/*******************************************************************************
 * Copyright (c) 2006, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.resources.mapping;

import org.eclipse.core.internal.utils.Policy;
import org.eclipse.core.resources.*;
import org.eclipse.core.resources.mapping.IResourceChangeDescriptionFactory;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IPath;

/**
 * Factory for creating a resource delta that describes a proposed change.
 */
public class ResourceChangeDescriptionFactory implements IResourceChangeDescriptionFactory {
	private ProposedResourceDelta root = new ProposedResourceDelta(ResourcesPlugin.getWorkspace().getRoot());

	/**
	 * Creates and a delta representing a deleted resource, and adds it to the provided
	 * parent delta.
	 * @param parentDelta The parent of the deletion delta to create
	 * @param resource The deleted resource to create a delta for
	 */
	private ProposedResourceDelta buildDeleteDelta(ProposedResourceDelta parentDelta, IResource resource) {
		//start with the existing delta for this resource, if any, to preserve other flags
		ProposedResourceDelta delta = parentDelta.getChild(resource.getName());
		if (delta == null) {
			delta = new ProposedResourceDelta(resource);
			parentDelta.add(delta);
		}
		delta.setKind(IResourceDelta.REMOVED);
		if (resource.getType() == IResource.FILE)
			return delta;
		//recurse to build deletion deltas for children
		try {
			IResource[] members = ((IContainer) resource).members();
			int childCount = members.length;
			if (childCount > 0) {
				ProposedResourceDelta[] childDeltas = new ProposedResourceDelta[childCount];
				for (int i = 0; i < childCount; i++)
					childDeltas[i] = buildDeleteDelta(delta, members[i]);
			}
		} catch (CoreException e) {
			//don't need to create deletion deltas for children of inaccessible resources
		}
		return delta;
	}

	@Override
	public void change(IFile file) {
		ProposedResourceDelta delta = getDelta(file);
		if (delta.getKind() == 0)
			delta.setKind(IResourceDelta.CHANGED);
		//the CONTENT flag only applies to the changed and moved from cases
		if (delta.getKind() == IResourceDelta.CHANGED || (delta.getFlags() & IResourceDelta.MOVED_FROM) != 0 || (delta.getFlags() & IResourceDelta.COPIED_FROM) != 0)
			delta.addFlags(IResourceDelta.CONTENT);
	}

	@Override
	public void close(IProject project) {
		delete(project);
		ProposedResourceDelta delta = getDelta(project);
		delta.addFlags(IResourceDelta.OPEN);
	}

	@Override
	public void copy(IResource resource, IPath destination) {
		moveOrCopyDeep(resource, destination, false /* copy */);
	}

	@Override
	public void create(IResource resource) {
		getDelta(resource).setKind(IResourceDelta.ADDED);
	}

	@Override
	public void delete(IResource resource) {
		if (resource.getType() == IResource.ROOT) {
			//the root itself cannot be deleted, so create deletions for each project
			IProject[] projects = ((IWorkspaceRoot) resource).getProjects(IContainer.INCLUDE_HIDDEN);
			for (IProject project : projects)
				buildDeleteDelta(root, project);
		} else {
			buildDeleteDelta(getDelta(resource.getParent()), resource);
		}
	}

	private void fail(CoreException e) {
		Policy.log(e.getStatus().getSeverity(), "An internal error occurred while accumulating a change description.", e); //$NON-NLS-1$
	}

	@Override
	public IResourceDelta getDelta() {
		return root;
	}

	ProposedResourceDelta getDelta(IResource resource) {
		ProposedResourceDelta delta = (ProposedResourceDelta) root.findMember(resource.getFullPath());
		if (delta != null) {
			return delta;
		}
		ProposedResourceDelta parent = getDelta(resource.getParent());
		delta = new ProposedResourceDelta(resource);
		parent.add(delta);
		return delta;
	}

	/*
	 * Return the resource at the destination path that corresponds to the source resource
	 * @param source the source resource
	 * @param sourcePrefix the path of the root of the move or copy
	 * @param destinationPrefix the path of the destination the root was copied to
	 * @return the destination resource
	 */
	protected IResource getDestinationResource(IResource source, IPath sourcePrefix, IPath destinationPrefix) {
		IPath relativePath = source.getFullPath().removeFirstSegments(sourcePrefix.segmentCount());
		IPath destinationPath = destinationPrefix.append(relativePath);
		IResource destination;
		IWorkspaceRoot wsRoot = ResourcesPlugin.getWorkspace().getRoot();
		switch (source.getType()) {
			case IResource.FILE :
				destination = wsRoot.getFile(destinationPath);
				break;
			case IResource.FOLDER :
				destination = wsRoot.getFolder(destinationPath);
				break;
			case IResource.PROJECT :
				destination = wsRoot.getProject(destinationPath.segment(0));
				break;
			default :
				// Shouldn't happen
				destination = null;
		}
		return destination;
	}

	@Override
	public void move(IResource resource, IPath destination) {
		moveOrCopyDeep(resource, destination, true /* move */);
	}

	/**
	 * Builds the delta representing a single resource being moved or copied.
	 *
	 * @param resource The resource being moved
	 * @param sourcePrefix The root of the sub-tree being moved
	 * @param destinationPrefix The root of the destination sub-tree
	 * @param move <code>true</code> for a move, <code>false</code> for a copy
	 * @return Whether to move or copy the child
	 */
	boolean moveOrCopy(IResource resource, final IPath sourcePrefix, final IPath destinationPrefix, final boolean move) {
		ProposedResourceDelta sourceDelta = getDelta(resource);
		if (sourceDelta.getKind() == IResourceDelta.REMOVED) {
			// There is already a removed delta here so there
			// is nothing to move/copy
			return false;
		}
		IResource destinationResource = getDestinationResource(resource, sourcePrefix, destinationPrefix);
		ProposedResourceDelta destinationDelta = getDelta(destinationResource);
		if ((destinationDelta.getKind() & (IResourceDelta.ADDED | IResourceDelta.CHANGED)) > 0) {
			// There is already a resource at the destination
			// TODO: What do we do
			return false;
		}
		// First, create the delta for the source
		IPath fromPath = resource.getFullPath();
		boolean wasAdded = false;
		final int sourceFlags = sourceDelta.getFlags();
		if (move) {
			// We transfer the source flags to the destination
			if (sourceDelta.getKind() == IResourceDelta.ADDED) {
				if ((sourceFlags & IResourceDelta.MOVED_FROM) != 0) {
					// The resource was moved from somewhere else so
					// we need to transfer the path to the new location
					fromPath = sourceDelta.getMovedFromPath();
					sourceDelta.setMovedFromPath(null);
				}
				// The source was added and then moved so we'll
				// make it an add at the destination
				sourceDelta.setKind(0);
				wasAdded = true;
			} else {
				// We reset the status to be a remove/move_to
				sourceDelta.setKind(IResourceDelta.REMOVED);
				sourceDelta.setFlags(IResourceDelta.MOVED_TO);
				sourceDelta.setMovedToPath(destinationPrefix.append(fromPath.removeFirstSegments(sourcePrefix.segmentCount())));
			}
		}
		// Next, create the delta for the destination
		if (destinationDelta.getKind() == IResourceDelta.REMOVED) {
			// The destination was removed and is being re-added
			destinationDelta.setKind(IResourceDelta.CHANGED);
			destinationDelta.addFlags(IResourceDelta.REPLACED);
		} else {
			destinationDelta.setKind(IResourceDelta.ADDED);
		}
		if (!wasAdded || !fromPath.equals(resource.getFullPath())) {
			// The source wasn't added so it is a move/copy
			destinationDelta.addFlags(move ? IResourceDelta.MOVED_FROM : IResourceDelta.COPIED_FROM);
			destinationDelta.setMovedFromPath(fromPath);
			// Apply the source flags
			if (move)
				destinationDelta.addFlags(sourceFlags);
		}

		return true;
	}

	/**
	 * Helper method that generate a move or copy delta for a sub-tree
	 * of resources being moved or copied.
	 */
	private void moveOrCopyDeep(IResource resource, IPath destination, final boolean move) {
		final IPath sourcePrefix = resource.getFullPath();
		final IPath destinationPrefix = destination;
		try {
			//build delta for the entire sub-tree if available
			if (resource.isAccessible()) {
				resource.accept(child -> moveOrCopy(child, sourcePrefix, destinationPrefix, move));
			} else {
				//just build a delta for the single resource
				moveOrCopy(resource, sourcePrefix, destination, move);
			}
		} catch (CoreException e) {
			fail(e);
		}
	}
}
