/*
 * 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.async;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

import com.lmax.disruptor.BlockingWaitStrategy;
import com.lmax.disruptor.BusySpinWaitStrategy;
import com.lmax.disruptor.ExceptionHandler;
import com.lmax.disruptor.SleepingWaitStrategy;
import com.lmax.disruptor.TimeoutBlockingWaitStrategy;
import com.lmax.disruptor.WaitStrategy;
import com.lmax.disruptor.YieldingWaitStrategy;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.util.Constants;
import org.apache.logging.log4j.core.util.Integers;
import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;
import org.apache.logging.log4j.util.Strings;

/**
 * Utility methods for getting Disruptor related configuration.
 */
final class DisruptorUtil {
    private static final Logger LOGGER = StatusLogger.getLogger();
    private static final int RINGBUFFER_MIN_SIZE = 128;
    private static final int RINGBUFFER_DEFAULT_SIZE = 256 * 1024;
    private static final int RINGBUFFER_NO_GC_DEFAULT_SIZE = 4 * 1024;

    /**
     * LOG4J2-2606: Users encountered excessive CPU utilization with Disruptor v3.4.2 when the application
     * was logging more than the underlying appender could keep up with and the ringbuffer became full,
     * especially when the number of application threads vastly outnumbered the number of cores.
     * CPU utilization is significantly reduced by restricting access to the enqueue operation.
     */
    static final boolean ASYNC_LOGGER_SYNCHRONIZE_ENQUEUE_WHEN_QUEUE_FULL = PropertiesUtil.getProperties()
            .getBooleanProperty("AsyncLogger.SynchronizeEnqueueWhenQueueFull", true);
    static final boolean ASYNC_CONFIG_SYNCHRONIZE_ENQUEUE_WHEN_QUEUE_FULL = PropertiesUtil.getProperties()
            .getBooleanProperty("AsyncLoggerConfig.SynchronizeEnqueueWhenQueueFull", true);

    private DisruptorUtil() {
    }

    static WaitStrategy createWaitStrategy(final String propertyName) {
        final String strategy = PropertiesUtil.getProperties().getStringProperty(propertyName, "Timeout");
        LOGGER.trace("property {}={}", propertyName, strategy);
        final String strategyUp = Strings.toRootUpperCase(strategy);
        final long timeoutMillis = parseAdditionalLongProperty(propertyName, "Timeout", 10L);
        // String (not enum) is deliberately used here to avoid IllegalArgumentException being thrown. In case of
        // incorrect property value, default WaitStrategy is created.
        switch (strategyUp) {
            case "SLEEP":
                final long sleepTimeNs =
                        parseAdditionalLongProperty(propertyName, "SleepTimeNs", 100L);
                final String key = getFullPropertyKey(propertyName, "Retries");
                final int retries =
                        PropertiesUtil.getProperties().getIntegerProperty(key, 200);
                return new SleepingWaitStrategy(retries, sleepTimeNs);
            case "YIELD":
                return new YieldingWaitStrategy();
            case "BLOCK":
                return new BlockingWaitStrategy();
            case "BUSYSPIN":
                return new BusySpinWaitStrategy();
            case "TIMEOUT":
                return new TimeoutBlockingWaitStrategy(timeoutMillis, TimeUnit.MILLISECONDS);
            default:
                return new TimeoutBlockingWaitStrategy(timeoutMillis, TimeUnit.MILLISECONDS);
        }
    }

    private static String getFullPropertyKey(final String strategyKey, final String additionalKey) {
        return strategyKey.startsWith("AsyncLogger.")
                ? "AsyncLogger." + additionalKey
                : "AsyncLoggerConfig." + additionalKey;
    }

    private static long parseAdditionalLongProperty(
            final String propertyName,
            final String additionalKey,
            final long defaultValue) {
        final String key = getFullPropertyKey(propertyName, additionalKey);
        return PropertiesUtil.getProperties().getLongProperty(key, defaultValue);
    }

    static int calculateRingBufferSize(final String propertyName) {
        int ringBufferSize = Constants.ENABLE_THREADLOCALS ? RINGBUFFER_NO_GC_DEFAULT_SIZE : RINGBUFFER_DEFAULT_SIZE;
        final String userPreferredRBSize = PropertiesUtil.getProperties().getStringProperty(propertyName,
                String.valueOf(ringBufferSize));
        try {
            int size = Integer.parseInt(userPreferredRBSize);
            if (size < RINGBUFFER_MIN_SIZE) {
                size = RINGBUFFER_MIN_SIZE;
                LOGGER.warn("Invalid RingBufferSize {}, using minimum size {}.", userPreferredRBSize,
                        RINGBUFFER_MIN_SIZE);
            }
            ringBufferSize = size;
        } catch (final Exception ex) {
            LOGGER.warn("Invalid RingBufferSize {}, using default size {}.", userPreferredRBSize, ringBufferSize);
        }
        return Integers.ceilingNextPowerOfTwo(ringBufferSize);
    }

    static ExceptionHandler<RingBufferLogEvent> getAsyncLoggerExceptionHandler() {
        final String cls = PropertiesUtil.getProperties().getStringProperty("AsyncLogger.ExceptionHandler");
        if (cls == null) {
            return new AsyncLoggerDefaultExceptionHandler();
        }
        try {
            @SuppressWarnings("unchecked")
            final Class<? extends ExceptionHandler<RingBufferLogEvent>> klass =
                (Class<? extends ExceptionHandler<RingBufferLogEvent>>) Loader.loadClass(cls);
            return klass.newInstance();
        } catch (final Exception ignored) {
            LOGGER.debug("Invalid AsyncLogger.ExceptionHandler value: error creating {}: ", cls, ignored);
            return new AsyncLoggerDefaultExceptionHandler();
        }
    }

    static ExceptionHandler<AsyncLoggerConfigDisruptor.Log4jEventWrapper> getAsyncLoggerConfigExceptionHandler() {
        final String cls = PropertiesUtil.getProperties().getStringProperty("AsyncLoggerConfig.ExceptionHandler");
        if (cls == null) {
            return new AsyncLoggerConfigDefaultExceptionHandler();
        }
        try {
            @SuppressWarnings("unchecked")
            final Class<? extends ExceptionHandler<AsyncLoggerConfigDisruptor.Log4jEventWrapper>> klass =
                    (Class<? extends ExceptionHandler<AsyncLoggerConfigDisruptor.Log4jEventWrapper>>) Loader.loadClass(cls);
            return klass.newInstance();
        } catch (final Exception ignored) {
            LOGGER.debug("Invalid AsyncLoggerConfig.ExceptionHandler value: error creating {}: ", cls, ignored);
            return new AsyncLoggerConfigDefaultExceptionHandler();
        }
    }

    /**
     * Returns the thread ID of the background appender thread. This allows us to detect Logger.log() calls initiated
     * from the appender thread, which may cause deadlock when the RingBuffer is full. (LOG4J2-471)
     *
     * @param executor runs the appender thread
     * @return the thread ID of the background appender thread
     */
    public static long getExecutorThreadId(final ExecutorService executor) {
        final Future<Long> result = executor.submit(() -> Thread.currentThread().getId());
        try {
            return result.get();
        } catch (final Exception ex) {
            final String msg = "Could not obtain executor thread Id. "
                    + "Giving up to avoid the risk of application deadlock.";
            throw new IllegalStateException(msg, ex);
        }
    }
}