import javax.microedition.rms.*;
import java.io.IOException;

/**
 * 該類是一個數據訪問對象（DAO）類，提供了對記錄存儲中課程對象的訪問方法。
 */
public class CurriculumDAO {
    private static final String RS_NAME = "CURRICULUM";     //記錄存儲名
    private static CurriculumDAO dao = null;    //數據訪問對象實例
    private RecordStore rs;                 //記錄存儲               
    private FindFilter filter;              //過濾器
    private RecordComparator comparator;    //比較器
    
    private CurriculumDAO() {
        filter = new FindFilter();          //創建過濾器
        comparator = new CurrComparator();  //創建比較器
    }
    
    //獲取一個數據訪問對象的實例
    public static CurriculumDAO getInstance() {
        if(dao == null) {
            dao = new CurriculumDAO();
        }
        
        return dao;
    }
    
    //打開課程對象的記錄存儲
    public void openRecordStore() throws DAOException {
        try {
            rs = RecordStore.openRecordStore(RS_NAME, true);    //打開記錄存儲，如果不存在就新建立一個記錄存儲
        }
        catch(RecordStoreException rse) {
            throw new DAOException("打開記錄存儲失敗！\n原因：\n" + rse.getMessage());
        }
    }
    
    //關閉課程對象的記錄存儲
    public void closeRecordStore() throws DAOException {
        try {
            rs.closeRecordStore();
        }
        catch(RecordStoreException rse) {
            throw new DAOException("關閉記錄存儲失敗！\n原因：\n" + rse.getMessage());
        }
    }
    
    //保存課程對象curr到記錄存儲中
    public void save(Curriculum curr) throws DAOException {
        if(find(curr.getDay(), curr.getTime()).length != 0) {
            throw new DAOException("保存課程對象失敗！\n原因：\n上課時間發生沖突！\n" 
                   + Curriculum.WEEKS_LABEL[curr.getDay()] + "  "
                   + Curriculum.JIE_LABEL[curr.getTime()] + "已經有課。");
        }
        
        try {
            byte[] data = curr.sequence(); //序列化課程對象curr
            int id = curr.getID();
            if(id == -1) {  //新增課程對象
                rs.addRecord(data, 0, data.length);
            }
            else {          //更新
                rs.setRecord(id, data, 0, data.length);
            }
        }
        catch(IOException ioe) {
            throw new DAOException("保存課程對象失敗！\n原因：\n" + ioe.getMessage());
        }
        catch(RecordStoreException rse) {
            throw new DAOException("保存課程對象失敗！\n原因：\n" + rse.getMessage());
        }
    }
    
    //刪除id課程對象
    public void delete(int id) throws DAOException {
        try {
            rs.deleteRecord(id);
        }
        catch(RecordStoreException rse) {
            throw new DAOException("刪除課程對象失敗！\n原因：\n" + rse.getMessage());
        }
    }
    
    //查找所有名字為name的課程對象
    public Curriculum[] find(String name) throws DAOException {
        filter.setCondition(name);  //設置過濾條件
        return getCurriculumArray(filter, comparator);
    }
    
    //查找week這天所有的課程對象
    public Curriculum[] find(int week) {
        filter.setCondition(week);  //設置過濾條件
        return getCurriculumArray(filter, comparator);
    }
    
    //查找指定日期，時間的課程
    public Curriculum[] find(int week, int time) {
        filter.setCondition(week, time);
        return getCurriculumArray(filter, comparator);
    }
    
    //獲取記錄存儲中所有的課程對象
    public Curriculum[] getAll() {
        return getCurriculumArray(null, comparator);
    }
    
    //獲取符合過濾器rf條件，并且排序的課程對象數組
    private Curriculum[] getCurriculumArray(RecordFilter rf, RecordComparator rc) {
        RecordEnumeration re = null;
        try {
            re = rs.enumerateRecords(rf, rc, false);
        }
        catch(RecordStoreException rse) {
            //
        }
        
        Curriculum[] curricula;
        if(re != null) {
            int size = re.numRecords();
            curricula = new Curriculum[size];
            byte[] data = null;
            for(int i=0; i<size; i++) {
                try {
                    int id = re.nextRecordId();
                    data = rs.getRecord(id);
                    curricula[i] = Curriculum.unSequence(data);//反序列化，生成課程對象
                    curricula[i].setID(id);
                } 
                catch(RecordStoreException rse) {
                    System.out.println("錯誤！" + rse.getMessage());
                }
                catch(IOException ioe) {
                    System.out.println("錯誤！" + ioe.getMessage());
                }
            }
        }
        else {
            curricula = new Curriculum[0];
        }
        
        return curricula;
    }
}