Tag.java

/*
 * Copyright 2010, 2011, 2012 mapsforge.org
 * Copyright 2013 Hannes Janetzek
 *
 * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
 *
 * This program 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 3 of the License, or (at your option) any later version.
 *
 * This program 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
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */
package org.oscim.core;

/**
 * A tag represents an immutable key-value pair. Keys are always intern().
 */

public class Tag {
	/** The key of the house number OpenStreetMap tag. */
	public static final String KEY_HOUSE_NUMBER = "addr:housenumber";

	/** The key of the name OpenStreetMap tag. */
	public static final String KEY_NAME = "name";

	/** The key of the reference OpenStreetMap tag. */
	public static final String KEY_REF = "ref";

	/** The key of the elevation OpenStreetMap tag. */
	public static final String KEY_ELE = "ele";

	public static final String KEY_AMENITY = "amenity";
	public static final String KEY_BUILDING = "building";
	public static final String KEY_HIGHWAY = "highway";
	public static final String KEY_LANDUSE = "landuse";
	public static final String KEY_HEIGHT = "height";
	public static final String KEY_MIN_HEIGHT = "min_height";

	public static final String VALUE_YES = "yes";
	public static final String VALUE_NO = "no";

	/**
	 * The key of this tag.
	 */
	public final String key;

	/**
	 * The value of this tag.
	 */
	public String value;

	/**
	 * true when value is intern().
	 */
	private final boolean intern;

	private int hashCodeValue = 0;

	/**
	 * @param key
	 *            the key of the tag.
	 * @param value
	 *            the value of the tag.
	 */
	public Tag(String key, String value) {
		this.key = key == null ? null : key.intern();
		this.value = value == null ? null : value.intern();
		this.intern = true;
	}

	/**
	 * Create Tag with interned Key.
	 * 
	 * @param key
	 *            the key of the tag.
	 * @param value
	 *            the value of the tag.
	 * @param internValue
	 *            true when value string should be intern()alized.
	 */
	public Tag(String key, String value, boolean internValue) {
		this.key = key;
		this.value = (value == null || !internValue) ? value : value.intern();
		this.intern = internValue;
	}

	public Tag(String key, String value, boolean internKey, boolean internValue) {
		this.key = (key == null || !internKey) ? key : key.intern();
		this.value = (value == null || !internValue) ? value : value.intern();
		this.intern = internValue;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		} else if (!(obj instanceof Tag)) {
			return false;
		}
		Tag other = (Tag) obj;

		if (key != other.key)
			return false;

		if (intern && other.intern) {
			if (value == other.value)
				return true;

		} else if (!intern && value.equals(other.value)) {
			return true;
		}
		return false;
	}

	@Override
	public int hashCode() {
		if (hashCodeValue == 0)
			hashCodeValue = calculateHashCode();

		return hashCodeValue;
	}

	@Override
	public String toString() {
		return new StringBuilder()
		    .append("Tag[")
		    .append(key)
		    .append(',')
		    .append(value)
		    .append(']')
		    .toString();
	}

	/**
	 * @return the hash code of this object.
	 */
	private int calculateHashCode() {
		int result = 7;
		result = 31 * result + ((key == null) ? 0 : key.hashCode());
		result = 31 * result + ((value == null) ? 0 : value.hashCode());
		return result;
	}

	/**
	 * @param tag
	 *            the textual representation of the tag.
	 */
	public static Tag parse(String tag) {
		int splitPosition = tag.indexOf('=');
		if (splitPosition < 0) {
			return new Tag(tag, "");
		}

		return new Tag(tag.substring(0, splitPosition), tag.substring(splitPosition + 1));
	}
}