package pt.ist.fenixframework.plugins.scheduler;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Timer;
import java.util.TimerTask;

import jvstm.TransactionalCommand;

import org.joda.time.DateTime;

import pt.ist.fenixframework.FenixFramework;
import pt.ist.fenixframework.plugins.scheduler.domain.SchedulerSystem;
import pt.ist.fenixframework.pstm.Transaction;

public class Scheduler extends TimerTask {

    private static final int SCHEDULER_INVOCATION_PERIOD = 120000; // (ms)

    public static void initialize() {
        new Scheduler();
    }

    private final Timer timer = new Timer(true);

    public Scheduler() {
        final DateTime dt = new DateTime().withMillisOfSecond(0).withSecondOfMinute(0).plusMinutes(1);
        timer.scheduleAtFixedRate(this, dt.toDate(), SCHEDULER_INVOCATION_PERIOD);
    }

    @Override
    public void run() {
        try {
            try {
                Transaction.withTransaction(false, new TransactionalCommand() {
                    @Override
                    public void doIt() {
                        SchedulerSystem.queueTasks();
                    }
                });
            } finally {
                Transaction.forceFinish();
            }
            runPendingTask();
        } catch (final Throwable t) {
            t.printStackTrace();
        }
    }

    private void runPendingTask() {
        try {
            Transaction.withTransaction(true, new TransactionalCommand() {
                @Override
                public void doIt() {
                    final Connection connection = Transaction.getCurrentJdbcConnection();
                    try {
                        runPendingTask(connection);
                    } catch (SQLException e) {
                        throw new Error(e);
                    }
                }
            });
        } finally {
            Transaction.forceFinish();
        }
    }

    private static String getAppDbAliasConnection() {
        final String dbAlias = FenixFramework.getConfig().getDbAlias();
        return dbAlias == null || dbAlias.isEmpty() ? "" : dbAlias;
    }

    private void runPendingTask(final Connection connection) throws SQLException {
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            final String lockVariable = SchedulerSystem.class.getName() + "_" + getAppDbAliasConnection();
            try {
                statement = connection.createStatement();
                resultSet = statement.executeQuery("SELECT GET_LOCK('" + lockVariable + "', 10)");
                if (resultSet.next() && (resultSet.getInt(1) == 1)) {
                    SchedulerSystem.runPendingTask();
                }
            } finally {
                Statement statement2 = null;
                try {
                    statement2 = connection.createStatement();
                    statement2.executeUpdate("DO RELEASE_LOCK('" + lockVariable + "')");
                } finally {
                    if (statement2 != null) {
                        try {
                            statement2.close();
                        } catch (final SQLException e) {
//			    e.printStackTrace();
                        }
                    }
                }
            }
        } finally {
            if (resultSet != null) {
                try {
                    resultSet.close();
                } catch (SQLException e) {
//		    e.printStackTrace();
                }
            }
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
//		    e.printStackTrace();
                }
            }
        }
    }

}