package foundation.data.object;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Types;

import foundation.persist.NamedSQL;
import foundation.persist.SQLRunner;
import foundation.persist.source.NamedDataSource;
import foundation.server.config.DBaseType;

public class Sequence {

	private NamedDataSource dataSource;
	private String tableName;
	private String nextSQL;
	private String currentSQL;
	
	public Sequence(String tableName) throws Exception {
		this(NamedDataSource.getInstance(), tableName);
	}
	
	public Sequence(NamedDataSource dataSource, String tableName) throws Exception {
		this.dataSource = dataSource;
		this.tableName = tableName;
		
		DBaseType type = dataSource.getDBaseType();
		
		//1. create next SQL
		NamedSQL namedSQL = NamedSQL.getInstance(type, "nextval");
		namedSQL.setTableName(tableName);
		nextSQL = namedSQL.toString();
		
		//2. create current SQL
		namedSQL = NamedSQL.getInstance(type, "currval");
		namedSQL.setTableName(tableName);
		currentSQL = namedSQL.toString();
	}

	public long next() throws Exception {
		long value = SQLRunner.getSequence(dataSource, this, SequenceValue.Next);
		return value;
	}
	
	public long current() throws Exception {
		long value = SQLRunner.getSequence(dataSource, this, SequenceValue.Current);
		return value;
	}

	public long exec(Connection conn, SequenceValue value) throws SQLException {
		long result = 0;
		
		String sql = (SequenceValue.Current == value) ? currentSQL : nextSQL;
		
		CallableStatement stmt = conn.prepareCall(sql);
		try {
			stmt.setString(1, tableName);
			stmt.registerOutParameter(2, Types.BIGINT);
			stmt.execute();
					
			result = stmt.getLong(2);			
		} 
		finally {
			try {
				if (stmt != null) {
					stmt.close();
				}
			} catch (SQLException e) {
			}			
		}

		return result;
	}
	
	public String getNextSQL() {
		return nextSQL;
	}

	public String getCurrentSQL() {
		return currentSQL;
	}

	@Override
	public String toString() {
		return tableName + " sequence";
	}
	
}