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/*
 * Copyright 2015 Martin Winandy
 *
 * Licensed 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.pmw.tinylog;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Thread-based mapped diagnostic context for logging. A child thread automatically inherits a copy of the mapped
 * diagnostic context of its parent.
 *
 * 
 * If logging context is used in a thread from a thread pool, {@link #clear()} should be called before putting the
 * thread back to the pool.
 * 
 */
public final class LoggingContext {

	private static final ThreadLocal> data = new InheritableThreadLocal>() {

		@Override
		protected Map initialValue() {
			return Collections. emptyMap();
		}

		@Override
		protected Map childValue(final Map parentValue) {
			return parentValue;
		}

	};

	/** */
	private LoggingContext() {
	}

	/**
	 * Get a read-only map with all context values.
	 *
	 * @return Read-only map
	 */
	public static Map getMapping() {
		return data.get();
	}

	/**
	 * Get the context value by a key.
	 *
	 * @param key
	 *            Key of mapping
	 * @return Context value or {@code null}
	 */
	public static String get(final String key) {
		return data.get().get(key);
	}

	/**
	 * Put a new context value.
	 *
	 * @param key
	 *            Key of mapping
	 * @param value
	 *            New value
	 */
	public static void put(final String key, final Object value) {
		Map map = new HashMap(data.get());
		if (value == null) {
			map.remove(key);
		} else {
			map.put(key, value.toString());
		}
		data.set(Collections. unmodifiableMap(map));
	}

	/**
	 * Remove a context value if existing.
	 *
	 * @param key
	 *            Key of mapping
	 */
	public static void remove(final String key) {
		Map map = new HashMap(data.get());
		map.remove(key);
		data.set(map.isEmpty() ? Collections. emptyMap() : Collections. unmodifiableMap(map));
	}

	/**
	 * Remove all existing context values.
	 */
	public static void clear() {
		data.set(Collections. emptyMap());
	}

}