/*
 * Copyright 2014 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
 *
 *      https://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.springframework.batch.core.jsr.job;

import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.core.BatchStatus;
import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.StartLimitExceededException;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.StepExecution;
import org.springframework.batch.core.explore.JobExplorer;
import org.springframework.batch.core.job.SimpleStepHandler;
import org.springframework.batch.core.repository.JobRepository;
import org.springframework.batch.core.repository.JobRestartException;
import org.springframework.batch.item.ExecutionContext;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

/**
 * Extends {@link SimpleStepHandler} to apply JSR-352 specific logic for whether to
 * start a step.
 *
 * @author Michael Minella
 * @since 3.0
 */
public class JsrStepHandler extends SimpleStepHandler {

        private static final Log logger = LogFactory.getLog(JsrStepHandler.class);

        private JobExplorer jobExplorer;

        /**
         * @param jobRepository instance of {@link JobRepository}.
         * @param jobExplorer instance of {@link JobExplorer}.
         */
        public JsrStepHandler(JobRepository jobRepository, JobExplorer jobExplorer) {
                super(jobRepository, new ExecutionContext());
                this.jobExplorer = jobExplorer;
        }

        @Override
        public void afterPropertiesSet() throws Exception {
                super.afterPropertiesSet();
                Assert.state(jobExplorer != null, "A JobExplorer must be provided");
        }


        /**
         * Given a step and configuration, return true if the step should start,
         * false if it should not, and throw an exception if the job should finish.
         * @param lastStepExecution the last step execution
         * @param jobExecution instance of {@link JobExecution}
         * @param step instance of {@link Step}
         *
         * @throws StartLimitExceededException if the start limit has been exceeded
         * for this step
         * @throws JobRestartException if the job is in an inconsistent state from
         * an earlier failure
         */
        @Override
        protected boolean shouldStart(StepExecution lastStepExecution, JobExecution jobExecution, Step step)
                        throws JobRestartException, StartLimitExceededException {
                BatchStatus stepStatus;
                String restartStep = null;
                if (lastStepExecution == null) {
                        jobExecution.getExecutionContext().put("batch.startedStep", step.getName());
                        stepStatus = BatchStatus.STARTING;
                }
                else {
                        stepStatus = lastStepExecution.getStatus();

                        JobExecution lastJobExecution = getLastJobExecution(jobExecution);

                        if(lastJobExecution.getExecutionContext().containsKey("batch.restartStep")) {
                                restartStep = lastJobExecution.getExecutionContext().getString("batch.restartStep");

                                if(CollectionUtils.isEmpty(jobExecution.getStepExecutions()) && lastJobExecution.getStatus() == BatchStatus.STOPPED && StringUtils.hasText(restartStep)) {
                                        if(!restartStep.equals(step.getName()) && !jobExecution.getExecutionContext().containsKey("batch.startedStep")) {
                                                logger.info("Job was stopped and should restart at step " + restartStep + ".  The current step is " + step.getName());
                                                return false;
                                        } else {
                                                // Indicates the starting point for execution evaluation per JSR-352
                                                jobExecution.getExecutionContext().put("batch.startedStep", step.getName());
                                        }
                                }
                        }
                }

                if (stepStatus == BatchStatus.UNKNOWN) {
                        throw new JobRestartException("Cannot restart step from UNKNOWN status. "
                                        + "The last execution ended with a failure that could not be rolled back, "
                                        + "so it may be dangerous to proceed. Manual intervention is probably necessary.");
                }

                if ((stepStatus == BatchStatus.COMPLETED && step.isAllowStartIfComplete() == false)
                                || stepStatus == BatchStatus.ABANDONED) {
                        // step is complete, false should be returned, indicating that the
                        // step should not be started
                        logger.info("Step already complete or not restartable, so no action to execute: " + lastStepExecution);
                        return false;
                }

                if (getJobRepository().getStepExecutionCount(jobExecution.getJobInstance(), step.getName()) < step.getStartLimit()) {
                        // step start count is less than start max, return true
                        return true;
                }
                else {
                        // start max has been exceeded, throw an exception.
                        throw new StartLimitExceededException("Maximum start limit exceeded for step: " + step.getName()
                                        + "StartMax: " + step.getStartLimit());
                }
        }

        /**
         * Since all JSR-352 jobs are run asynchronously, {@link JobRepository#getLastJobExecution(String, org.springframework.batch.core.JobParameters)}
         * could return the currently running {@link JobExecution}.  To get around this, we use the {@link JobExplorer}
         * to get a list of the executions and get the most recent one that is <em>not</em> the currently running
         * {@link JobExecution}.
         *
         * @param jobExecution
         * @return the last executed JobExecution.
         */
        private JobExecution getLastJobExecution(JobExecution jobExecution) {
                List<JobExecution> jobExecutions = jobExplorer.getJobExecutions(jobExecution.getJobInstance());
                JobExecution lastJobExecution = null;

                for (JobExecution curJobExecution : jobExecutions) {
                        if(lastJobExecution == null && curJobExecution.getId().longValue() != jobExecution.getId().longValue()) {
                                lastJobExecution = curJobExecution;
                        } else if(curJobExecution.getId().longValue() != jobExecution.getId().longValue() && (lastJobExecution == null || curJobExecution.getId().longValue() > lastJobExecution.getId().longValue())) {
                                lastJobExecution = curJobExecution;
                        }
                }
                return lastJobExecution;
        }
}