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/*******************************************************************************
 * Copyright (c) 2000, 2008 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.jface.text.link;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Stack;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jface.text.IDocument;


/**
 * A linked mode manager ensures exclusive access of linked position infrastructures to documents. There
 * is at most one LinkedModeManager installed on the same document. The getManager
 * methods will return the existing instance if any of the specified documents already have an installed
 * manager.
 *
 * @since 3.0
 */
class LinkedModeManager {

	/**
	 * Our implementation of ILinkedModeListener.
	 */
	private class Listener implements ILinkedModeListener {

		/*
		 * @see org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel.ILinkedModeListener#left(org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel, int)
		 */
		public void left(LinkedModeModel model, int flags) {
			LinkedModeManager.this.left(model, flags);
		}

		/*
		 * @see org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel.ILinkedModeListener#suspend(org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel)
		 */
		public void suspend(LinkedModeModel model) {
			// not interested
		}

		/*
		 * @see org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel.ILinkedModeListener#resume(org.eclipse.jdt.internal.ui.text.link2.LinkedModeModel, int)
		 */
		public void resume(LinkedModeModel model, int flags) {
			// not interested
		}

	}

	/** Global map from documents to managers. */
	private static Map fgManagers= new HashMap();

	/**
	 * Returns whether there exists a LinkedModeManager on document.
	 *
	 * @param document the document of interest
	 * @return true if there exists a LinkedModeManager on document, false otherwise
	 */
	public static boolean hasManager(IDocument document) {
		return fgManagers.get(document) != null;
	}

	/**
	 * Returns whether there exists a LinkedModeManager on any of the documents.
	 *
	 * @param documents the documents of interest
	 * @return true if there exists a LinkedModeManager on any of the documents, false otherwise
	 */
	public static boolean hasManager(IDocument[] documents) {
		for (int i= 0; i < documents.length; i++) {
			if (hasManager(documents[i]))
				return true;
		}
		return false;
	}

	/**
	 * Returns the manager for the given documents. If force is
	 * true, any existing conflicting managers are canceled, otherwise,
	 * the method may return null if there are conflicts.
	 *
	 * @param documents the documents of interest
	 * @param force whether to kill any conflicting managers
	 * @return a manager able to cover the requested documents, or null if there is a conflict and force was set to false
	 */
	public static LinkedModeManager getLinkedManager(IDocument[] documents, boolean force) {
		if (documents == null || documents.length == 0)
			return null;

		Set mgrs= new HashSet();
		LinkedModeManager mgr= null;
		for (int i= 0; i < documents.length; i++) {
			mgr= (LinkedModeManager) fgManagers.get(documents[i]);
			if (mgr != null)
				mgrs.add(mgr);
		}
		if (mgrs.size() > 1)
			if (force) {
				for (Iterator it= mgrs.iterator(); it.hasNext(); ) {
					LinkedModeManager m= (LinkedModeManager) it.next();
					m.closeAllEnvironments();
				}
			} else {
				return null;
			}

		if (mgrs.size() == 0)
			mgr= new LinkedModeManager();

		for (int i= 0; i < documents.length; i++)
			fgManagers.put(documents[i], mgr);

		return mgr;
	}

	/**
	 * Cancels any linked mode manager for the specified document.
	 *
	 * @param document the document whose LinkedModeManager should be canceled
	 */
	public static void cancelManager(IDocument document) {
		LinkedModeManager mgr= (LinkedModeManager) fgManagers.get(document);
		if (mgr != null)
			mgr.closeAllEnvironments();
	}

	/** The hierarchy of environments managed by this manager. */
	private Stack fEnvironments= new Stack();
	private Listener fListener= new Listener();

	/**
	 * Notify the manager about a leaving model.
	 *
	 * @param model the model to nest
	 * @param flags the reason and commands for leaving linked mode
	 */
	private void left(LinkedModeModel model, int flags) {
		if (!fEnvironments.contains(model))
			return;

		while (!fEnvironments.isEmpty()) {
			LinkedModeModel env= (LinkedModeModel) fEnvironments.pop();
			if (env == model)
				break;
			env.exit(ILinkedModeListener.NONE);
		}

		if (fEnvironments.isEmpty()) {
			removeManager();
		}
	}

	private void closeAllEnvironments() {
		while (!fEnvironments.isEmpty()) {
			LinkedModeModel env= (LinkedModeModel) fEnvironments.pop();
			env.exit(ILinkedModeListener.NONE);
		}

		removeManager();
	}

	private void removeManager() {
		for (Iterator it= fgManagers.keySet().iterator(); it.hasNext();) {
			IDocument doc= (IDocument) it.next();
			if (fgManagers.get(doc) == this)
				it.remove();
		}
	}

    /**
     * Tries to nest the given LinkedModeModel onto the top of
     * the stack of environments managed by the receiver. If force
     * is true, any environments on the stack that create a conflict
     * are killed.
     *
     * @param model the model to nest
     * @param force whether to force the addition of the model
     * @return true if nesting was successful, false otherwise (only possible if force is false
     */
    public boolean nestEnvironment(LinkedModeModel model, boolean force) {
    	Assert.isNotNull(model);

    	try {
    		while (true) {
    			if (fEnvironments.isEmpty()) {
    				model.addLinkingListener(fListener);
    				fEnvironments.push(model);
    				return true;
    			}

    			LinkedModeModel top= (LinkedModeModel) fEnvironments.peek();
    			if (model.canNestInto(top)) {
    				model.addLinkingListener(fListener);
    				fEnvironments.push(model);
    				return true;
    			} else if (!force) {
    				return false;
    			} else { // force
    				fEnvironments.pop();
    				top.exit(ILinkedModeListener.NONE);
    				// continue;
    			}
    		}
    	} finally {
    		// if we remove any, make sure the new one got inserted
    		Assert.isTrue(fEnvironments.size() > 0);
    	}
    }

	/**
	 * Returns the LinkedModeModel that is on top of the stack of
	 * environments managed by the receiver.
	 *
	 * @return the topmost LinkedModeModel
	 */
	public LinkedModeModel getTopEnvironment() {
		if (fEnvironments.isEmpty())
			return null;
		return (LinkedModeModel) fEnvironments.peek();
	}
}