/*******************************************************************************
 * 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
 *
 
 *******************************************************************************/
package org.eclipse.dltk.internal.core;

import java.util.HashSet;
import java.util.Iterator;

import org.eclipse.core.resources.IProject;
import org.eclipse.core.resources.IProjectDescription;
import org.eclipse.core.resources.IWorkspaceRoot;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.dltk.compiler.CharOperation;
import org.eclipse.dltk.core.IBuildpathEntry;
import org.eclipse.dltk.core.ModelException;
import org.eclipse.dltk.internal.core.util.Util;


public class ProjectReferenceChange {
	
	private ScriptProject project;
	private IBuildpathEntry[] oldResolvedBuildpath;
	
	public ProjectReferenceChange(ScriptProject project, IBuildpathEntry[] oldResolvedBuildpath) {
		this.project = project;
		this.oldResolvedBuildpath = oldResolvedBuildpath;
	}

	/*
	 * Update projects references so that the build order is consistent with the buildpath
	 */
	public void updateProjectReferencesIfNecessary() throws ModelException {
		
		String[] oldRequired = this.oldResolvedBuildpath == null ? CharOperation.NO_STRINGS : this.project.projectPrerequisites(this.oldResolvedBuildpath);
		IBuildpathEntry[] newResolvedBuildpath = this.project.getResolvedBuildpath();
		String[] newRequired = this.project.projectPrerequisites(newResolvedBuildpath);
		try {
			IProject projectResource = this.project.getProject();
			IProjectDescription description = projectResource.getDescription();
			 
			IProject[] projectReferences = description.getDynamicReferences();
			
			HashSet oldReferences = new HashSet(projectReferences.length);
			for (int i = 0; i < projectReferences.length; i++){
				String projectName = projectReferences[i].getName();
				oldReferences.add(projectName);
			}
			HashSet newReferences = (HashSet)oldReferences.clone();
	
			for (int i = 0; i < oldRequired.length; i++){
				String projectName = oldRequired[i];
				newReferences.remove(projectName);
			}
			for (int i = 0; i < newRequired.length; i++){
				String projectName = newRequired[i];
				newReferences.add(projectName);
			}
	
			Iterator iter;
			int newSize = newReferences.size();
			
			checkIdentity: {
				if (oldReferences.size() == newSize){
					iter = newReferences.iterator();
					while (iter.hasNext()){
						if (!oldReferences.contains(iter.next())){
							break checkIdentity;
						}
					}
					return;
				}
			}
			String[] requiredProjectNames = new String[newSize];
			int index = 0;
			iter = newReferences.iterator();
			while (iter.hasNext()){
				requiredProjectNames[index++] = (String)iter.next();
			}
			Util.sort(requiredProjectNames); // ensure that if changed, the order is consistent
			
			IProject[] requiredProjectArray = new IProject[newSize];
			IWorkspaceRoot wksRoot = projectResource.getWorkspace().getRoot();
			for (int i = 0; i < newSize; i++){
				requiredProjectArray[i] = wksRoot.getProject(requiredProjectNames[i]);
			}
			description.setDynamicReferences(requiredProjectArray);
			projectResource.setDescription(description, null);
	
		} catch(CoreException e){
			//TODO: DLTK: External project support
//			if (!ExternalScriptProject.EXTERNAL_PROJECT_NAME.equals(this.project.getElementName()))
//				throw new ModelException(e);
		}
	}
}
