/*
 * 版权所有 (c) 2010-2011，MiCode 开源社区 (www.micode.net)
 * 根据 Apache 许可证 2.0 版本（"许可证"）授权；
 * 除非符合许可证的规定，否则不得使用本文件。
 * 您可以从以下网址获取许可证副本：
 * http://www.apache.org/licenses/LICENSE-2.0
 * 除非适用法律要求或书面同意，本软件按"原样"分发，
 * 没有任何明示或暗示的保证或条件。
 * 详见许可证中规定的权限和限制。
 *（注：这是一份标准的Apache许可证2.0版本的开源声明）
*/

// 笔记应用的数据库辅助类，用于创建和管理SQLite数据库
package net.micode.notes.data;

// 导入所需的Android类
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

// 导入项目中的笔记数据相关常量
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.DataConstants;
import net.micode.notes.data.Notes.NoteColumns;

// SQLiteOpenHelper的子类，用于管理笔记数据库
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 数据库名称常量
    private static final String DB_NAME = "note.db";

    // 数据库版本号常量
    private static final int DB_VERSION = 4;

    // 内部接口，定义数据库表名
    public interface TABLE {
        public static final String NOTE = "note";  // 笔记表名
        public static final String DATA = "data";  // 数据表名
    }

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

    // 单例实例
    private static NotesDatabaseHelper mInstance;

    // 创建笔记表的SQL语句
    private static final String CREATE_NOTE_TABLE_SQL =
            "CREATE TABLE " + TABLE.NOTE + "(" +
                    NoteColumns.ID + " INTEGER PRIMARY KEY," +                 // ID主键
                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +  // 父ID
                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," + // 提醒日期
                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," + // 背景色ID
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期(当前时间戳)
                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," + // 是否有附件
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期
                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," + // 笔记数量
                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +       // 内容摘要
                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +        // 类型
                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +   // 小部件ID
                    NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," + // 小部件类型
                    NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +     // 同步ID
                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," + // 本地修改标志
                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 原始父ID
                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +      // Google任务ID
                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +      // 版本号
                    ")";

    // 创建数据表的SQL语句
    private static final String CREATE_DATA_TABLE_SQL =
            "CREATE TABLE " + TABLE.DATA + "(" +
                    DataColumns.ID + " INTEGER PRIMARY KEY," +                // ID主键
                    DataColumns.MIME_TYPE + " TEXT NOT NULL," +              // MIME类型
                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +    // 关联的笔记ID
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期
                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +     // 内容
                    DataColumns.DATA1 + " INTEGER," +                         // 通用数据列1
                    DataColumns.DATA2 + " INTEGER," +                         // 通用数据列2
                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +       // 通用数据列3
                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +       // 通用数据列4
                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +        // 通用数据列5
                    ")";

    // 创建数据表note_id索引的SQL语句
    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
            "CREATE INDEX IF NOT EXISTS note_id_index ON " +
                    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";

    /**
     * 触发器：当笔记的父ID更新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";

    /**
     * 触发器：当笔记的父ID更新时减少原文件夹的笔记计数
     */
    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";

    /**
     * 触发器：当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";

    /**
     * 触发器：当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";

    /**
     * 触发器：当插入数据且类型为普通笔记时更新笔记内容
     */
    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";

    /**
     * 触发器：当更新数据且类型为普通笔记时更新笔记内容
     */
    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";

    /**
     * 触发器：当删除数据且类型为普通笔记时清空笔记内容
     */
    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";

    /**
     * 触发器：当删除笔记时删除关联的所有数据
     */
    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";

    /**
     * 触发器：当删除文件夹时删除其中的所有笔记
     */
    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";

    /**
     * 触发器：当文件夹被移动到回收站时，将其中的笔记也移动到回收站
     */
    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";

    // 构造函数
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    // 创建笔记表
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);   // 执行建表SQL
        reCreateNoteTableTriggers(db);      // 重建触发器
        createSystemFolder(db);             // 创建系统文件夹
        Log.d(TAG, "note table has been created");  // 日志记录
    }

    // 重建笔记表触发器
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 删除旧触发器
        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");

        // 创建新触发器
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER);
        db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER);
        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
    }

    // 创建系统文件夹
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();

        /*
         * 创建通话记录文件夹
         */
        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)
         */
        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)
         */
        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
         */
        values.clear();
        values.put(NoteColumns.ID,  Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE,  Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE,  null, values);
    }

    // 创建数据表
    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL);   // 执行建表SQL
        reCreateDataTableTriggers(db);      // 重建触发器
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);   // 创建索引
        Log.d(TAG, "data table has been created");  // 日志记录
    }

    // 重建数据表触发器
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 删除旧触发器
        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");

        // 创建新触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
    }

    // 获取单例实例(线程安全)
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    // 数据库创建时的回调方法
    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);  // 创建笔记表
        createDataTable(db);  // 创建数据表
    }

    // 数据库升级时的回调方法
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false;  // 是否需要重建触发器
        boolean skipV2 = false;           // 是否跳过V2升级

        // 从版本1升级到版本2
        if (oldVersion == 1) {
            upgradeToV2(db);     // 执行V2升级
            skipV2 = true;       // 此次升级包含从V2到V3的升级
            oldVersion++;         // 版本号递增
        }

        // 从版本2升级到版本3(如果不需要跳过)
        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);     // 执行V3升级
            reCreateTriggers = true;  // 需要重建触发器
            oldVersion++;         // 版本号递增
        }

        // 从版本3升级到版本4
        if (oldVersion == 3) {
            upgradeToV4(db);     // 执行V4升级
            oldVersion++;         // 版本号递增
        }

        // 如果需要重建触发器
        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);  // 重建笔记表触发器
            reCreateDataTableTriggers(db);  // 重建数据表触发器
        }

        // 如果升级未完成，抛出异常
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion + "fails");
        }
    }

    // 升级到版本2的实现
    private void upgradeToV2(SQLiteDatabase db) {
        // 删除旧表(如果存在)
        db.execSQL("DROP  TABLE IF EXISTS " + TABLE.NOTE);
        db.execSQL("DROP  TABLE IF EXISTS " + TABLE.DATA);
        // 重新创建表
        createNoteTable(db);  // 创建笔记表
        createDataTable(db);  // 创建数据表
    }

    // 升级到版本3的实现
    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");

        // 添加gtask_id列
        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);
    }

    // 升级到版本4的实现
    private void upgradeToV4(SQLiteDatabase db) {
        // 添加version列
        db.execSQL("ALTER  TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0");
    }
}