package io.trygvis.async;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class SqlEffectExecutor {

    private final DataSource dataSource;

    public SqlEffectExecutor(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    public <A> A transaction(SqlEffect<A> effect) throws SQLException {
        int pid;

        try (Connection c = dataSource.getConnection()) {
            pid = getPid(c);
            System.out.println("pid = " + pid);

            boolean ok = false;
            try {
                A a = effect.doInConnection(c);
                c.commit();
                ok = true;
                return a;
            } finally {
                System.out.println("Closing, pid = " + pid);
                if (!ok) {
                    try {
                        c.rollback();
                    } catch (SQLException e) {
                        // ignore
                    }
                }
            }
        }
    }

    public void transaction(final SqlEffect.Void effect) throws SQLException {
        transaction(new SqlEffect<Object>() {
            @Override
            public Object doInConnection(Connection c) throws SQLException {
                effect.doInConnection(c);
                return null;
            }
        });
    }

    private int getPid(Connection c) throws SQLException {
        int pid;
        try (Statement statement = c.createStatement()) {
            ResultSet rs = statement.executeQuery("SELECT pg_backend_pid()");
            rs.next();
            pid = rs.getInt(1);
        }
        return pid;
    }
}