/*
 * 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;   //存储一组数据
import android.content.Context;         //可以理解为一个接口（抽象类），它提供了有关应用程序的全局信息
import android.database.sqlite.SQLiteDatabase;          //用于数据库管理
import android.database.sqlite.SQLiteOpenHelper;        //用来管理数据的创建和版本更新
import android.util.Log;

import net.micode.notes.data.Notes.DataColumns;     //接口
import net.micode.notes.data.Notes.DataConstants;    //内部类       
import net.micode.notes.data.Notes.NoteColumns;         //接口


public class NotesDatabaseHelper extends SQLiteOpenHelper {     //定义一个类，继承于数据库帮助类
    private static final String DB_NAME = "note.db";            //数据库名字

    private static final int DB_VERSION = 4;                    //版本号

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

        public static final String DATA = "data";
    }

    private static final String TAG = "NotesDatabaseHelper";

    private static NotesDatabaseHelper mInstance;               //自定义对象

    private static final String CREATE_NOTE_TABLE_SQL =             //数据库要存储的各种笔记信息
        "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" +
        ")";

    private static final String CREATE_DATA_TABLE_SQL =     //数据库存储数据信息
        "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 =     //数据库存储
        "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
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =          //数据库，文件夹数量的增多
        "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
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =          //数据库，文件数量减少
        "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
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =          //插入
        "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
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =    //删除
        "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}
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =    //更新，插入
        "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
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =    //目录更新
        "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
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =  //目录删除
        "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
     */
    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =       //笔记数据删除
        "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
     */
    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =             //删除文件，更新操作
        "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
     */
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =            //垃圾删除
        "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) {           //构造函数
        super(context, DB_NAME, null, DB_VERSION);      //直接用super调用父类的构造函数
    }

    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);      //创建一个数据库
        reCreateNoteTableTriggers(db);          //创建数据库
        createSystemFolder(db);                 //验证是否有文件存在，如果没有建立一个文件
        Log.d(TAG, "note table has been created");//调试debug，意味着创建失败
    }

    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");   //增加监听事件
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");    //监听事件
        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);
    }

    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();         //与数据库关联，对数据库进行增删改查

        /**
         * call record foler for call notes
         */
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);            //类型两种，类型数量2个
        db.insert(TABLE.NOTE, null, values);            //与value建立关联
        /**
         * root folder which is default folder
         */
        values.clear();     //清空
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);        //插入

        /**
         * temporary folder which is used for moving note
         */
        values.clear();     //清空
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);        //插入

        /**
         * 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);
    }

    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL);                  //创建数据表格
        reCreateDataTableTriggers(db);
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        Log.d(TAG, "data table has been created");
    }

    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);
    }

    static synchronized NotesDatabaseHelper getInstance(Context context) {      //线程锁
        if (mInstance == null) {        //如果自定义对象为空，
            mInstance = new NotesDatabaseHelper(context);       //则为该对象申请内存
        }
        return mInstance;       //返回
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);        //创建笔记的数据库
        createDataTable(db);        //创建数据的数据库
    }

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

        if (oldVersion == 1) {      //升级版本 一升二
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        }

        if (oldVersion == 2 && !skipV2) {       //二升三
            upgradeToV3(db);
            reCreateTriggers = true;
            oldVersion++;
        }

        if (oldVersion == 3) {      //版本升级 三升四
            upgradeToV4(db);
            oldVersion++;
        }

        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);      //重新创建note触发器
            reCreateDataTableTriggers(db);      //重新创建data触发器
        }

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

    private void upgradeToV2(SQLiteDatabase db) {       //版本二
        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) {
        // drop unused triggers
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");       //插入
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");       //删除
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");       //更新
        // 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();         //创建存储数据表
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);           //表1       
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);            //表2
        db.insert(TABLE.NOTE, null, values);                        //插入到数据库
    }

    private void upgradeToV4(SQLiteDatabase db) {           //版本四
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}