/*
 * #%L
 * Netarchivesuite - harvester
 * %%
 * Copyright (C) 2005 - 2014 The Royal Danish Library, the Danish State and University Library,
 *             the National Library of France and the Austrian National Library.
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */
package dk.netarkivet.harvester.scheduler.jobgen;

import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import dk.netarkivet.common.utils.Settings;
import dk.netarkivet.harvester.HarvesterSettings;
import dk.netarkivet.harvester.datamodel.DomainConfiguration;
import dk.netarkivet.harvester.datamodel.HarvestDefinition;
import dk.netarkivet.harvester.datamodel.Job;
import dk.netarkivet.harvester.datamodel.JobDAO;

/**
 * Job generator implementation. Generates jobs with a fixed number of domain configurations. Configuration allows to
 * choose a different count for partial and full harvests. The last job generated may have less configurations in it, as
 * job generation happens on a per-harvest basis.
 *
 * @see HarvesterSettings#JOBGEN_FIXED_CONFIG_COUNT_SNAPSHOT
 * @see HarvesterSettings#JOBGEN_FIXED_CONFIG_COUNT_FOCUSED
 */
public class FixedDomainConfigurationCountJobGenerator extends AbstractJobGenerator {

    /** Logger for this class. */
    private static final Logger log = LoggerFactory.getLogger(FixedDomainConfigurationCountJobGenerator.class);

    /**
     * A compound key used to split domain configurations in jobs.
     */
    private class DomainConfigurationKey {

        /** The name of the Heritrix crawl order template. */
        private final String orderXmlName;
        /** The crawl budget in URI. */
        private final long maxObjects;
        /** The crawl budget in bytes. */
        private final long maxBytes;

        /**
         * Constructor from a domain configuration.
         *
         * @param cfg the related {@link DomainConfiguration}
         */
        DomainConfigurationKey(DomainConfiguration cfg) {
            this.orderXmlName = cfg.getOrderXmlName();
            long cMaxBytes = cfg.getMaxBytes();
            long cMaxObjects = cfg.getMaxObjects();
            if (cMaxBytes == 0 || cMaxObjects == 0) {
                // All domain configurations with a zero budget (either size or URI count
                // end up in the same group
                this.maxBytes = 0;
                this.maxObjects = 0;
            } else {
                this.maxBytes = cMaxBytes;
                this.maxObjects = cMaxObjects;
            }
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + (int) (maxBytes ^ (maxBytes >>> 32));
            result = prime * result + (int) (maxObjects ^ (maxObjects >>> 32));
            result = prime * result + ((orderXmlName == null) ? 0 : orderXmlName.hashCode());
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null || !DomainConfigurationKey.class.equals(obj.getClass())) {
                return false;
            }
            DomainConfigurationKey dc = (DomainConfigurationKey) obj;
            return orderXmlName.equals(dc.orderXmlName) && maxBytes == dc.maxBytes && maxObjects == dc.maxObjects;
        }

        @Override
        public String toString() {
            return orderXmlName + ":" + maxObjects + ":" + maxBytes;
        }
    }

    /**
     * Simple marker class to improve code readability.
     * <p>
     * Maps jobs currently being filled, for a given harvest definition, with domain configurations by harvest template
     * name. These jobs keep getting new configurations until no more configurations are left to process or the
     * configured size has been reached.
     */
    @SuppressWarnings("serial")
    private class HarvestJobGenerationState extends HashMap<DomainConfigurationKey, Job> {
    }

    /**
     * Compare two configurations in alphabetical order of their name.
     */
    private static class ConfigNamesComparator implements Comparator<DomainConfiguration> {

        @Override
        public int compare(DomainConfiguration dc1, DomainConfiguration dc2) {
            return dc1.getName().compareTo(dc2.getName());
        }

    }

    /** Constant : how many {@link DomainConfiguration}s we want in a focused harvest job. */
    private static long CONFIG_COUNT_FOCUSED = Settings.getLong(HarvesterSettings.JOBGEN_FIXED_CONFIG_COUNT_FOCUSED);

    /** Constant : how many {@link DomainConfiguration}s we want in a snapshot harvest job. */
    private static long CONFIG_COUNT_SNAPSHOT = Settings.getLong(HarvesterSettings.JOBGEN_FIXED_CONFIG_COUNT_SNAPSHOT);

    /** Constant : exclude {@link DomainConfiguration}s with a budget of zero (bytes or objects). */
    private static boolean EXCLUDE_ZERO_BUDGET = Settings
            .getBoolean(HarvesterSettings.JOBGEN_FIXED_CONFIG_COUNT_EXCLUDE_ZERO_BUDGET);

    /** The singleton instance. */
    public static FixedDomainConfigurationCountJobGenerator instance;

    /**
     * Maps jobs currently being filled with domain configurations by harvest template name. These jobs keep getting new
     * configurations until no more configurations are left to process or the configured size has been reached.
     */
    private Map<Long, HarvestJobGenerationState> state;

    /** The job DAO instance (singleton). */
    private JobDAO dao = JobDAO.getInstance();

    private FixedDomainConfigurationCountJobGenerator() {
        this.state = new HashMap<Long, HarvestJobGenerationState>();
    }

    /**
     * @return the singleton instance, builds it if necessary.
     */
    public synchronized static FixedDomainConfigurationCountJobGenerator getInstance() {
        if (instance == null) {
            instance = new FixedDomainConfigurationCountJobGenerator();
        }
        return instance;
    }

    @Override
    protected Comparator<DomainConfiguration> getDomainConfigurationSubsetComparator(HarvestDefinition harvest) {
        return new ConfigNamesComparator();
    }

    @Override
    protected boolean checkSpecificAcceptConditions(Job job, DomainConfiguration cfg) {
        return job.getDomainConfigurationMap().size() < (job.isSnapshot() ? CONFIG_COUNT_SNAPSHOT
                : CONFIG_COUNT_FOCUSED);
    }

    @Override
    public int generateJobs(HarvestDefinition harvest) {
        HarvestJobGenerationState jobsUnderConstruction = getStateForHarvest(harvest);

        try {
            int jobsComplete = super.generateJobs(harvest);

            // Look if we have jobs that have not reached their limit, but are complete
            // as we have finished processing the harvest
            if (!jobsUnderConstruction.isEmpty()) {
                for (Job job : jobsUnderConstruction.values()) {
                    // The job is ready, post-process and store it in DB
                    editJobOrderXml(job);
                    dao.create(job);

                    // Increment counter
                    ++jobsComplete;
                }
            }

            return jobsComplete;
        } finally {
            dropStateForHarvest(harvest);
        }
    }

    @Override
    protected int processDomainConfigurationSubset(HarvestDefinition harvest,
            Iterator<DomainConfiguration> domainConfSubset) {
        HarvestJobGenerationState jobsUnderConstruction = getExistingStateForHarvest(harvest);
        int jobsComplete = 0;
        while (domainConfSubset.hasNext()) {
            DomainConfiguration cfg = domainConfSubset.next();

            // Should we exclude a configuration with a budget of zero?
            if (EXCLUDE_ZERO_BUDGET && (0 == cfg.getMaxBytes() || 0 == cfg.getMaxObjects())) {
                log.info("[JobGen] Config '{}' for '{}' excluded (0{})", cfg.getName(), cfg.getDomainName(),
                        (cfg.getMaxBytes() == 0 ? " bytes" : " objects"));
                continue;
            }

            DomainConfigurationKey domainConfigKey = new DomainConfigurationKey(cfg);
            Job match = jobsUnderConstruction.get(domainConfigKey);
            if (match == null) {
                match = initNewJob(harvest, cfg);
            } else {
                if (canAccept(match, cfg, null)) {
                    match.addConfiguration(cfg);
                } else {
                    // The job is ready, post-process and store it in DB
                    editJobOrderXml(match);
                    dao.create(match);

                    // Increment counter
                    ++jobsComplete;

                    // Start construction of a new job
                    initNewJob(harvest, cfg);
                }
            }
        }
        return jobsComplete;
    }

    /**
     * Initializes a new job.
     *
     * @param harvest the {@link HarvestDefinition} being processed.
     * @param cfg the first {@link DomainConfiguration} for this job.
     * @return the {@link Job} instance
     */
    private Job initNewJob(HarvestDefinition harvest, DomainConfiguration cfg) {
        HarvestJobGenerationState jobsUnderConstruction = getExistingStateForHarvest(harvest);
        Job job = getNewJob(harvest, cfg);
        jobsUnderConstruction.put(new DomainConfigurationKey(cfg), job);
        return job;
    }

    private synchronized HarvestJobGenerationState getStateForHarvest(final HarvestDefinition harvest,
            final boolean failIfNotExists) {

        long harvestId = harvest.getOid();
        HarvestJobGenerationState harvestState = this.state.get(harvestId);
        if (harvestState == null) {
            if (failIfNotExists) {
                throw new NoSuchElementException("No job generation state for harvest " + harvestId);
            }
            harvestState = new HarvestJobGenerationState();
            this.state.put(harvestId, harvestState);
        }

        return harvestState;
    }

    private HarvestJobGenerationState getStateForHarvest(final HarvestDefinition harvest) {
        return getStateForHarvest(harvest, false);
    }

    private HarvestJobGenerationState getExistingStateForHarvest(final HarvestDefinition harvest) {
        return getStateForHarvest(harvest, true);
    }

    private synchronized void dropStateForHarvest(final HarvestDefinition harvest) {
        long harvestId = harvest.getOid();
        HarvestJobGenerationState harvestState = this.state.remove(harvestId);
        if (harvestState == null) {
            throw new NoSuchElementException("No job generation state for harvest " + harvestId);
        }
    }

}