Toc.java

/* 
 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Contributors:
 *     bstefanescu
 *
 * $Id$
 */

package org.nuxeo.ecm.platform.rendering.wiki;

/**
 * Table of contents model.
 * <p>
 * A simple linked list of toc entries.
 *
 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
 */
public class Toc {

    protected final Entry head;

    protected Entry tail;

    public Toc() {
        head = new Entry();
        tail = head;
        head.title = "Table of Contents";
        head.id = null;
    }

    /**
     * Adds a heading to the TOC list and returns the ID of that heading (to be used for anchors).
     *
     * @param title the heading title
     * @param level the heading level
     * @return the heading id
     */
    public String addHeading(String title, int level) {
        Entry entry = new Entry();
        entry.title = title;
        entry.level = level;
        if (level == tail.level) { // same level
            tail.next = entry;
            entry.parent = tail.parent;
            entry.index = tail.index + 1;
        } else if (level > tail.level) {
            entry.parent = tail;
            tail.firstChild = entry;
            entry.index = 1;
        } else {
            Entry prev = tail.parent;
            // FIXME: null consistency check
            while (prev.level > level && prev != null) {
                prev = prev.parent;
            }
            // FIXME: null consistency check
            if (prev == null || prev.parent == null) {
                throw new IllegalStateException("Invalid headers. Header levels underflowed");
            }
            prev.next = entry;
            entry.parent = prev.parent;
            entry.index = prev.index + 1;
        }
        if (entry.parent.id != null) {
            entry.id = entry.parent.id + "." + entry.index;
        } else {
            entry.id = "" + entry.index;
        }
        tail = entry;
        return entry.id;
    }

    public static class Entry {
        public Entry parent;

        public Entry next;

        public Entry firstChild;

        public String id;

        public String title;

        public int level;

        public int index;
    }

}