/*
 * 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;

//引入Notes中接口
public class NotesDatabaseHelper extends SQLiteOpenHelper { // 该类为便签SQL表的定义以及操作，易于进行文件夹与便签的各种操作，例如添加或删除的行为
    private static final String DB_NAME = "note.db"; // 数据库名称

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

    public interface TABLE { // 定义一个数据库表接口
        public static final String NOTE = "note"; // 便签名

        public static final String DATA = "data"; // 便签数据
    }

    private static final String TAG = "NotesDatabaseHelper"; // 日志类型

    private static NotesDatabaseHelper mInstance; // 创建NotesDatabaseHelper类对象

    private static final String CREATE_NOTE_TABLE_SQL = // SQL语句，创建便签表，包含ID、父ID、提醒日期、背景颜色ID、创建日期、是否有附件、修改日期、便签数、便签内容、便签类型、便签小部件ID、便签小部件类型、同步ID、本地修改时间、原始ID、便签的同步状态、版本号
            "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," +

                    NoteColumns.LOCKED + " INTEGER NOT NULL DEFAULT 0," +
                    NoteColumns.PICTURE + " TEXT NOT NULL DEFAULT ''" +

                    ")";

    private static final String CREATE_DATA_TABLE_SQL = // 创建数据表的SQL语句
            "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 ''" +
                    ")";

    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL = "CREATE INDEX IF NOT EXISTS note_id_index ON " +
            TABLE.DATA + "(" + DataColumns.NOTE_ID + ");"; // 创建查询操作表索引，用于查找

    /**
     * Increase folder's note count when move note to the folder
     */
    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"; // 创建触发器，方便进行操作，当移动便签时统计新的父文件夹内便签数量

    /**
     * Decrease folder's note count when move note from folder
     */
    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"; // 与上一个方法作用相反，统计旧的父文件夹便签数量

    /**
     * Increase folder's note count when insert new note to the folder
     */
    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"; // 创建便签时增加统计数量

    /**
     * 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 "
            +
            " 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"; // 删除时减少数量

    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     */
    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"; // 更新便签数据时更改table表内容

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has
     * changed
     */
    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"; // 改变便签数据时更改table表内容

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has
     * deleted
     */
    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"; // 删除便签数据时改变table表内容

    /**
     * Delete datas belong to note which has been deleted
     */
    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"; // 删除便签时删除便签内容

    /**
     * Delete notes belong to folder which has been deleted
     */
    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"; // 删除文件夹时删除内部的便签

    /**
     * Move notes belong to folder which has been moved to trash folder
     */
    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"; // 移动便签的父文件夹时便签也一起更改

    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    } // 创建一个数据库

    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db); // 重新创建触发器
        createSystemFolder(db); // 创建系统文件夹
        Log.d(TAG, "note table has been created"); // 创建一个新的便签表，返回日志
    }

    private void reCreateNoteTableTriggers(SQLiteDatabase db) { // 数据库对象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);
    } // 用于执行SQL语句，运行重新创建便签表触发器函数

    private void createSystemFolder(SQLiteDatabase db) { // 创建系统级文件夹
        ContentValues values = new ContentValues(); // 为字典类创建对象

        /**
         * 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); // 为通讯便签创建记录文件夹，并添加键值对

        /**
         * 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); // 创建根文件夹，是默认的、最终的父文件夹

        /**
         * 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); // 为移动中的便签创建的临时文件夹

        /**
         * 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); // 创建垃圾桶
    }

    public void createDataTable(SQLiteDatabase db) { // 创建数据表
        db.execSQL(CREATE_DATA_TABLE_SQL); // SQL输入保存的语句
        reCreateDataTableTriggers(db);
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        Log.d(TAG, "data table has been created"); // 日志记录
    }

    private void reCreateDataTableTriggers(SQLiteDatabase db) { // 为数据表重新创建触发器
        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"); // 删除触发器

        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); // 重新创建被删除的触发器
    }

    static synchronized NotesDatabaseHelper getInstance(Context context) { // synchronized是同步的意思，同步方法，用于返回NotesDatabaseHelper的对象实例mInstance
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    } // 静态同步方法，用于返回NotesDatabaseHelper的对象实例mInstance

    @Override // 重写方法
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db); // 创建便签表
        createDataTable(db); // 创建数据表
    } // 用于初始化表

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // 用于检查并升级数据库版本
        boolean reCreateTriggers = false;
        boolean skipV2 = false;

        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        } // 检测到版本为1，升级版本

        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true; // 重建触发器标志
            oldVersion++; // 检测到版本为2，升级版本
        }

        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        } // 检测到版本为3，升级版本

        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        } // 进行触发器的重建

        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails"); // 版本不匹配则抛出异常
        }
    }

    private void upgradeToV2(SQLiteDatabase db) { // 升级版本并重建表
        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) { // 升级版本并重建表
        // 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);
    } // 删除不用的触发器，并添加不为空的新列，添加键值对

    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    } // 添加新的不为空的列
}