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Scattersphere Core library, used to run the main server.
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/*
 * Scattersphere
 * Copyright 2014-2015, Scattersphere Project.
 *
 * 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 net.scattersphere.registry;

import net.scattersphere.job.Job;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.*;

/**
 * This is a registry that is used to store known {@link Job}s that can be referenced by Scattersphere.
 *
 * Created by kenji on 11/26/14.
 */
public class JobRegistry {

    private static final JobRegistry instance = new JobRegistry();

    private final Map> registry = new HashMap<>();
    private final Logger LOG = LoggerFactory.getLogger(JobRegistry.class);

    /**
     * Returns the default instance of this class.
     *
     * @return Default {@link JobRegistry} object.
     */
    public static JobRegistry instance() {
        return instance;
    }

    /**
     * This function loads in the registry of registered jobs from a properties file.  Each registered job is then stored
     * in a cache, and instantiated as required.
     *
     * @param props The properties to load job definitions from.
     */
    public void loadFromProperties(Properties props) {
        if (props.getProperty("jobs.count") == null) {
            LOG.error("Unable to initialize: job registry missing key \"jobs.count\"");
            System.exit(-1);
        }

        int jobsCount = Integer.parseInt(props.getProperty("jobs.count"));

        if (jobsCount <= 0) {
            LOG.error("Unable to initialize: invalid number of jobs: {}", jobsCount);
            System.exit(-1);
        }

        LOG.debug("Initializing job registry: jobsCount={}", jobsCount);

        int jobsRegistered = 0;
        int jobsWarned = 0;

        for(int i = 1; i < (jobsCount + 1); i++) {
            String jobClassname = props.getProperty("jobs." + i + ".classname");
            String jobName = props.getProperty("jobs." + i + ".name");

            if (jobClassname == null) {
                LOG.warn("Unable to start job at position {}: class name missing.", i);
                jobsWarned++;
                continue;
            }

            if (jobName == null) {
                LOG.warn("Unable to start job at position {}: job name missing.", i);
                jobsWarned++;
                continue;
            }

            Class jobClass = null;

            try {
                jobClass = Class.forName(jobClassname);
            } catch(Exception ex) {
                LOG.error("Unable to start job at position {}: unable to find job in classpath: {}", i, jobClassname, ex);
                continue;
            }

            registry.put(jobName, jobClass);

            jobsRegistered++;
        }

        LOG.info("*** Job Registry: registered={} skipped={}", jobsRegistered, jobsWarned);
    }

    /**
     * Retrieves a {@link Job} by the name specified.
     *
     * @param job The name o f the job to retrieve.
     * @return {@link Job} object if found, {@code null} if not found.
     */
    public Job get(String job) {
        if (registry.get(job) == null) {
            LOG.debug("Unable to find job by name: {}", job);
            return null;
        }

        Class jobClass = registry.get(job);
        Job jobObject = null;

        try {
            jobObject = (Job) jobClass.newInstance();
        } catch(Exception ex) {
            LOG.warn("Unable to create new instance of job: {}", job, ex);
            ex.printStackTrace();
        }

        return jobObject;
    }

    /**
     * Returns a list of the names of jobs available.  Any jobs that could not be registered or instantiated are omitted
     * from this list.
     *
     * @return {@code Map} of {@link String}, {@link Job}s containing the names of the registered jobs.
     */
    public Map> getJobs() {
        return registry;
    }

}