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package java.util.logging;

import java.lang.ref.WeakReference;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.Locale;

import java.util.MissingResourceException;

import java.util.Objects;

import java.util.ResourceBundle;

import java.util.concurrent.CopyOnWriteArrayList;

import java.util.function.Supplier;

import jdk.internal.misc.JavaUtilResourceBundleAccess;

import jdk.internal.misc.SharedSecrets;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.Reflection;

import static jdk.internal.logger.DefaultLoggerFinder.isSystem;

/**

 * A Logger object is used to log messages for a specific

 * system or application component.  Loggers are normally named,

 * using a hierarchical dot-separated namespace.  Logger names

 * can be arbitrary strings, but they should normally be based on

 * the package name or class name of the logged component, such

 * as java.net or javax.swing.  In addition it is possible to create

 * "anonymous" Loggers that are not stored in the Logger namespace.

 * <p>

 * Logger objects may be obtained by calls on one of the getLogger

 * factory methods.  These will either create a new Logger or

 * return a suitable existing Logger. It is important to note that

 * the Logger returned by one of the {@code getLogger} factory methods

 * may be garbage collected at any time if a strong reference to the

 * Logger is not kept.

 * <p>

 * Logging messages will be forwarded to registered Handler

 * objects, which can forward the messages to a variety of

 * destinations, including consoles, files, OS logs, etc.

 * <p>

 * Each Logger keeps track of a "parent" Logger, which is its

 * nearest existing ancestor in the Logger namespace.

 * <p>

 * Each Logger has a "Level" associated with it.  This reflects

 * a minimum Level that this logger cares about.  If a Logger's

 * level is set to {@code null}, then its effective level is inherited

 * from its parent, which may in turn obtain it recursively from its

 * parent, and so on up the tree.

 * <p>

 * The log level can be configured based on the properties from the

 * logging configuration file, as described in the description

 * of the LogManager class.  However it may also be dynamically changed

 * by calls on the Logger.setLevel method.  If a logger's level is

 * changed the change may also affect child loggers, since any child

 * logger that has {@code null} as its level will inherit its

 * effective level from its parent.

 * <p>

 * On each logging call the Logger initially performs a cheap

 * check of the request level (e.g., SEVERE or FINE) against the

 * effective log level of the logger.  If the request level is

 * lower than the log level, the logging call returns immediately.

 * <p>

 * After passing this initial (cheap) test, the Logger will allocate

 * a LogRecord to describe the logging message.  It will then call a

 * Filter (if present) to do a more detailed check on whether the

 * record should be published.  If that passes it will then publish

 * the LogRecord to its output Handlers.  By default, loggers also

 * publish to their parent's Handlers, recursively up the tree.

 * <p>

 * Each Logger may have a {@code ResourceBundle} associated with it.

 * The {@code ResourceBundle} may be specified by name, using the

 * {@link #getLogger(java.lang.String, java.lang.String)} factory

 * method, or by value - using the {@link

 * #setResourceBundle(java.util.ResourceBundle) setResourceBundle} method.

 * This bundle will be used for localizing logging messages.

 * If a Logger does not have its own {@code ResourceBundle} or resource bundle

 * name, then it will inherit the {@code ResourceBundle} or resource bundle name

 * from its parent, recursively up the tree.

 * <p>

 * Most of the logger output methods take a "msg" argument.  This

 * msg argument may be either a raw value or a localization key.

 * During formatting, if the logger has (or inherits) a localization

 * {@code ResourceBundle} and if the {@code ResourceBundle} has a mapping for

 * the msg string, then the msg string is replaced by the localized value.

 * Otherwise the original msg string is used.  Typically, formatters use

 * java.text.MessageFormat style formatting to format parameters, so

 * for example a format string "{0} {1}" would format two parameters

 * as strings.

 * <p>

 * A set of methods alternatively take a "msgSupplier" instead of a "msg"

 * argument.  These methods take a {@link Supplier}{@code <String>} function

 * which is invoked to construct the desired log message only when the message

 * actually is to be logged based on the effective log level thus eliminating

 * unnecessary message construction. For example, if the developer wants to

 * log system health status for diagnosis, with the String-accepting version,

 * the code would look like:

 * <pre>{@code

 *

 *  class DiagnosisMessages {

 *    static String systemHealthStatus() {

 *      // collect system health information

 *      ...

 *    }

 *  }

 *  ...

 *  logger.log(Level.FINER, DiagnosisMessages.systemHealthStatus());

 * }</pre>

 * With the above code, the health status is collected unnecessarily even when

 * the log level FINER is disabled. With the Supplier-accepting version as

 * below, the status will only be collected when the log level FINER is

 * enabled.

 * <pre>{@code

 *

 *  logger.log(Level.FINER, DiagnosisMessages::systemHealthStatus);

 * }</pre>

 * <p>

 * When looking for a {@code ResourceBundle}, the logger will first look at

 * whether a bundle was specified using {@link

 * #setResourceBundle(java.util.ResourceBundle) setResourceBundle}, and then

 * only whether a resource bundle name was specified through the {@link

 * #getLogger(java.lang.String, java.lang.String) getLogger} factory method.

 * If no {@code ResourceBundle} or no resource bundle name is found,

 * then it will use the nearest {@code ResourceBundle} or resource bundle

 * name inherited from its parent tree.<br>

 * When a {@code ResourceBundle} was inherited or specified through the

 * {@link

 * #setResourceBundle(java.util.ResourceBundle) setResourceBundle} method, then

 * that {@code ResourceBundle} will be used. Otherwise if the logger only

 * has or inherited a resource bundle name, then that resource bundle name

 * will be mapped to a {@code ResourceBundle} object, using the default Locale

 * at the time of logging.

 * <br id="ResourceBundleMapping">When mapping resource bundle names to

 * {@code ResourceBundle} objects, the logger will first try to use the

 * Thread's {@linkplain java.lang.Thread#getContextClassLoader() context class

 * loader} to map the given resource bundle name to a {@code ResourceBundle}.

 * If the thread context class loader is {@code null}, it will try the

 * {@linkplain java.lang.ClassLoader#getSystemClassLoader() system class loader}

 * instead.  If the {@code ResourceBundle} is still not found, it will use the

 * class loader of the first caller of the {@link

 * #getLogger(java.lang.String, java.lang.String) getLogger} factory method.

 * <p>

 * Formatting (including localization) is the responsibility of

 * the output Handler, which will typically call a Formatter.

 * <p>

 * Note that formatting need not occur synchronously.  It may be delayed

 * until a LogRecord is actually written to an external sink.

 * <p>

 * The logging methods are grouped in five main categories:

 * <ul>

 * <li><p>

 *     There are a set of "log" methods that take a log level, a message

 *     string, and optionally some parameters to the message string.

 * <li><p>

 *     There are a set of "logp" methods (for "log precise") that are

 *     like the "log" methods, but also take an explicit source class name

 *     and method name.

 * <li><p>

 *     There are a set of "logrb" method (for "log with resource bundle")

 *     that are like the "logp" method, but also take an explicit resource

 *     bundle object for use in localizing the log message.

 * <li><p>

 *     There are convenience methods for tracing method entries (the

 *     "entering" methods), method returns (the "exiting" methods) and

 *     throwing exceptions (the "throwing" methods).

 * <li><p>

 *     Finally, there are a set of convenience methods for use in the

 *     very simplest cases, when a developer simply wants to log a

 *     simple string at a given log level.  These methods are named

 *     after the standard Level names ("severe", "warning", "info", etc.)

 *     and take a single argument, a message string.

 * </ul>

 * <p>

 * For the methods that do not take an explicit source name and

 * method name, the Logging framework will make a "best effort"

 * to determine which class and method called into the logging method.

 * However, it is important to realize that this automatically inferred

 * information may only be approximate (or may even be quite wrong!).

 * Virtual machines are allowed to do extensive optimizations when

 * JITing and may entirely remove stack frames, making it impossible

 * to reliably locate the calling class and method.

 * <P>

 * All methods on Logger are multi-thread safe.

 * <p>

 * <b>Subclassing Information:</b> Note that a LogManager class may

 * provide its own implementation of named Loggers for any point in

 * the namespace.  Therefore, any subclasses of Logger (unless they

 * are implemented in conjunction with a new LogManager class) should

 * take care to obtain a Logger instance from the LogManager class and

 * should delegate operations such as "isLoggable" and "log(LogRecord)"

 * to that instance.  Note that in order to intercept all logging

 * output, subclasses need only override the log(LogRecord) method.

 * All the other logging methods are implemented as calls on this

 * log(LogRecord) method.

 *

 * @since 1.4

 */

public class Logger {

    private static final Handler emptyHandlers[] = new Handler[0];

    private static final int offValue = Level.OFF.intValue();

    static final String SYSTEM_LOGGER_RB_NAME = "sun.util.logging.resources.logging";

    // This class is immutable and it is important that it remains so.

    private static final class LoggerBundle {

        final String resourceBundleName; // Base name of the bundle.

        final ResourceBundle userBundle; // Bundle set through setResourceBundle.

        private LoggerBundle(String resourceBundleName, ResourceBundle bundle) {

            this.resourceBundleName = resourceBundleName;

            this.userBundle = bundle;

        }

        boolean isSystemBundle() {

            return SYSTEM_LOGGER_RB_NAME.equals(resourceBundleName);

        }

        static LoggerBundle get(String name, ResourceBundle bundle) {

            if (name == null && bundle == null) {

                return NO_RESOURCE_BUNDLE;

            } else if (SYSTEM_LOGGER_RB_NAME.equals(name) && bundle == null) {

                return SYSTEM_BUNDLE;

            } else {

                return new LoggerBundle(name, bundle);

            }

        }

    }

    // This instance will be shared by all loggers created by the system

    // code

    private static final LoggerBundle SYSTEM_BUNDLE =

            new LoggerBundle(SYSTEM_LOGGER_RB_NAME, null);

    // This instance indicates that no resource bundle has been specified yet,

    // and it will be shared by all loggers which have no resource bundle.

    private static final LoggerBundle NO_RESOURCE_BUNDLE =

            new LoggerBundle(null, null);

    // Calling SharedSecrets.getJavaUtilResourceBundleAccess()

    // forces the initialization of ResourceBundle.class, which

    // can be too early if the VM has not finished booting yet.

    private static final class RbAccess {

        static final JavaUtilResourceBundleAccess RB_ACCESS =

            SharedSecrets.getJavaUtilResourceBundleAccess();

    }

    // A value class that holds the logger configuration data.

    // This configuration can be shared between an application logger

    // and a system logger of the same name.

    private static final class ConfigurationData {

        // The delegate field is used to avoid races while

        // merging configuration. This will ensure that any pending

        // configuration action on an application logger will either

        // be finished before the merge happens, or will be forwarded

        // to the system logger configuration after the merge is completed.

        // By default delegate=this.

        private volatile ConfigurationData delegate;

        volatile boolean useParentHandlers;

        volatile Filter filter;

        volatile Level levelObject;

        volatile int levelValue;  // current effective level value

        final CopyOnWriteArrayList<Handler> handlers =

            new CopyOnWriteArrayList<>();

        ConfigurationData() {

            delegate = this;

            useParentHandlers = true;

            levelValue = Level.INFO.intValue();

        }

        void setUseParentHandlers(boolean flag) {

            useParentHandlers = flag;

            if (delegate != this) {

                // merge in progress - propagate value to system peer.

                final ConfigurationData system = delegate;

                synchronized (system) {

                    system.useParentHandlers = useParentHandlers;

                }

            }

        }

        void setFilter(Filter f) {

            filter = f;

            if (delegate != this) {

                // merge in progress - propagate value to system peer.

                final ConfigurationData system = delegate;

                synchronized (system) {

                    system.filter = filter;

                }

            }

        }

        void setLevelObject(Level l) {

            levelObject = l;

            if (delegate != this) {

                // merge in progress - propagate value to system peer.

                final ConfigurationData system = delegate;

                synchronized (system) {

                    system.levelObject = levelObject;

                }

            }

        }

        void setLevelValue(int v) {

            levelValue = v;

            if (delegate != this) {

                // merge in progress - propagate value to system peer.

                final ConfigurationData system = delegate;

                synchronized (system) {

                    system.levelValue = levelValue;

                }

            }

        }

        void addHandler(Handler h) {

            if (handlers.add(h)) {

                if (delegate != this) {

                    // merge in progress - propagate value to system peer.

                    final ConfigurationData system = delegate;

                    synchronized (system) {

                        system.handlers.addIfAbsent(h);

                    }

                }

            }

        }

        void removeHandler(Handler h) {

            if (handlers.remove(h)) {

                if (delegate != this) {

                    // merge in progress - propagate value to system peer.

                    final ConfigurationData system = delegate;

                    synchronized (system) {

                        system.handlers.remove(h);

                    }

                }

            }

        }

        ConfigurationData merge(Logger systemPeer) {

            if (!systemPeer.isSystemLogger) {

                // should never come here

                throw new InternalError("not a system logger");

            }

            ConfigurationData system = systemPeer.config;

            if (system == this) {

                // nothing to do

                return system;

            }

            synchronized (system) {

                // synchronize before checking on delegate to counter

                // race conditions where two threads might attempt to

                // merge concurrently

                if (delegate == system) {

                    // merge already performed;

                    return system;

                }

                // publish system as the temporary delegate configuration.

                // This should take care of potential race conditions where

                // an other thread might attempt to call e.g. setlevel on

                // the application logger while merge is in progress.

                // (see implementation of ConfigurationData::setLevel)

                delegate = system;

                // merge this config object data into the system config

                system.useParentHandlers = useParentHandlers;

                system.filter = filter;

                system.levelObject = levelObject;

                system.levelValue = levelValue;

                // Prevent race condition in case two threads attempt to merge

                // configuration and add handlers at the same time. We don't want

                // to add the same handlers twice.

                //

                // Handlers are created and loaded by LogManager.addLogger. If we

                // reach here, then it means that the application logger has

                // been created first and added with LogManager.addLogger, and the

                // system logger was created after - and no handler has been added

                // to it by LogManager.addLogger. Therefore, system.handlers

                // should be empty.

                //

                // A non empty cfg.handlers list indicates a race condition

                // where two threads might attempt to merge the configuration

                // or add handlers concurrently. Though of no consequence for

                // the other data (level etc...) this would be an issue if we

                // added the same handlers twice.

                //

                for (Handler h : handlers) {

                    if (!system.handlers.contains(h)) {

                        systemPeer.addHandler(h);

                    }

                }

                system.handlers.retainAll(handlers);

                system.handlers.addAllAbsent(handlers);

            }

            // sanity: update effective level after merging

            synchronized(treeLock) {

                systemPeer.updateEffectiveLevel();

            }

            return system;

        }

    }

    // The logger configuration data. Ideally, this should be final

    // for system loggers, and replace-once for application loggers.

    // When an application requests a logger by name, we do not know a-priori

    // whether that corresponds to a system logger name or not.

    // So if no system logger by that name already exists, we simply return an

    // application logger.

    // If a system class later requests a system logger of the same name, then

    // the application logger and system logger configurations will be merged

    // in a single instance of ConfigurationData that both loggers will share.

    private volatile ConfigurationData config;

    private volatile LogManager manager;

    private String name;

    private volatile LoggerBundle loggerBundle = NO_RESOURCE_BUNDLE;

    private boolean anonymous;

    // Cache to speed up behavior of findResourceBundle:

    private ResourceBundle catalog;     // Cached resource bundle

    private String catalogName;         // name associated with catalog

    private Locale catalogLocale;       // locale associated with catalog

    // The fields relating to parent-child relationships and levels

    // are managed under a separate lock, the treeLock.

    private static final Object treeLock = new Object();

    // We keep weak references from parents to children, but strong

    // references from children to parents.

    private volatile Logger parent;    // our nearest parent.

    private ArrayList<LogManager.LoggerWeakRef> kids;   // WeakReferences to loggers that have us as parent

    private WeakReference<Module> callerModuleRef;

    private final boolean isSystemLogger;

    /**

     * GLOBAL_LOGGER_NAME is a name for the global logger.

     *

     * @since 1.6

     */

    public static final String GLOBAL_LOGGER_NAME = "global";

    /**

     * Return global logger object with the name Logger.GLOBAL_LOGGER_NAME.

     *

     * @return global logger object

     * @since 1.7

     */

    public static final Logger getGlobal() {

        // In order to break a cyclic dependence between the LogManager

        // and Logger static initializers causing deadlocks, the global

        // logger is created with a special constructor that does not

        // initialize its log manager.

        //

        // If an application calls Logger.getGlobal() before any logger

        // has been initialized, it is therefore possible that the

        // LogManager class has not been initialized yet, and therefore

        // Logger.global.manager will be null.

        //

        // In order to finish the initialization of the global logger, we

        // will therefore call LogManager.getLogManager() here.

        //

        // To prevent race conditions we also need to call

        // LogManager.getLogManager() unconditionally here.

        // Indeed we cannot rely on the observed value of global.manager,

        // because global.manager will become not null somewhere during

        // the initialization of LogManager.

        // If two threads are calling getGlobal() concurrently, one thread

        // will see global.manager null and call LogManager.getLogManager(),

        // but the other thread could come in at a time when global.manager

        // is already set although ensureLogManagerInitialized is not finished

        // yet...

        // Calling LogManager.getLogManager() unconditionally will fix that.