/*
 * 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.log4j.legacy.core;

import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Optional;
import java.util.function.Supplier;
import org.apache.log4j.bridge.AppenderAdapter;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Configurator;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.apache.logging.log4j.spi.LoggerContext;

/**
 * Delegates to {@code Logger} methods implemented by {@code log4j-core} if appropriate.
 */
public final class CategoryUtil {

    private static org.apache.logging.log4j.core.Logger asCore(final Logger logger) {
        return (org.apache.logging.log4j.core.Logger) logger;
    }

    private static <T> T get(final Logger logger, final Supplier<T> run, final T defaultValue) {
        return isCore(logger) ? run.get() : defaultValue;
    }

    /**
     * Gets the appenders attached directly to this logger.
     *
     * @param logger The target logger.
     * @return A Map containing the Appender's name as the key and the Appender as the value.
     */
    public static Map<String, Appender> getAppenders(final Logger logger) {
        return get(logger, () -> getDirectAppenders(logger), Collections.emptyMap());
    }

    private static Map<String, Appender> getDirectAppenders(final Logger logger) {
        return CategoryUtil.getExactLoggerConfig(logger)
                .map(LoggerConfig::getAppenders)
                .orElse(Collections.emptyMap());
    }

    private static Optional<LoggerConfig> getExactLoggerConfig(final Logger logger) {
        return Optional.of(asCore(logger).get()).filter(lc -> logger.getName().equals(lc.getName()));
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#getFilters()} if appropriate.
     *
     * @param logger The target logger.
     * @return An Iterator over all the Filters associated with the Logger.
     */
    public static Iterator<Filter> getFilters(final Logger logger) {
        return get(logger, asCore(logger)::getFilters, null);
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#getContext()} if appropriate.
     *
     * @param logger The target logger.
     * @return the LoggerContext.
     */
    public static LoggerContext getLoggerContext(final Logger logger) {
        return get(logger, asCore(logger)::getContext, null);
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#getParent()} if appropriate.
     *
     * @param logger The target logger.
     * @return The parent Logger.
     */
    public static Logger getParent(final Logger logger) {
        return get(logger, asCore(logger)::getParent, null);
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#isAdditive()} if appropriate.
     *
     * @param logger The target logger.
     * @return true if the associated LoggerConfig is additive, false otherwise.
     */
    public static boolean isAdditive(final Logger logger) {
        return get(logger, asCore(logger)::isAdditive, false);
    }

    private static boolean isCore(final Logger logger) {
        return logger instanceof org.apache.logging.log4j.core.Logger;
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#setAdditive(boolean)} if appropriate.
     *
     * @param logger The target logger.
     * @param additive Boolean value to indicate whether the Logger is additive or not.
     */
    public static void setAdditivity(final Logger logger, final boolean additive) {
        if (isCore(logger)) {
            asCore(logger).setAdditive(additive);
        }
    }

    /**
     * Delegates to {@link org.apache.logging.log4j.core.Logger#setLevel(Level)} if appropriate.
     *
     * @param logger The target logger.
     * @param level The Level to use on this Logger, may be null.
     */
    public static void setLevel(final Logger logger, final Level level) {
        if (isCore(logger)) {
            Configurator.setLevel(asCore(logger), level);
        }
    }

    /**
     * Returns the level explicitly set on the logger.
     * <p>
     *     If the Log4j API implementation does not support it, returns the effective level instead.
     * </p>
     */
    public static Level getExplicitLevel(final Logger logger) {
        return isCore(logger) ? getExplicitLevel(asCore(logger)) : logger.getLevel();
    }

    private static Level getExplicitLevel(final org.apache.logging.log4j.core.Logger logger) {
        final LoggerConfig config = logger.get();
        return config.getName().equals(logger.getName()) ? config.getExplicitLevel() : null;
    }

    /**
     * Adds an appender to the logger. This method requires a check for the presence
     * of Log4j Core or it will cause a {@code ClassNotFoundException}.
     *
     * @param logger   The target logger.
     * @param appender A Log4j2 appender.
     */
    public static void addAppender(final Logger logger, final Appender appender) {
        if (appender instanceof AppenderAdapter.Adapter) {
            appender.start();
        }
        asCore(logger).addAppender(appender);
    }

    /**
     * Sends the event to all appenders directly connected with the logger. This
     * method requires a check for the presence of Log4j Core or it will cause a
     * {@code ClassNotFoundException}.
     *
     * @param logger The target logger.
     * @param event  The event to send.
     */
    public static void log(final Logger logger, final LogEvent event) {
        getExactLoggerConfig(logger).ifPresent(lc -> lc.log(event));
    }

    private CategoryUtil() {}
}
