/*
 * 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;


/**
 * 便签应用数据库辅助类，继承自SQLiteOpenHelper
 * 负责创建和管理数据库表结构、定义触发器、处理版本升级
 * 采用单例模式确保全局唯一数据库实例
 */
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 数据库文件名
    private static final String DB_NAME = "note.db";
    // 数据库版本号（当前为4）
    private static final int DB_VERSION = 4;

    /**
     * 数据库表名接口，定义note表和data表的常量名
     */
    public interface TABLE {
        public static final String NOTE = "note";       // 便签/文件夹主表
        public static final String DATA = "data";      // 便签详细数据/附件表
    }

    private static final String TAG = "NotesDatabaseHelper";
    // 单例实例引用
    private static NotesDatabaseHelper mInstance;

    /**
     * 创建note表的SQL语句（存储便签和文件夹基本信息）
     * 字段说明：
     * - ID: 主键
     * - PARENT_ID: 父文件夹ID
     * - ALERTED_DATE: 提醒日期（时间戳）
     * - BG_COLOR_ID: 背景色ID
     * - CREATED_DATE: 创建日期（默认当前时间戳）
     * - HAS_ATTACHMENT: 是否有附件（1=有）
     * - MODIFIED_DATE: 最后修改日期（默认当前时间戳）
     * - NOTES_COUNT: 文件夹包含的便签数
     * - SNIPPET: 便签内容或文件夹名称
     * - TYPE: 类型（便签/文件夹/系统）
     * - WIDGET_ID: 关联的桌面小部件ID
     * - WIDGET_TYPE: 小部件类型
     * - SYNC_ID: 同步ID（用于云同步）
     * - LOCAL_MODIFIED: 本地修改标识（1=已修改）
     * - ORIGIN_PARENT_ID: 原始父文件夹ID（移动时使用）
     * - GTASK_ID: Google任务ID
     * - VERSION: 数据版本号（用于冲突检测）
     */
    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" +
                    ")";

    /**
     * 创建data表的SQL语句（存储便签附件或扩展数据）
     * 字段说明：
     * - ID: 主键
     * - MIME_TYPE: 数据类型（如图片/音频）
     * - NOTE_ID: 关联的便签ID（外键）
     * - CREATED_DATE: 创建日期（默认当前时间戳）
     * - MODIFIED_DATE: 最后修改日期（默认当前时间戳）
     * - CONTENT: 数据内容（文本类型）
     * - DATA1-DATA5: 通用数据列（含义由MIME类型决定）
     */
    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 ''" +
                    ")";

    // 创建data表note_id索引的SQL（加速按便签ID查询）
    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：当便签移动到新文件夹时，增加目标文件夹的便签计数
     * 触发时机：note表的parent_id更新后
     */
    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：当便签移出文件夹时，减少原文件夹的便签计数
     * 触发时机：note表的parent_id更新后
     */
    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：当新便签插入到文件夹时，增加目标文件夹的便签计数
     * 触发时机：note表插入新记录后
     */
    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：当便签从文件夹删除时，减少原文件夹的便签计数
     * 触发时机：note表删除记录后
     */
    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：当插入文本便签数据时，更新note表的内容
     * 触发时机：data表插入MIME_TYPE为文本便签的记录后
     */
    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：当文本便签数据更新时，更新note表的内容
     * 触发时机：data表更新MIME_TYPE为文本便签的记录后
     */
    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：当删除文本便签数据时，清空note表的内容
     * 触发时机：data表删除MIME_TYPE为文本便签的记录后
     */
    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：当便签被删除时，级联删除其关联的附件数据
     * 触发时机：note表删除记录后
     */
    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：当文件夹被删除时，级联删除其包含的所有便签
     * 触发时机：note表删除记录后（仅针对文件夹类型）
     */
    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，将其包含的便签同步移动到回收站
     * 触发时机：note表更新parent_id为回收站ID后
     */
    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";

    /**
     * 构造方法，调用父类SQLiteOpenHelper初始化
     * @param context 应用上下文
     */
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    /**
     * 创建note表及相关触发器，并初始化系统文件夹
     * @param db 可写的SQLiteDatabase实例
     */
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db);
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }

    /**
     * 重建note表相关触发器（先删除旧触发器再创建新触发器）
     * @param db 可写的SQLiteDatabase实例
     */
    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);
    }

    /**
     * 创建系统默认文件夹（通话记录、根目录、临时文件夹、回收站）
     * @param db 可写的SQLiteDatabase实例
     */
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();

        /**
         * 通话记录文件夹（存储通话便签）
         */
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        /**
         * 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);

        /**
         * 临时文件夹（用于移动便签时的过渡存储）
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        /**
         * 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data表及相关触发器，并创建note_id索引
     * @param db 可写的SQLiteDatabase实例
     */
    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");
    }

    /**
     * 重建data表相关触发器（先删除旧触发器再创建新触发器）
     * @param db 可写的SQLiteDatabase实例
     */
    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);
    }

    /**
     * 获取数据库辅助类的单例实例（线程安全）
     * @param context 应用上下文
     * @return NotesDatabaseHelper实例
     */
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    /**
     * 数据库创建回调（首次创建数据库时调用）
     * 调用createNoteTable和createDataTable创建表结构
     * @param db 可写的SQLiteDatabase实例
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }

    /**
     * 数据库版本升级回调
     * 根据旧版本号执行对应的升级逻辑
     * @param db 可写的SQLiteDatabase实例
     * @param oldVersion 旧版本号
     * @param newVersion 新版本号
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false;
        boolean skipV2 = false;

        // 版本1升级到版本2（全量重建表结构）
        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // 该升级包含了版本2到版本3的逻辑
            oldVersion++;
        }

        // 版本2升级到版本3（添加GTASK_ID列和回收站文件夹）
        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true;
            oldVersion++;
        }

        // 版本3升级到版本4（添加VERSION列）
        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        }

        // 若触发器在升级过程中被修改，重新创建触发器
        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }

        // 若版本升级未完成，抛出异常（防止数据不一致）
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }

    /**
     * 版本1升级到版本2的具体实现（全量重建表结构）
     * @param db 可写的SQLiteDatabase实例
     */
    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);
    }

    /**
     * 版本2升级到版本3的具体实现（添加GTASK_ID列和回收站文件夹）
     * @param db 可写的SQLiteDatabase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");
        // 添加Google任务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);
    }

    /**
     * 版本3升级到版本4的具体实现（添加VERSION列）
     * @param db 可写的SQLiteDatabase实例
     */
    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}