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/* 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.camunda.bpm.engine.impl.context;

import java.util.Stack;
import java.util.concurrent.Callable;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.camunda.bpm.application.ProcessApplicationInterface;
import org.camunda.bpm.application.ProcessApplicationReference;
import org.camunda.bpm.application.ProcessApplicationUnavailableException;
import org.camunda.bpm.engine.ProcessEngineException;
import org.camunda.bpm.engine.impl.cfg.ProcessEngineConfigurationImpl;
import org.camunda.bpm.engine.impl.interceptor.CommandContext;
import org.camunda.bpm.engine.impl.jobexecutor.JobExecutorContext;
import org.camunda.bpm.engine.impl.pvm.runtime.InterpretableExecution;


/**
 * @author Tom Baeyens
 * @author Daniel Meyer
 */
public class Context {

  private final static Logger LOGGER = Logger.getLogger(Context.class.getName());

  protected static ThreadLocal> commandContextThreadLocal = new ThreadLocal>();
  protected static ThreadLocal> processEngineConfigurationStackThreadLocal = new ThreadLocal>();
  protected static ThreadLocal> executionContextStackThreadLocal = new ThreadLocal>();
  protected static ThreadLocal jobExecutorContextThreadLocal = new ThreadLocal();
  protected static ThreadLocal> processApplicationContext = new ThreadLocal>();

  public static CommandContext getCommandContext() {
    Stack stack = getStack(commandContextThreadLocal);
    if (stack.isEmpty()) {
      return null;
    }
    return stack.peek();
  }

  public static void setCommandContext(CommandContext commandContext) {
    getStack(commandContextThreadLocal).push(commandContext);
  }

  public static void removeCommandContext() {
    getStack(commandContextThreadLocal).pop();
  }

  public static ProcessEngineConfigurationImpl getProcessEngineConfiguration() {
    Stack stack = getStack(processEngineConfigurationStackThreadLocal);
    if (stack.isEmpty()) {
      return null;
    }
    return stack.peek();
  }

  public static void setProcessEngineConfiguration(ProcessEngineConfigurationImpl processEngineConfiguration) {
    getStack(processEngineConfigurationStackThreadLocal).push(processEngineConfiguration);
  }

  public static void removeProcessEngineConfiguration() {
    getStack(processEngineConfigurationStackThreadLocal).pop();
  }

  public static ExecutionContext getExecutionContext() {
    Stack stack = getStack(executionContextStackThreadLocal);
    if(stack == null || stack.isEmpty()) {
      return null;
    } else {
      return stack.peek();
    }
  }

  public static void setExecutionContext(InterpretableExecution execution) {
    getStack(executionContextStackThreadLocal).push(new ExecutionContext(execution));
  }

  public static void removeExecutionContext() {
    getStack(executionContextStackThreadLocal).pop();
  }

  protected static  Stack getStack(ThreadLocal> threadLocal) {
    Stack stack = threadLocal.get();
    if (stack==null) {
      stack = new Stack();
      threadLocal.set(stack);
    }
    return stack;
  }

  public static JobExecutorContext getJobExecutorContext() {
    return jobExecutorContextThreadLocal.get();
  }

  public static void setJobExecutorContext(JobExecutorContext jobExecutorContext) {
    jobExecutorContextThreadLocal.set(jobExecutorContext);
  }

  public static void removeJobExecutorContext() {
    jobExecutorContextThreadLocal.remove();
  }


  public static ProcessApplicationReference getCurrentProcessApplication() {
    Stack stack = getStack(processApplicationContext);
    if(stack.isEmpty()) {
      return null;
    } else {
      return stack.peek();
    }
  }

  public static void setCurrentProcessApplication(ProcessApplicationReference reference) {
    Stack stack = getStack(processApplicationContext);
    stack.push(reference);
  }

  public static void removeCurrentProcessApplication() {
    Stack stack = getStack(processApplicationContext);
    stack.pop();
  }

  /**
   * @param callback
   * @param processApplicationReference
   */
  public static  T executeWithinProcessApplication(Callable callback, ProcessApplicationReference processApplicationReference) {
    String paName = processApplicationReference.getName();
    try {
      ProcessApplicationInterface processApplication = processApplicationReference.getProcessApplication();
      setCurrentProcessApplication(processApplicationReference);

      try {
        LOGGER.log(Level.FINE, "[PA-CONTEXT] Switch to {0}", paName);
        return processApplication.execute(callback);

      } catch (Exception e) {

        // unwrap exception
        if(e.getCause() != null && e.getCause() instanceof RuntimeException) {
          throw (RuntimeException) e.getCause();
        }else {
          throw new ProcessEngineException("Unexpected exeption while executing within process application ", e);
        }

      } finally {
        LOGGER.log(Level.FINE, "[PA-CONTEXT] Return from {0}", paName);
        removeCurrentProcessApplication();
      }


    } catch (ProcessApplicationUnavailableException e) {
      throw new ProcessEngineException("Cannot switch to process application '"+paName+"' for execution: "+e.getMessage(), e);
    }
  }
}