/*
 * 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 org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;

Creates AsyncQueueFullPolicy instances based on user-specified system properties. The AsyncQueueFullPolicy created by this factory is used in AsyncLogger, AsyncLoggerConfig and AsyncAppender to control if events are logged in the current thread, the background thread, or discarded. 
 Property "log4j2.AsyncQueueFullPolicy" controls the routing behaviour. If this property is not specified or has value "Default", this factory creates DefaultAsyncQueueFullPolicy objects. 
 
 If this property has value "Discard", this factory creates DiscardingAsyncQueueFullPolicy objects. By default, this router discards events of level INFO, DEBUG and TRACE if the queue is full. This can be adjusted with property "log4j2.DiscardThreshold" (name of the level at which to start discarding). 
 
 For any other value, this factory interprets the value as the fully qualified name of a class implementing the AsyncQueueFullPolicy interface. The class must have a default constructor. 
Since:
2.6/**
 * Creates {@link AsyncQueueFullPolicy} instances based on user-specified system properties. The {@code AsyncQueueFullPolicy}
 * created by this factory is used in AsyncLogger, AsyncLoggerConfig and AsyncAppender
 * to control if events are logged in the current thread, the background thread, or discarded.
 * <p>
 * Property {@code "log4j2.AsyncQueueFullPolicy"} controls the routing behaviour. If this property is not specified or has
 * value {@code "Default"}, this factory creates {@link DefaultAsyncQueueFullPolicy} objects.
 * </p> <p>
 * If this property has value {@code "Discard"}, this factory creates {@link DiscardingAsyncQueueFullPolicy} objects.
 * By default, this router discards events of level {@code INFO}, {@code DEBUG} and {@code TRACE} if the queue is full.
 * This can be adjusted with property {@code "log4j2.DiscardThreshold"} (name of the level at which to start
 * discarding).
 * </p> <p>
 * For any other value, this
 * factory interprets the value as the fully qualified name of a class implementing the {@link AsyncQueueFullPolicy}
 * interface. The class must have a default constructor.
 * </p>
 *
 * @since 2.6
 */
public class AsyncQueueFullPolicyFactory {
    static final String PROPERTY_NAME_ASYNC_EVENT_ROUTER = "log4j2.AsyncQueueFullPolicy";
    static final String PROPERTY_VALUE_DEFAULT_ASYNC_EVENT_ROUTER = "Default";
    static final String PROPERTY_VALUE_DISCARDING_ASYNC_EVENT_ROUTER = "Discard";
    static final String PROPERTY_NAME_DISCARDING_THRESHOLD_LEVEL = "log4j2.DiscardThreshold";

    private static final Logger LOGGER = StatusLogger.getLogger();

    
Creates and returns AsyncQueueFullPolicy instances based on user-specified system properties. 
 Property "log4j2.AsyncQueueFullPolicy" controls the routing behaviour. If this property is not specified or has value "Default", this method returns DefaultAsyncQueueFullPolicy objects. 
 
 If this property has value "Discard", this method returns DiscardingAsyncQueueFullPolicy objects. 
 
 For any other value, this method interprets the value as the fully qualified name of a class implementing the AsyncQueueFullPolicy interface. The class must have a default constructor. 
Returns:
a new AsyncQueueFullPolicy/**
     * Creates and returns {@link AsyncQueueFullPolicy} instances based on user-specified system properties.
     * <p>
     * Property {@code "log4j2.AsyncQueueFullPolicy"} controls the routing behaviour. If this property is not specified or
     * has value {@code "Default"}, this method returns {@link DefaultAsyncQueueFullPolicy} objects.
     * </p> <p>
     * If this property has value {@code "Discard"}, this method returns {@link DiscardingAsyncQueueFullPolicy} objects.
     * </p> <p>
     * For any other value, this method interprets the value as the fully qualified name of a class implementing the
     * {@link AsyncQueueFullPolicy} interface. The class must have a default constructor.
     * </p>
     *
     * @return a new AsyncQueueFullPolicy
     */
    public static AsyncQueueFullPolicy create() {
        final String router = PropertiesUtil.getProperties().getStringProperty(PROPERTY_NAME_ASYNC_EVENT_ROUTER);
        if (router == null || isRouterSelected(
                router, DefaultAsyncQueueFullPolicy.class, PROPERTY_VALUE_DEFAULT_ASYNC_EVENT_ROUTER)) {
            return new DefaultAsyncQueueFullPolicy();
        }
        if (isRouterSelected(
                router, DiscardingAsyncQueueFullPolicy.class, PROPERTY_VALUE_DISCARDING_ASYNC_EVENT_ROUTER)) {
            return createDiscardingAsyncQueueFullPolicy();
        }
        return createCustomRouter(router);
    }

    private static boolean isRouterSelected(
            String propertyValue,
            Class<? extends AsyncQueueFullPolicy> policy,
            String shortPropertyValue) {
        return propertyValue != null && (shortPropertyValue.equalsIgnoreCase(propertyValue)
                || policy.getName().equals(propertyValue)
                || policy.getSimpleName().equals(propertyValue));
    }

    private static AsyncQueueFullPolicy createCustomRouter(final String router) {
        try {
            final Class<? extends AsyncQueueFullPolicy> cls = Loader.loadClass(router).asSubclass(AsyncQueueFullPolicy.class);
            LOGGER.debug("Creating custom AsyncQueueFullPolicy '{}'", router);
            return cls.newInstance();
        } catch (final Exception ex) {
            LOGGER.debug("Using DefaultAsyncQueueFullPolicy. Could not create custom AsyncQueueFullPolicy '{}': {}", router,
                    ex.toString());
            return new DefaultAsyncQueueFullPolicy();
        }
    }

    private static AsyncQueueFullPolicy createDiscardingAsyncQueueFullPolicy() {
        final PropertiesUtil util = PropertiesUtil.getProperties();
        final String level = util.getStringProperty(PROPERTY_NAME_DISCARDING_THRESHOLD_LEVEL, Level.INFO.name());
        final Level thresholdLevel = Level.toLevel(level, Level.INFO);
        LOGGER.debug("Creating custom DiscardingAsyncQueueFullPolicy(discardThreshold:{})", thresholdLevel);
        return new DiscardingAsyncQueueFullPolicy(thresholdLevel);
    }
}