/*
 * Copyright (c) 2016, 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.
 *
 * 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 org.graalvm.compiler.hotspot;

import java.util.Formatter;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * Mechanism for checking that the current Java runtime environment supports the minimum JVMCI API
 * required by Graal. The {@code JVMCI_VERSION_CHECK} environment variable can be used to ignore a
 * failed check ({@code JVMCI_VERSION_CHECK=ignore}) or print a warning (
 * {@code JVMCI_VERSION_CHECK=warn}) and continue. Otherwise, a failed check results in an
 * {@link InternalError} being raised or, if called from {@link #main(String[])}, the VM exiting
 * with a result code of {@code -1}
 *
 * This class only depends on the JDK so that it can be used without building Graal.
 */
public final class JVMCIVersionCheck {

    // 0.57 introduces HotSpotJVMCIRuntime.excludeFromJVMCICompilation
    private static final int JVMCI8_MIN_MAJOR_VERSION = 0;
    private static final int JVMCI8_MIN_MINOR_VERSION = 57;

    private static void failVersionCheck(Map<String, String> props, boolean exit, String reason, Object... args) {
        Formatter errorMessage = new Formatter().format(reason, args);
        String javaHome = props.get("java.home");
        String vmName = props.get("java.vm.name");
        errorMessage.format("Set the JVMCI_VERSION_CHECK environment variable to \"ignore\" to suppress ");
        errorMessage.format("this error or to \"warn\" to emit a warning and continue execution.%n");
        errorMessage.format("Currently used Java home directory is %s.%n", javaHome);
        errorMessage.format("Currently used VM configuration is: %s%n", vmName);
        if (props.get("java.specification.version").compareTo("1.9") < 0) {
            errorMessage.format("Download the latest JVMCI JDK 8 from " +
                            "http://www.oracle.com/technetwork/oracle-labs/program-languages/downloads/index.html or " +
                            "https://github.com/graalvm/openjdk8-jvmci-builder/releases");
        } else {
            errorMessage.format("Download JDK 11 or later.");
        }
        String value = System.getenv("JVMCI_VERSION_CHECK");
        if ("warn".equals(value)) {
            System.err.println(errorMessage.toString());
        } else if ("ignore".equals(value)) {
            return;
        } else if (exit) {
            System.err.println(errorMessage.toString());
            System.exit(-1);
        } else {
            throw new InternalError(errorMessage.toString());
        }
    }

    private final String javaSpecVersion;
    private final String vmVersion;
    private int cursor;
    private final Map<String, String> props;

    private JVMCIVersionCheck(Map<String, String> props, String javaSpecVersion, String vmVersion) {
        this.props = props;
        this.javaSpecVersion = javaSpecVersion;
        this.vmVersion = vmVersion;
    }

    static void check(Map<String, String> props, boolean exitOnFailure) {
        JVMCIVersionCheck checker = new JVMCIVersionCheck(props, props.get("java.specification.version"), props.get("java.vm.version"));
        checker.run(exitOnFailure, JVMCI8_MIN_MAJOR_VERSION, JVMCI8_MIN_MINOR_VERSION);
    }

    /**
     * Entry point for testing.
     */
    public static void check(Map<String, String> props,
                    int jvmci8MinMajorVersion,
                    int jvmci8MinMinorVersion,
                    String javaSpecVersion,
                    String javaVmVersion,
                    boolean exitOnFailure) {
        JVMCIVersionCheck checker = new JVMCIVersionCheck(props, javaSpecVersion, javaVmVersion);
        checker.run(exitOnFailure, jvmci8MinMajorVersion, jvmci8MinMinorVersion);
    }

    /**
     * Parses a positive decimal number at {@link #cursor}.
     *
     * @return -1 if there is no positive decimal number at {@link #cursor}
     */
    private int parseNumber() {
        int result = -1;
        while (cursor < vmVersion.length()) {
            int digit = vmVersion.charAt(cursor) - '0';
            if (digit >= 0 && digit <= 9) {
                if (result == -1) {
                    result = digit;
                } else {
                    long r = (long) result * (long) 10;
                    if ((int) r != r) {
                        // Overflow
                        return -1;
                    }
                    result = (int) r + digit;
                }
                cursor++;
            } else {
                break;
            }
        }
        return result;
    }

    /**
     * Parse {@code "."} or {@code "-b"} at {@link #cursor}.
     *
     * @return {@code true} iff there was an expected separator at {@link #cursor}
     */
    private boolean parseSeparator() {
        if (cursor < vmVersion.length()) {
            char ch = vmVersion.charAt(cursor);
            if (ch == '.') {
                cursor++;
                return true;
            }
            if (ch == '-') {
                cursor++;
                if (cursor < vmVersion.length()) {
                    if (vmVersion.charAt(cursor) == 'b') {
                        cursor++;
                        return true;
                    }
                }
                return false;
            }
        }
        return false;
    }

    private void run(boolean exitOnFailure, int jvmci8MinMajorVersion, int jvmci8MinMinorVersion) {
        // Don't use regular expressions to minimize Graal startup time
        if (javaSpecVersion.compareTo("1.9") < 0) {
            cursor = vmVersion.indexOf("-jvmci-");
            if (cursor >= 0) {
                cursor += "-jvmci-".length();
                int major = parseNumber();
                if (major == -1) {
                    failVersionCheck(props, exitOnFailure, "The VM does not support the minimum JVMCI API version required by Graal.%n" +
                                    "Cannot read JVMCI major version from java.vm.version property: %s.%n", vmVersion);
                    return;
                }

                if (parseSeparator()) {
                    int minor = parseNumber();
                    if (minor == -1) {
                        failVersionCheck(props, exitOnFailure, "The VM does not support the minimum JVMCI API version required by Graal.%n" +
                                        "Cannot read JVMCI minor version from java.vm.version property: %s.%n", vmVersion);
                        return;
                    }

                    if (major > jvmci8MinMajorVersion || (major >= jvmci8MinMajorVersion && minor >= jvmci8MinMinorVersion)) {
                        return;
                    }
                    failVersionCheck(props, exitOnFailure, "The VM does not support the minimum JVMCI API version required by Graal: %d.%d < %d.%d.%n",
                                    major, minor, jvmci8MinMajorVersion, jvmci8MinMinorVersion);
                    return;
                }
            }
            failVersionCheck(props, exitOnFailure, "The VM does not support the minimum JVMCI API version required by Graal.%n" +
                            "Cannot read JVMCI version from java.vm.version property: %s.%n", vmVersion);
        } else if (javaSpecVersion.compareTo("11") < 0) {
            failVersionCheck(props, exitOnFailure, "Graal is not compatible with the JVMCI API in JDK 9 and 10.%n");
        } else {
            if (vmVersion.contains("SNAPSHOT")) {
                return;
            }
            if (vmVersion.contains("internal")) {
                // Allow local builds
                return;
            }
            if (vmVersion.startsWith("11-ea+")) {
                String buildString = vmVersion.substring("11-ea+".length());
                try {
                    int build = Integer.parseInt(buildString);
                    if (build < 20) {
                        failVersionCheck(props, exitOnFailure, "Graal requires build 20 or later of JDK 11 early access binary, got build %d.%n", build);
                        return;
                    }
                } catch (NumberFormatException e) {
                    failVersionCheck(props, exitOnFailure, "Could not parse the JDK 11 early access build number from java.vm.version property: %s.%n", vmVersion);
                    return;
                }
            } else {
                // Graal is compatible with all JDK versions as of 11 GA.
            }
        }
    }

    /**
     * Command line interface for performing the check.
     */
    public static void main(String[] args) {
        Properties sprops = System.getProperties();
        Map<String, String> props = new HashMap<>(sprops.size());
        for (String name : sprops.stringPropertyNames()) {
            props.put(name, sprops.getProperty(name));
        }
        check(props, true);
    }
}