package org.slf4j.helpers;

import org.slf4j.spi.MDCAdapter;

import java.util.HashMap;
import java.util.Set;

/**
 * Basic MDC implementation, that can be used for logging systems that
 * lack out-of-the-box MDC support
 */
public class BasicMDCAdapter implements MDCAdapter {

  private static InheritableThreadLocal inheritableThreadLocal = new InheritableThreadLocal();

  public void put(String key, String val) {
    if (key == null) {
      throw new IllegalArgumentException("key cannot be null");
    }
    HashMap map = (HashMap) inheritableThreadLocal.get();
    if (map == null) {
      map = new HashMap();
      inheritableThreadLocal.set(map);
    }
    map.put(key, val);
  }

  public String get(String key) {
    HashMap hashMap = (HashMap) inheritableThreadLocal.get();
    if ((hashMap != null) && (key != null)) {
      return (String) hashMap.get(key);
    } else {
      return null;
    }
  }

  public void remove(String key) {
    HashMap map = (HashMap) inheritableThreadLocal.get();
    if (map != null) {
      map.remove(key);
    }
  }

  public void clear() {
    HashMap hashMap = (HashMap) inheritableThreadLocal.get();
    if (hashMap != null) {
      hashMap.clear();
      inheritableThreadLocal.remove();
    }
  }

  /**
   * Returns the keys in the MDC as a {@link Set} of {@link String}s
   * The returned value can be null.
   * @return the keys in the MDC
   */
  public Set getKeys() {
    HashMap hashMap = (HashMap) inheritableThreadLocal.get();
    if (hashMap != null) {
      return hashMap.keySet();
    } else {
      return null;
    }
  }

}