/**
    * Copyright (c) 2004-2011 QOS.ch
    * All rights reserved.
    *
    * Permission is hereby granted, free  of charge, to any person obtaining
    * a  copy  of this  software  and  associated  documentation files  (the
    * "Software"), to  deal in  the Software without  restriction, including
    * without limitation  the rights to  use, copy, modify,  merge, publish,
    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
   * permit persons to whom the Software  is furnished to do so, subject to
   * the following conditions:
   *
   * The  above  copyright  notice  and  this permission  notice  shall  be
   * included in all copies or substantial portions of the Software.
   *
   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   */
  package org.slf4j;
  
  import java.io.IOException;
  import java.net.URL;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Enumeration;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.ServiceLoader;
  import java.util.Set;
  import java.util.concurrent.LinkedBlockingQueue;
  
  import org.slf4j.event.SubstituteLoggingEvent;
  import org.slf4j.helpers.NOP_FallbackServiceProvider;
  import org.slf4j.helpers.SubstituteServiceProvider;
  import org.slf4j.helpers.SubstituteLogger;
  
  import org.slf4j.helpers.Util;
  import org.slf4j.spi.SLF4JServiceProvider;
  
  /**
   * The <code>LoggerFactory</code> is a utility class producing Loggers for
   * various logging APIs, most notably for log4j, logback and JDK 1.4 logging.
   * Other implementations such as {@link org.slf4j.helpers.NOPLogger NOPLogger} and
   * SimpleLogger are also supported.
   * 
   * <p><code>LoggerFactory</code> is essentially a wrapper around an
   * {@link ILoggerFactory} instance bound with <code>LoggerFactory</code> at
   * compile time.
   * 
   * <p>
   * Please note that all methods in <code>LoggerFactory</code> are static.
   * 
   * @author Alexander Dorokhine
   * @author Robert Elliot
   * @author Ceki G&uuml;lc&uuml;
   * 
   */
  public final class LoggerFactory {
  
      static final String CODES_PREFIX = "http://www.slf4j.org/codes.html";
  
      static final String NO_PROVIDERS_URL = CODES_PREFIX + "#noProviders";
      static final String IGNORED_BINDINGS_URL = CODES_PREFIX + "#ignoredBindings";
  
      static final String NO_STATICLOGGERBINDER_URL = CODES_PREFIX + "#StaticLoggerBinder";
      static final String MULTIPLE_BINDINGS_URL = CODES_PREFIX + "#multiple_bindings";
      static final String NULL_LF_URL = CODES_PREFIX + "#null_LF";
      static final String VERSION_MISMATCH = CODES_PREFIX + "#version_mismatch";
      static final String SUBSTITUTE_LOGGER_URL = CODES_PREFIX + "#substituteLogger";
      static final String LOGGER_NAME_MISMATCH_URL = CODES_PREFIX + "#loggerNameMismatch";
      static final String REPLAY_URL = CODES_PREFIX + "#replay";
  
      static final String UNSUCCESSFUL_INIT_URL = CODES_PREFIX + "#unsuccessfulInit";
      static final String UNSUCCESSFUL_INIT_MSG = "org.slf4j.LoggerFactory in failed state. Original exception was thrown EARLIER. See also "
                      + UNSUCCESSFUL_INIT_URL;
  
      static final int UNINITIALIZED = 0;
      static final int ONGOING_INITIALIZATION = 1;
      static final int FAILED_INITIALIZATION = 2;
      static final int SUCCESSFUL_INITIALIZATION = 3;
      static final int NOP_FALLBACK_INITIALIZATION = 4;
  
      static volatile int INITIALIZATION_STATE = UNINITIALIZED;
      static final SubstituteServiceProvider SUBST_PROVIDER = new SubstituteServiceProvider();
      static final NOP_FallbackServiceProvider NOP_FALLBACK_SERVICE_PROVIDER = new NOP_FallbackServiceProvider();
  
      // Support for detecting mismatched logger names.
      static final String DETECT_LOGGER_NAME_MISMATCH_PROPERTY = "slf4j.detectLoggerNameMismatch";
      static final String JAVA_VENDOR_PROPERTY = "java.vendor.url";
  
      static boolean DETECT_LOGGER_NAME_MISMATCH = Util.safeGetBooleanSystemProperty(DETECT_LOGGER_NAME_MISMATCH_PROPERTY);
  
      static volatile SLF4JServiceProvider PROVIDER;
 
     private static List<SLF4JServiceProvider> findServiceProviders() {
         ServiceLoader<SLF4JServiceProvider> serviceLoader = ServiceLoader.load(SLF4JServiceProvider.class);
         List<SLF4JServiceProvider> providerList = new ArrayList<>();
         for (SLF4JServiceProvider provider : serviceLoader) {
             providerList.add(provider);
         }
         return providerList;
     }
 
     /**
      * It is LoggerFactory's responsibility to track version changes and manage
      * the compatibility list.
      * <p>
      * <p>
      * It is assumed that all versions in the 1.6 are mutually compatible.
      */
     static private final String[] API_COMPATIBILITY_LIST = new String[] { "2.0" };
 
     // private constructor prevents instantiation
     private LoggerFactory() {
     }
 
     /**
      * Force LoggerFactory to consider itself uninitialized.
      * <p>
      * <p>
      * This method is intended to be called by classes (in the same package) for
      * testing purposes. This method is internal. It can be modified, renamed or
      * removed at any time without notice.
      * <p>
      * <p>
      * You are strongly discouraged from calling this method in production code.
      */
     static void reset() {
         INITIALIZATION_STATE = UNINITIALIZED;
     }
 
     private final static void performInitialization() {
         bind();
         if (INITIALIZATION_STATE == SUCCESSFUL_INITIALIZATION) {
             versionSanityCheck();
         }
     }
 
     private final static void bind() {
         try {
             List<SLF4JServiceProvider> providersList = findServiceProviders();
             reportMultipleBindingAmbiguity(providersList);
             if (providersList != null && !providersList.isEmpty()) {
                 PROVIDER = providersList.get(0);
                 // SLF4JServiceProvider.initialize() is intended to be called here and nowhere else.
                 PROVIDER.initialize();
                 INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
                 reportActualBinding(providersList);
             } else {
                 INITIALIZATION_STATE = NOP_FALLBACK_INITIALIZATION;
                 Util.report("No SLF4J providers were found.");
                 Util.report("Defaulting to no-operation (NOP) logger implementation");
                 Util.report("See " + NO_PROVIDERS_URL + " for further details.");
 
                 Set<URL> staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
                 reportIgnoredStaticLoggerBinders(staticLoggerBinderPathSet);
             }
             postBindCleanUp();
         } catch (Exception e) {
             failedBinding(e);
             throw new IllegalStateException("Unexpected initialization failure", e);
         }
     }
 
     private static void reportIgnoredStaticLoggerBinders(Set<URL> staticLoggerBinderPathSet) {
         if (staticLoggerBinderPathSet.isEmpty()) {
             return;
         }
         Util.report("Class path contains SLF4J bindings targeting slf4j-api versions prior to 1.8.");
         for (URL path : staticLoggerBinderPathSet) {
             Util.report("Ignoring binding found at [" + path + "]");
         }
         Util.report("See " + IGNORED_BINDINGS_URL + " for an explanation.");
 
     }
 
     // We need to use the name of the StaticLoggerBinder class, but we can't
     // reference the class itself.
     private static final String STATIC_LOGGER_BINDER_PATH = "org/slf4j/impl/StaticLoggerBinder.class";
 
     static Set<URL> findPossibleStaticLoggerBinderPathSet() {
         // use Set instead of list in order to deal with bug #138
         // LinkedHashSet appropriate here because it preserves insertion order
         // during iteration
         Set<URL> staticLoggerBinderPathSet = new LinkedHashSet<>();
         try {
             ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();
             Enumeration<URL> paths;
             if (loggerFactoryClassLoader == null) {
                 paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);
             } else {
                 paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);
             }
             while (paths.hasMoreElements()) {
                 URL path = paths.nextElement();
                 staticLoggerBinderPathSet.add(path);
             }
         } catch (IOException ioe) {
             Util.report("Error getting resources from path", ioe);
         }
         return staticLoggerBinderPathSet;
     }
 
     private static void postBindCleanUp() {
         fixSubstituteLoggers();
         replayEvents();
         // release all resources in SUBST_FACTORY
         SUBST_PROVIDER.getSubstituteLoggerFactory().clear();
     }
 
     private static void fixSubstituteLoggers() {
         synchronized (SUBST_PROVIDER) {
             SUBST_PROVIDER.getSubstituteLoggerFactory().postInitialization();
             for (SubstituteLogger substLogger : SUBST_PROVIDER.getSubstituteLoggerFactory().getLoggers()) {
                 Logger logger = getLogger(substLogger.getName());
                 substLogger.setDelegate(logger);
             }
         }
 
     }
 
     static void failedBinding(Throwable t) {
         INITIALIZATION_STATE = FAILED_INITIALIZATION;
         Util.report("Failed to instantiate SLF4J LoggerFactory", t);
     }
 
     private static void replayEvents() {
         final LinkedBlockingQueue<SubstituteLoggingEvent> queue = SUBST_PROVIDER.getSubstituteLoggerFactory().getEventQueue();
         final int queueSize = queue.size();
         int count = 0;
         final int maxDrain = 128;
         List<SubstituteLoggingEvent> eventList = new ArrayList<>(maxDrain);
         while (true) {
             int numDrained = queue.drainTo(eventList, maxDrain);
             if (numDrained == 0)
                 break;
             for (SubstituteLoggingEvent event : eventList) {
                 replaySingleEvent(event);
                 if (count++ == 0)
                     emitReplayOrSubstituionWarning(event, queueSize);
             }
             eventList.clear();
         }
     }
 
     private static void emitReplayOrSubstituionWarning(SubstituteLoggingEvent event, int queueSize) {
         if (event.getLogger().isDelegateEventAware()) {
             emitReplayWarning(queueSize);
         } else if (event.getLogger().isDelegateNOP()) {
             // nothing to do
         } else {
             emitSubstitutionWarning();
         }
     }
 
     private static void replaySingleEvent(SubstituteLoggingEvent event) {
         if (event == null)
             return;
 
         SubstituteLogger substLogger = event.getLogger();
         String loggerName = substLogger.getName();
         if (substLogger.isDelegateNull()) {
             throw new IllegalStateException("Delegate logger cannot be null at this state.");
         }
 
         if (substLogger.isDelegateNOP()) {
             // nothing to do
         } else if (substLogger.isDelegateEventAware()) {
             substLogger.log(event);
         } else {
             Util.report(loggerName);
         }
     }
 
     private static void emitSubstitutionWarning() {
         Util.report("The following set of substitute loggers may have been accessed");
         Util.report("during the initialization phase. Logging calls during this");
         Util.report("phase were not honored. However, subsequent logging calls to these");
         Util.report("loggers will work as normally expected.");
         Util.report("See also " + SUBSTITUTE_LOGGER_URL);
     }
 
     private static void emitReplayWarning(int eventCount) {
         Util.report("A number (" + eventCount + ") of logging calls during the initialization phase have been intercepted and are");
         Util.report("now being replayed. These are subject to the filtering rules of the underlying logging system.");
         Util.report("See also " + REPLAY_URL);
     }
 
     private final static void versionSanityCheck() {
         try {
             String requested = PROVIDER.getRequestedApiVersion();
 
             boolean match = false;
             for (String aAPI_COMPATIBILITY_LIST : API_COMPATIBILITY_LIST) {
                 if (requested.startsWith(aAPI_COMPATIBILITY_LIST)) {
                     match = true;
                 }
             }
             if (!match) {
                 Util.report("The requested version " + requested + " by your slf4j binding is not compatible with "
                                 + Arrays.asList(API_COMPATIBILITY_LIST).toString());
                 Util.report("See " + VERSION_MISMATCH + " for further details.");
             }
         } catch (java.lang.NoSuchFieldError nsfe) {
             // given our large user base and SLF4J's commitment to backward
             // compatibility, we cannot cry here. Only for implementations
             // which willingly declare a REQUESTED_API_VERSION field do we
             // emit compatibility warnings.
         } catch (Throwable e) {
             // we should never reach here
             Util.report("Unexpected problem occured during version sanity check", e);
         }
     }
 
     private static boolean isAmbiguousProviderList(List<SLF4JServiceProvider> providerList) {
         return providerList.size() > 1;
     }
 
     /**
      * Prints a warning message on the console if multiple bindings were found
      * on the class path. No reporting is done otherwise.
      * 
      */
     private static void reportMultipleBindingAmbiguity(List<SLF4JServiceProvider> providerList) {
         if (isAmbiguousProviderList(providerList)) {
             Util.report("Class path contains multiple SLF4J providers.");
             for (SLF4JServiceProvider provider : providerList) {
                 Util.report("Found provider [" + provider + "]");
             }
             Util.report("See " + MULTIPLE_BINDINGS_URL + " for an explanation.");
         }
     }
 
     private static void reportActualBinding(List<SLF4JServiceProvider> providerList) {
         // binderPathSet can be null under Android
         if (!providerList.isEmpty() && isAmbiguousProviderList(providerList)) {
             Util.report("Actual provider is of type [" + providerList.get(0) + "]");
         }
     }
 
     /**
      * Return a logger named according to the name parameter using the
      * statically bound {@link ILoggerFactory} instance.
      * 
      * @param name
      *            The name of the logger.
      * @return logger
      */
     public static Logger getLogger(String name) {
         ILoggerFactory iLoggerFactory = getILoggerFactory();
         return iLoggerFactory.getLogger(name);
     }
 
     /**
      * Return a logger named corresponding to the class passed as parameter,
      * using the statically bound {@link ILoggerFactory} instance.
      * 
      * <p>
      * In case the the <code>clazz</code> parameter differs from the name of the
      * caller as computed internally by SLF4J, a logger name mismatch warning
      * will be printed but only if the
      * <code>slf4j.detectLoggerNameMismatch</code> system property is set to
      * true. By default, this property is not set and no warnings will be
      * printed even in case of a logger name mismatch.
      * 
      * @param clazz
      *            the returned logger will be named after clazz
      * @return logger
      * 
      * 
      * @see <a
      *      href="http://www.slf4j.org/codes.html#loggerNameMismatch">Detected
      *      logger name mismatch</a>
      */
     public static Logger getLogger(Class<?> clazz) {
         Logger logger = getLogger(clazz.getName());
         if (DETECT_LOGGER_NAME_MISMATCH) {
             Class<?> autoComputedCallingClass = Util.getCallingClass();
             if (autoComputedCallingClass != null && nonMatchingClasses(clazz, autoComputedCallingClass)) {
                 Util.report(String.format("Detected logger name mismatch. Given name: \"%s\"; computed name: \"%s\".", logger.getName(),
                                 autoComputedCallingClass.getName()));
                 Util.report("See " + LOGGER_NAME_MISMATCH_URL + " for an explanation");
             }
         }
         return logger;
     }
 
     private static boolean nonMatchingClasses(Class<?> clazz, Class<?> autoComputedCallingClass) {
         return !autoComputedCallingClass.isAssignableFrom(clazz);
     }
 
     /**
      * Return the {@link ILoggerFactory} instance in use.
      * <p>
      * <p>
      * ILoggerFactory instance is bound with this class at compile time.
      * 
      * @return the ILoggerFactory instance in use
      */
     public static ILoggerFactory getILoggerFactory() {
         return getProvider().getLoggerFactory();
     }
 
     /**
      * Return the {@link SLF4JServiceProvider} in use.
     
      * @return provider in use
      * @since 1.8.0
      */
     static SLF4JServiceProvider getProvider() {
         if (INITIALIZATION_STATE == UNINITIALIZED) {
             synchronized (LoggerFactory.class) {
                 if (INITIALIZATION_STATE == UNINITIALIZED) {
                     INITIALIZATION_STATE = ONGOING_INITIALIZATION;
                     performInitialization();
                 }
             }
         }
         switch (INITIALIZATION_STATE) {
         case SUCCESSFUL_INITIALIZATION:
             return PROVIDER;
         case NOP_FALLBACK_INITIALIZATION:
             return NOP_FALLBACK_SERVICE_PROVIDER;
         case FAILED_INITIALIZATION:
             throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
         case ONGOING_INITIALIZATION:
             // support re-entrant behavior.
             // See also http://jira.qos.ch/browse/SLF4J-97
             return SUBST_PROVIDER;
         }
         throw new IllegalStateException("Unreachable code");
     }
 }