/*
    * Copyright 2016 the original author or authors.
    *
    * 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.openehealth.ipf.commons.ihe.hl7v2.storage;
  
  import ca.uhn.hl7v2.model.Message;
  import net.sf.ehcache.Ehcache;
  import net.sf.ehcache.Element;
  import org.apache.commons.lang3.Validate;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.Serializable;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * An Ehcache-based implementation of {@link InteractiveContinuationStorage}.
   *
   * @author Dmytro Rud
   */
  public class EhcacheInteractiveContinuationStorage implements InteractiveContinuationStorage {
  
      private static final transient Logger LOG = LoggerFactory.getLogger(EhcacheInteractiveContinuationStorage.class);
      private final Ehcache ehcache;
  
  
      public EhcacheInteractiveContinuationStorage(Ehcache ehcache) {
          requireNonNull(ehcache);
          this.ehcache = ehcache;
      }
  
  
      @Override
      public void put(String continuationPointer, String chainId, Message fragment) {
          InteractiveContinuationChain chain;
          Element element = ehcache.get(chainId);
          if (element != null) {
              chain = (InteractiveContinuationChain) element.getObjectValue();
          } else {
              LOG.debug("Create chain for storage key {}", chainId);
              chain = new InteractiveContinuationChain();
              ehcache.put(new Element(chainId, chain));
          }
          chain.put(continuationPointer, fragment);
      }
  
  
      @Override
      public Message get(
              String continuationPointer,
              String chainId)
      {
          Element element = ehcache.get(chainId);
          if (element != null) {
              InteractiveContinuationChain chain = (InteractiveContinuationChain) element.getObjectValue();
              return chain.get(continuationPointer);
          }
          return null;
      }
  
  
      @Override
      public boolean delete(String chainId) {
          return ehcache.remove(chainId);
      }
  
  
      
      /**
       * Chain of interactive continuation fragments of a query's response.
       * <p>
       * Keys correspond to continuation pointers of the fragments;
       * the key of the first fragment is <code>null</code>.
       */
      private static class InteractiveContinuationChain implements Serializable {
          private final Map<String, Message> responseMessages =
              Collections.synchronizedMap(new HashMap<String, Message>());
  
          public void put(String continuationPointer, Message message) {
              responseMessages.put(continuationPointer, message);
          }
  
          public Message get(String continuationPointer) {
             return responseMessages.get(continuationPointer);
         }
     }
 
 }