/*
 * Copyright (c) 1999, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import java.io.PrintStream;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;

class VersionProps {

    private static final String launcher_name =
        "openjdk";

    private static final String java_version =
        "11.0.9-internal";

    private static final String java_version_date =
        "2020-10-20";

    // This field is read by HotSpot
    private static final String java_runtime_name =
        "OpenJDK Runtime Environment";

    // This field is read by HotSpot
    private static final String java_runtime_version =
        "11.0.9-internal+0-adhoc.jenkins.jdk-updatesjdk11u";

    private static final String VERSION_NUMBER =
        "11.0.9";

    private static final String VERSION_BUILD =
        "0";

    private static final String VERSION_PRE =
        "internal";

    private static final String VERSION_OPT =
        "adhoc.jenkins.jdk-updatesjdk11u";

    private static final boolean isLTS =
        "adhoc.jenkins.jdk-updatesjdk11u".startsWith("LTS");

    private static final String VENDOR =
        "Oracle Corporation";

    private static final String VENDOR_URL =
        "https://openjdk.java.net/";

    // The remaining VENDOR_* fields must not be final,
    // so that they can be redefined by jlink plugins

    // This field is read by HotSpot
    private static String VENDOR_VERSION =
        "";

    private static String VENDOR_URL_BUG =
        "https://bugreport.java.com/bugreport/";

    // This field is read by HotSpot
    private static String VENDOR_URL_VM_BUG =
        "https://bugreport.java.com/bugreport/crash.jsp";

    static {
        init();
    }

    public static void init() {
        System.setProperty("java.version", java_version);
        System.setProperty("java.version.date", java_version_date);
        System.setProperty("java.runtime.version", java_runtime_version);
        System.setProperty("java.runtime.name", java_runtime_name);
        if (!VENDOR_VERSION.isEmpty())
            System.setProperty("java.vendor.version", VENDOR_VERSION);

        System.setProperty("java.vendor", VENDOR);
        System.setProperty("java.vendor.url", VENDOR_URL);
        System.setProperty("java.vendor.url.bug", VENDOR_URL_BUG);
    }

    private static int parseVersionNumber(String version, int prevIndex, int index) {
        if (index - prevIndex > 1 &&
            Character.digit(version.charAt(prevIndex), 10) <= 0)
            throw new IllegalArgumentException("Leading zeros not supported (" +
                    version.substring(prevIndex, index) + ")");
        return Integer.parseInt(version, prevIndex, index, 10);
    }

    // This method is reflectively used by regression tests.
    static List<Integer> parseVersionNumbers(String version) {
        // Let's find the size of an array required to hold $VNUM components
        int size = 0;
        int prevIndex = 0;
        do {
            prevIndex = version.indexOf('.', prevIndex) + 1;
            size++;
        } while (prevIndex > 0);
        Integer[] verNumbers = new Integer[size];

        // Fill in the array with $VNUM components
        int n = 0;
        prevIndex = 0;
        int index = version.indexOf('.');
        while (index > -1) {
            verNumbers[n] = parseVersionNumber(version, prevIndex, index);
            prevIndex = index + 1; // Skip the period
            index = version.indexOf('.', prevIndex);
            n++;
        }
        verNumbers[n] = parseVersionNumber(version, prevIndex, version.length());

        if (verNumbers[0] == 0 || verNumbers[n] == 0)
            throw new IllegalArgumentException("Leading/trailing zeros not allowed (" +
                    Arrays.toString(verNumbers) + ")");

        return List.of(verNumbers);
    }

    static List<Integer> versionNumbers() {
        return parseVersionNumbers(VERSION_NUMBER);
    }

    static Optional<String> pre() {
        return optionalOf(VERSION_PRE);
    }

    static Optional<Integer> build() {
        return VERSION_BUILD.isEmpty() ?
                Optional.empty() :
                Optional.of(Integer.parseInt(VERSION_BUILD));
    }

    static Optional<String> optional() {
        return optionalOf(VERSION_OPT);
    }

    // Treat empty strings as value not being present
    private static Optional<String> optionalOf(String value) {
        if (!value.isEmpty()) {
            return Optional.of(value);
        } else {
            return Optional.empty();
        }
    }

    
In case you were wondering this method is called by java -version.
/**
     * In case you were wondering this method is called by java -version.
     */
    public static void print(boolean err) {
        print(err, false);
    }

    
This is the same as print except that it adds an extra line-feed
at the end, typically used by the -showversion in the launcher
/**
     * This is the same as print except that it adds an extra line-feed
     * at the end, typically used by the -showversion in the launcher
     */
    public static void println(boolean err) {
        print(err, true);
    }

    
Print version info.
/**
     * Print version info.
     */
    private static void print(boolean err, boolean newln) {
        PrintStream ps = err ? System.err : System.out;

        /* First line: platform version. */
        if (err) {
            ps.println(launcher_name + " version \"" + java_version + "\""
                       + " " + java_version_date
                       + (isLTS ? " LTS" : ""));
        } else {
            /* Use a format more in line with GNU conventions */
            ps.println(launcher_name + " " + java_version
                       + " " + java_version_date
                       + (isLTS ? " LTS" : ""));
        }

        /* Second line: runtime version (ie, libraries). */
        String jdk_debug_level = System.getProperty("jdk.debug", "release");
        if ("release".equals(jdk_debug_level)) {
           /* Do not show debug level "release" builds */
            jdk_debug_level = "";
        } else {
            jdk_debug_level = jdk_debug_level + " ";
        }

        String vendor_version = (VENDOR_VERSION.isEmpty()
                                 ? "" : " " + VENDOR_VERSION);

        ps.println(java_runtime_name + vendor_version
                   + " (" + jdk_debug_level + "build " + java_runtime_version + ")");

        /* Third line: JVM information. */
        String java_vm_name    = System.getProperty("java.vm.name");
        String java_vm_version = System.getProperty("java.vm.version");
        String java_vm_info    = System.getProperty("java.vm.info");
        ps.println(java_vm_name + vendor_version
                   + " (" + jdk_debug_level + "build " + java_vm_version + ", "
                            + java_vm_info + ")");

    }

}