/*
 * Copyright (c) 2014 DataTorrent, Inc. ALL Rights Reserved.
 *
 * 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 com.datatorrent.contrib.cassandra;

import com.datastax.driver.core.*;
import com.datastax.driver.core.exceptions.DriverException;
import com.datatorrent.api.annotation.ShipContainingJars;
import com.datatorrent.lib.db.TransactionableStore;

import javax.annotation.Nonnull;

/**
 * <p>CassandraTransactionalStore class which inherits CassandraStore class and provides transaction support to the operators.</p>
 *
 */
@ShipContainingJars(classes = {com.datastax.driver.core.Cluster.class})
public class CassandraTransactionalStore extends CassandraStore implements TransactionableStore {

	public static String DEFAULT_APP_ID_COL = "dt_app_id";
	public static String DEFAULT_OPERATOR_ID_COL = "dt_operator_id";
	public static String DEFAULT_WINDOW_COL = "dt_window";
	public static String DEFAULT_META_TABLE = "dt_meta";

	@Nonnull
	protected String metaTableAppIdColumn;
	@Nonnull
	protected String metaTableOperatorIdColumn;
	@Nonnull
	protected String metaTableWindowColumn;
	@Nonnull
	private String metaTable;

	private transient boolean inTransaction;
	private transient PreparedStatement lastWindowFetchCommand;
	private transient PreparedStatement lastWindowUpdateCommand;
	private transient PreparedStatement lastWindowDeleteCommand;

	private transient Statement lastWindowFetchStatement;
	private transient Statement lastWindowUpdateStatement;
	private transient Statement lastWindowDeleteStatement;

  protected transient BatchStatement batchCommand;

	public CassandraTransactionalStore()
	{
		super();
		metaTable = DEFAULT_META_TABLE;
		metaTableAppIdColumn = DEFAULT_APP_ID_COL;
		metaTableOperatorIdColumn = DEFAULT_OPERATOR_ID_COL;
		metaTableWindowColumn = DEFAULT_WINDOW_COL;
    batchCommand = new BatchStatement();
		inTransaction = false;
	}

	/**
	 * Sets the name of the meta table.<br/>
	 * <b>Default:</b> {@value #DEFAULT_META_TABLE}
	 *
	 * @param metaTable meta table name.
	 */
	public void setMetaTable(@Nonnull String metaTable)
	{
		this.metaTable = metaTable;
	}

	/**
	 * Sets the name of app id column.<br/>
	 * <b>Default:</b> {@value #DEFAULT_APP_ID_COL}
	 *
	 * @param appIdColumn application id column name.
	 */
	public void setMetaTableAppIdColumn(@Nonnull String appIdColumn)
	{
		this.metaTableAppIdColumn = appIdColumn;
	}

	/**
	 * Sets the name of operator id column.<br/>
	 * <b>Default:</b> {@value #DEFAULT_OPERATOR_ID_COL}
	 *
	 * @param operatorIdColumn operator id column name.
	 */
	public void setMetaTableOperatorIdColumn(@Nonnull String operatorIdColumn)
	{
		this.metaTableOperatorIdColumn = operatorIdColumn;
	}

	/**
	 * Sets the name of the window column.<br/>
	 * <b>Default:</b> {@value #DEFAULT_WINDOW_COL}
	 *
	 * @param windowColumn window column name.
	 */
	public void setMetaTableWindowColumn(@Nonnull String windowColumn)
	{
		this.metaTableWindowColumn = windowColumn;
	}

	public Statement getLastWindowUpdateStatement() {
		return lastWindowUpdateStatement;
	}

  public BatchStatement getBatchCommand()
  {
    return batchCommand;
  }

  @Override
	public void connect()
	{
		super.connect();
		try {
			String command = "SELECT " + metaTableWindowColumn + " FROM " + keyspace +"."+ metaTable + " WHERE " + metaTableAppIdColumn +
					" = ? AND " + metaTableOperatorIdColumn + " = ?";
			logger.debug(command);
			lastWindowFetchCommand = session.prepare(command);

			command = "UPDATE " + keyspace +"."+ metaTable + " SET " + metaTableWindowColumn + " = ? where " + metaTableAppIdColumn + " = ? " +
					" and " + metaTableOperatorIdColumn + " = ?";
			logger.debug(command);
			lastWindowUpdateCommand = session.prepare(command);

			command = "DELETE FROM " + keyspace +"."+ metaTable + " where " + metaTableAppIdColumn + " = ? and " + 
					metaTableOperatorIdColumn + " = ?";
			logger.debug(command);
			lastWindowDeleteCommand = session.prepare(command);
		}
		catch (DriverException e) {
			throw new RuntimeException(e);
		}
		catch (Exception e)
		{
			throw new RuntimeException(e);
		}
	}

	@Override
	public void disconnect()
	{
		if (lastWindowUpdateCommand != null) {
			try {
				lastWindowUpdateCommand.disableTracing();
			}
			catch (DriverException e) {
				throw new RuntimeException(e);
			}
		}
		super.disconnect();
	}

	@Override
	public void beginTransaction()
	{
		inTransaction = true;
	}

	@Override
	public void commitTransaction()
	{
    session.execute(batchCommand);
    batchCommand.clear();
    inTransaction = false;
	}

	@Override
	public void rollbackTransaction()
	{
    batchCommand.clear();
		inTransaction = false;
	}

	@Override
	public boolean isInTransaction()
	{
		return inTransaction;
	}

	@Override
	public long getCommittedWindowId(String appId, int operatorId)
	{
		try {
			BoundStatement boundStatement = new BoundStatement(lastWindowFetchCommand);
			lastWindowFetchStatement = boundStatement.bind(appId,operatorId);
			long lastWindow = -1;
			ResultSet resultSet = session.execute(lastWindowFetchStatement);
			if (!resultSet.isExhausted()) {
				lastWindow = resultSet.one().getLong(0);
			}
			lastWindowFetchCommand.disableTracing();
			return lastWindow;
		}
		catch (DriverException ex) {
			throw new RuntimeException(ex);
		}
	}

	@Override
	public void storeCommittedWindowId(String appId, int operatorId, long windowId)
	{
		try {
			BoundStatement boundStatement = new BoundStatement(lastWindowUpdateCommand);
			lastWindowUpdateStatement = boundStatement.bind(windowId,appId,operatorId);
      batchCommand.add(lastWindowUpdateStatement);
		}
		catch (DriverException e) {
			throw new RuntimeException(e);
		}
	}

	@Override
	public void removeCommittedWindowId(String appId, int operatorId)
	{
		try {
			BoundStatement boundStatement = new BoundStatement(lastWindowDeleteCommand);
			lastWindowDeleteStatement = boundStatement.bind(appId,operatorId);
			session.execute(lastWindowDeleteStatement);
			lastWindowDeleteCommand.disableTracing();
		}
		catch (DriverException e) {
			throw new RuntimeException(e);
		}
	}
}