/*
    * 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.chemistry.opencmis.client.bindings.spi.http;
  
  import java.math.BigInteger;
  import java.util.Map;
  
  import org.apache.chemistry.opencmis.client.bindings.spi.BindingSession;
  import org.apache.chemistry.opencmis.commons.exceptions.CmisBaseException;
  import org.apache.chemistry.opencmis.commons.exceptions.CmisRuntimeException;
  import org.apache.chemistry.opencmis.commons.impl.ClassLoaderUtil;
  import org.apache.chemistry.opencmis.commons.impl.UrlBuilder;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A HTTP Invoker that delays HTTP requests and thereby throttles the client.
   * 
   * This HTTP Invoker is only a wrapper that delegates the work to another HTTP
   * Invoker, which is defined with the session parameter
   * {@link DELEGTAE_HTTP_INVOKER_CLASS}.
   * 
   * The session parameter {@link DELAY_TIME} defines the delay in milliseconds.
   */
  public class DelayingHttpInvoker implements HttpInvoker {
  
      private static final Logger LOG = LoggerFactory.getLogger(DelayingHttpInvoker.class);
  
      /**
       * Session parameter: class name of the HTTP Invoker doing the the real
       * work. (Optional. Default is the {@link DefaultHttpInvoker}.)
       */
      public static final String DELEGTAE_HTTP_INVOKER_CLASS = "org.apache.chemistry.opencmis.binding.httpinvoker.delay.delegate.classname";
      /**
       * Session parameter: Delay time in milliseconds. (Required.)
       */
      public static final String DELAY_TIME = "org.apache.chemistry.opencmis.binding.httpinvoker.delay.delaytime";
  
      protected static final String DELEGTAE_HTTP_INVOKER = "org.apache.chemistry.opencmis.client.bindings.spi.http.limiter.httpInvoker";
      protected static final String LAST_EXECUTION = "org.apache.chemistry.opencmis.client.bindings.spi.http.limiter.lastExecution";
  
      public DelayingHttpInvoker() {
      }
  
      @Override
      public Response invokeGET(UrlBuilder url, BindingSession session) {
          delay(session);
          return getHttpInvoker(session).invokeGET(url, session);
      }
  
      @Override
      public Response invokeGET(UrlBuilder url, BindingSession session, BigInteger offset, BigInteger length) {
          delay(session);
          return getHttpInvoker(session).invokeGET(url, session, offset, length);
      }
  
      @Override
      public Response invokePOST(UrlBuilder url, String contentType, Output writer, BindingSession session) {
          delay(session);
          return getHttpInvoker(session).invokePOST(url, contentType, writer, session);
      }
  
      @Override
      public Response invokePUT(UrlBuilder url, String contentType, Map<String, String> headers, Output writer,
              BindingSession session) {
          delay(session);
          return getHttpInvoker(session).invokePUT(url, contentType, headers, writer, session);
      }
  
      @Override
      public Response invokeDELETE(UrlBuilder url, BindingSession session) {
          delay(session);
          return getHttpInvoker(session).invokeDELETE(url, session);
      }
  
      protected void delay(BindingSession session) {
          session.writeLock();
          try {
              int delayTime = session.get(DELAY_TIME, -1);
              if (delayTime < 0) {
                  if (LOG.isInfoEnabled()) {
                      LOG.info("No delay time configured.");
                  }
                 return;
             }
 
             Object lastExcution = session.get(LAST_EXECUTION);
             if (lastExcution instanceof Long) {
                 long lastExcutionLong = (Long) lastExcution;
                 long now = System.currentTimeMillis();
                 if (now - lastExcutionLong < delayTime) {
                     try {
                         Thread.sleep(delayTime - (now - lastExcutionLong));
                     } catch (InterruptedException e) {
                         if (LOG.isDebugEnabled()) {
                             LOG.debug("Interrupted sleep", e);
                         }
                     }
                 }
             }
 
             session.put(LAST_EXECUTION, System.currentTimeMillis());
 
         } finally {
             session.writeUnlock();
         }
     }
 
     protected HttpInvoker getHttpInvoker(BindingSession session) {
         HttpInvoker invoker = (HttpInvoker) session.get(DELEGTAE_HTTP_INVOKER);
 
         if (invoker != null) {
             return invoker;
         }
 
         session.writeLock();
         try {
             // try again
             invoker = (HttpInvoker) session.get(DELEGTAE_HTTP_INVOKER);
             if (invoker != null) {
                 return invoker;
             }
 
             // ok, we have to create it...
             try {
                 String invokerName = (String) session.get(DELEGTAE_HTTP_INVOKER_CLASS);
                 if (invokerName == null) {
                     invoker = new DefaultHttpInvoker();
                 } else {
                     invoker = (HttpInvoker) ClassLoaderUtil.loadClass(invokerName).newInstance();
                 }
             } catch (CmisBaseException e) {
                 throw e;
             } catch (Exception e) {
                 throw new CmisRuntimeException("Delegate HTTP invoker cannot be initialized: " + e.getMessage(), e);
             }
 
             // we have an Invoker object -> put it into the session
             session.put(DELEGTAE_HTTP_INVOKER, invoker, true);
         } finally {
             session.writeUnlock();
         }
 
         return invoker;
     }
 }