/*
 * Copyright (c) 2016, 2018, 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
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 */


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.runtime.JVMCI;
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.
/**
 * 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 java.specification.version system property after any leading "1." has been stripped. /**
     * 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.
/**
     * Determines if the Java runtime is version 8 or earlier.
     */
    public static final boolean Java8OrEarlier = JAVA_SPECIFICATION_VERSION <= 8;

    
Determines if the Java runtime is version 11 or earlier.
/**
     * Determines if the Java runtime is version 11 or earlier.
     */
    public static final boolean Java11OrEarlier = JAVA_SPECIFICATION_VERSION <= 11;

    private GraalServices() {
    }

    
Gets an Iterable of the providers available for a given service. 
Throws:
SecurityException – if on JDK8 and a security manager is present and it denies JVMCIPermission/**
     * 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) {
        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 GraalServices. 
Params:
other – all JVMCI packages will be opened to the module defining this class/**
     * 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)) {
                    // JVMCI initialization opens all JVMCI packages
                    // to Graal which is a prerequisite for Graal to
                    // open JVMCI packages to other modules.
                    JVMCI.initialize();

                    jvmciModule.addOpens(pkg, otherModule);
                }
            }
        }
    }

    
Gets the provider for a given service for which at most one provider must be available.
Params:
service – the service whose provider is being requested
required – specifies if an InternalError should be thrown if no provider of service is available
Throws:
SecurityException – if on JDK8 and a security manager is present and it denies JVMCIPermission
Returns:
the requested provider if available else null/**
     * 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 c. /**
     * 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.
/**
     * 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 Object.toString() on an instance of c will only run trusted code. /**
     * 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 fixed timestamp. /**
     * 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.
/**
     * 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.
 If the thread of the specified ID is not alive or does not exist, this method returns -1. If thread memory allocation measurement is disabled, this method returns -1. A thread is alive if it has been started and has not yet died. 

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.
Params:
id – the thread ID of a thread
Throws:
IllegalArgumentException – if id <= 0.
UnsupportedOperationException – if the Java virtual machine implementation does not support thread memory allocation measurement.
Returns:
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; -1 otherwise./**
     * 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 getThreadAllocatedBytes(long) with the id of the current thread. /**
     * 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.
Throws:
UnsupportedOperationException – if the Java virtual machine does not support CPU time measurement for the current thread
Returns:
the total CPU time for the current thread if CPU time measurement is enabled; -1 otherwise./**
     * 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.
/**
     * 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.
/**
     * 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 main method. This method returns an empty list if there is no input argument to the Java virtual machine. 

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.

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.
Returns:
the input arguments to the JVM or null if they are unavailable/**
     * 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();
    }
}