/*******************************************************************************
 * Copyright 2017 Graz University of Technology
 * EAAF-Core Components has been developed in a cooperation between EGIZ,  
 * A-SIT+, A-SIT, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.2 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * https://joinup.ec.europa.eu/news/understanding-eupl-v12
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
package at.gv.egiz.eaaf.core.api.idp.process;


import java.io.InputStream;

import at.gv.egiz.eaaf.core.api.IRequest;
import at.gv.egiz.eaaf.core.exceptions.ProcessExecutionException;
import at.gv.egiz.eaaf.core.impl.idp.process.ProcessDefinitionParserException;
import at.gv.egiz.eaaf.core.impl.idp.process.ProcessInstance;
import at.gv.egiz.eaaf.core.impl.idp.process.model.ProcessDefinition;

/**
 * Process engine providing means for starting and resuming processes.
 * 
 * @author tknall
 */
public interface ProcessEngine {

	/**
	 * Registers a new process definition. Note that existing definitions with the same identifier will be replaced.
	 * 
	 * @param processDefinition
	 *            The process definition to be registered.
	 */
	void registerProcessDefinition(ProcessDefinition processDefinition);

	/**
	 * Registers a new process definition given as {@link InputStream}. Note that existing definitions with the same identifier will be replaced.
	 *
	 * @param processDefinitionInputStream The input stream to the definition to be registered.
	 * @throws ProcessDefinitionParserException Thrown in case of an error parsing the process definition.
	 * @return The process definition's identifier.
	 */
	String registerProcessDefinition(InputStream processDefinitionInputStream) throws ProcessDefinitionParserException;

	/**
	 * Creates a process instance according to the referenced process definition, persists it into the database and returns it identifier.
	 * <p/>
	 * Note that the method returns the identifier of a process instance which will be needed in order to start a process or to continue
	 * process execution after asynchronous task execution (refer to {@link #start(String)} and
	 * {@link #signal(String)} for further information).
	 * 
	 * @param processDefinitionId
	 *            The identifier of the respective process definition.
	 * @param executionContext The execution context (may be {@code null}).
	 * @return The id of the newly created process instance (never {@code null}).
	 * @throws ProcessExecutionException
	 *             Thrown in case of error, e.g. when a {@code processDefinitionId} is referenced that does not exist.
	 */
	String createProcessInstance(String processDefinitionId, ExecutionContext executionContext) throws ProcessExecutionException;

	/**
	 * Creates a process instance according to the referenced process definition, persists it into the database and returns it identifier.
	 * <p/>
	 * Note that the method returns the identifier of a process instance which will be needed in order to start a process or to continue
	 * process execution after asynchronous task execution (refer to {@link #start(String)} and
	 * {@link #signal(String)} for further information).
	 * 
	 * @param processDefinitionId
	 *            The identifier of the respective process definition.
	 * @return The id of the newly created process instance (never {@code null}).
	 * @throws ProcessExecutionException
	 *             Thrown in case of error, e.g. when a {@code processDefinitionId} is referenced that does not exist.
	 */
	String createProcessInstance(String processDefinitionId) throws ProcessExecutionException;

	
	/**
	 * Delete a process instance 
	 * 
	 * @param processInstanceId
	 *            The identifier of the respective process.
	 * @throws ProcessExecutionException
	 *             Thrown in case of error, e.g. when a {@code processInstanceId} is referenced that does not exist.
	 */
	void deleteProcessInstance(String processInstanceId) throws ProcessExecutionException;
	
	/**
	 * Returns the process instance with a given {@code processInstanceId}.
	 * 
	 * @param processInstanceId
	 *            The process instance id.
	 * @return The process instance (never {@code null}).
	 * @throws IllegalArgumentException
	 *             In case the process instance does not/no longer exist.
	 * @throws RuntimeException
	 *             In case the process instance could not be retrieved from persistence.
	 */
	ProcessInstance getProcessInstance(String processInstanceId);

	/**
	 * Starts the process using the given {@code pendingReq}.
	 * 
	 * @param pendingReq
	 *            The protocol request for which a process should be started.
	 * @throws ProcessExecutionException
	 *             Thrown in case of error.
	 */
	void start(IRequest pendingReq) throws ProcessExecutionException;


	/**
	 * Resumes process execution after an asynchronous task has been executed.
	 * 
	 * @param pendingReq
	 *            The process instance id.
	 * @throws ProcessExecutionException
	 *             Thrown in case of error.
	 */
	void signal(IRequest pendingReq) throws ProcessExecutionException;

}