/*

 * Copyright (c) 2015, 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

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package jdk.internal.logger;

import java.io.FilePermission;

import java.security.AccessController;

import java.security.Permission;

import java.security.PrivilegedAction;

import java.util.Iterator;

import java.util.Locale;

import java.util.ServiceConfigurationError;

import java.util.ServiceLoader;

import sun.security.util.SecurityConstants;

/**

 * Helper class used to load the {@link java.lang.System.LoggerFinder}.

 */

public final class LoggerFinderLoader {

    private static volatile System.LoggerFinder service;

    private static final Object lock = new int[0];

    static final Permission CLASSLOADER_PERMISSION =

            SecurityConstants.GET_CLASSLOADER_PERMISSION;

    static final Permission READ_PERMISSION =

            new FilePermission("<<ALL FILES>>",

                    SecurityConstants.FILE_READ_ACTION);

    public static final RuntimePermission LOGGERFINDER_PERMISSION =

                new RuntimePermission("loggerFinder");

    // This is used to control how the LoggerFinderLoader handles

    // errors when instantiating the LoggerFinder provider.

    // ERROR => throws ServiceConfigurationError

    // WARNING => Do not fail, use plain default (simple logger) implementation,

    //            prints warning on console. (this is the default)

    // DEBUG => Do not fail, use plain default (simple logger) implementation,

    //          prints warning and exception stack trace on console.

    // QUIET => Do not fail and stay silent.

    private static enum ErrorPolicy { ERROR, WARNING, DEBUG, QUIET };

    // This class is static and cannot be instantiated.

    private LoggerFinderLoader() {

        throw new InternalError("LoggerFinderLoader cannot be instantiated");

    }

    // Return the loaded LoggerFinder, or load it if not already loaded.

    private static System.LoggerFinder service() {

        if (service != null) return service;

        synchronized(lock) {

            if (service != null) return service;

            service = loadLoggerFinder();

        }

        // Since the LoggerFinder is already loaded - we can stop using

        // temporary loggers.

        BootstrapLogger.redirectTemporaryLoggers();

        return service;

    }

    // Get configuration error policy

    private static ErrorPolicy configurationErrorPolicy() {

        if (errorPolicy == null || errorPolicy.isEmpty()) {

            return ErrorPolicy.WARNING;

        }

        try {

            return ErrorPolicy.valueOf(errorPolicy.toUpperCase(Locale.ROOT));

        } catch (IllegalArgumentException x) {

            return ErrorPolicy.WARNING;

        }

    }

    // Whether multiple provider should be considered as an error.

    // This is further submitted to the configuration error policy.

    private static boolean ensureSingletonProvider() {

    }

    private static Iterator<System.LoggerFinder> findLoggerFinderProviders() {

        final Iterator<System.LoggerFinder> iterator;

        if (System.getSecurityManager() == null) {

            iterator = ServiceLoader.load(System.LoggerFinder.class,

                        ClassLoader.getSystemClassLoader()).iterator();

        } else {

            final PrivilegedAction<Iterator<System.LoggerFinder>> pa =

                    () -> ServiceLoader.load(System.LoggerFinder.class,

                        ClassLoader.getSystemClassLoader()).iterator();

            iterator = AccessController.doPrivileged(pa, null,

                        LOGGERFINDER_PERMISSION, CLASSLOADER_PERMISSION,

                        READ_PERMISSION);

        }

        return iterator;

    }

    // Loads the LoggerFinder using ServiceLoader. If no LoggerFinder

    // is found returns the default (possibly JUL based) implementation

    private static System.LoggerFinder loadLoggerFinder() {

        System.LoggerFinder result;

        try {

            // Iterator iterates with the access control context stored

            // at ServiceLoader creation time.

            final Iterator<System.LoggerFinder> iterator =

                    findLoggerFinderProviders();

            if (iterator.hasNext()) {

                result = iterator.next();

                if (iterator.hasNext() && ensureSingletonProvider()) {

                    throw new ServiceConfigurationError(

                            "More than on LoggerFinder implementation");

                }

            } else {

                result = loadDefaultImplementation();

            }

        } catch (Error | RuntimeException x) {

            // next caller will get the plain default impl (not linked

            // to java.util.logging)

            service = result = new DefaultLoggerFinder();

            ErrorPolicy errorPolicy = configurationErrorPolicy();

            if (errorPolicy == ErrorPolicy.ERROR) {

                // rethrow any exception as a ServiceConfigurationError.

                if (x instanceof Error) {

                    throw x;

                } else {

                    throw new ServiceConfigurationError(

                        "Failed to instantiate LoggerFinder provider; Using default.", x);

                }

            } else if (errorPolicy != ErrorPolicy.QUIET) {

                // if QUIET just silently use the plain default impl

                // otherwise, log a warning, possibly adding the exception

                // stack trace (if DEBUG is specified).

                SimpleConsoleLogger logger =

                        new SimpleConsoleLogger("jdk.internal.logger", false);

                logger.log(System.Logger.Level.WARNING,

                        "Failed to instantiate LoggerFinder provider; Using default.");

                if (errorPolicy == ErrorPolicy.DEBUG) {

                    logger.log(System.Logger.Level.WARNING,

                        "Exception raised trying to instantiate LoggerFinder", x);

                }

            }

        }

        return result;

    }

    private static System.LoggerFinder loadDefaultImplementation() {

        final SecurityManager sm = System.getSecurityManager();

        final Iterator<DefaultLoggerFinder> iterator;

        if (sm == null) {

            iterator = ServiceLoader.loadInstalled(DefaultLoggerFinder.class).iterator();

        } else {

            // We use limited do privileged here - the minimum set of

            // permissions required to 'see' the META-INF/services resources

            // seems to be CLASSLOADER_PERMISSION and READ_PERMISSION.

            // Note that do privileged is required because

            // otherwise the SecurityManager will prevent the ServiceLoader

            // from seeing the installed provider.

            PrivilegedAction<Iterator<DefaultLoggerFinder>> pa = () ->

                    ServiceLoader.loadInstalled(DefaultLoggerFinder.class).iterator();

            iterator = AccessController.doPrivileged(pa, null,

                    LOGGERFINDER_PERMISSION, CLASSLOADER_PERMISSION,

                    READ_PERMISSION);

        }

        DefaultLoggerFinder result = null;

        try {

            // Iterator iterates with the access control context stored

            // at ServiceLoader creation time.

            if (iterator.hasNext()) {

                result = iterator.next();

            }

        } catch (RuntimeException x) {

            throw new ServiceConfigurationError(

                    "Failed to instantiate default LoggerFinder", x);

        }

        if (result == null) {

            result = new DefaultLoggerFinder();

        }

        return result;

    }

    public static System.LoggerFinder getLoggerFinder() {

        final SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(LOGGERFINDER_PERMISSION);

        }

        return service();

    }

}