/*
 * 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;


public class NotesDatabaseHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "note.db";
    //表示数据库的名称为 "note.db"。这个常量用于指定应用程序中使用的数据库的名称。

    private static final int DB_VERSION = 4;
    //表示数据库的版本号为 4。

    public interface TABLE { //接口
        public static final String NOTE = "note";
        //表示数据库中的一个表名为 "note"。这个常量用于指定应用程序中使用的表名。

        public static final String DATA = "data";
        //表示数据库中的一个表名为 "data"。这个常量也用于指定应用程序中使用的表名。
    }

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

    private static NotesDatabaseHelper mInstance;//类静态变量

    //创建一个名为"NOTE"的数据库表的SQL语句
    private static final String CREATE_NOTE_TABLE_SQL =
            "CREATE TABLE " + TABLE.NOTE + "(" +
                    NoteColumns.ID + " INTEGER PRIMARY KEY," +    //ID,主键
                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +  //父ID
                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," + //提醒日期
                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," + //背景颜色ID
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + //创建日期
                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +//是否有附件
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +//修改日期
                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +//笔记数量
                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +//摘要
                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +//类型
                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +//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ID
                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +//本地修改
                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +//原始父ID
                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +//文本类型
                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +//版本
                    ")";

    //创建一个名为"DATA"的数据库表的SQL语句
    private static final String CREATE_DATA_TABLE_SQL =
            "CREATE TABLE " + TABLE.DATA + "(" +
                    DataColumns.ID + " INTEGER PRIMARY KEY," +//ID,主键
                    DataColumns.MIME_TYPE + " TEXT NOT NULL," +//MIME类型
                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +//笔记ID
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +//创建日期
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +//修改日期
                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +//内容
                    DataColumns.DATA1 + " INTEGER," +
                    DataColumns.DATA2 + " INTEGER," +
                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
                    ")";

    //在"DATA"的数据库表上创建一个名为"note_id_index"的索引的SQL语句。
    // 该索引是基于"NOTE_ID"字段的，旨在提高根据笔记ID进行查询时的检索效率。
    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
     */
    //创建一个触发器,在"NOTE"表中的"parent_id"字段更新之后执行，目的是在更新父文件夹ID后自动增加相应文件夹的笔记计数（notes_count）。
    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
     */
    //创建一个触发器,在"NOTE"表中的"parent_id"字段更新之后执行，目的是在更新父文件夹ID后自动减少相应文件夹的笔记计数（notes_count）。
    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"NOTE"表中插入新记录之后执行，目的是在新笔记被添加到特定文件夹时自动增加该文件夹的笔记计数（notes_count）。
    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
     */
    //在删除笔记时自动减少相应父文件夹的笔记计数（notes_count）。
    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}
     */
    //向"DATA"表中插入记录之后执行，当插入数据的MIME类型为"NOTE"时会更新"NOTE"表中相应笔记的摘要（snippet）字段。
    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
     */
    //在更新"DATA"表中的记录之后执行，当更新数据的MIME类型为"NOTE"时，会更新"NOTE"表中相应笔记的摘要（snippet）字段。
    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
     */
    //在删除"DATA"表中的记录之后执行，当被删除数据的MIME类型为"NOTE"时，会将对应笔记的摘要（snippet）字段置空。
    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
     */
    //在删除"NOTE"表中的记录之后执行，会同时删除"DATA"表中与被删除笔记相关联的记录。
    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
     */
    //触发器在删除"NOTE"表中的记录之后执行，会同时删除"NOTE"表中与被删除文件夹相关联的所有笔记记录。
    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
     */
    //更新"NOTE"表中的记录之后执行，当将笔记移动到垃圾箱（Trash Folder）时，会将相关笔记的父级ID（Parent ID）更新为垃圾箱的ID。
    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";

    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }//调用了父类 SQLiteOpenHelper 的构造函数

    //数据库中创建笔记表
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db);//重新创建与笔记表相关的触发器
        createSystemFolder(db);//在数据库中创建系统文件夹
        Log.d(TAG, "note table has been created");
    }

    //重新创建与笔记表相关的触发器
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        //删除与笔记表相关的触发器
        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");
        //重新创建与笔记表相关的触发器
        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);
    }

    //在数据库中创建系统文件夹
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();
//        创建通话记录文件夹：向 Note 表插入一条记录，指定 ID 为 Notes.ID_CALL_RECORD_FOLDER，类型为系统类型。
//        创建根文件夹：向 Note 表插入一条记录，指定 ID 为 Notes.ID_ROOT_FOLDER，类型为系统类型。
//        创建临时文件夹：向 Note 表插入一条记录，指定 ID 为 Notes.ID_TEMPARAY_FOLDER，类型为系统类型。
//        创建垃圾箱文件夹：向 Note 表插入一条记录，指定 ID 为 Notes.ID_TRASH_FOLER，类型为系统类型。

        /**
         * 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);
    }

    //在数据库中创建DATA表
    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL);//创建数据表
        reCreateDataTableTriggers(db);//重新创建与DATA表相关的触发器
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);//索引
        Log.d(TAG, "data table has been created");//日志
    }

    //重新创建与DATA表相关的触发器
    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);
    }

    //用于获取 NotesDatabaseHelper 的单例实例
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    @Override//为什么重载
    //创建数据库
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }

    @Override
    //处理数据库的升级操作
    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) {  //如果需要重新创建触发器
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }

        if (oldVersion != newVersion) {       //如果数据库升级失败
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }

    //将数据库升级到版本 2
    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);
    }

    //将数据库升级到版本 3
    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);
    }

    //将数据库升级到版本 4
    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}