/*
 *  Copyright 2012 Axel Winkler, Daniel Dunér
 * 
 *  This file is part of Daxplore Presenter.
 *
 *  Daxplore Presenter is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  Daxplore Presenter is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with Daxplore Presenter.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.daxplore.presenter.server.storage;

import java.util.List;

import javax.jdo.PersistenceManager;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;

import org.daxplore.presenter.server.throwable.BadRequestException;
import org.daxplore.presenter.shared.QueryDefinition;
import org.daxplore.presenter.shared.SharedTools;

/**
 * A representation of a StatDataItem and it's key that can be
 * persisted (stored) using a {@link PersistenceManager}.
 * 
 * <p>This acts like an item in a hash table (represented by the
 * {@linkplain PersistenceManager}), making it possible to fetch data items
 * with a specific key.</p>
 */
@PersistenceCapable
public class StatDataItemStore {
	@PrimaryKey
	private String key;
	@Persistent
	private List<String> jsonChunks;
	@Persistent
	private String prefix;

	/**
	 * Instantiate a new stat data item, which is a piece of anonymized
	 * statistical data that can be presented to users.
	 * 
	 * <p>The key should be on the format "prefix#name". The prefix defines
	 * which presenter the setting belongs to and the name is the name
	 * of the data item.</p>
	 * 
	 * @param key
	 *            a key on the format "prefix#name"
	 * @param json
	 *            the data item as json
	 */
	public StatDataItemStore(String key, String json) {
		this.key = key;
		jsonChunks = SharedTools.splitString(json, 500); //JDO has a String length limit of 500
		this.prefix = key.substring(0, key.indexOf('#'));
	}

	/**
	 * Get the key.
	 * 
	 * @return the key
	 */
	public String getKey() {
		return key;
	}

	/**
	 * Get the stat data item as a json string.
	 * 
	 * @return the data
	 */
	public String getJson() {
		return SharedTools.join(jsonChunks, "");
	}
	
	public static String getStats(PersistenceManager pm, String prefix, QueryDefinition queryDefinition) throws BadRequestException {
		String questionID = queryDefinition.getQuestionID();
		String perspectiveID = queryDefinition.getPerspectiveID();
		String key = String.format("%s#Q=%s&P=%s", prefix, questionID, perspectiveID);
		try {
			return pm.getObjectById(StatDataItemStore.class, key).getJson();
		} catch (Exception e) {
			throw new BadRequestException("Could not read data item '" + key + "'", e);
		}
	}
}