/*

 * Copyright (c) 2016, 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.serviceprovider;

import static java.lang.Thread.currentThread;

import java.io.IOException;

import java.io.InputStream;

import java.util.Iterator;

import java.util.List;

import java.util.ServiceConfigurationError;

import java.util.ServiceLoader;

import java.util.concurrent.atomic.AtomicLong;

import jdk.vm.ci.services.JVMCIPermission;

import jdk.vm.ci.services.Services;

/**

 * Interface to functionality that abstracts over which JDK version Graal is running on.

 */

public final class GraalServices {

    private static int getJavaSpecificationVersion() {

        String value = System.getProperty("java.specification.version");

        if (value.startsWith("1.")) {

            value = value.substring(2);

        }

        return Integer.parseInt(value);

    }

    /**

     * The integer value corresponding to the value of the {@code java.specification.version} system

     * property after any leading {@code "1."} has been stripped.

     */

    public static final int JAVA_SPECIFICATION_VERSION = getJavaSpecificationVersion();

    /**

     * Determines if the Java runtime is version 8 or earlier.

     */

    public static final boolean Java8OrEarlier = JAVA_SPECIFICATION_VERSION <= 8;

    private GraalServices() {

    }

    /**

     * Gets an {@link Iterable} of the providers available for a given service.

     *

     * @throws SecurityException if on JDK8 and a security manager is present and it denies

     *             {@link JVMCIPermission}

     */

    public static <S> Iterable<S> load(Class<S> service) {

        assert !service.getName().startsWith("jdk.vm.ci") : "JVMCI services must be loaded via " + Services.class.getName();

        Iterable<S> iterable = ServiceLoader.load(service);

        return new Iterable<>() {

            @Override

            public Iterator<S> iterator() {

                Iterator<S> iterator = iterable.iterator();

                return new Iterator<>() {

                    @Override

                    public boolean hasNext() {

                        return iterator.hasNext();

                    }

                    @Override

                    public S next() {

                        S provider = iterator.next();

                        // Allow Graal extensions to access JVMCI

                        openJVMCITo(provider.getClass());

                        return provider;

                    }

                    @Override

                    public void remove() {

                        iterator.remove();

                    }

                };

            }

        };

    }

    /**

     * Opens all JVMCI packages to the module of a given class. This relies on JVMCI already having

     * opened all its packages to the module defining {@link GraalServices}.

     *

     * @param other all JVMCI packages will be opened to the module defining this class

     */

    static void openJVMCITo(Class<?> other) {

        Module jvmciModule = JVMCI_MODULE;

        Module otherModule = other.getModule();

        if (jvmciModule != otherModule) {

            for (String pkg : jvmciModule.getPackages()) {

                if (!jvmciModule.isOpen(pkg, otherModule)) {

                    jvmciModule.addOpens(pkg, otherModule);

                }

            }

        }

    }

    /**

     * Gets the provider for a given service for which at most one provider must be available.

     *

     * @param service the service whose provider is being requested

     * @param required specifies if an {@link InternalError} should be thrown if no provider of

     *            {@code service} is available

     * @return the requested provider if available else {@code null}

     * @throws SecurityException if on JDK8 and a security manager is present and it denies

     *             {@link JVMCIPermission}

     */

    public static <S> S loadSingle(Class<S> service, boolean required) {

        assert !service.getName().startsWith("jdk.vm.ci") : "JVMCI services must be loaded via " + Services.class.getName();

        Iterable<S> providers = load(service);

        S singleProvider = null;

        try {

            for (Iterator<S> it = providers.iterator(); it.hasNext();) {

                singleProvider = it.next();

                if (it.hasNext()) {

                    S other = it.next();

                    throw new InternalError(String.format("Multiple %s providers found: %s, %s", service.getName(), singleProvider.getClass().getName(), other.getClass().getName()));

                }

            }

        } catch (ServiceConfigurationError e) {

            // If the service is required we will bail out below.

        }

        if (singleProvider == null) {

            if (required) {

                throw new InternalError(String.format("No provider for %s found", service.getName()));

            }

        }

        return singleProvider;

    }

    /**

     * Gets the class file bytes for {@code c}.

     */

    public static InputStream getClassfileAsStream(Class<?> c) throws IOException {

        String classfilePath = c.getName().replace('.', '/') + ".class";

        return c.getModule().getResourceAsStream(classfilePath);

    }

    private static final Module JVMCI_MODULE = Services.class.getModule();

    /**

     * A JVMCI package dynamically exported to trusted modules.

     */

    private static final String JVMCI_RUNTIME_PACKAGE = "jdk.vm.ci.runtime";

    static {

        assert JVMCI_MODULE.getPackages().contains(JVMCI_RUNTIME_PACKAGE);

    }

    /**

     * Determines if invoking {@link Object#toString()} on an instance of {@code c} will only run

     * trusted code.

     */

    public static boolean isToStringTrusted(Class<?> c) {

        Module module = c.getModule();

        Module jvmciModule = JVMCI_MODULE;

        assert jvmciModule.getPackages().contains("jdk.vm.ci.runtime");

        if (module == jvmciModule || jvmciModule.isOpen(JVMCI_RUNTIME_PACKAGE, module)) {

            // Can access non-statically-exported package in JVMCI

            return true;

        }

        return false;

    }

    /**

     * Gets a unique identifier for this execution such as a process ID or a

     * {@linkplain #getGlobalTimeStamp() fixed timestamp}.

     */

    public static String getExecutionID() {

        return Long.toString(ProcessHandle.current().pid());

    }

    private static final AtomicLong globalTimeStamp = new AtomicLong();

    /**

     * Gets a time stamp for the current process. This method will always return the same value for

     * the current VM execution.

     */

    public static long getGlobalTimeStamp() {

        if (globalTimeStamp.get() == 0) {

            globalTimeStamp.compareAndSet(0, System.currentTimeMillis());

        }

        return globalTimeStamp.get();

    }

    /**

     * Returns an approximation of the total amount of memory, in bytes, allocated in heap memory

     * for the thread of the specified ID. The returned value is an approximation because some Java

     * virtual machine implementations may use object allocation mechanisms that result in a delay

     * between the time an object is allocated and the time its size is recorded.

     * <p>

     * If the thread of the specified ID is not alive or does not exist, this method returns

     * {@code -1}. If thread memory allocation measurement is disabled, this method returns

     * {@code -1}. A thread is alive if it has been started and has not yet died.

     * <p>

     * If thread memory allocation measurement is enabled after the thread has started, the Java

     * virtual machine implementation may choose any time up to and including the time that the

     * capability is enabled as the point where thread memory allocation measurement starts.

     *

     * @param id the thread ID of a thread

     * @return an approximation of the total memory allocated, in bytes, in heap memory for a thread

     *         of the specified ID if the thread of the specified ID exists, the thread is alive,

     *         and thread memory allocation measurement is enabled; {@code -1} otherwise.

     *

     * @throws IllegalArgumentException if {@code id} {@code <=} {@code 0}.

     * @throws UnsupportedOperationException if the Java virtual machine implementation does not

     *             {@linkplain #isThreadAllocatedMemorySupported() support} thread memory allocation

     *             measurement.

     */

    public static long getThreadAllocatedBytes(long id) {

        JMXService jmx = JMXService.instance;

        if (jmx == null) {

            throw new UnsupportedOperationException();

        }

        return jmx.getThreadAllocatedBytes(id);

    }

    /**

     * Convenience method for calling {@link #getThreadAllocatedBytes(long)} with the id of the

     * current thread.

     */

    public static long getCurrentThreadAllocatedBytes() {

        return getThreadAllocatedBytes(currentThread().getId());

    }

    /**

     * Returns the total CPU time for the current thread in nanoseconds. The returned value is of

     * nanoseconds precision but not necessarily nanoseconds accuracy. If the implementation

     * distinguishes between user mode time and system mode time, the returned CPU time is the

     * amount of time that the current thread has executed in user mode or system mode.

     *

     * @return the total CPU time for the current thread if CPU time measurement is enabled;

     *         {@code -1} otherwise.

     *

     * @throws UnsupportedOperationException if the Java virtual machine does not

     *             {@linkplain #isCurrentThreadCpuTimeSupported() support} CPU time measurement for

     *             the current thread

     */

    public static long getCurrentThreadCpuTime() {

        JMXService jmx = JMXService.instance;

        if (jmx == null) {

            throw new UnsupportedOperationException();

        }

        return jmx.getCurrentThreadCpuTime();

    }

    /**

     * Determines if the Java virtual machine implementation supports thread memory allocation

     * measurement.

     */

    public static boolean isThreadAllocatedMemorySupported() {

        JMXService jmx = JMXService.instance;

        if (jmx == null) {

            return false;

        }

        return jmx.isThreadAllocatedMemorySupported();

    }

    /**

     * Determines if the Java virtual machine supports CPU time measurement for the current thread.

     */

    public static boolean isCurrentThreadCpuTimeSupported() {

        JMXService jmx = JMXService.instance;

        if (jmx == null) {

            return false;

        }

        return jmx.isCurrentThreadCpuTimeSupported();

    }

    /**

     * Gets the input arguments passed to the Java virtual machine which does not include the

     * arguments to the {@code main} method. This method returns an empty list if there is no input

     * argument to the Java virtual machine.

     * <p>

     * Some Java virtual machine implementations may take input arguments from multiple different

     * sources: for examples, arguments passed from the application that launches the Java virtual

     * machine such as the 'java' command, environment variables, configuration files, etc.

     * <p>

     * Typically, not all command-line options to the 'java' command are passed to the Java virtual

     * machine. Thus, the returned input arguments may not include all command-line options.

     *

     * @return the input arguments to the JVM or {@code null} if they are unavailable

     */

    public static List<String> getInputArguments() {

        JMXService jmx = JMXService.instance;

        if (jmx == null) {

            return null;

        }

        return jmx.getInputArguments();

    }

}