/*
 * 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 {
    // 数据库名称
    private static final String DB_NAME = "note.db";

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

    // 定义数据库中的表名
    public interface TABLE {
        // 表名：note
        public static final String NOTE = "note";

        // 表名：data
        public static final String DATA = "data";
    }

    private static final String TAG = "NotesDatabaseHelper";

// 单例模式，用于获取NotesDatabaseHelper的实例
    private static NotesDatabaseHelper mInstance;

// 创建Note表的SQL语句
    private static final String CREATE_NOTE_TABLE_SQL =
        "CREATE TABLE " + TABLE.NOTE + "(" +
            NoteColumns.ID + " INTEGER PRIMARY KEY," + // ID列，主键
            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 父ID列，默认值为0
            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," + // 提醒日期列，默认值为0
            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," + // 背景颜色ID列，默认值为0
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期列，默认值为当前时间戳
            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," + // 是否有附件列，默认值为0
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期列，默认值为当前时间戳
            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," + // 笔记数量列，默认值为0
            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," + // 摘要列，默认值为空字符串
            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," + // 类型列，默认值为0
            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," + // 小部件ID列，默认值为0
            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," + // 小部件类型列，默认值为-1
            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," + // 同步ID列，默认值为0
            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," + // 本地修改列，默认值为0
            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 原始父ID列，默认值为0
            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," + // Google任务ID列，默认值为空字符串
            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" + // 版本列，默认值为0
        ")";

// 定义创建数据表的SQL语句
    private static final String CREATE_DATA_TABLE_SQL =
        "CREATE TABLE " + TABLE.DATA + "(" +
            // 定义ID列，类型为INTEGER，为主键
            DataColumns.ID + " INTEGER PRIMARY KEY," +
            // 定义MIME_TYPE列，类型为TEXT，不能为空
            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
            // 定义NOTE_ID列，类型为INTEGER，不能为空，默认值为0
            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
            // 定义CREATED_DATE列，类型为INTEGER，不能为空，默认值为当前时间
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            // 定义MODIFIED_DATE列，类型为INTEGER，不能为空，默认值为当前时间
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            // 定义CONTENT列，类型为TEXT，不能为空，默认值为空字符串
            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
            // 定义DATA1列，类型为INTEGER
            DataColumns.DATA1 + " INTEGER," +
            // 定义DATA2列，类型为INTEGER
            DataColumns.DATA2 + " INTEGER," +
            // 定义DATA3列，类型为TEXT，不能为空，默认值为空字符串
            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
            // 定义DATA4列，类型为TEXT，不能为空，默认值为空字符串
            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
            // 定义DATA5列，类型为TEXT，不能为空，默认值为空字符串
            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
        ")";

// 定义一个常量，用于创建索引的SQL语句
    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
     */
// 定义一个静态常量，用于创建一个触发器，在更新Note表的PARENT_ID字段后，增加对应文件夹的NOTES_COUNT字段
    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
     */
// 创建一个名为decrease_folder_count_on_update的触发器，在更新Note表的parent_id字段后执行
    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
     */
// 创建一个触发器，在插入笔记后，增加父文件夹的笔记数量
    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
     */
// 定义一个静态常量，用于创建一个触发器，在删除笔记后减少父文件夹中的笔记数量
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER decrease_folder_count_on_delete " + // 创建触发器
        " AFTER DELETE ON " + TABLE.NOTE + // 在删除笔记后触发
        " BEGIN " + // 开始
        "  UPDATE " + TABLE.NOTE + // 更新笔记表
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" + // 将父文件夹中的笔记数量减1
        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID + // 条件：父文件夹的ID等于被删除笔记的父文件夹ID
        "  AND " + NoteColumns.NOTES_COUNT + ">0;" + // 条件：父文件夹中的笔记数量大于0
        " END";

    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     */
// 定义一个常量，用于存储在插入数据时更新备注内容的触发器
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
        "CREATE TRIGGER update_note_content_on_insert " +
        " AFTER INSERT ON " + TABLE.DATA + // 在DATA表上创建一个名为update_note_content_on_insert的触发器
        " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" + // 当新插入的MIME_TYPE为NOTE时
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE + // 更新NOTE表
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT + // 将新插入的CONTENT赋值给NOTE表的SNIPPET
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" + // 在NOTE表中，当ID等于新插入的NOTE_ID时
        " END";

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has changed
     */
// 定义一个常量，用于创建一个触发器，在更新数据表中的数据时，更新笔记表中的内容
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_update " + // 创建触发器
        " AFTER UPDATE ON " + TABLE.DATA + // 在更新数据表时触发
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" + // 当旧数据的MIME类型为NOTE时触发
        " BEGIN" + // 开始
        "  UPDATE " + TABLE.NOTE + // 更新笔记表
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT + // 将新数据的CONTENT赋值给笔记表的SNIPPET
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" + // 根据新数据的NOTE_ID更新笔记表
        " END";

    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
     */
// 定义一个常量，用于创建一个触发器，在删除数据表中的数据时，更新笔记表中的内容
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_delete " + // 创建触发器
        " AFTER delete ON " + TABLE.DATA + // 在删除数据表中的数据时
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" + // 当删除的数据的MIME类型为NOTE时
        " BEGIN" + // 开始
        "  UPDATE " + TABLE.NOTE + // 更新笔记表
        "   SET " + NoteColumns.SNIPPET + "=''" + // 将笔记表中的内容设置为空
        "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" + // 在笔记表中，ID等于删除的数据的NOTE_ID
        " END";

    /**
     * Delete datas belong to note which has been deleted
     */
// 定义一个静态常量，用于创建一个触发器，在删除笔记时删除相关数据
    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
        "CREATE TRIGGER delete_data_on_delete " + // 创建触发器
        " AFTER DELETE ON " + TABLE.NOTE + // 在删除笔记时触发
        " BEGIN" + // 开始
        "  DELETE FROM " + TABLE.DATA + // 删除数据
        "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" + // 条件：笔记ID等于旧笔记ID
        " END"; // 结束

    /**
     * Delete notes belong to folder which has been deleted
     */
// 定义一个静态常量，用于删除文件夹时删除笔记的触发器
    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
        "CREATE TRIGGER folder_delete_notes_on_delete " + // 创建一个名为folder_delete_notes_on_delete的触发器
        " AFTER DELETE ON " + TABLE.NOTE + // 在删除笔记后触发
        " BEGIN" + // 开始
        "  DELETE FROM " + TABLE.NOTE + // 从笔记表中删除
        "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" + // 笔记的父ID等于被删除笔记的ID
        " END"; // 结束

    /**
     * Move notes belong to folder which has been moved to trash folder
     */
// 创建一个名为folder_move_notes_on_trash的触发器，在更新NOTE表后触发
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
        "CREATE TRIGGER folder_move_notes_on_trash " +
        " AFTER UPDATE ON " + TABLE.NOTE + // 在NOTE表上更新后触发
        " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER + // 当新记录的父ID等于垃圾桶文件夹ID时
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE + // 更新NOTE表
        "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER + // 将父ID设置为垃圾桶文件夹ID
        "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" + // 在旧记录的父ID等于旧记录的ID时
        " END";

    public NotesDatabaseHelper(Context context) {
        // 调用父类的构造方法，传入上下文、数据库名称、游标工厂、数据库版本号
        super(context, DB_NAME, null, DB_VERSION);
    }

    public void createNoteTable(SQLiteDatabase db) {
        // 执行SQL语句，创建note表
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        // 重新创建note表的触发器
        reCreateNoteTableTriggers(db);
        // 创建系统文件夹
        createSystemFolder(db);
        // 打印日志，表示note表已经创建
        Log.d(TAG, "note table has been created");
    }

// 重新创建Note表触发器
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 删除increase_folder_count_on_update触发器
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
        // 删除decrease_folder_count_on_update触发器
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
        // 删除decrease_folder_count_on_delete触发器
        // 删除delete_data_on_delete触发器
// 删除所有触发器
        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");

// 创建触发器
        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);
    }

    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);
    }

    public void createDataTable(SQLiteDatabase db) {
        // 执行创建数据表的SQL语句
        db.execSQL(CREATE_DATA_TABLE_SQL);
        // 重新创建数据表触发器
        reCreateDataTableTriggers(db);
        // 执行创建数据表索引的SQL语句
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        // 打印日志，表示数据表已经创建
        Log.d(TAG, "data table has been created");
    }

// 重新创建数据表触发器
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 删除update_note_content_on_insert触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
        // 删除update_note_content_on_update触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
        // 删除update_note_content_on_delete触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");

        // 创建update_note_content_on_insert触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
        // 创建update_note_content_on_update触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
        // 创建update_note_content_on_delete触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
    }

// 静态同步方法，用于获取NotesDatabaseHelper的实例
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        // 如果mInstance为空，则创建一个新的NotesDatabaseHelper实例
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        // 返回mInstance实例
        return mInstance;
    }

    @Override
    // 重写onCreate方法，当数据库创建时调用
    public void onCreate(SQLiteDatabase db) {
        // 创建Note表
        createNoteTable(db);
        // 创建Data表
        createDataTable(db);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 定义两个布尔变量，用于判断是否需要重新创建触发器和是否跳过v2版本
        boolean reCreateTriggers = false;
        boolean skipV2 = false;

        // 如果旧版本是1，则升级到v2版本，并跳过v2版本
        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        }

// 如果旧版本为2且不跳过V2版本，则升级到V3版本，并重新创建触发器，同时旧版本加1
        if (oldVersion == 2 && !skipV2) {
  // 升级到V3版本
            upgradeToV3(db);
  // 重新创建触发器
            reCreateTriggers = true;
  // 版本号加1
            oldVersion++;
        }

// 如果旧版本号为3
        if (oldVersion == 3) {
            // 升级到版本4
            upgradeToV4(db);
            // 版本号加1
            oldVersion++;
        }

// 如果需要重新创建触发器，则执行以下代码
        if (reCreateTriggers) {
            // 重新创建NoteTable触发器
            reCreateNoteTableTriggers(db);
            // 重新创建DataTable触发器
            reCreateDataTableTriggers(db);
        }

// 如果旧版本不等于新版本，则抛出异常
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }

// 升级到V2版本
    private void upgradeToV2(SQLiteDatabase db) {
        // 删除旧版本的NOTE表
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        // 删除旧版本的DATA表
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
        // 创建新版本的NOTE表
        createNoteTable(db);
        // 创建新版本的DATA表
        createDataTable(db);
    }

  // 升级数据库到V3版本
    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);
    }

    private void upgradeToV4(SQLiteDatabase db) {
        // 执行SQL语句，将Note表中的VERSION列添加为INTEGER类型，默认值为0
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}