/*
 * Copyright 2010-2011 Ning, Inc.
 *
 * Ning licenses this file to you 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 com.ning.billing.util.dao;

import com.ning.billing.util.ChangeType;
import com.ning.billing.util.callcontext.CallContext;
import com.ning.billing.util.entity.Entity;
import com.ning.billing.util.entity.collection.dao.UpdatableEntityCollectionSqlDao;
import org.skife.jdbi.v2.sqlobject.mixins.Transactional;
import org.skife.jdbi.v2.sqlobject.mixins.Transmogrifier;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.UUID;

public abstract class AuditedCollectionDaoBase<T extends Entity> implements AuditedCollectionDao<T> {
    @Override
    public void saveEntitiesFromTransaction(Transmogrifier transactionalDao, UUID objectId, ObjectType objectType, List<T> entities, CallContext context) {
        UpdatableEntityCollectionSqlDao<T> dao = transmogrifyDao(transactionalDao);

        // get list of existing entities
        List<T> existingEntities = dao.load(objectId.toString(), objectType);
        List<T> entitiesToUpdate = new ArrayList<T>();

        // sort into entities to update (entitiesToUpdate), entities to add (entities), and entities to delete (existingEntities)
        Iterator<T> entityIterator = entities.iterator();
        while (entityIterator.hasNext()) {
            T entity = entityIterator.next();

            Iterator<T> existingEntityIterator = existingEntities.iterator();
            while (existingEntityIterator.hasNext()) {
                T existingEntity = existingEntityIterator.next();
                if (entity.equals(existingEntity)) {
                    // if the entities match, remove from both lists
                    // this requires that the id is *not* part of the equals statement
                    entityIterator.remove();
                    existingEntityIterator.remove();

                    // if the entities have the same hash code (e.g. same data), don't bother updating
                    if (entity.hashCode() != existingEntity.hashCode()) {
                        entitiesToUpdate.add(entity);
                    }
                }
            }
        }

        if (entities.size() != 0) {
            dao.insertFromTransaction(objectId.toString(), objectType, entities, context);
        }

        if (entitiesToUpdate.size() != 0) {
            dao.updateFromTransaction(objectId.toString(), objectType, entitiesToUpdate, context);
        }

        // get all custom entities (including those that are about to be deleted) from the database in order to get the record ids
        List<Mapper<UUID, Long>> recordIds = dao.getRecordIds(objectId.toString(), objectType);
        Map<UUID, Long> recordIdMap = convertToHistoryMap(recordIds);

        if (existingEntities.size() != 0) {
            dao.deleteFromTransaction(objectId.toString(), objectType, existingEntities, context);
        }

        List<EntityHistory<T>> entityHistories = new ArrayList<EntityHistory<T>>();
        entityHistories.addAll(convertToHistory(entities, recordIdMap, ChangeType.INSERT));
        entityHistories.addAll(convertToHistory(entitiesToUpdate, recordIdMap, ChangeType.UPDATE));
        entityHistories.addAll(convertToHistory(existingEntities, recordIdMap, ChangeType.DELETE));

        Long maxHistoryRecordId = dao.getMaxHistoryRecordId();
        dao.addHistoryFromTransaction(objectId.toString(), objectType, entityHistories, context);

        // have to fetch history record ids to update audit log
        List<Mapper<Long, Long>> historyRecordIds = dao.getHistoryRecordIds(maxHistoryRecordId);
        Map<Long, Long> historyRecordIdMap = convertToAuditMap(historyRecordIds);
        List<EntityAudit> entityAudits = convertToAudits(entityHistories, historyRecordIdMap);

        dao.insertAuditFromTransaction(entityAudits, context);
    }

    @Override
    public void saveEntities(UUID objectId, ObjectType objectType, List<T> entities, CallContext context) {
        this.saveEntitiesFromTransaction(getSqlDao(), objectId, objectType, entities, context);
    }

    @Override
    public Map<String, T> loadEntities(final UUID objectId, final ObjectType objectType) {
        UpdatableEntityCollectionSqlDao<T> thisDao = getSqlDao();
        return getMap(thisDao, objectId, objectType);
    }

    @Override
    public Map<String, T> loadEntitiesFromTransaction(final Transmogrifier dao, final UUID objectId, final ObjectType objectType) {
        UpdatableEntityCollectionSqlDao<T> thisDao = transmogrifyDao(dao);
        return getMap(thisDao, objectId, objectType);
    }

    private Map<String, T> getMap(final UpdatableEntityCollectionSqlDao<T> dao, final UUID objectId, final ObjectType objectType) {
        List<T> entities = dao.load(objectId.toString(), objectType);
        Map<String, T> results = new HashMap<String, T>();
        for (T entity : entities) {
            results.put(getKey(entity), entity);
        }
        return results;
    }

    protected List<EntityHistory<T>> convertToHistory(List<T> entities, Map<UUID, Long> recordIds, ChangeType changeType) {
        List<EntityHistory<T>> histories = new ArrayList<EntityHistory<T>>();

        for (T entity : entities) {
            UUID id = entity.getId();
            histories.add(new EntityHistory<T>(id, recordIds.get(id), entity, changeType));
        }

        return histories;
    }

    protected List<EntityAudit> convertToAudits(List<EntityHistory<T>> histories, Map<Long, Long> historyRecordIds) {
        List<EntityAudit> audits = new ArrayList<EntityAudit>();

        for (EntityHistory<T> history : histories) {
            Long recordId = history.getValue();
            Long historyRecordId = historyRecordIds.get(recordId);
            audits.add(new EntityAudit(getTableName(), historyRecordId, history.getChangeType()));
        }

        return audits;
    }

    protected Map<UUID, Long> convertToHistoryMap(List<Mapper<UUID, Long>> recordIds) {
        Map<UUID, Long> recordIdMap = new HashMap<UUID, Long>();
        for (Mapper<UUID, Long> recordId : recordIds) {
            recordIdMap.put(recordId.getKey(), recordId.getValue());
        }
        return recordIdMap;
    }

    protected Map<Long, Long> convertToAuditMap(List<Mapper<Long, Long>> historyRecordIds) {
        Map<Long, Long> historyRecordIdMap = new HashMap<Long, Long>();
        for (Mapper<Long, Long> historyRecordId : historyRecordIds) {
            historyRecordIdMap.put(historyRecordId.getKey(), historyRecordId.getValue());
        }
        return historyRecordIdMap;
    }

    protected abstract TableName getTableName();
    protected abstract UpdatableEntityCollectionSqlDao<T> transmogrifyDao(Transmogrifier transactionalDao);
    protected abstract UpdatableEntityCollectionSqlDao<T> getSqlDao();
    protected abstract String getKey(T entity);
}
