/*
* Copyright 2008 Federal Chancellery Austria and
* Graz University of Technology
*
* 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 at.gv.egiz.bku.slcommands.impl;

import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

import javax.xml.bind.JAXBElement;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import at.gv.egiz.bku.slcommands.SLCommand;
import at.gv.egiz.bku.slcommands.SLCommandContext;
import at.gv.egiz.bku.slexceptions.SLCommandException;
import at.gv.egiz.stal.ErrorResponse;
import at.gv.egiz.stal.STAL;
import at.gv.egiz.stal.STALRequest;
import at.gv.egiz.stal.STALResponse;

/**
 * This class serves as abstract base class for the implementation of a security
 * layer command.
 * 
 * @author mcentner
 * 
 * @param <T>
 *          the type of the corresponding request value
 */
public abstract class SLCommandImpl<T> implements SLCommand {

  /**
   * The <code>SLCommandContext</code> for this <code>SLCommand</code>.
   */
  protected SLCommandContext cmdCtx;

  /**
   * The request element of this command.
   */
  protected JAXBElement<T> request;

  /**
   * An iterator over the <code>STALResponse</code>s received in
   * {@link SLCommandImpl#requestSTAL(List)}.
   */
  protected Iterator<STALResponse> stalResponses;

  @SuppressWarnings("unchecked")
  @Override
  public void init(SLCommandContext ctx, Object request)
      throws SLCommandException {

    this.request = (JAXBElement<T>) request;

    this.cmdCtx = ctx;
    assert this.cmdCtx != null;

  }

  /**
   * Returns the request value.
   * 
   * It is a convenience method for <code>request.getValue()</code>.
   * 
   * @see JAXBElement#getValue()
   * @return the request value
   */
  protected T getRequestValue() {
    return request.getValue();
  }

  /**
   * @return the corresponding <code>SLCommandContext</code>
   */
  protected SLCommandContext getCmdCtx() {
    return cmdCtx;
  }

  /**
   * Calls {@link STAL#handleRequest(List)} with the given
   * <code>stalRequests</code>.
   * 
   * @param stalRequests
   * @throws SLCommandException
   */
     protected void requestSTAL(List<STALRequest> stalRequests) throws SLCommandException {
    List<STALResponse> responses = cmdCtx.getSTAL().handleRequest(stalRequests);
    if (responses == null) {
      Log log = LogFactory.getLog(this.getClass());
      log.info("Received no responses from STAL.");
      throw new SLCommandException(4000);
    } else if (responses.size() != stalRequests.size()) {
      Log log = LogFactory.getLog(this.getClass());
      log.info("Received invalid count of responses from STAL. Expected "
          + stalRequests.size() + ", but got " + responses.size() + ".");
      // throw new SLCommandException(4000);
    }
    stalResponses = responses.iterator();
  }

  /**
   * @return <code>true</code> if there are more {@link STALResponse}s to be
   *         fetched with {@link #nextResponse(Class)}, or <code>false</code>
   *         otherwise.
   */
  protected boolean hasNextResponse() {
    return (stalResponses != null) ? stalResponses.hasNext() : false;
  }

  /**
   * Returns the next response of type <code>responseClass</code> that has been
   * received by {@link #requestSTAL(List)}.
   * 
   * @param responseClass
   *          the response must be an instance of
   * @return the next response of type <code>responseClass</code>
   * 
   * @throws NoSuchElementException
   *           if there is no more response
   * @throws SLCommandException
   *           if the next response is of type {@link ErrorResponse} or not of
   *           type <code>responseClass</code>
   */
  protected STALResponse nextResponse(
      Class<? extends STALResponse> responseClass) throws SLCommandException {

    if (stalResponses == null) {
      throw new NoSuchElementException();
    }

    STALResponse response = stalResponses.next();

    if (response instanceof ErrorResponse) {
      throw new SLCommandException(((ErrorResponse) response).getErrorCode());
    }

    if (!(responseClass.isAssignableFrom(response.getClass()))) {
      Log log = LogFactory.getLog(this.getClass());
      log.info("Received " + response.getClass() + " from STAL but expected "
          + responseClass);
      throw new SLCommandException(4000);
    }

    return response;

  }
}