/*
 * 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.logging.log4j.core.impl;

import java.util.List;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.ThreadContext;
import org.apache.logging.log4j.core.ContextDataInjector;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.ReusableLogEvent;
import org.apache.logging.log4j.core.async.ThreadNameCachingStrategy;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.time.Clock;
import org.apache.logging.log4j.core.time.NanoClock;
import org.apache.logging.log4j.message.Message;
import org.apache.logging.log4j.plugins.Inject;
import org.apache.logging.log4j.spi.recycler.Recycler;
import org.apache.logging.log4j.spi.recycler.RecyclerFactory;

/**
 * Garbage-free LogEventFactory that recycles mutable {@link LogEvent} instances.
 * @since 2.6
 * @see Recycler
 */
public class ReusableLogEventFactory implements LogEventFactory {
    private static final ThreadNameCachingStrategy THREAD_NAME_CACHING_STRATEGY = ThreadNameCachingStrategy.create();

    private final ContextDataInjector injector;
    private final Clock clock;
    private final NanoClock nanoClock;
    private final Recycler<MutableLogEvent> recycler;

    @Inject
    public ReusableLogEventFactory(
            final ContextDataInjector injector,
            final Clock clock,
            final NanoClock nanoClock,
            final RecyclerFactory recyclerFactory) {
        this.injector = injector;
        this.clock = clock;
        this.nanoClock = nanoClock;
        this.recycler = recyclerFactory.create(() -> {
            final MutableLogEvent event = new MutableLogEvent();
            final Thread currentThread = Thread.currentThread();
            event.setThreadId(currentThread.getId());
            event.setThreadName(currentThread.getName());
            event.setThreadPriority(currentThread.getPriority());
            return event;
        });
    }

    /**
     * Creates a log event.
     *
     * @param loggerName The name of the Logger.
     * @param marker An optional Marker.
     * @param fqcn The fully qualified class name of the caller.
     * @param level The event Level.
     * @param message The Message.
     * @param properties Properties to be added to the log event.
     * @param t An optional Throwable.
     * @return The LogEvent.
     */
    @Override
    public LogEvent createEvent(
            final String loggerName,
            final Marker marker,
            final String fqcn,
            final Level level,
            final Message message,
            final List<Property> properties,
            final Throwable t) {
        return createEvent(loggerName, marker, fqcn, null, level, message, properties, t);
    }

    /**
     * Creates a log event.
     *
     * @param loggerName The name of the Logger.
     * @param marker An optional Marker.
     * @param fqcn The fully qualified class name of the caller.
     * @param level The event Level.
     * @param message The Message.
     * @param properties Properties to be added to the log event.
     * @param t An optional Throwable.
     * @return The LogEvent.
     */
    @Override
    public LogEvent createEvent(
            final String loggerName,
            final Marker marker,
            final String fqcn,
            final StackTraceElement location,
            final Level level,
            final Message message,
            final List<Property> properties,
            final Throwable t) {
        MutableLogEvent result = recycler.acquire();
        // No need to clear here, values are cleared in release when reserved is set to false.
        // If the event was dirty we'd create a new one.

        result.setLoggerName(loggerName);
        result.setMarker(marker);
        result.setLoggerFqcn(fqcn);
        result.setLevel(level == null ? Level.OFF : level);
        result.setMessage(message);
        result.initTime(clock, nanoClock);
        result.setThrown(t);
        result.setSource(location);
        result.setContextData(injector.injectContextData(properties, result.getContextData()));
        result.setContextStack(
                ThreadContext.getDepth() == 0 ? ThreadContext.EMPTY_STACK : ThreadContext.cloneStack()); // mutable copy

        if (THREAD_NAME_CACHING_STRATEGY == ThreadNameCachingStrategy.UNCACHED) {
            result.setThreadName(Thread.currentThread().getName()); // Thread.getName() allocates Objects on each call
            result.setThreadPriority(Thread.currentThread().getPriority());
        }
        return result;
    }

    @Override
    public void recycle(final LogEvent event) {
        if (event instanceof ReusableLogEvent) {
            ((ReusableLogEvent) event).clear();
            if (event instanceof MutableLogEvent) {
                recycler.release((MutableLogEvent) event);
            }
        }
    }

    /**
     * Switches the {@code reserved} flag off if the specified event is a MutableLogEvent, otherwise does nothing.
     * This flag is used internally to verify that a reusable log event is no longer in use and can be reused.
     * @param logEvent the log event to make available again
     * @since 2.7
     * @deprecated use {@link #recycle(LogEvent)}
     */
    @Deprecated(since = "3.0.0")
    public static void release(final LogEvent logEvent) { // LOG4J2-1583
        if (logEvent instanceof ReusableLogEvent) {
            ((ReusableLogEvent) logEvent).clear();
        }
    }
}
