/*
 * Copyright (c) OSGi Alliance (2004, 2009). All Rights Reserved.
 * 
 * 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.
 */
package org.eclipse.equinox.p2.cudf.metadata;

import java.util.NoSuchElementException;
import java.util.StringTokenizer;

/**
 * Version identifier for bundles and packages.
 * 
 * <p>
 * Version identifiers have four components.
 * <ol>
 * <li>Major version. A non-negative integer.</li>
 * <li>Minor version. A non-negative integer.</li>
 * <li>Micro version. A non-negative integer.</li>
 * <li>Qualifier. A text string. See <code>Version(String)</code> for the
 * format of the qualifier string.</li>
 * </ol>
 * 
 * <p>
 * <code>Version</code> objects are immutable.
 * 
 * @since 1.3
 * @Immutable
 * @version $Revision: 1.4 $
 */

public class Version implements Comparable {
	private final int major;
	private static final String SEPARATOR = "."; //$NON-NLS-1$

	/**
	 * The empty version "0.0.0".
	 */
	public static final Version emptyVersion = new Version(0, 0, 0);
	public static final Version maxVersion = new Version(Integer.MAX_VALUE);

	/**
	 * Creates a version identifier from the specified numerical components.
	 * 
	 * <p>
	 * The qualifier is set to the empty string.
	 * 
	 * @param major Major component of the version identifier.
	 * @param minor Minor component of the version identifier.
	 * @param micro Micro component of the version identifier.
	 * @throws IllegalArgumentException If the numerical components are
	 *         negative.
	 */

	public Version(int major) {
		this.major = major;
	}

	public Version(int major, int minor, int micro) {
		this(major, minor, micro, null);
	}

	/**
	 * Creates a version identifier from the specified components.
	 * 
	 * @param major Major component of the version identifier.
	 * @param minor Minor component of the version identifier.
	 * @param micro Micro component of the version identifier.
	 * @param qualifier Qualifier component of the version identifier. If
	 *        <code>null</code> is specified, then the qualifier will be set to
	 *        the empty string.
	 * @throws IllegalArgumentException If the numerical components are negative
	 *         or the qualifier string is invalid.
	 */
	public Version(int major, int minor, int micro, String qualifier) {
		if (qualifier == null) {
			qualifier = ""; //$NON-NLS-1$
		}

		this.major = major;
	}

	/**
	 * Created a version identifier from the specified string.
	 * 
	 * <p>
	 * Here is the grammar for version strings.
	 * 
	 * <pre>
	 * version ::= major('.'minor('.'micro('.'qualifier)?)?)?
	 * major ::= digit+
	 * minor ::= digit+
	 * micro ::= digit+
	 * qualifier ::= (alpha|digit|'_'|'-')+
	 * digit ::= [0..9]
	 * alpha ::= [a..zA..Z]
	 * </pre>
	 * 
	 * There must be no whitespace in version.
	 * 
	 * @param version String representation of the version identifier.
	 * @throws IllegalArgumentException If <code>version</code> is improperly
	 *         formatted.
	 */
	public Version(String version) {
		int maj = 0;
		int min = 0;
		int mic = 0;
		String qual = ""; //$NON-NLS-1$

		try {
			StringTokenizer st = new StringTokenizer(version, SEPARATOR, true);
			maj = Integer.parseInt(st.nextToken());

			if (st.hasMoreTokens()) {
				st.nextToken(); // consume delimiter
				min = Integer.parseInt(st.nextToken());

				if (st.hasMoreTokens()) {
					st.nextToken(); // consume delimiter
					mic = Integer.parseInt(st.nextToken());

					if (st.hasMoreTokens()) {
						st.nextToken(); // consume delimiter
						qual = st.nextToken();

						if (st.hasMoreTokens()) {
							throw new IllegalArgumentException("invalid format"); //$NON-NLS-1$
						}
					}
				}
			}
		} catch (NoSuchElementException e) {
			throw new IllegalArgumentException("invalid format"); //$NON-NLS-1$
		}

		major = maj;
	}

	/**
	 * Parses a version identifier from the specified string.
	 * 
	 * <p>
	 * See <code>Version(String)</code> for the format of the version string.
	 * 
	 * @param version String representation of the version identifier. Leading
	 *        and trailing whitespace will be ignored.
	 * @return A <code>Version</code> object representing the version
	 *         identifier. If <code>version</code> is <code>null</code> or
	 *         the empty string then <code>emptyVersion</code> will be
	 *         returned.
	 * @throws IllegalArgumentException If <code>version</code> is improperly
	 *         formatted.
	 */
	public static Version parseVersion(String version) {
		if (version == null) {
			return emptyVersion;
		}

		version = version.trim();
		if (version.length() == 0) {
			return emptyVersion;
		}

		return new Version(version);
	}

	/**
	 * Returns the major component of this version identifier.
	 * 
	 * @return The major component.
	 */
	public int getMajor() {
		return major;
	}

	public String toString() {
		return Integer.toString(major);
	}

	/**
	 * Returns a hash code value for the object.
	 * 
	 * @return An integer which is a hash code value for this object.
	 */
	public int hashCode() {
		return (major << 24);
	}

	/**
	 * Compares this <code>Version</code> object to another object.
	 * 
	 * <p>
	 * A version is considered to be <b>equal to </b> another version if the
	 * major, minor and micro components are equal and the qualifier component
	 * is equal (using <code>String.equals</code>).
	 * 
	 * @param object The <code>Version</code> object to be compared.
	 * @return <code>true</code> if <code>object</code> is a
	 *         <code>Version</code> and is equal to this object;
	 *         <code>false</code> otherwise.
	 */
	public boolean equals(Object object) {
		if (object == this) { // quicktest
			return true;
		}

		if (!(object instanceof Version)) {
			return false;
		}

		Version other = (Version) object;
		return (major == other.major);
	}

	/**
	 * Compares this <code>Version</code> object to another object.
	 * 
	 * <p>
	 * A version is considered to be <b>less than </b> another version if its
	 * major component is less than the other version's major component, or the
	 * major components are equal and its minor component is less than the other
	 * version's minor component, or the major and minor components are equal
	 * and its micro component is less than the other version's micro component,
	 * or the major, minor and micro components are equal and it's qualifier
	 * component is less than the other version's qualifier component (using
	 * <code>String.compareTo</code>).
	 * 
	 * <p>
	 * A version is considered to be <b>equal to</b> another version if the
	 * major, minor and micro components are equal and the qualifier component
	 * is equal (using <code>String.compareTo</code>).
	 * 
	 * @param object The <code>Version</code> object to be compared.
	 * @return A negative integer, zero, or a positive integer if this object is
	 *         less than, equal to, or greater than the specified
	 *         <code>Version</code> object.
	 * @throws ClassCastException If the specified object is not a
	 *         <code>Version</code>.
	 */
	public int compareTo(Object object) {
		if (object == this) { // quicktest
			return 0;
		}

		Version other = (Version) object;

		return major - other.major;
	}
}