {@link #getMovedToElement}.
	 */
	public int F_MOVED_TO = 0x000020;

	/**
	 * Change flag indicating that a classpath entry corresponding to the element has been added to the project's classpath. 
	 * This flag is only valid if the element is an {@link IPackageFragmentRoot}.
	 */
	public int F_ADDED_TO_CLASSPATH = 0x000040;

	/**
	 * Change flag indicating that a classpath entry corresponding to the element has been removed from the project's 
	 * classpath. This flag is only valid if the element is an {@link IPackageFragmentRoot}.
	 */
	public int F_REMOVED_FROM_CLASSPATH = 0x000080;

	/**
	 * Change flag indicating that a classpath entry corresponding to the element has changed position in the project's 
	 * classpath. This flag is only valid if the element is an {@link IPackageFragmentRoot}.
	 * @deprecated Use {@link #F_REORDER} instead.
	 */
	public int F_CLASSPATH_REORDER = 0x000100;
	/**
	 * Change flag indicating that the element has changed position relatively to its siblings. 
	 * If the element is an {@link IPackageFragmentRoot},  a classpath entry corresponding 
	 * to the element has changed position in the project's classpath.
	 * 
	 * @since 2.1
	 */
	public int F_REORDER = 0x000100;

	/**
	 * Change flag indicating that the underlying {@link org.eclipse.core.resources.IProject} has been
	 * opened. This flag is only valid if the element is an {@link IJavaProject}. 
	 */
	public int F_OPENED = 0x000200;

	/**
	 * Change flag indicating that the underlying {@link org.eclipse.core.resources.IProject} has been
	 * closed. This flag is only valid if the element is an {@link IJavaProject}. 
	 */
	public int F_CLOSED = 0x000400;

	/**
	 * Change flag indicating that one of the supertypes of an {@link IType}
	 * has changed.
	 */
	public int F_SUPER_TYPES = 0x000800;

	/**
	 * Change flag indicating that the source attachment path or the source attachment root path of a classpath entry 
	 * corresponding to the element was added. This flag is only valid if the element is an 
	 * {@link IPackageFragmentRoot}.
	 */
	public int F_SOURCEATTACHED = 0x001000;	

	/**
	 * Change flag indicating that the source attachment path or the source attachment root path of a classpath entry 
	 * corresponding to the element was removed. This flag is only valid if the element is an 
	 * {@link IPackageFragmentRoot}.
	 */
	public int F_SOURCEDETACHED = 0x002000;	
	
	/**
	 * Change flag indicating that this is a fine-grained delta, that is, an analysis down
	 * to the members level was done to determine if there were structural changes to
	 * members.
	 * <p>
	 * Clients can use this flag to find out if a compilation unit 
     * that have a {@link #F_CONTENT} change should assume that there are 
     * no finer grained changes ({@link #F_FINE_GRAINED} is set) or if 
     * finer grained changes were not considered ({@link #F_FINE_GRAINED} 
     * is not set). 
     * 
     * @since 2.0
	 */
	public int F_FINE_GRAINED = 0x004000;

	/**
	 * Change flag indicating that the element's archive content on the classpath has changed.
	 * This flag is only valid if the element is an {@link IPackageFragmentRoot}
	 * which is an archive.
	 * 
	 * @see IPackageFragmentRoot#isArchive()
	 * @since 2.0
	 */
	public int F_ARCHIVE_CONTENT_CHANGED = 0x008000;
	
	/**
	 * Change flag indicating that a compilation unit has become a primary working copy, or that a 
	 * primary working copy has reverted to a compilation unit.
	 * This flag is only valid if the element is an {@link ICompilationUnit}.
	 * 
	 * @since 3.0
	 */
	public int F_PRIMARY_WORKING_COPY = 0x010000;

	/**
	 * Change flag indicating that the raw classpath (or the output folder) of a project has changed. 
	 * This flag is only valid if the element is an {@link IJavaProject}.
	 *
	 * @since 3.0
	 */
	public int F_CLASSPATH_CHANGED = 0x020000;

	/**
	 * Change flag indicating that the resource of a primary compilation unit has changed.
	 * This flag is only valid if the element is a primary {@link ICompilationUnit}.
	 * 
	 * @since 3.0
	 */
	public int F_PRIMARY_RESOURCE = 0x040000;

	/**
	 * Change flag indicating that a reconcile operation has affected the compilation unit AST created in a 
	 * previous reconcile operation. Use {@link #getCompilationUnitAST()} to retrieve the AST (if any is available).
	 * This flag is only valid if the element is an {@link ICompilationUnit} in working copy mode.
	 * 
	 * @since 3.2
	 */
	public int F_AST_AFFECTED = 0x080000;
	
	/**
	 * Change flag indicating that the categories of the element have changed.
	 * This flag is only valid if the element is an {@link IMember}. 
	 * 
	 * @since 3.2
	 */
	public int F_CATEGORIES = 0x100000;
	
	/**
	 * Returns deltas for the children that have been added.
	 * @return deltas for the children that have been added
	 */
	public IJavaElementDelta[] getAddedChildren();

	/**
	 * Returns deltas for the affected (added, removed, or changed) children.
	 * @return deltas for the affected (added, removed, or changed) children
	 */
	public IJavaElementDelta[] getAffectedChildren();
	
	/**
	 * Returns the compilation unit AST created by the last reconcile operation on this delta's element.
	 * This returns a non-null value if and only if:
	 * <ul>
	 * <li>the last reconcile operation on this working copy requested an AST</li>
	 * <li>this delta's element is an {@link ICompilationUnit} in working copy mode</li>
	 * <li>the delta comes from a {@link ElementChangedEvent#POST_RECONCILE} event
	 * </ul>
	 * 
	 * @return the AST created during the last reconcile operation
	 * @see ICompilationUnit#reconcile(int, boolean, WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)
	 * @see #F_AST_AFFECTED
	 * @since 3.2
	 */
	public CompilationUnit getCompilationUnitAST();

	/**
	 * Returns deltas for the children which have changed.
	 * @return deltas for the children which have changed
	 */
	public IJavaElementDelta[] getChangedChildren();

	/**
	 * Returns the element that this delta describes a change to.
	 * @return the element that this delta describes a change to
	 */
	public IJavaElement getElement();

	/**
	 * Returns flags that describe how an element has changed. 
	 * Such flags should be tested using the <code>&</code> operand. For example:
	 * <pre>
	 * if ((delta.getFlags() & IJavaElementDelta.F_CONTENT) != 0) {
	 * 	// the delta indicates a content change
	 * }
	 * </pre>
	 *
	 * @return flags that describe how an element has changed
	 */
	public int getFlags();

	/**
	 * Returns the kind of this delta - one of {@link #ADDED}, {@link #REMOVED},
	 * or {@link #CHANGED}.
	 * 
	 * @return the kind of this delta
	 */
	public int getKind();

	/**
	 * Returns an element describing this element before it was moved
	 * to its current location, or <code>null</code> if the
	 * {@link #F_MOVED_FROM} change flag is not set. 
	 * 
	 * @return an element describing this element before it was moved
	 * to its current location, or <code>null</code> if the
	 * {@link #F_MOVED_FROM} change flag is not set
	 */
	public IJavaElement getMovedFromElement();

	/**
	 * Returns an element describing this element in its new location,
	 * or <code>null</code> if the {@link #F_MOVED_TO} change
	 * flag is not set.
	 * 
	 * @return an element describing this element in its new location,
	 * or <code>null</code> if the {@link #F_MOVED_TO} change
	 * flag is not set
	 */
	public IJavaElement getMovedToElement();

	/**
	 * Returns deltas for the children which have been removed.
	 * 
	 * @return deltas for the children which have been removed
	 */
	public IJavaElementDelta[] getRemovedChildren();

	/**
	 * Returns the collection of resource deltas.
	 * <p>
	 * Note that resource deltas, like Java element deltas, are generally only valid
	 * for the dynamic scope of an event notification. Clients must not hang on to
	 * these objects.
	 * </p>
	 *
	 * @return the underlying resource deltas, or <code>null</code> if none
	 */
	public IResourceDelta[] getResourceDeltas();
}
