/*
 * 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.
 */

// 包声明，表明该类属于 net.micode.notes.data 包
package net.micode.notes.data;

// 导入用于存储键值对，通常用于数据库操作中插入数据
import android.content.ContentValues;
// 导入 Android 上下文类，用于获取应用程序的环境信息
import android.content.Context;
// 导入 SQLite 数据库操作类，用于对数据库进行读写操作
import android.database.sqlite.SQLiteDatabase;
// 导入 SQLite 数据库辅助类，用于管理数据库的创建和版本更新
import android.database.sqlite.SQLiteOpenHelper;
// 导入日志工具类，用于在开发和调试过程中记录信息
import android.util.Log;

// 导入 Notes 类中的 DataColumns 接口，用于引用数据列的常量
import net.micode.notes.data.Notes.DataColumns;
// 导入 Notes 类中的 DataConstants 类，用于引用数据相关的常量
import net.micode.notes.data.Notes.DataConstants;
// 导入 Notes 类中的 NoteColumns 接口，用于引用笔记列的常量
import net.micode.notes.data.Notes.NoteColumns;

/**
 * NotesDatabaseHelper 类继承自 SQLiteOpenHelper，用于管理笔记应用的 SQLite 数据库。
 * 它负责创建数据库、表，以及处理数据库版本升级等操作。
 */
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
    private static final int DB_VERSION = 4;

    /**
     * TABLE 接口定义了数据库中表的名称常量
     */
    public interface TABLE {
        // 笔记表的名称
        public static final String NOTE = "note";
        // 数据表的名称
        public static final String DATA = "data";
    }

    // 日志标签，用于在日志中标识该类的信息
    private static final String TAG = "NotesDatabaseHelper";
    // 单例模式下的实例对象
    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," +
                    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" +
                    ")";

    // 创建数据表的 SQL 语句
    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 ''" +
                    ")";

    // 创建数据表中 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 + ");";

    /**
     * 当笔记移动到文件夹时，增加文件夹的笔记数量的触发器 SQL 语句
     */
    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";

    /**
     * 当笔记从文件夹移出时，减少文件夹的笔记数量的触发器 SQL 语句
     */
    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";

    /**
     * 当新笔记插入到文件夹时，增加文件夹的笔记数量的触发器 SQL 语句
     */
    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";

    /**
     * 当笔记从文件夹删除时，减少文件夹的笔记数量的触发器 SQL 语句
     */
    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 {@link DataConstants#NOTE} 的数据时，更新笔记内容的触发器 SQL 语句
     */
    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 {@link DataConstants#NOTE} 的数据更新时，更新笔记内容的触发器 SQL 语句
     */
    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 {@link DataConstants#NOTE} 的数据删除时，更新笔记内容的触发器 SQL 语句
     */
    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";

    /**
     * 当笔记删除时，删除该笔记关联的数据的触发器 SQL 语句
     */
    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";

    /**
     * 当文件夹删除时，删除该文件夹下的所有笔记的触发器 SQL 语句
     */
    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";

    /**
     * 当文件夹移动到回收站时，将该文件夹下的所有笔记也移动到回收站的触发器 SQL 语句
     */
    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，用于初始化 NotesDatabaseHelper 实例
     * @param context 应用程序上下文
     */
    public NotesDatabaseHelper(Context context) {
        // 调用父类 SQLiteOpenHelper 的构造函数，传入上下文、数据库名、游标工厂和数据库版本号
        super(context, DB_NAME, null, DB_VERSION);
    }

    /**
     * 创建笔记表，并设置相关触发器和创建系统文件夹
     * @param db SQLite 数据库对象
     */
    public void createNoteTable(SQLiteDatabase db) {
        // 执行创建笔记表的 SQL 语句
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        // 重新创建笔记表的触发器
        reCreateNoteTableTriggers(db);
        // 创建系统文件夹
        createSystemFolder(db);
        // 记录日志，表明笔记表已创建
        Log.d(TAG, "note table has been created");
    }

    /**
     * 重新创建笔记表的触发器
     * @param db SQLite 数据库对象
     */
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 删除旧的触发器
        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);
        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，如通话记录文件夹、根文件夹、临时文件夹和回收站文件夹
     * @param db SQLite 数据库对象
     */
    private void createSystemFolder(SQLiteDatabase db) {
        // 用于存储要插入的数据
        ContentValues values = new ContentValues();

        /**
         * 创建通话记录文件夹
         */
        // 设置文件夹的 ID
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        // 设置文件夹的类型为系统文件夹
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        // 插入数据到笔记表
        db.insert(TABLE.NOTE, null, values);

        /**
         * 创建根文件夹
         */
        // 清空之前存储的数据
        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
         */
        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，并设置相关触发器和创建索引
     * @param db SQLite 数据库对象
     */
    public void createDataTable(SQLiteDatabase db) {
        // 执行创建数据表的 SQL 语句
        db.execSQL(CREATE_DATA_TABLE_SQL);
        // 重新创建数据表的触发器
        reCreateDataTableTriggers(db);
        // 执行创建数据表中 note_id 索引的 SQL 语句
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        // 记录日志，表明数据表已创建
        Log.d(TAG, "data table has been created");
    }

    /**
     * 重新创建数据表的触发器
     * @param db SQLite 数据库对象
     */
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 删除旧的触发器
        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 NotesDatabaseHelper 的单例实例
     * @param context 应用程序上下文
     * @return NotesDatabaseHelper 实例
     */
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        // 检查实例是否为空
        if (mInstance == null) {
            // 如果为空，则创建新的实例
            mInstance = new NotesDatabaseHelper(context);
        }
        // 返回实例
        return mInstance;
    }

    /**
     * 当数据库第一次创建时调用，用于创建笔记表和数据表
     * @param db SQLite 数据库对象
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建笔记表
        createNoteTable(db);
        // 创建数据表
        createDataTable(db);
    }

    /**
     * 当数据库版本升级时调用，根据旧版本和新版本进行相应的升级操作
     * @param db         SQLite 数据库对象
     * @param oldVersion 旧的数据库版本号
     * @param newVersion 新的数据库版本号
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 标记是否需要重新创建触发器
        boolean reCreateTriggers = false;
        // 标记是否跳过从版本 2 到版本 3 的升级
        boolean skipV2 = false;

        // 如果旧版本是 1
        if (oldVersion == 1) {
            // 升级到版本 2
            upgradeToV2(db);
            // 标记跳过从版本 2 到版本 3 的升级
            skipV2 = true;
            // 旧版本号加 1
            oldVersion++;
        }

        // 如果旧版本是 2 且不跳过升级
        if (oldVersion == 2 && !skipV2) {
            // 升级到版本 3
            upgradeToV3(db);
            // 标记需要重新创建触发器
            reCreateTriggers = true;
            oldVersion++;
        }

        // 如果旧版本是 3
        if (oldVersion == 3) {
            // 升级到版本 4
            upgradeToV4(db);
            oldVersion++;
        }

        // 如果需要重新创建触发器
        if (reCreateTriggers) {
            // 重新创建笔记表的触发器
            reCreateNoteTableTriggers(db);
            // 重新创建数据表的触发器
            reCreateDataTableTriggers(db);
        }

        // 如果旧版本号不等于新版本号，说明升级失败，抛出异常
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }

    /**
     * 将数据库从版本 1 升级到版本 2
     * @param db SQLite 数据库对象
     */
    private void upgradeToV2(SQLiteDatabase db) {
        // 删除旧的笔记表
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        // 删除旧的数据表
        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);
    }

    /**
     * 将数据库从版本 2 升级到版本 3
     * @param db SQLite 数据库对象
     */
    private void upgradeToV3(SQLiteDatabase db) {
        // 删除无用的触发器
        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 gtask_id 列
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                + " TEXT NOT NULL DEFAULT ''");
        // 创建回收站系统文件夹
        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);
    }

    /**
     * 将数据库从版本 3 升级到版本 4
     * @param db SQLite 数据库对象
     */
    private void upgradeToV4(SQLiteDatabase db) {
        // 为笔记表添加 version 列
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}