/*
    * 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.shiro.util;
  
  import org.apache.shiro.mgt.SecurityManager;
  import org.apache.shiro.subject.Subject;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  
  
  /**
   * A ThreadContext provides a means of binding and unbinding objects to the
   * current thread based on key/value pairs.
   * <p/>
   * <p>An internal {@link java.util.HashMap} is used to maintain the key/value pairs
   * for each thread.</p>
   * <p/>
   * <p>If the desired behavior is to ensure that bound data is not shared across
   * threads in a pooled or reusable threaded environment, the application (or more likely a framework) must
   * bind and remove any necessary values at the beginning and end of stack
   * execution, respectively (i.e. individually explicitly or all via the <tt>clear</tt> method).</p>
   *
   * @see #remove()
   * @since 0.1
   */
  public abstract class ThreadContext {
  
      /**
       * Private internal log instance.
       */
      private static final Logger log = LoggerFactory.getLogger(ThreadContext.class);
  
      public static final String SECURITY_MANAGER_KEY = ThreadContext.class.getName() + "_SECURITY_MANAGER_KEY";
      public static final String SUBJECT_KEY = ThreadContext.class.getName() + "_SUBJECT_KEY";
  
      private static final ThreadLocal<Map<Object, Object>> resources = new InheritableThreadLocalMap<Map<Object, Object>>();
  
      /**
       * Default no-argument constructor.
       */
      protected ThreadContext() {
      }
  
      /**
       * Returns the ThreadLocal Map. This Map is used internally to bind objects
       * to the current thread by storing each object under a unique key.
       *
       * @return the map of bound resources
       */
      public static Map<Object, Object> getResources() {
          if (resources.get() == null){
              return Collections.emptyMap();
          } else {
              return new HashMap<Object, Object>(resources.get());
          }
      }
  
      /**
       * Allows a caller to explicitly set the entire resource map.  This operation overwrites everything that existed
       * previously in the ThreadContext - if you need to retain what was on the thread prior to calling this method,
       * call the {@link #getResources()} method, which will give you the existing state.
       *
       * @param newResources the resources to replace the existing {@link #getResources() resources}.
       * @since 1.0
       */
      public static void setResources(Map<Object, Object> newResources) {
          if (CollectionUtils.isEmpty(newResources)) {
              return;
          }
          ensureResourcesInitialized();
          resources.get().clear();
          resources.get().putAll(newResources);
      }
  
      /**
       * Returns the value bound in the {@code ThreadContext} under the specified {@code key}, or {@code null} if there
       * is no value for that {@code key}.
       *
       * @param key the map key to use to lookup the value
      * @return the value bound in the {@code ThreadContext} under the specified {@code key}, or {@code null} if there
      *         is no value for that {@code key}.
      * @since 1.0
      */
     private static Object getValue(Object key) {
         Map<Object, Object> perThreadResources = resources.get();
         return perThreadResources != null ? perThreadResources.get(key) : null;
     }
 
     private static void ensureResourcesInitialized(){
         if (resources.get() == null){
            resources.set(new HashMap<Object, Object>());
         }
     }
 
     /**
      * Returns the object for the specified <code>key</code> that is bound to
      * the current thread.
      *
      * @param key the key that identifies the value to return
      * @return the object keyed by <code>key</code> or <code>null</code> if
      *         no value exists for the specified <code>key</code>
      */
     public static Object get(Object key) {
         if (log.isTraceEnabled()) {
             String msg = "get() - in thread [" + Thread.currentThread().getName() + "]";
             log.trace(msg);
         }
 
         Object value = getValue(key);
         if ((value != null) && log.isTraceEnabled()) {
             String msg = "Retrieved value of type [" + value.getClass().getName() + "] for key [" +
                     key + "] " + "bound to thread [" + Thread.currentThread().getName() + "]";
             log.trace(msg);
         }
         return value;
     }
 
     /**
      * Binds <tt>value</tt> for the given <code>key</code> to the current thread.
      * <p/>
      * <p>A <tt>null</tt> <tt>value</tt> has the same effect as if <tt>remove</tt> was called for the given
      * <tt>key</tt>, i.e.:
      * <p/>
      * <pre>
      * if ( value == null ) {
      *     remove( key );
      * }</pre>
      *
      * @param key   The key with which to identify the <code>value</code>.
      * @param value The value to bind to the thread.
      * @throws IllegalArgumentException if the <code>key</code> argument is <tt>null</tt>.
      */
     public static void put(Object key, Object value) {
         if (key == null) {
             throw new IllegalArgumentException("key cannot be null");
         }
 
         if (value == null) {
             remove(key);
             return;
         }
 
         ensureResourcesInitialized();
         resources.get().put(key, value);
 
         if (log.isTraceEnabled()) {
             String msg = "Bound value of type [" + value.getClass().getName() + "] for key [" +
                     key + "] to thread " + "[" + Thread.currentThread().getName() + "]";
             log.trace(msg);
         }
     }
 
     /**
      * Unbinds the value for the given <code>key</code> from the current
      * thread.
      *
      * @param key The key identifying the value bound to the current thread.
      * @return the object unbound or <tt>null</tt> if there was nothing bound
      *         under the specified <tt>key</tt> name.
      */
     public static Object remove(Object key) {
         Map<Object, Object> perThreadResources = resources.get();
         Object value = perThreadResources != null ? perThreadResources.remove(key) : null;
 
         if ((value != null) && log.isTraceEnabled()) {
             String msg = "Removed value of type [" + value.getClass().getName() + "] for key [" +
                     key + "]" + "from thread [" + Thread.currentThread().getName() + "]";
             log.trace(msg);
         }
 
         return value;
     }
 
     /**
      * {@link ThreadLocal#remove Remove}s the underlying {@link ThreadLocal ThreadLocal} from the thread.
      * <p/>
      * This method is meant to be the final 'clean up' operation that is called at the end of thread execution to
      * prevent thread corruption in pooled thread environments.
      *
      * @since 1.0
      */
     public static void remove() {
         resources.remove();
     }
 
     /**
      * Convenience method that simplifies retrieval of the application's SecurityManager instance from the current
      * thread. If there is no SecurityManager bound to the thread (probably because framework code did not bind it
      * to the thread), this method returns <tt>null</tt>.
      * <p/>
      * It is merely a convenient wrapper for the following:
      * <p/>
      * <code>return (SecurityManager)get( SECURITY_MANAGER_KEY );</code>
      * <p/>
      * This method only returns the bound value if it exists - it does not remove it
      * from the thread.  To remove it, one must call {@link #unbindSecurityManager() unbindSecurityManager()} instead.
      *
      * @return the Subject object bound to the thread, or <tt>null</tt> if there isn't one bound.
      * @since 0.9
      */
     public static SecurityManager getSecurityManager() {
         return (SecurityManager) get(SECURITY_MANAGER_KEY);
     }
 
 
     /**
      * Convenience method that simplifies binding the application's SecurityManager instance to the ThreadContext.
      * <p/>
      * <p>The method's existence is to help reduce casting in code and to simplify remembering of
      * ThreadContext key names.  The implementation is simple in that, if the SecurityManager is not <tt>null</tt>,
      * it binds it to the thread, i.e.:
      * <p/>
      * <pre>
      * if (securityManager != null) {
      *     put( SECURITY_MANAGER_KEY, securityManager);
      * }</pre>
      *
      * @param securityManager the application's SecurityManager instance to bind to the thread.  If the argument is
      *                        null, nothing will be done.
      * @since 0.9
      */
     public static void bind(SecurityManager securityManager) {
         if (securityManager != null) {
             put(SECURITY_MANAGER_KEY, securityManager);
         }
     }
 
     /**
      * Convenience method that simplifies removal of the application's SecurityManager instance from the thread.
      * <p/>
      * The implementation just helps reduce casting and remembering of the ThreadContext key name, i.e it is
      * merely a convenient wrapper for the following:
      * <p/>
      * <code>return (SecurityManager)remove( SECURITY_MANAGER_KEY );</code>
      * <p/>
      * If you wish to just retrieve the object from the thread without removing it (so it can be retrieved later
      * during thread execution), use the {@link #getSecurityManager() getSecurityManager()} method instead.
      *
      * @return the application's SecurityManager instance previously bound to the thread, or <tt>null</tt> if there
      *         was none bound.
      * @since 0.9
      */
     public static SecurityManager unbindSecurityManager() {
         return (SecurityManager) remove(SECURITY_MANAGER_KEY);
     }
 
     /**
      * Convenience method that simplifies retrieval of a thread-bound Subject.  If there is no
      * Subject bound to the thread, this method returns <tt>null</tt>.  It is merely a convenient wrapper
      * for the following:
      * <p/>
      * <code>return (Subject)get( SUBJECT_KEY );</code>
      * <p/>
      * This method only returns the bound value if it exists - it does not remove it
      * from the thread.  To remove it, one must call {@link #unbindSubject() unbindSubject()} instead.
      *
      * @return the Subject object bound to the thread, or <tt>null</tt> if there isn't one bound.
      * @since 0.2
      */
     public static Subject getSubject() {
         return (Subject) get(SUBJECT_KEY);
     }
 
 
     /**
      * Convenience method that simplifies binding a Subject to the ThreadContext.
      * <p/>
      * <p>The method's existence is to help reduce casting in your own code and to simplify remembering of
      * ThreadContext key names.  The implementation is simple in that, if the Subject is not <tt>null</tt>,
      * it binds it to the thread, i.e.:
      * <p/>
      * <pre>
      * if (subject != null) {
      *     put( SUBJECT_KEY, subject );
      * }</pre>
      *
      * @param subject the Subject object to bind to the thread.  If the argument is null, nothing will be done.
      * @since 0.2
      */
     public static void bind(Subject subject) {
         if (subject != null) {
             put(SUBJECT_KEY, subject);
         }
     }
 
     /**
      * Convenience method that simplifies removal of a thread-local Subject from the thread.
      * <p/>
      * The implementation just helps reduce casting and remembering of the ThreadContext key name, i.e it is
      * merely a convenient wrapper for the following:
      * <p/>
      * <code>return (Subject)remove( SUBJECT_KEY );</code>
      * <p/>
      * If you wish to just retrieve the object from the thread without removing it (so it can be retrieved later during
      * thread execution), you should use the {@link #getSubject() getSubject()} method for that purpose.
      *
      * @return the Subject object previously bound to the thread, or <tt>null</tt> if there was none bound.
      * @since 0.2
      */
     public static Subject unbindSubject() {
         return (Subject) remove(SUBJECT_KEY);
     }
     
     private static final class InheritableThreadLocalMap<T extends Map<Object, Object>> extends InheritableThreadLocal<Map<Object, Object>> {
 
         /**
          * This implementation was added to address a
          * <a href="http://jsecurity.markmail.org/search/?q=#query:+page:1+mid:xqi2yxurwmrpqrvj+state:results">
          * user-reported issue</a>.
          * @param parentValue the parent value, a HashMap as defined in the {@link #initialValue()} method.
          * @return the HashMap to be used by any parent-spawned child threads (a clone of the parent HashMap).
          */
         @SuppressWarnings({"unchecked"})
         protected Map<Object, Object> childValue(Map<Object, Object> parentValue) {
             if (parentValue != null) {
                 return (Map<Object, Object>) ((HashMap<Object, Object>) parentValue).clone();
             } else {
                 return null;
             }
         }
     }
 }