/*******************************************************************************
 * 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.impl.idp.process;

import java.io.Serializable;
import java.util.Date;

import org.apache.commons.lang3.RandomStringUtils;
import org.apache.commons.lang3.time.DurationFormatUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import at.gv.egiz.eaaf.core.api.idp.process.ExecutionContext;
import at.gv.egiz.eaaf.core.impl.idp.process.model.ProcessDefinition;
import at.gv.egiz.eaaf.core.impl.idp.process.support.SecureRandomHolder;

/**
 * Represents a process being executed. The process instance provides information about the process and its state.
 * 
 * @author tknall
 * 
 */
public class ProcessInstance implements Serializable {

	private static final long serialVersionUID = 1L;
	private static final int RND_ID_LENGTH = 22;

	private ProcessDefinition processDefinition;
	private String nextId;
	private Date lru;
	private ExecutionContext executionContext;
	private ProcessInstanceState state = ProcessInstanceState.NOT_STARTED;

	private Logger log = LoggerFactory.getLogger(getClass());

	/**
	 * Creates a new process instance, based on a given process definition and a
	 * given execution context. If the given execution context is {@code null} a new execution context will be created.<p/>
	 * The process instance id of the execution context will be newly generated if it is {@code null} in the execution context.
	 * 
	 * @param processDefinition
	 *            The process definition.
	 * @param executionContext
	 *            The execution context (may be {@code null}). If {@code null} a new execution context will be created internally.
	 */
	ProcessInstance(ProcessDefinition processDefinition, ExecutionContext executionContext) {
		this.processDefinition = processDefinition;
		nextId = processDefinition.getStartEvent().getId();
		if (executionContext == null) {
			executionContext = new ExecutionContextImpl();
		}
		if (executionContext.getProcessInstanceId() == null) {
			String pdIdLocalPart = RandomStringUtils.random(RND_ID_LENGTH, 0, 0, true, true, null,
					SecureRandomHolder.getInstance());
			executionContext.setProcessInstanceId(this.processDefinition.getId() + "-" + pdIdLocalPart);
		} else {
			log.debug("Using process instance id from execution context.");
		}
		log.debug("Creating process instance with id '{}'.", executionContext.getProcessInstanceId());
		this.executionContext = executionContext;
		touch();
	}

	/**
	 * Returns the underlying process definition.
	 * 
	 * @return The underlying process definition.
	 */
	ProcessDefinition getProcessDefinition() {
		touch();
		return processDefinition;
	}

	/**
	 * Returns the id of the process node to be executed next.
	 * 
	 * @return The process node pointer indicating the process node to be executed next.
	 */
	public String getNextId() {
		touch();
		return nextId;
	}

	/**
	 * Sets the internal pointer to the process node to be executed next.
	 * 
	 * @param nextId
	 *            The process node id to be executed next.
	 */
	void setNextId(String nextId) {
		touch();
		this.nextId = nextId;
	}

	/**
	 * Returns the current state of the process instance.
	 * 
	 * @return The current state.
	 */
	public ProcessInstanceState getState() {
		touch();
		return state;
	}

	/**
	 * Sets the current state of the process instance.
	 * 
	 * @param state
	 *            The current state.
	 */
	void setState(ProcessInstanceState state) {
		touch();
		this.state = state;
	}

	public String getId() {
		touch();
		return executionContext.getProcessInstanceId();
	}

	/**
	 * Updates the last recently used date of the process instance.
	 */
	private void touch() {
		lru = new Date();
	}

	/**
	 * Returns the date the process instance has been accessed last.
	 * 
	 * @return The last recently used date.
	 */
	Date getLru() {
		return lru;
	}

	/**
	 * Returns the associated execution context.
	 * @return The execution context (never {@code null}).
	 */
	public ExecutionContext getExecutionContext() {
		touch();
		return executionContext;
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder();
		builder.append("ProcessInstance [");
		builder.append("id=").append(executionContext.getProcessInstanceId());
		builder.append(", idle since=").append(
				DurationFormatUtils.formatDurationWords(new Date().getTime() - this.lru.getTime(), true, true));
		if (processDefinition != null) {
			builder.append(", processDefinition.id=");
			builder.append(processDefinition.getId());
		}
		if (nextId != null) {
			builder.append(", nextId=");
			builder.append(nextId);
		}
		builder.append(", executionContext=").append(executionContext);
		builder.append("]");
		return builder.toString();
	}

}