/*
 * ItemMapper.java
 * 
 * MSE06B班張智力的實驗報告
 * 
 * 2006年12月11日
 */

package olts.dao;

import java.util.*;
import java.io.*;
import java.sql.*;
import olts.item.*;
import olts.util.ErrorRecorder;

/**
 * ItemMapper類，負責(zé)獲取題目、增加題目、修改題目、刪除題目的數(shù)據(jù)庫操作
 */
public class ItemMapper {
	
    /**
     * ItemMapper對象，SingleTon模式的單一對象
     */
	private static ItemMapper itemMapper;
    
    /**
     * Connection對象，數(shù)據(jù)庫連接器
     */
	private Connection conn;
    
    /**
     * Statement對象
     */
	private Statement stmt;
    
    /**
     * driver屬性，記錄odbc的驅(qū)動程序名
     */
	private String driver;
    
    /**
     * url屬性，記錄數(shù)據(jù)源的url字段
     */
	private String url;
    
    /**
     * List對象，在數(shù)據(jù)庫中取出試題數(shù)據(jù)，組織成<code>Item<code>對象，并存放在該List對象容器中
     */
	private List itemLibrary = new LinkedList();

    /**
     * 構(gòu)造函數(shù)，從driver.ini文件中讀出驅(qū)動程序名并初始化數(shù)據(jù)源的url。
     */
	private ItemMapper(){
		try{
			File file = new File("driver.ini");
			BufferedReader reader = new BufferedReader(new FileReader(file));
			driver = reader.readLine();
			url = "jdbc:odbc:OLTSDB";
			reader.close();
		}catch(IOException e){
			ErrorRecorder.record(e);
			driver = "sun.jdbc.odbc.JdbcOdbcDriver";
		}
	}
	
    /**
     * getItemMapper方法，SingleTon模式下用于返回單一對象的方法。
     * @return
     */
	public static ItemMapper getItemMapper(){
		if(itemMapper == null){
			itemMapper = new ItemMapper();
			return itemMapper;
		}
		else return itemMapper;
	}
	
    /**
     * getItemLibrary方法，從數(shù)據(jù)庫中查詢Item數(shù)據(jù)，返回一隊列的Item對象
     * @return List 返回一個Item對象的容器
     * @throws SQLException 當發(fā)生SQL語法、數(shù)據(jù)庫等錯誤時拋出該異常
     */
	public List getItemLibrary(String sql)throws SQLException{
        itemLibrary.clear();
        try{
			Class.forName(driver);
			conn = DriverManager.getConnection(url);
			stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery(sql);
			while(rs.next()){
				String content = rs.getString("content");
                String standAnswer = rs.getString("standAnswer");
                int difficulty = rs.getInt("difficulty");
                int score = rs.getInt("score");
                int time = rs.getInt("expecttime");
                String subject = rs.getString("subject");
                int type = rs.getInt("type");
                switch(type){
                case 1: itemLibrary.add(new SingleChoiceItem(content, standAnswer, difficulty, score, time, subject)); break;
                case 2: itemLibrary.add(new MultiChoiceItem(content, standAnswer, difficulty, score, time, subject)); break;
                case 3: itemLibrary.add(new TrueFalseItem(content, standAnswer, difficulty, score, time, subject)); break;
                case 4: itemLibrary.add(new BlankFillItem(content, standAnswer, difficulty, score, time, subject)); break;
                }
			}
            rs.close();
            stmt.close();
            conn.close();
		}catch(ClassNotFoundException cnfe){
			ErrorRecorder.record(cnfe);
		}
		return itemLibrary;
	}
	
    /**
     * addItem方法，提供向數(shù)據(jù)庫添加一條Item記錄的方法。
     * @param item 要加入數(shù)據(jù)庫的Item記錄
     * @param type 該記錄的試題類型
     * @return boolean 當添加Item記錄成功時返回true，不成功時返回false
     * @throws SQLException 當發(fā)生SQL語法、數(shù)據(jù)庫等錯誤時拋出該異常
     */
	public boolean addItem(Item item, int type)throws SQLException{
		boolean b = false;
        try{
			Class.forName(driver);
			conn = DriverManager.getConnection(url);
            PreparedStatement pstmt = conn.prepareStatement("insert into ItemTable(content, standAnswer, difficulty, score, time, subject, type) values(?,?,?,?,?,?,?)");
            pstmt.setString(1, item.content);
            pstmt.setString(2, item.standAnswer);
            pstmt.setInt(3, item.difficulty);
            pstmt.setInt(4, item.score);
            pstmt.setInt(5, item.time);
            pstmt.setString(6, item.subject);
            pstmt.setInt(7, type);
            b = pstmt.execute();
            pstmt.close();
            conn.close();
		}catch(ClassNotFoundException cnfe){
			ErrorRecorder.record(cnfe);
		}
		return b;
	}
	
    /**
     * alterItem方法，提供向數(shù)據(jù)庫修改Item記錄的方法
     * @return int 返回該修改操作影響的行數(shù)
     * @throws SQLException 當發(fā)生SQL語法、數(shù)據(jù)庫等錯誤時拋出該異常
     */
	public int alterItem()throws SQLException{
		try{
			Class.forName(driver);
			stmt = conn.createStatement();
			stmt.execute("Update  ");
		}catch(ClassNotFoundException cnfe){
			ErrorRecorder.record(cnfe);
		}
		return 0;
	}

}