ITagDatabase.java

package models.database;

import java.util.Collection;
import java.util.List;

import models.Tag;

/**
 * A tag database is both a factory for creating new tags and a container
 * tracking all the created tags.
 */
public interface ITagDatabase {

	/**
	 * All tags in the system. This means that if
	 * <code>all().contains(tag)</code> then
	 * <code>tag.getQuestions().isEmpty() == false</code>, and if there is a
	 * question q <code>q.getTags().contains(tag)</code> then
	 * <code>all().contains(tag)</code>.
	 * 
	 * @return Collection of all tags referenced by at least one question.
	 */
	public Collection<Tag> all();

	/**
	 * Get the tag with this name. This ensures, that the name is present in the
	 * DB and that there is only one
	 * 
	 * @param name
	 * @return
	 */

	public Tag get(String name);

	/**
	 * Suggest tag names that start with a given term so that the tag name could
	 * e.g. be auto-completed.
	 * 
	 * @param start
	 *            the start of all the tag names
	 * @return the string
	 */
	public List<String> suggestTagNames(String start);

	/**
	 * Removes each and every Tag from the DB. This means, that
	 * <ul>
	 * <li>No questions can be in the DB anymore
	 * <li>or all questions are untagged
	 * </ul>
	 */
	public void clear();
}