/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.util.compat;

import java.io.File;
import java.io.IOException;
import java.lang.management.ManagementFactory;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.SocketAddress;
import java.net.URL;
import java.net.URLConnection;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.security.PrivilegedExceptionAction;
import java.util.Deque;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionException;
import java.util.jar.JarFile;

import javax.net.ssl.SSLEngine;
import javax.net.ssl.SSLParameters;
import javax.security.auth.Subject;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;

/**
 * This is the base implementation class for JRE compatibility and provides an implementation based on Java 8.
 * Subclasses may extend this class and provide alternative implementations for later JRE versions
 */
public class JreCompat {

    private static final Log log = LogFactory.getLog(JreCompat.class);
    private static final StringManager sm = StringManager.getManager(JreCompat.class);

    private static final int RUNTIME_MAJOR_VERSION = 8;

    private static final JreCompat instance;
    private static final boolean graalAvailable;
    private static final boolean jre9Available;
    private static final boolean jre11Available;
    private static final boolean jre12Available;
    private static final boolean jre16Available;
    private static final boolean jre19Available;
    private static final boolean jre21Available;
    private static final boolean jre22Available;

    protected static final String USE_CANON_CACHES_CMD_ARG = "-Dsun.io.useCanonCaches=";
    protected static volatile Boolean canonCachesDisabled;
    protected static final Object canonCachesDisabledLock = new Object();
    protected static volatile Optional<Field> useCanonCachesField;
    protected static final Object useCanonCachesFieldLock = new Object();
    protected static final Method setApplicationProtocolsMethod;
    protected static final Method getApplicationProtocolMethod;

    static {
        boolean result = false;
        try {
            Class<?> nativeImageClazz = Class.forName("org.graalvm.nativeimage.ImageInfo");
            result = Boolean.TRUE.equals(nativeImageClazz.getMethod("inImageCode").invoke(null));
        } catch (ClassNotFoundException e) {
            // Must be Graal
        } catch (ReflectiveOperationException | IllegalArgumentException e) {
            // Should never happen
        }
        graalAvailable = result || System.getProperty("org.graalvm.nativeimage.imagecode") != null;

        // This is Tomcat 9 with a minimum Java version of Java 8.
        // Look for the highest supported JVM first
        if (Jre22Compat.isSupported()) {
            instance = new Jre22Compat();
            jre22Available = true;
            jre21Available = true;
            jre19Available = true;
            jre16Available = true;
            jre12Available = true;
            jre9Available = true;
        } else if (Jre21Compat.isSupported()) {
            instance = new Jre21Compat();
            jre22Available = false;
            jre21Available = true;
            jre19Available = true;
            jre16Available = true;
            jre12Available = true;
            jre9Available = true;
        } else if (Jre19Compat.isSupported()) {
            instance = new Jre19Compat();
            jre22Available = false;
            jre21Available = false;
            jre19Available = true;
            jre16Available = true;
            jre12Available = true;
            jre9Available = true;
        } else if (Jre16Compat.isSupported()) {
            instance = new Jre16Compat();
            jre22Available = false;
            jre21Available = false;
            jre19Available = false;
            jre16Available = true;
            jre12Available = true;
            jre9Available = true;
        } else if (Jre12Compat.isSupported()) {
            instance = new Jre12Compat();
            jre22Available = false;
            jre21Available = false;
            jre19Available = false;
            jre16Available = false;
            jre12Available = true;
            jre9Available = true;
        } else if (Jre9Compat.isSupported()) {
            instance = new Jre9Compat();
            jre22Available = false;
            jre21Available = false;
            jre19Available = false;
            jre16Available = false;
            jre12Available = false;
            jre9Available = true;
        } else {
            instance = new JreCompat();
            jre22Available = false;
            jre21Available = false;
            jre19Available = false;
            jre16Available = false;
            jre12Available = false;
            jre9Available = false;
        }
        jre11Available = instance.jarFileRuntimeMajorVersion() >= 11;

        Method m1 = null;
        Method m2 = null;
        try {
            m1 = SSLParameters.class.getMethod("setApplicationProtocols", String[].class);
            m2 = SSLEngine.class.getMethod("getApplicationProtocol");
        } catch (ReflectiveOperationException | IllegalArgumentException e) {
            // Only the newest Java 8 have the ALPN API, so ignore
        }
        setApplicationProtocolsMethod = m1;
        getApplicationProtocolMethod = m2;
    }


    public static JreCompat getInstance() {
        return instance;
    }


    public static boolean isGraalAvailable() {
        return graalAvailable;
    }


    public static boolean isAlpnSupported() {
        return setApplicationProtocolsMethod != null && getApplicationProtocolMethod != null;
    }


    public static boolean isJre9Available() {
        return jre9Available;
    }


    public static boolean isJre11Available() {
        return jre11Available;
    }


    public static boolean isJre12Available() {
        return jre12Available;
    }


    public static boolean isJre16Available() {
        return jre16Available;
    }


    public static boolean isJre19Available() {
        return jre19Available;
    }


    public static boolean isJre21Available() {
        return jre21Available;
    }


    public static boolean isJre22Available() {
        return jre22Available;
    }


    // Java 8 implementation of Java 9 methods

    /**
     * Test if the provided exception is an instance of java.lang.reflect.InaccessibleObjectException.
     *
     * @param t The exception to test
     *
     * @return {@code true} if the exception is an instance of InaccessibleObjectException, otherwise {@code false}
     */
    public boolean isInstanceOfInaccessibleObjectException(Throwable t) {
        // Exception does not exist prior to Java 9
        return false;
    }


    /**
     * Set the application protocols the server will accept for ALPN
     *
     * @param sslParameters The SSL parameters for a connection
     * @param protocols     The application protocols to be allowed for that connection
     */
    public void setApplicationProtocols(SSLParameters sslParameters, String[] protocols) {
        if (setApplicationProtocolsMethod != null) {
            try {
                setApplicationProtocolsMethod.invoke(sslParameters, (Object) protocols);
            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                throw new UnsupportedOperationException(e);
            }
        } else {
            throw new UnsupportedOperationException(sm.getString("jreCompat.noApplicationProtocols"));
        }
    }


    /**
     * Get the application protocol that has been negotiated for connection associated with the given SSLEngine.
     *
     * @param sslEngine The SSLEngine for which to obtain the negotiated protocol
     *
     * @return The name of the negotiated protocol
     */
    public String getApplicationProtocol(SSLEngine sslEngine) {
        if (getApplicationProtocolMethod != null) {
            try {
                return (String) getApplicationProtocolMethod.invoke(sslEngine);
            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                throw new UnsupportedOperationException(e);
            }
        } else {
            throw new UnsupportedOperationException(sm.getString("jreCompat.noApplicationProtocol"));
        }
    }


    /**
     * Disables caching for JAR URL connections. For Java 8 and earlier, this also disables caching for ALL URL
     * connections.
     *
     * @throws IOException If a dummy JAR URLConnection can not be created
     */
    public void disableCachingForJarUrlConnections() throws IOException {
        // Doesn't matter that this JAR doesn't exist - just as
        // long as the URL is well-formed
        URL url = new URL("jar:file://dummy.jar!/");
        URLConnection uConn = url.openConnection();
        uConn.setDefaultUseCaches(false);
    }


    /**
     * Obtains the URLs for all the JARs on the module path when the JVM starts and adds them to the provided Deque.
     *
     * @param classPathUrlsToProcess The Deque to which the modules should be added
     */
    public void addBootModulePath(Deque<URL> classPathUrlsToProcess) {
        // NO-OP for Java 8. There is no module path.
    }


    /**
     * Creates a new JarFile instance. When running on Java 9 and later, the JarFile will be multi-release JAR aware.
     * While this isn't strictly required to be in this package, it is provided as a convenience method.
     *
     * @param s The JAR file to open
     *
     * @return A JarFile instance based on the provided path
     *
     * @throws IOException If an I/O error occurs creating the JarFile instance
     */
    public final JarFile jarFileNewInstance(String s) throws IOException {
        return jarFileNewInstance(new File(s));
    }


    /**
     * Creates a new JarFile instance. When running on Java 9 and later, the JarFile will be multi-release JAR aware.
     *
     * @param f The JAR file to open
     *
     * @return A JarFile instance based on the provided file
     *
     * @throws IOException If an I/O error occurs creating the JarFile instance
     */
    public JarFile jarFileNewInstance(File f) throws IOException {
        return new JarFile(f);
    }


    /**
     * Is this JarFile a multi-release JAR file.
     *
     * @param jarFile The JarFile to test
     *
     * @return {@code true} If it is a multi-release JAR file and is configured to behave as such.
     */
    public boolean jarFileIsMultiRelease(JarFile jarFile) {
        // Java 8 doesn't support multi-release so default to false
        return false;
    }


    public int jarFileRuntimeMajorVersion() {
        return RUNTIME_MAJOR_VERSION;
    }


    /**
     * Is the accessibleObject accessible (as a result of appropriate module exports) on the provided instance?
     *
     * @param base             The specific instance to be tested.
     * @param accessibleObject The method/field/constructor to be tested.
     *
     * @return {code true} if the AccessibleObject can be accessed otherwise {code false}
     */
    public boolean canAccess(Object base, AccessibleObject accessibleObject) {
        // Java 8 doesn't support modules so default to true
        return true;
    }


    /**
     * Is the given class in an exported package?
     *
     * @param type The class to test
     *
     * @return Always {@code true} for Java 8. {@code true} if the enclosing package is exported for Java 9+
     */
    public boolean isExported(Class<?> type) {
        return true;
    }


    /**
     * What is the module of the given class?
     *
     * @param type The class to test
     *
     * @return Always {@code true} for Java 8. {@code true} if the enclosing package is exported for Java 9+
     */
    public String getModuleName(Class<?> type) {
        return "NO_MODULE_JAVA_8";
    }


    // Java 8 implementations of Java 16 methods

    /**
     * Return Unix domain socket address for given path.
     *
     * @param path The path
     *
     * @return the socket address
     */
    public SocketAddress getUnixDomainSocketAddress(String path) {
        return null;
    }


    /**
     * Create server socket channel using the Unix domain socket ProtocolFamily.
     *
     * @return the server socket channel
     */
    public ServerSocketChannel openUnixDomainServerSocketChannel() {
        throw new UnsupportedOperationException(sm.getString("jreCompat.noUnixDomainSocket"));
    }


    /**
     * Create socket channel using the Unix domain socket ProtocolFamily.
     *
     * @return the socket channel
     */
    public SocketChannel openUnixDomainSocketChannel() {
        throw new UnsupportedOperationException(sm.getString("jreCompat.noUnixDomainSocket"));
    }


    // Java 8 implementations of Java 19 methods

    /**
     * Obtains the executor, if any, used to create the provided thread.
     *
     * @param thread The thread to examine
     *
     * @return The executor, if any, that created the provided thread
     *
     * @throws NoSuchFieldException     If a field used via reflection to obtain the executor cannot be found
     * @throws SecurityException        If a security exception occurs while trying to identify the executor
     * @throws IllegalArgumentException If the instance object does not match the class of the field when obtaining a
     *                                      field value via reflection
     * @throws IllegalAccessException   If a field is not accessible due to access restrictions
     */
    public Object getExecutor(Thread thread)
            throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {

        Object result = null;

        // Runnable wrapped by Thread
        // "target" in Sun/Oracle JDK
        // "runnable" in IBM JDK
        // "action" in Apache Harmony
        Object target = null;
        for (String fieldName : new String[] { "target", "runnable", "action" }) {
            try {
                Field targetField = thread.getClass().getDeclaredField(fieldName);
                targetField.setAccessible(true);
                target = targetField.get(thread);
                break;
            } catch (NoSuchFieldException nfe) {
                continue;
            }
        }

        // "java.util.concurrent" code is in public domain,
        // so all implementations are similar including our
        // internal fork.
        if (target != null && target.getClass().getCanonicalName() != null && (target.getClass().getCanonicalName()
                .equals("org.apache.tomcat.util.threads.ThreadPoolExecutor.Worker") ||
                target.getClass().getCanonicalName().equals("java.util.concurrent.ThreadPoolExecutor.Worker"))) {
            Field executorField = target.getClass().getDeclaredField("this$0");
            executorField.setAccessible(true);
            result = executorField.get(target);
        }

        return result;
    }


    // Java 8 implementations of Java 21 methods

    /**
     * Create a thread builder for virtual threads using the given name to name the threads.
     *
     * @param name The base name for the threads
     *
     * @return The thread buidler for virtual threads
     */
    public Object createVirtualThreadBuilder(String name) {
        throw new UnsupportedOperationException(sm.getString("jreCompat.noVirtualThreads"));
    }


    /**
     * Create a thread with the given thread builder and use it to execute the given runnable.
     *
     * @param threadBuilder The thread builder to use to create a thread
     * @param command       The command to run
     */
    public void threadBuilderStart(Object threadBuilder, Runnable command) {
        throw new UnsupportedOperationException(sm.getString("jreCompat.noVirtualThreads"));
    }


    /*
     * This is a slightly different usage of JreCompat.
     *
     * Subject.doAs() was deprecated in Java 18 and replaced with Subject.callAs(). As of Java 23, calling
     * Subject.doAs() will trigger an UnsupportedOperationException unless the java.security.manager system property is
     * set. To avoid Tomcat installations using Spnego authentication having to set this value, JreCompat is used to
     * call Subject.callAs() instead.
     *
     * Because Java versions 18 to 22 inclusive support both the old and the new method, the switch over can occur at
     * any Java version from 18 to 22 inclusive. Java 21 onwards was selected as it as an LTS version and that removes
     * the need to add a Jre18Compat class.
     *
     * So, the slightly longer description for this method is:
     *
     * Java 8 implementation of a method replaced between Java 18 and 22 with the replacement method being used by
     * Tomcat when running on Java 21 onwards.
     */

    public <T> T callAs(Subject subject, Callable<T> action) throws CompletionException {
        try {
            return Subject.doAs(subject, new PrivilegedExceptionAction<T>() {

                @Override
                public T run() throws Exception {
                    return action.call();
                }
            });
        } catch (Exception e) {
            throw new CompletionException(e);
        }
    }


    /*
     * The behaviour of the canonical file name cache varies by Java version.
     *
     * The cache was removed in Java 21 so these methods and the associated code can be removed once the minimum Java
     * version is 21.
     *
     * For 12 <= Java <= 20, the cache was present but disabled by default.
     *
     * For Java < 12, the cache was enabled by default. Tomcat assumes the cache is enabled unless proven otherwise.
     *
     * Tomcat 10.1 has a minimum Java version of 11.
     *
     * The static field in java.io.FileSystem will be set before any application code gets a chance to run. Therefore,
     * the value of that field can be determined by looking at the command line arguments. This enables us to determine
     * the status without having using reflection.
     *
     * This is Java 11.
     */
    public boolean isCanonCachesDisabled() {
        if (canonCachesDisabled != null) {
            return canonCachesDisabled.booleanValue();
        }
        synchronized (canonCachesDisabledLock) {
            if (canonCachesDisabled != null) {
                return canonCachesDisabled.booleanValue();
            }

            boolean cacheEnabled = true;
            List<String> args = ManagementFactory.getRuntimeMXBean().getInputArguments();
            for (String arg : args) {
                // To consider the cache disabled
                // - there must be at least one command line argument that disables it
                // - there must be no command line arguments that enable it
                if (arg.startsWith(USE_CANON_CACHES_CMD_ARG)) {
                    String valueAsString = arg.substring(USE_CANON_CACHES_CMD_ARG.length());
                    boolean valueAsBoolean = Boolean.valueOf(valueAsString).booleanValue();
                    if (valueAsBoolean) {
                        canonCachesDisabled = Boolean.FALSE;
                        return false;
                    } else {
                        cacheEnabled = false;
                    }
                }
            }
            if (cacheEnabled) {
                canonCachesDisabled = Boolean.FALSE;
            } else {
                canonCachesDisabled = Boolean.TRUE;
            }
            return canonCachesDisabled.booleanValue();
        }
    }


    /**
     * Disable the global canonical file cache.
     *
     * @return {@code true} if the global canonical file cache was already disabled prior to this call or was disabled
     *             as a result of this call, otherwise {@code false}
     */
    public boolean disableCanonCaches() {
        ensureUseCanonCachesFieldIsPopulated();
        if (!useCanonCachesField.isPresent()) {
            log.warn(sm.getString("jreCompat.useCanonCaches.none"));
            return false;
        }
        try {
            useCanonCachesField.get().set(null, Boolean.FALSE);
        } catch (ReflectiveOperationException | IllegalArgumentException e) {
            log.warn(sm.getString("jreCompat.useCanonCaches.failed"), e);
            return false;
        }
        synchronized (canonCachesDisabledLock) {
            canonCachesDisabled = Boolean.TRUE;
        }
        return true;
    }


    protected void ensureUseCanonCachesFieldIsPopulated() {
        if (useCanonCachesField != null) {
            return;
        }
        synchronized (useCanonCachesFieldLock) {
            if (useCanonCachesField != null) {
                return;
            }

            Field f = null;
            try {
                Class<?> clazz = Class.forName("java.io.FileSystem");
                f = clazz.getDeclaredField("useCanonCaches");
                // Need this because the 'useCanonCaches' field is private final
                f.setAccessible(true);
            } catch (ReflectiveOperationException | IllegalArgumentException e) {
                // Make sure field is not set.
                f = null;
                log.warn(sm.getString("jreCompat.useCanonCaches.init"), e);
            }

            if (f == null) {
                useCanonCachesField = Optional.empty();
            } else {
                useCanonCachesField = Optional.of(f);
            }
        }
    }
}
