/*******************************************************************************
 * Copyright (c) 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.jst.jsp.ui.internal.contentassist;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.templates.DocumentTemplateContext;
import org.eclipse.jface.text.templates.Template;
import org.eclipse.jface.text.templates.TemplateBuffer;
import org.eclipse.jface.text.templates.TemplateContextType;
import org.eclipse.jface.text.templates.TemplateException;

/**
 * Just like DocumentTemplateContext except if an insert offset is passed in,
 * during evaluation, the "prefix" before the template will be checked to see
 * if it matches the template name. If so, overwrite the template name.
 * Otherwise, just insert the template at the insert offset location (by not
 * overwriting the prefix text)
 */
public class ReplaceNameTemplateContext extends DocumentTemplateContext {
	private int fInsertOffset = -1;

	/**
	 * Creates a document template context.
	 * 
	 * @param type
	 *            the context type
	 * @param document
	 *            the document this context applies to
	 * @param offset
	 *            the offset of the document region
	 * @param length
	 *            the length of the document region
	 */
	public ReplaceNameTemplateContext(TemplateContextType type, IDocument document, int offset, int length) {
		this(type, document, new Position(offset, length));
	}

	/**
	 * Creates a document template context. The supplied <code>Position</code>
	 * will be queried to compute the <code>getStart</code> and
	 * <code>getEnd</code> methods, which will therefore answer updated
	 * position data if it is registered with the document.
	 * 
	 * @param type
	 *            the context type
	 * @param document
	 *            the document this context applies to
	 * @param position
	 *            the position describing the area of the document which forms
	 *            the template context
	 * @since 3.1
	 */
	public ReplaceNameTemplateContext(TemplateContextType type, IDocument document, Position position) {
		super(type, document, position);
	}

	/**
	 * Creates a document template context.
	 * 
	 * @param type
	 *            the context type
	 * @param document
	 *            the document this context applies to
	 * @param offset
	 *            the offset of the document region
	 * @param length
	 *            the length of the document region
	 * @param insertOffset
	 *            the offset of the document region where insert was
	 *            originally requested
	 */
	public ReplaceNameTemplateContext(TemplateContextType type, IDocument document, int offset, int length, int insertOffset) {
		this(type, document, new Position(offset, length));
		fInsertOffset = insertOffset;
	}

	/*
	 * @see org.eclipse.jface.text.templates.TemplateContext#evaluate(org.eclipse.jface.text.templates.Template)
	 */
	public TemplateBuffer evaluate(Template template) throws BadLocationException, TemplateException {
		TemplateBuffer buffer = super.evaluate(template);
		if (buffer != null) {
			if (fInsertOffset > -1 && fInsertOffset > getStart()) {
				String prefix = getDocument().get(getStart(), fInsertOffset - getStart());
				if (!template.getName().startsWith(prefix)) {
					// generate a new buffer that actually contains the
					// text that was going to be overwritten
					buffer = new TemplateBuffer(prefix + buffer.getString(), buffer.getVariables());
				}
			}
		}
		return buffer;
	}
}