/*******************************************************************************
 * Copyright (c) 2000, 2006 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.pde.internal.ui.editor;

import java.util.List;
import java.util.Vector;
import org.eclipse.jface.action.IAction;
import org.eclipse.osgi.util.NLS;
import org.eclipse.pde.core.*;
import org.eclipse.pde.internal.ui.PDEUIMessages;
import org.eclipse.ui.forms.editor.IFormPage;

public abstract class ModelUndoManager implements IModelUndoManager, IModelChangedListener {
	private boolean ignoreChanges;
	private List operations;
	private int undoLevelLimit = 10;
	private int cursor = -1;
	private IAction undoAction;
	private IAction redoAction;
	private PDEFormEditor editor;

	public ModelUndoManager(PDEFormEditor editor) {
		this.editor = editor;
		operations = new Vector();
	}

	/*
	 * @see IModelUndoManager#connect(IModelChangeProvider)
	 */
	public void connect(IModelChangeProvider provider) {
		provider.addModelChangedListener(this);
		if (operations == null)
			initialize();
	}

	/*
	 * @see IModelUndoManager#disconnect(IModelChangeProvider)
	 */
	public void disconnect(IModelChangeProvider provider) {
		provider.removeModelChangedListener(this);
	}

	private void initialize() {
		operations = new Vector();
		cursor = -1;
		updateActions();
	}

	/*
	 * @see IModelUndoManager#isUndoable()
	 */
	public boolean isUndoable() {
		return cursor >= 0;
	}

	/*
	 * @see IModelUndoManager#isRedoable()
	 */
	public boolean isRedoable() {
		if (operations == null)
			initialize();
		return (cursor + 1) < operations.size();
	}

	/*
	 * @see IModelUndoManager#undo()
	 */
	public void undo() {
		IModelChangedEvent op = getCurrentOperation();
		if (op == null)
			return;
		ignoreChanges = true;
		openRelatedPage(op);
		execute(op, true);
		cursor--;
		updateActions();
		ignoreChanges = false;
	}

	/*
	 * @see IModelUndoManager#redo()
	 */
	public void redo() {
		cursor++;
		IModelChangedEvent op = getCurrentOperation();
		if (op == null)
			return;
		ignoreChanges = true;
		openRelatedPage(op);
		execute(op, false);
		ignoreChanges = false;
		updateActions();
	}

	protected abstract String getPageId(Object object);

	protected abstract void execute(IModelChangedEvent op, boolean undo);

	private void openRelatedPage(IModelChangedEvent op) {
		Object obj = op.getChangedObjects()[0];
		String pageId = getPageId(obj);
		if (pageId != null) {
			IFormPage cpage = editor.getActivePageInstance();
			IFormPage newPage = editor.findPage(pageId);
			if (cpage != newPage)
				editor.setActivePage(newPage.getId());
		}
	}

	/*
	 * @see IModelChangedListener#modelChanged(IModelChangedEvent)
	 */
	public void modelChanged(IModelChangedEvent event) {
		if (ignoreChanges)
			return;

		if (event.getChangeType() == IModelChangedEvent.WORLD_CHANGED) {
			initialize();
			return;
		}
		addOperation(event);
	}

	private IModelChangedEvent getCurrentOperation() {
		if (cursor == -1 || cursor == operations.size())
			return null;
		return (IModelChangedEvent) operations.get(cursor);
	}

	private IModelChangedEvent getNextOperation() {
		int peekCursor = cursor + 1;
		if (peekCursor >= operations.size())
			return null;
		return (IModelChangedEvent) operations.get(peekCursor);
	}

	private void addOperation(IModelChangedEvent operation) {
		operations.add(operation);
		int size = operations.size();
		if (size > undoLevelLimit) {
			int extra = size - undoLevelLimit;
			// trim
			for (int i = 0; i < extra; i++) {
				operations.remove(i);
			}
		}
		cursor = operations.size() - 1;
		updateActions();
	}

	public void setActions(IAction undoAction, IAction redoAction) {
		this.undoAction = undoAction;
		this.redoAction = redoAction;
		updateActions();
	}

	private void updateActions() {
		if (undoAction != null && redoAction != null) {
			undoAction.setEnabled(isUndoable());
			undoAction.setText(getUndoText());
			redoAction.setEnabled(isRedoable());
			redoAction.setText(getRedoText());
		}
	}

	private String getUndoText() {
		IModelChangedEvent op = getCurrentOperation();
		if (op == null) {
			return PDEUIMessages.UpdateManager_noUndo;
		}
		return NLS.bind(PDEUIMessages.UpdateManager_undo, getOperationText(op));
	}

	private String getRedoText() {
		IModelChangedEvent op = getNextOperation();
		if (op == null) {
			return PDEUIMessages.UpdateManager_noRedo;
		}
		return NLS.bind(PDEUIMessages.UpdateManager_redo, getOperationText(op));
	}

	private String getOperationText(IModelChangedEvent op) {
		String opText = ""; //$NON-NLS-1$
		switch (op.getChangeType()) {
			case IModelChangedEvent.INSERT :
				opText = PDEUIMessages.UpdateManager_op_add;
				break;
			case IModelChangedEvent.REMOVE :
				opText = PDEUIMessages.UpdateManager_op_remove;
				break;
			case IModelChangedEvent.CHANGE :
				opText = PDEUIMessages.UpdateManager_op_change;
				break;
		}
		return opText;
	}

	public void setUndoLevelLimit(int limit) {
		this.undoLevelLimit = limit;
	}

	public void setIgnoreChanges(boolean ignore) {
		this.ignoreChanges = ignore;
	}
}