/*
 * 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.bridge;

import org.apache.log4j.spi.Filter;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.filter.AbstractFilter;
import org.apache.logging.log4j.core.filter.CompositeFilter;

/**
 * Binds a Log4j 1.x Filter with Log4j 2.
 */
public final class FilterAdapter extends AbstractFilter {

    private final Filter filter;

    /**
     * Adapts a Log4j 1.x filter into a Log4j 2.x filter. Applying this method to
     * the result of
     * {@link FilterWrapper#adapt(org.apache.logging.log4j.core.Filter)} should
     * return the original Log4j 2.x filter.
     *
     * @param filter a Log4j 1.x filter
     * @return a Log4j 2.x filter or {@code null} if the parameter is {@code null}
     */
    public static org.apache.logging.log4j.core.Filter adapt(final Filter filter) {
        if (filter instanceof org.apache.logging.log4j.core.Filter) {
            return (org.apache.logging.log4j.core.Filter) filter;
        }
        // Don't unwrap the head of a filter chain
        if (filter instanceof FilterWrapper && filter.getNext() == null) {
            return ((FilterWrapper) filter).getFilter();
        }
        if (filter != null) {
            return new FilterAdapter(filter);
        }
        return null;
    }

    /**
     * Appends one filter to another using Log4j 2.x concatenation utilities.
     * @param first
     * @param second
     * @return
     */
    public static Filter addFilter(final Filter first, final Filter second) {
        if (first == null) {
            return second;
        }
        if (second == null) {
            return first;
        }
        final CompositeFilter composite;
        if (first instanceof FilterWrapper && ((FilterWrapper) first).getFilter() instanceof CompositeFilter) {
            composite = (CompositeFilter) ((FilterWrapper) first).getFilter();
        } else {
            composite = CompositeFilter.createFilters(adapt(first));
        }
        return FilterWrapper.adapt(composite.addFilter(adapt(second)));
    }

    private FilterAdapter(final Filter filter) {
        this.filter = filter;
    }

    @Override
    public Result filter(final LogEvent event) {
        final LoggingEvent loggingEvent = new LogEventAdapter(event);
        Filter next = filter;
        while (next != null) {
            switch (next.decide(loggingEvent)) {
                case Filter.ACCEPT:
                    return Result.ACCEPT;
                case Filter.DENY:
                    return Result.DENY;
                default:
            }
            next = next.getNext();
        }
        return Result.NEUTRAL;
    }

    /**
     * Gets the actual filter.
     *
     * @return the actual filter.
     * @since 2.17.1
     */
    public Filter getFilter() {
        return filter;
    }

    @Override
    public void start() {
        filter.activateOptions();
    }
}
