/*
 * Copyright 2012-2015 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * Thermostat 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 Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.vm.gc.common.internal;

import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.redhat.thermostat.common.utils.LoggingUtils;
import com.redhat.thermostat.storage.core.Category;
import com.redhat.thermostat.storage.core.CategoryAdapter;
import com.redhat.thermostat.storage.core.Cursor;
import com.redhat.thermostat.storage.core.DescriptorParsingException;
import com.redhat.thermostat.storage.core.Key;
import com.redhat.thermostat.storage.core.PreparedStatement;
import com.redhat.thermostat.storage.core.StatementDescriptor;
import com.redhat.thermostat.storage.core.StatementExecutionException;
import com.redhat.thermostat.storage.core.Storage;
import com.redhat.thermostat.storage.core.VmLatestPojoListGetter;
import com.redhat.thermostat.storage.core.VmRef;
import com.redhat.thermostat.storage.model.DistinctResult;
import com.redhat.thermostat.vm.gc.common.VmGcStatDAO;
import com.redhat.thermostat.vm.gc.common.model.VmGcStat;

public class VmGcStatDAOImpl implements VmGcStatDAO {
    
    private static Logger logger = LoggingUtils.getLogger(VmGcStatDAOImpl.class);
    // ADD vm-gc-stats SET 'agentId' = ?s , \
    //                     'vmId' = ?s , \
    //                     'timeStamp' = ?l , \
    //                     'collectorName' = ?s , \
    //                     'runCount' = ?l , \
    //                     'wallTime' = ?l
    static final String DESC_ADD_VM_GC_STAT = "ADD " + vmGcStatCategory.getName() +
            " SET '" + Key.AGENT_ID.getName() + "' = ?s , " +
                 "'" + Key.VM_ID.getName() + "' = ?s , " +
                 "'" + Key.TIMESTAMP.getName() + "' = ?l , " +
                 "'" + collectorKey.getName() + "' = ?s , " +
                 "'" + runCountKey.getName() + "' = ?l , " +
                 "'" + wallTimeKey.getName() + "' = ?l";
    // The assumption is that VM id's are unique. Which it is. It's a UUID.
    static final String DESC_QUERY_DISTINCT_COLLECTORS = "QUERY-DISTINCT(" +
            collectorKey.getName() + ") " + vmGcStatCategory.getName() +
            " WHERE '" + Key.VM_ID.getName() + "' = ?s";
    

    private final Storage storage;
    private final VmLatestPojoListGetter<VmGcStat> getter;
    private final Category<DistinctResult> aggregateCategory;

    VmGcStatDAOImpl(Storage storage) {
        this.storage = storage;
        storage.registerCategory(vmGcStatCategory);
        // getDistinctCollectorNames uses an adapted category. Be sure to
        // register it after the source category has been registered. This is
        // necessary in order for web storage to work with the adapted
        // category.
        CategoryAdapter<VmGcStat, DistinctResult> adapter = new CategoryAdapter<>(vmGcStatCategory);
        this.aggregateCategory = adapter.getAdapted(DistinctResult.class);
        storage.registerCategory(aggregateCategory);
        getter = new VmLatestPojoListGetter<>(storage, vmGcStatCategory);
    }

    @Override
    public List<VmGcStat> getLatestVmGcStats(VmRef ref, long since) {
        return getter.getLatest(ref, since);
    }

    @Override
    public void putVmGcStat(VmGcStat stat) {
        StatementDescriptor<VmGcStat> desc = new StatementDescriptor<>(vmGcStatCategory, DESC_ADD_VM_GC_STAT);
        PreparedStatement<VmGcStat> prepared;
        try {
            prepared = storage.prepareStatement(desc);
            prepared.setString(0, stat.getAgentId());
            prepared.setString(1, stat.getVmId());
            prepared.setLong(2, stat.getTimeStamp());
            prepared.setString(3, stat.getCollectorName());
            prepared.setLong(4, stat.getRunCount());
            prepared.setLong(5, stat.getWallTime());
            prepared.execute();
        } catch (DescriptorParsingException e) {
            logger.log(Level.SEVERE, "Preparing stmt '" + desc + "' failed!", e);
        } catch (StatementExecutionException e) {
            logger.log(Level.SEVERE, "Executing stmt '" + desc + "' failed!", e);
        }
    }

    @Override
    public Set<String> getDistinctCollectorNames(VmRef ref) {
        StatementDescriptor<DistinctResult> desc = new StatementDescriptor<>(aggregateCategory, DESC_QUERY_DISTINCT_COLLECTORS);
        PreparedStatement<DistinctResult> prepared;
        try {
            prepared = storage.prepareStatement(desc);
            prepared.setString(0, ref.getVmId());
            Cursor<DistinctResult> cursor = prepared.executeQuery();
            // DistinctResult comes as a single value if any
            if (cursor.hasNext()) {
                DistinctResult result = cursor.next();
                Set<String> collNames = new HashSet<>();
                for (String col: result.getValues()) {
                    collNames.add(col);
                }
                return collNames;
            } else {
                // Something wrong with the query?
                logger.log(Level.FINE, "Query '" + desc + "' returned no result!");
                return Collections.emptySet();
            }
        } catch (DescriptorParsingException e) {
            logger.log(Level.SEVERE, "Preparing stmt '" + desc + "' failed!", e);
        } catch (StatementExecutionException e) {
            logger.log(Level.SEVERE, "Executing stmt '" + desc + "' failed!", e);
        }
        return Collections.emptySet();
    }

}