/*
 * 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.
 */


// 为Note数据库管理类定义了一个包名称
package net.micode.notes.data;

// 导入所需的类
// 导入ContentValues类，用于存储和传递以键值对形式存储的数据，便于操作数据库中的行
import android.content.ContentValues;
// 导入Context类，代表应用程序环境的上下文，可以访问应用级别的资源、类和服务
import android.content.Context;
// 导入SQLiteDatabase类，代表SQLite数据库的一个实例，提供创建、查询、更新和删除数据库中数据的方法
import android.database.sqlite.SQLiteDatabase;
// 导入SQLiteOpenHelper类，用于管理数据库的创建和版本管理，是SQLite数据库访问的一个辅助类
import android.database.sqlite.SQLiteOpenHelper;
// 导入Log类，用于输出日志，方便调试和测试
import android.util.Log;

// 导入DataColumns接口，定义了Notes数据库中data表的数据库列名和类型
import net.micode.notes.data.Notes.DataColumns;
// 导入DataConstants类，定义了与Notes数据相关联的一些常量值
import net.micode.notes.data.Notes.DataConstants;
// 导入NoteColumns接口，定义了Notes数据库中note表的数据库列名和类型
import net.micode.notes.data.Notes.NoteColumns;

// 创建一个数据库帮助类，用于处理记事本应用的数据库创建和版本管理
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 定义数据库的名称和版本
    private static final String DB_NAME = "note.db";

    private static final int DB_VERSION = 4;
    // 定义表名的常量接口

    public interface TABLE {
        public static final String NOTE = "note";

        public static final String DATA = "data";
    }
    // 日志记录的标签

    private static final String TAG = "NotesDatabaseHelper";
    // 使用单例模式，保证只有一个实例化对象

    private static NotesDatabaseHelper mInstance;
    // 包含创建Note表SQL语句的字符串

    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" +
                    ")";
    // 包含创建Data表SQL语句的字符串

    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 ''" +
                    ")";
    // 包含创建Data的Note表索引SQL语句的字符串

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

    /**
     * Increase folder's note count when move note to the folder
     */
    // 包含创建触发器的SQL语句的字符串
    // 触发器用于在更新、插入或删除note时自动更新相关的信息。
    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";

    /**
     * Decrease folder's note count when move note from folder
     */
    //在更新笔记的PARENT_ID字段后，更新父文件夹的NOTES_COUNT字段，将其减少1。
    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";

    /**
     * Increase folder's note count when insert new note to the folder
     */
    //在插入新笔记到文件夹时，更新父文件夹的NOTES_COUNT字段，将其增加1。
    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";

    /**
     * Decrease folder's note count when delete note from the folder
     */
    //在从文件夹中删除笔记时，更新父文件夹的NOTES_COUNT字段，将其减少1。
    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";

    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     */
    //在插入类型为"NOTE"的新数据时，更新笔记的内容。
    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";

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has changed
     */
    //当类型为"NOTE"的数据发生更改时，更新笔记的内容。
    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";

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
     */
    //当类型为"NOTE"的数据被删除时，更新笔记的内容。
    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";

    /**
     * Delete datas belong to note which has been deleted
     */
    //当删除一个笔记时，删除与该笔记关联的数据。
    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";

    /**
     * Delete notes belong to folder which has been deleted
     */
    //当删除一个文件夹时，删除属于该文件夹的所有笔记。
    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";

    /**
     * Move notes belong to folder which has been moved to trash folder
     */
    //当将一个文件夹移动到垃圾文件夹时，将属于该文件夹的所有笔记也移动到垃圾文件夹中。
    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";
    // 用来实例化NotesDatabaseHelper的公共构造函数。
    // 需要传入Context对象来实例化SQLiteOpenHelper。

    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }
    // 用于创建Note表的方法

    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db);
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }
    //方法用于重新创建笔记表的触发器。它首先删除现有的触发器，
    // 然后执行一系列的CREATE TRIGGER语句来创建新的触发器。
    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);
    }
    //用于创建系统文件夹。它向NOTE表中插入了一些系统文件夹的记录，
    // 包括通话记录文件夹、根文件夹、临时文件夹和垃圾文件夹。
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();

        /**
         * call record foler for call notes
         */
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        /**
         * 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);

        /**
         * 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);

        /**
         * 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);
    }
    //用于创建数据表。它首先执行一个CREATE TABLE语句来创建数据表，
    // 然后调用reCreateDataTableTriggers方法来重新创建数据表的触发器。
    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");
    }
    //用于重新创建数据表的触发器。
    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);
    }
    // getInstance方法用于获取NotesDatabaseHelper的单例对象。
    // 如果还没有创建，它会创建一个新的实例并返回；如果已经创建，它将返回现有实例。

    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }
    // 当数据库首次创建时调用onCreate方法。这个方法里调用前面定义的创建表的方法

    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }
    // 如果数据库版本升级，onUpgrade方法将被调用。
    // 这个方法包含多种情况下的升级逻辑，以确保数据库结构是最新的。

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false;
        boolean skipV2 = false;

        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        }

        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true;
            oldVersion++;
        }

        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        }

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

        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }
    // 包含从数据库版本1升级到版本2的方法。

    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);
    }
    // 包含从数据库版本2升级到版本3的方法。

    private void upgradeToV3(SQLiteDatabase db) {
        // drop unused triggers
        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
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                + " TEXT NOT NULL DEFAULT ''");
        // add a trash system folder
        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);
    }
    // 包含从数据库版本3升级到版本4的方法。

    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}

