/*******************************************************************************
 *
 * Copyright (c) 2011, Oracle Corporation
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *
 *    Kohsuke Kawaguchi
 *
 *
 *******************************************************************************/ 

package hudson.util;

import java.util.StringTokenizer;

/**
 * Immutable representation of a dot or '-'-separated digits (such as "1.0.1" or
 * "1.0-52").
 *
 * {@link VersionNumber}s are {@link Comparable}.
 *
 * <h2>Special tokens</h2> <p> We allow a component to be not just a number, but
 * also "ea", "ea1", "ea2". "ea" is treated as "ea0", and eaN < M for any M >
 * 0.
 *
 * <p> '*' is also allowed as a component, and '*' > M for any M > 0.
 *
 * <p> 'SNAPSHOT' is also allowed as a component, and "N.SNAPSHOT" is
 * interpreted as "N-1.*"
 *
 * <pre>
 * 2.0.* > 2.0.1 > 2.0.1-SNAPSHOT > 2.0.0.99 > 2.0.0 > 2.0.ea > 2.0
 * </pre>
 *
 * @author Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 * @since 1.139
 */
public class VersionNumber implements Comparable<VersionNumber> {

    private final int[] digits;

    /**
     * Parses a string like "1.0.2" into the version number.
     *
     * @throws IllegalArgumentException if the parsing fails.
     */
    public VersionNumber(String num) {
        StringTokenizer tokens = new StringTokenizer(num, ".-_");
        digits = new int[tokens.countTokens()];
        if (digits.length < 2) {
            throw new IllegalArgumentException("Failed to parse " + num + " as version number");
        }

        int i = 0;
        while (tokens.hasMoreTokens()) {
            String token = tokens.nextToken().toLowerCase();
            if (token.equals("*")) {
                digits[i++] = 1000;
            } else if (token.startsWith("snapshot")) {
                digits[i - 1]--;
                digits[i++] = 1000;
                break;
            } else if (token.startsWith("ea")) {
                if (token.length() == 2) {
                    digits[i++] = -1000;    // just "ea"
                } else {
                    digits[i++] = -1000 + Integer.parseInt(token.substring(2)); // "eaNNN"
                }
            } else {
                int n = 0;
                try {
                    n = Integer.parseInt(token);
                } catch (NumberFormatException e) {
                    // ignore
                }
                digits[i++] = n;
            }
        }
    }

    public int digit(int idx) {
        return digits[idx];
    }

    @Override
    public String toString() {
        StringBuilder buf = new StringBuilder();
        for (int i = 0; i < digits.length; i++) {
            if (i != 0) {
                buf.append('.');
            }
            buf.append(Integer.toString(digits[i]));
        }
        return buf.toString();
    }

    public boolean isOlderThan(VersionNumber rhs) {
        return compareTo(rhs) < 0;
    }

    public boolean isNewerThan(VersionNumber rhs) {
        return compareTo(rhs) > 0;
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof VersionNumber)) {
            return false;
        }
        return compareTo((VersionNumber) o) == 0;
    }

    @Override
    public int hashCode() {
        int x = 0;
        for (int i : digits) {
            x = (x << 1) | i;
        }
        return x;
    }

    public int compareTo(VersionNumber rhs) {
        for (int i = 0;; i++) {
            if (i == this.digits.length && i == rhs.digits.length) {
                return 0;   // equals
            }
            if (i == this.digits.length) {
                return -1;  // rhs is larger
            }
            if (i == rhs.digits.length) {
                return 1;
            }

            int r = this.digits[i] - rhs.digits[i];
            if (r != 0) {
                return r;
            }
        }
    }
}