/*
 * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.micode.notes.data;

import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.DataConstants;
import net.micode.notes.data.Notes.NoteColumns;


/**
 * 小米便签数据库帮助类
 * 负责创建、升级数据库，管理表结构和触发器
 */
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 数据库名称
    private static final String DB_NAME = "note.db";

    // 数据库版本号
    private static final int DB_VERSION = 9;

    // 数据库表名定义
    public interface TABLE {
        // 笔记表：存储笔记和文件夹的基本信息
        public static final String NOTE = "note";

        // 数据表：存储笔记的详细内容，支持多种类型的笔记数据
        public static final String DATA = "data";
    }

    // 日志标签
    private static final String TAG = "NotesDatabaseHelper";

    // 单例实例，确保整个应用只有一个数据库帮助类实例
    private static NotesDatabaseHelper mInstance;

    // 创建笔记表的SQL语句
    // 笔记表存储笔记和文件夹的基本信息，包括：
    // - ID：唯一标识符
    // - PARENT_ID：父文件夹ID
    // - ALERTED_DATE：提醒日期
    // - BG_COLOR_ID：背景颜色ID
    // - CREATED_DATE：创建日期
    // - HAS_ATTACHMENT：是否有附件
    // - MODIFIED_DATE：修改日期
    // - NOTES_COUNT：子笔记数量（仅文件夹使用）
    // - SNIPPET：笔记内容片段或文件夹名称
    // - TYPE：类型（笔记、文件夹、系统文件夹）
    // - WIDGET_ID：关联的小部件ID
    // - WIDGET_TYPE：小部件类型
    // - SYNC_ID：同步ID
    // - LOCAL_MODIFIED：本地是否修改
    // - ORIGIN_PARENT_ID：原始父文件夹ID
    // - GTASK_ID：Google任务ID
    // - VERSION：版本号
    private static final String CREATE_NOTE_TABLE_SQL =
            "CREATE TABLE " + TABLE.NOTE + "(" +
                    NoteColumns.ID + " INTEGER PRIMARY KEY," +
                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
                    NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.IS_PINNED + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.PIN_PRIORITY + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.IS_LOCKED + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.LOCK_PASSWORD + " TEXT NOT NULL DEFAULT ''," +
                    NoteColumns.TAGS + " TEXT NOT NULL DEFAULT ''" +
                    ")";

    // 创建数据表的SQL语句
    // 数据表存储笔记的详细内容，支持多种类型的笔记数据，包括：
    // - ID：唯一标识符
    // - MIME_TYPE：数据类型，如文本笔记、通话笔记等
    // - NOTE_ID：关联的笔记ID
    // - CREATED_DATE：创建日期
    // - MODIFIED_DATE：修改日期
    // - CONTENT：数据内容
    // - DATA1, DATA2, DATA3, DATA4, DATA5：扩展字段，根据不同数据类型存储不同信息
    private static final String CREATE_DATA_TABLE_SQL =
            "CREATE TABLE " + TABLE.DATA + "(" +
                    DataColumns.ID + " INTEGER PRIMARY KEY," +
                    DataColumns.MIME_TYPE + " TEXT NOT NULL," +
                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
                    DataColumns.DATA1 + " INTEGER," +
                    DataColumns.DATA2 + " INTEGER," +
                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
                    ")";

    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
            "CREATE INDEX IF NOT EXISTS note_id_index ON " +
                    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";

    /**
     * 当将笔记移动到文件夹时，增加文件夹的笔记计数
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
            "CREATE TRIGGER increase_folder_count_on_update "+
                    " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
                    " BEGIN " +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
                    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
                    " END";

    /**
     * 当将笔记从文件夹移出时，减少文件夹的笔记计数
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
            "CREATE TRIGGER decrease_folder_count_on_update " +
                    " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
                    " BEGIN " +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
                    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
                    "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
                    " END";

    /**
     * 当向文件夹插入新笔记时，增加文件夹的笔记计数
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
            "CREATE TRIGGER increase_folder_count_on_insert " +
                    " AFTER INSERT ON " + TABLE.NOTE +
                    " BEGIN " +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
                    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
                    " END";

    /**
     * 当从文件夹删除笔记时，减少文件夹的笔记计数
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
            "CREATE TRIGGER decrease_folder_count_on_delete " +
                    " AFTER DELETE ON " + TABLE.NOTE +
                    " BEGIN " +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
                    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
                    "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
                    " END";

    /**
     * 当插入类型为普通笔记的数据时，更新笔记内容
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
            "CREATE TRIGGER update_note_content_on_insert " +
                    " AFTER INSERT ON " + TABLE.DATA +
                    " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
                    " BEGIN" +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
                    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
                    " END";

    /**
     * 当类型为普通笔记的数据发生变化时，更新笔记内容
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
            "CREATE TRIGGER update_note_content_on_update " +
                    " AFTER UPDATE ON " + TABLE.DATA +
                    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
                    " BEGIN" +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
                    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
                    " END";

    /**
     * 当类型为普通笔记的数据被删除时，更新笔记内容
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
            "CREATE TRIGGER update_note_content_on_delete " +
                    " AFTER delete ON " + TABLE.DATA +
                    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
                    " BEGIN" +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.SNIPPET + "=''" +
                    "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
                    " END";

    /**
     * 删除属于已删除笔记的数据
     */
    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
            "CREATE TRIGGER delete_data_on_delete " +
                    " AFTER DELETE ON " + TABLE.NOTE +
                    " BEGIN" +
                    "  DELETE FROM " + TABLE.DATA +
                    "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
                    " END";

    /**
     * 删除属于已删除文件夹的笔记
     */
    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
            "CREATE TRIGGER folder_delete_notes_on_delete " +
                    " AFTER DELETE ON " + TABLE.NOTE +
                    " BEGIN" +
                    "  DELETE FROM " + TABLE.NOTE +
                    "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
                    " END";

    /**
     * 将属于已移至回收站的文件夹的笔记也移至回收站
     */
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
            "CREATE TRIGGER folder_move_notes_on_trash " +
                    " AFTER UPDATE ON " + TABLE.NOTE +
                    " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
                    " BEGIN" +
                    "  UPDATE " + TABLE.NOTE +
                    "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
                    "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
                    " END";

    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    /**
     * 创建笔记表及其相关触发器和系统文件夹
     * @param db SQLite数据库实例
     */
    public void createNoteTable(SQLiteDatabase db) {
        // 创建笔记表
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        // 重新创建笔记表相关触发器
        reCreateNoteTableTriggers(db);
        // 创建系统文件夹
        createSystemFolder(db);
        // 记录日志
        Log.d(TAG, "note table has been created");
    }

    /**
     * 重新创建笔记表相关触发器，确保触发器的正确性和一致性
     * @param db SQLite数据库实例
     */
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 删除已存在的触发器
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");

        // 创建新的触发器
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER); // 更新笔记父文件夹时增加目标文件夹的笔记计数
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER); // 更新笔记父文件夹时减少原文件夹的笔记计数
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER); // 删除笔记时减少父文件夹的笔记计数
        db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER); // 删除笔记时删除关联的数据
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER); // 插入笔记时增加父文件夹的笔记计数
        db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER); // 删除文件夹时删除其所有子笔记
        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER); // 将文件夹移到回收站时，将其所有子笔记也移到回收站
    }

    /**
     * 创建系统文件夹
     * 系统文件夹用于管理不同类型的笔记，包括：
     * - 通话记录文件夹：存储通话记录
     * - 根文件夹：默认文件夹，用于存储普通笔记
     * - 临时文件夹：用于移动笔记时的临时存储
     * - 回收站文件夹：用于存储被删除的笔记和文件夹
     * @param db SQLite数据库实例
     */
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();

        // 创建通话记录文件夹：用于存储通话记录
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建根文件夹：默认文件夹，用于存储普通笔记
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建临时文件夹：用于移动笔记时的临时存储
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建回收站文件夹：用于存储被删除的笔记和文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    /**
     * 获取NotesDatabaseHelper的单例实例
     * 使用同步方法确保线程安全，避免多线程环境下创建多个实例
     * @param context 上下文对象
     * @return NotesDatabaseHelper的单例实例
     */
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    /**
     * 创建数据表及其相关触发器和索引
     * @param db SQLite数据库实例
     */
    public void createDataTable(SQLiteDatabase db) {
        // 创建数据表
        db.execSQL(CREATE_DATA_TABLE_SQL);
        // 重新创建数据表相关触发器
        reCreateDataTableTriggers(db);
        // 为data表的note_id字段创建索引，提高查询效率
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        // 记录日志
        Log.d(TAG, "data table has been created");
    }

    /**
     * 重新创建数据表相关触发器，确保触发器的正确性和一致性
     * @param db SQLite数据库实例
     */
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 删除已存在的数据表触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");

        // 创建新的数据表触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER); // 插入文本笔记数据时更新笔记内容
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER); // 更新文本笔记数据时更新笔记内容
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER); // 删除文本笔记数据时清空笔记内容
    }

    /**
     * 创建数据库时调用，初始化数据库表结构和数据
     * @param db SQLite数据库实例
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建笔记表及其相关触发器和系统文件夹
        createNoteTable(db);
        // 创建数据表及其相关触发器和索引
        createDataTable(db);
    }

    /**
     * 数据库升级时调用，处理不同版本之间的升级逻辑
     * @param db SQLite数据库实例
     * @param oldVersion 旧数据库版本号
     * @param newVersion 新数据库版本号
     * @throws IllegalStateException 升级失败时抛出异常
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false; // 是否需要重新创建触发器
        boolean skipV2 = false; // 是否跳过v2版本升级

        // 从v1升级到v2
        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // v2到v3的升级已包含在v1到v2的升级中
            oldVersion++;
        }

        // 从v2升级到v3
        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true; // v3升级需要重新创建触发器
            oldVersion++;
        }

        // 从v3升级到v4
        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        }

        // 从v4升级到v5
        if (oldVersion == 4) {
            upgradeToV5(db);
            oldVersion++;
        }

        if (oldVersion == 5) {
            upgradeToV6(db);
            oldVersion++;
        }

        if (oldVersion == 6) {
            upgradeToV7(db);
            oldVersion++;
        }

        if (oldVersion == 7) {
            upgradeToV8(db);
            oldVersion++;
        }
        
        if (oldVersion == 8) {
            upgradeToV9(db);
            oldVersion++;
        }

        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }

        // 检查升级是否成功
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion + " fails");
        }
    }

    /**
     * 将数据库从v1升级到v2
     * 此版本升级重建了整个数据库结构
     * @param db SQLite数据库实例
     */
    private void upgradeToV2(SQLiteDatabase db) {
        // 删除旧的笔记表和数据表
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
        // 创建新的笔记表
        createNoteTable(db);
        // 创建新的数据表
        createDataTable(db);
    }

    /**
     * 将数据库从v2升级到v3
     * 此版本升级添加了Google任务ID字段和回收站文件夹
     * @param db SQLite数据库实例
     */
    private void upgradeToV3(SQLiteDatabase db) {
        // 删除不再使用的触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");
        // 为笔记表添加Google任务ID字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                + " TEXT NOT NULL DEFAULT ''");
        // 添加回收站系统文件夹
        ContentValues values = new ContentValues();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    /**
     * 将数据库从v3升级到v4
     * 此版本升级添加了版本号字段，用于记录笔记的版本
     * @param db SQLite数据库实例
     */
    private void upgradeToV4(SQLiteDatabase db) {
        // 为笔记表添加版本号字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }

    /**
     * 将数据库从v4升级到v5
     * 此版本升级添加了置顶状态和置顶优先级字段，用于支持便签置顶功能
     * @param db SQLite数据库实例
     */
    private void upgradeToV5(SQLiteDatabase db) {
        // 为笔记表添加置顶状态字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.IS_PINNED
                + " INTEGER NOT NULL DEFAULT 0");
        // 为笔记表添加置顶优先级字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.PIN_PRIORITY
                + " INTEGER NOT NULL DEFAULT 0");
    }

    /**
     * 将数据库从v5升级到v6
     * 此版本升级添加了便签锁定状态和密码字段，用于支持便签密码锁功能
     * @param db SQLite数据库实例
     */
    private void upgradeToV6(SQLiteDatabase db) {
        // 为笔记表添加锁定状态字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.IS_LOCKED
                + " INTEGER NOT NULL DEFAULT 0");
        // 为笔记表添加密码字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.LOCK_PASSWORD
                + " TEXT NOT NULL DEFAULT ''");
    }

    /**
     * 将数据库从v6升级到v7
     * 此版本升级添加了密码类型字段，用于支持手势密码和数字密码
     * @param db SQLite数据库实例
     */
    private void upgradeToV7(SQLiteDatabase db) {
        // 为笔记表添加密码类型字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.PASSWORD_TYPE
                + " TEXT NOT NULL DEFAULT 'gesture'");
        // 为笔记表添加数字密码字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.NUMERIC_PASSWORD
                + " TEXT NOT NULL DEFAULT ''");
    }

    /**
     * 将数据库从v7升级到v8
     * 此版本升级添加了标题字段，用于支持便签标题功能
     * @param db SQLite数据库实例
     */
    private void upgradeToV8(SQLiteDatabase db) {
        // 为笔记表添加标题字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.TITLE
                + " TEXT NOT NULL DEFAULT ''");
    }
    
    /**
     * 将数据库从v8升级到v9
     * 此版本升级添加了标签字段，用于支持便签标签功能
     * @param db SQLite数据库实例
     */
    private void upgradeToV9(SQLiteDatabase db) {
        // 为笔记表添加标签字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.TAGS
                + " TEXT NOT NULL DEFAULT ''");
    }
}