/*
 * 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;//声明包

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;//数据库操作中保存数据信息


public class NotesDatabaseHelper extends SQLiteOpenHelper {//继承于SQLiteOpenHelper的类NotesDatabaseHelper，用于实现对便签或者 文件的数据库操作，例如删除便签
    private static final String DB_NAME = "note.db";//定义数据库的名称为“note.db”

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

    public interface TABLE {//将接口分成note和data
        public static final String NOTE = "note";//创建便签表的数据库

        public static final String DATA = "data";//数据库中需要存储的项目的名称，就类似创建一个表格的表头的内容。
    }

    private static final String TAG = "NotesDatabaseHelper";//存储便签编号的一个数据表格

    private static NotesDatabaseHelper mInstance;//创建类NotesDatabaseHelper的对象——mInstance

    private static final String CREATE_NOTE_TABLE_SQL =//文件夹增加Note后需要更改的数据的表格
        "CREATE TABLE " + TABLE.NOTE + "(" +//文件夹减少Note后需要更改的数据的表格
            NoteColumns.ID + " INTEGER PRIMARY KEY," +//文件夹插入Note后需要更改的数据的表格
            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +//文件夹删除Note后需要更改的数据的表格
            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +//应用界面颜色选择
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +// 创建时间数据
            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," +//文件夹中便签数据初始化为0
            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +//Note中数据删除更改的数据表格。
            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" +//数据库中需要存储的项目的名称，就相当于创建一个表格的表头的内容
        ")";

    private static final String CREATE_DATA_TABLE_SQL =//创建SQL的data表
        "CREATE TABLE " + TABLE.DATA + "(" +//note删除数据触发
            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 ''" +
        ")";//文件夹删除note触发

    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =//文件夹移除note时触发垃圾回收
        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";//存储便签编号的一个数据表格
//以下几个都是在创建触发器(trigger)。触发器是一些在特定的数据库事件(database-event) 发生时自动进行的数据库操作
    /**
     * Increase folder's note count when move note to the folder
     *///Increase增加文件Decrease减少文件
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =//将新的note移入该文件夹时，更新该文件夹note的数量
        "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";// 在文件夹中移入一个Note之后需要更改的数据的表格

    /**
     * Decrease folder's note count when move note from folder
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =//notes从文件夹移除后，数量减一，并且进行一系列的操作
        "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" + ";" +//在文件夹中移出一个Note之后需要更改的数据的表格
        " END";
//便签从文件夹移除后，数量减一，并且进行一系列的操作进行更新
    /**
     * Increase folder's note count when insert new note to the folder
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =//在文件夹中新建notes后，数量加1
        "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";//在文件夹中插入一个Note之后需要更改的数据的表格

    /**
     * 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 " +//定义一个更新文件夹中便签数目的SQL语句。当有便签从该文件夹中删除时使用
        " 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";//在文件夹中删除一个Note之后需要更改的数据的表格

    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     *///构建一条SQL语句，用于实现在note中输入data后，进行当前状态的更新
    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";//在文件夹中对一个Note导入新的数据之后需要更改的数据的表格

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has changed
     *///在data数据改变后对整个应用进行数据刷新
    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";//Note数据被修改后需要更改的数据的表格

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
     *///在数据被删除时，进行更新。
    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";//Note数据被删除后需要更改的数据的表格

    /**
     * Delete datas belong to note which has been deleted
     *///实现在note被删除后，将该note对应的data删除的功能
    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";//删除已删除的便签的数据后需要更改的数据的表格

    /**
     * Delete notes belong to folder which has been deleted
     *///用于实现在文件夹被删除后，将该文件夹中的note删除的功能
    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";//删除已删除的文件夹的便签后需要更改的数据的表格

    /**
     * Move notes belong to folder which has been moved to trash folder
     *///恢复删除的notes,并且更新一些数据
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =//将垃圾文件夹里的note还原，并更新数据表格
        "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";//还原垃圾桶中便签后需要更改的数据的表格

    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }//构造函数，传入数据库的名称和版本

    public void createNoteTable(SQLiteDatabase db) {//标注出数据库的名称和版本
        db.execSQL(CREATE_NOTE_TABLE_SQL);//创建表头
        reCreateNoteTableTriggers(db);
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }//创建表格，存储标签属性

    private void reCreateNoteTableTriggers(SQLiteDatabase db) {//创建一个储存标签属性的表格
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");//创建增加文件夹的触发器
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");//创建减少文件夹的触发器
        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");
//在删除原来的触发器后，创建新的触发器
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);//创建自己的数据库操作
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);//创建更新减少文件夹的触发器
        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);//创建删除notes的触发器
        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);//创建将回收站中的notes还原的触发器
    }//execSQL通过添加sql语句可以执行sql操作
//execSQL通过添加sql语句可以执行sql操作
    private void createSystemFolder(SQLiteDatabase db) {//创建几个系统文件夹
        ContentValues values = new ContentValues();//向数据库中插入数据，就要新建一个contentValues的对象。但只能存储基本类型数据

        /**
         * call record foler for call notes
         *///储存呼叫记录的文件夹
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);//放入数据(NoteColumns的id,呼叫记录文件夹的ld）
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);//插入ContantValues对象

        /**
         * root folder which is default folder
         *///对默认文件夹（根文件夹）进行操作
        values.clear();//对根文件夹（默认文件夹）进行修改，首先先把values容器清空，在对他添加内容，最后放入数据库
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);//将数据库ID与通话记录文件夹ID形成映射
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);//将数据库中数据类型与通话记录文件夹类型形成映射
        db.insert(TABLE.NOTE, null, values);

        /**
         * temporary folder which is used for moving note
         *///移动note的临时文件夹
        values.clear();// 临时文件夹的修改操作
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);//将数据库ID与通话记录文件夹ID形成映射
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        /**
         * create trash folder
         *///创建垃圾文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);//将数据库ID与通话记录文件夹ID形成映射
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    public void createDataTable(SQLiteDatabase db) {//将数据库ID与通话记录文件夹ID形成映射
        db.execSQL(CREATE_DATA_TABLE_SQL);//用来重新创建note对应的data的表项
        reCreateDataTableTriggers(db);//重新建立数据表的触发器
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        Log.d(TAG, "data table has been created");
    }

    private void reCreateDataTableTriggers(SQLiteDatabase db) {//删除重建表格
        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) {//如果NotesDatabaseHelper的实例创建失败，那就重新建一个，重新分配内从空间
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {//在NotesDatabaseHelper对象生命周期开始时创建Note table和Datatable
        createNoteTable(db);//函数：生命周期开始的时候oncreate 被调用，这里对其进行重写，加入notes表单和数据表单
        createDataTable(db);
    }//实现两个表格

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//数据库版本的更新
        boolean reCreateTriggers = false;//是否重新建立note及data的表项
        boolean skipV2 = false;

        if (oldVersion == 1) {//代码段：如果版本是一则更新到版本二
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        }

        if (oldVersion == 2 && !skipV2) {//判断旧版本是不是2号版本且没有跳过2号版本，就更新到3号版本
            upgradeToV3(db);
            reCreateTriggers = true;
            oldVersion++;
        }

        if (oldVersion == 3) {//v3-v4
            upgradeToV4(db);
            oldVersion++;
        }

        if (reCreateTriggers) {//重新创建的同时，创建新的note table和datatable
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }

        if (oldVersion != newVersion) {//旧版本与最新版本不一致，抛出异常
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }

    private void upgradeToV2(SQLiteDatabase db) {//将数据库的版本更新到V2
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
        createNoteTable(db);
        createDataTable(db);
    }

    private void upgradeToV3(SQLiteDatabase db) {//gengxinv3
        // 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在数据库的便签（note）表单中加上一个默认的垃圾文件夹，不用用户自己创建
        ContentValues values = new ContentValues();//添加垃圾系统文件夹
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);//插入到表中
    }

    private void upgradeToV4(SQLiteDatabase db) {//数据库版本升级到V4
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}