/*
 * 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; //1

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;
/**
 * 笔记数据库帮助类，负责数据库的创建、升级以及表结构管理
 * 采用单例模式确保全局唯一数据库实例
 */

public class NotesDatabaseHelper extends SQLiteOpenHelper {
     // 数据库元数据配置
    private static final String DB_NAME = "note.db";// 数据库文件名

    private static final int DB_VERSION = 4;// 当前数据库版本
     // 表名常量接口
    public interface TABLE {
        public static final String NOTE = "note";// 主表：存储笔记元信息（标题、创建时间、父目录等）

        public static final String DATA = "data";// 数据表：存储笔记具体内容及扩展数据
    }

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

    private static NotesDatabaseHelper mInstance; // 单例实例
    // Note表建表语句
    private static final String CREATE_NOTE_TABLE_SQL =
        "CREATE TABLE " + TABLE.NOTE + "(" +
            NoteColumns.ID + " INTEGER PRIMARY KEY," +// 笔记唯一标识
            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +// 所属文件夹ID（树形结构）
            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +// 提醒时间（毫秒时间戳）
            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +// 背景颜色标识
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +// 是否有附件（0/1布尔值）
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +// 最后修改时间
            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," + // 子项数量（用于文件夹）
            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +// 内容摘要
            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," + // 笔记类型（普通笔记、文件夹等）
            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +// 关联的小部件ID
            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +// 小部件类型
            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +// 同步标识
            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +// 本地修改标记
            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +// 原始父目录（用于同步）
            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +// Google Task关联ID
            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" + // 数据版本号（乐观锁）
        ")";
// Data表建表语句
    private static final String CREATE_DATA_TABLE_SQL =
        "CREATE TABLE " + TABLE.DATA + "(" +
            DataColumns.ID + " INTEGER PRIMARY KEY," +// 数据项唯一标识
            DataColumns.MIME_TYPE + " TEXT NOT NULL," +// MIME类型（文本、清单、媒体等）
            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)," +// 同步创建时间
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +// 同步修改时间
            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +// 主要内容存储
            DataColumns.DATA1 + " INTEGER," +// 扩展字段1（类型相关数据）
            DataColumns.DATA2 + " INTEGER," +// 扩展字段2（如清单项状态）
            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +// 扩展字段3（如地理位置）
            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +// 扩展字段4（如附件路径）
            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +// 扩展字段5（保留字段）
        ")";
// 数据表索引：加速按笔记ID查询数据项
    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：当更新笔记的父目录时，增加新文件夹的计数
    // 场景示例：把笔记A从文件夹X移动到文件夹Y时，Y的计数+1
    /**
     * Increase folder's note count when move note to the folder
     */
    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：当更新笔记的父目录时，减少原文件夹的计数
    // 场景示例：同上移动操作时，X的计数-1（需>0时生效）
    /**
     * Decrease folder's note count when move note from folder
     */
    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：插入新笔记时增加所在文件夹的计数
    /**
     * Increase folder's note count when insert new note to the folder
     */
    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：删除笔记时减少原文件夹的计数（防止负数）
    /**
     * Decrease folder's note count when delete note from the folder
     */
    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";
/**
     * 插入NOTE类型数据时自动更新笔记摘要
     * 场景：当在data表插入类型为普通笔记的数据时，自动更新note表的snippet字段
     */
    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     */
    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 + "'" +// 仅处理普通笔记类型
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +// 使用新插入的内容更新摘要
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +// 通过NOTE_ID关联
        " END";
 /**
     * 更新NOTE类型数据时同步更新笔记摘要
     * 场景：修改已有笔记内容时（如编辑文本），自动更新对应笔记摘要
     */
    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has changed
     */
    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 + "'" +// 仅处理原类型为笔记的记录
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +// 同步最新内容到摘要
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
        " END";
/**
     * 删除NOTE类型数据时清空笔记摘要
     * 场景：当删除笔记的正文数据时，自动清空对应笔记的摘要
     */
    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
     */
    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 + "=''" +// 清空摘要内容
        "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
        " END";
/**
     * 笔记级联删除触发器
     * 场景：当删除note表的记录时，自动删除关联的data表数据
     * 作用：防止产生孤儿数据（没有对应笔记的数据项）
     */
    /**
     * Delete datas belong to note which has been deleted
     */
    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 + ";" +// 根据被删除笔记ID清理数据
        " END";
 /**
     * 文件夹级联删除触发器
     * 场景：当删除文件夹时，自动删除其下所有笔记
     * 注意：会触发delete_data_on_delete触发器进行二次清理
     */
    /**
     * Delete notes belong to folder which has been deleted
     */
    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 + ";" +// 删除所有父目录为被删文件夹的笔记
        " END";
 /**
     * 文件夹移动至回收站操作触发器
     * 场景：当文件夹被移动到回收站时，自动将其子项也移动到回收站
     * 设计目的：保持文件夹结构的完整性
     */
    /**
     * Move notes belong to folder which has been moved to trash folder
     */
    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 +// 检测是否移动到回收站
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +// 批量更新子项父目录为回收站
        "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" + // 选择原父目录下的所有笔记
        " END";
 /**
     * 初始化系统文件夹（首次创建数据库时调用）
     * 插入预定义的系统文件夹：
     * 1. 通话记录文件夹（ID_CALL_RECORD_FOLDER）
     * 2. 根文件夹（ID_ROOT_FOLDER）
     * 3. 临时文件夹（ID_TEMPARAY_FOLDER）
     * 4. 回收站（ID_TRASH_FOLER）
     */
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db);
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }

    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        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");

        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);
    }

    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();
 // 插入通话记录文件夹
        /**
         * call record foler for call notes
         */
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);// 标记为系统文件夹
        db.insert(TABLE.NOTE, null, values);
 // 插入根文件夹（默认笔记存储位置）
        /**
         * root folder which is default folder
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
 // 插入临时文件夹（用于笔记移动操作时的暂存区）
        /**
         * temporary folder which is used for moving note
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
 // 插入回收站（软删除数据存储位置）
        /**
         * create trash folder
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL);
        reCreateDataTableTriggers(db);
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        Log.d(TAG, "data table has been created");
    }

    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        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");

        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);
    }

    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }
 /**
     * 数据库版本升级控制中心
     * 升级策略：
     * V1 → V2：完全重建表结构（破坏性升级）
     * V2 → V3：添加Google Task支持 + 创建回收站
     * V3 → V4：添加版本控制字段
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false;
        boolean skipV2 = false;
// V1到V2升级策略：完全重建表结构
        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3// 包含V2到V3的升级逻辑
            oldVersion++;
        }
 // V2到V3升级策略：非破坏性升级
        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true;// 需要重建触发器
            oldVersion++;
        }
 // V3到V4升级策略：添加版本字段
        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        }
// 重建触发器（当表结构变化可能影响触发器时）
        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }
// 版本检查容错
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }
/**
     * 升级到V2版本（破坏性升级）
     * 操作说明：
     * 1. 删除旧表
     * 2. 重建表结构
     * 3. 初始化系统文件夹
     */
    private void upgradeToV2(SQLiteDatabase db) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
        createNoteTable(db);
        createDataTable(db);
    }
 /**
     * 升级到V3版本（功能增强）
     * 主要变更：
     * 1. 移除过期的修改时间触发器
     * 2. 新增GTASK_ID字段（用于Google Tasks同步）
     * 3. 初始化回收站文件夹
     */
    private void upgradeToV3(SQLiteDatabase db) {
        // drop unused triggers// 移除旧版的时间更新触发器
        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");
        // add a column for gtask id// 添加Google Task关联字段
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                + " TEXT NOT NULL DEFAULT ''");
        // add a trash system folder// 插入回收站系统文件夹
        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V4版本（数据版本控制）
     * 新增字段：VERSION（用于实现乐观锁机制）
     */
    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}