/*
 * 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;

// NotesDatabaseHelper类继承自SQLiteOpenHelper，用于管理和操作与笔记相关的SQLite数据库
// 它负责创建数据库表、索引以及各种数据库触发器等操作
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 数据库名称
    private static final String DB_NAME = "note.db";
    // 数据库版本号，用于数据库升级等操作时的版本控制
    private static final int DB_VERSION = 4;

    // 定义内部接口TABLE，用于规范数据库中表的名称常量
    public interface TABLE {
        // 表示存储笔记基本信息的表名
        public static final String NOTE = "note";
        // 表示存储笔记相关数据（比如内容等具体数据）的表名
        public static final String DATA = "data";
    }

    // 用于日志输出的标签，方便在Logcat中查看该类相关的日志信息
    private static final String TAG = "NotesDatabaseHelper";
    // 采用单例模式，保存该类的唯一实例
    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," +
                    // 父级笔记的ID，默认值为0，表示没有父级
                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 提醒日期，默认值为0，表示没有设置提醒
                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
                    // 背景颜色ID，默认值为0
                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 创建日期，默认值为当前时间（以特定格式转换后的时间戳）
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    // 是否有附件，默认值为0，表示没有附件
                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
                    // 修改日期，默认值为当前时间（以特定格式转换后的时间戳）
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    // 该笔记下的子笔记数量，默认值为0
                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
                    // 笔记的摘要内容，默认值为空字符串
                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
                    // 笔记类型，默认值为0
                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
                    // 小部件ID，默认值为0
                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 小部件类型，默认值为 -1
                    NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
                    // 同步ID，默认值为0
                    NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 本地是否修改，默认值为0
                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
                    // 原始父级ID，默认值为0
                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 与GTask相关的ID，默认值为空字符串
                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
                    // 版本号，默认值为0
                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
                    ")";

    // 创建data表的SQL语句，用于存储笔记相关的具体数据信息
    private static final String CREATE_DATA_TABLE_SQL =
            "CREATE TABLE " + TABLE.DATA + "(" +
                    DataColumns.ID + " INTEGER PRIMARY KEY," +
                    // 数据的MIME类型，不能为空
                    DataColumns.MIME_TYPE + " TEXT NOT NULL," +
                    // 关联的笔记ID，默认值为0，表示未关联笔记
                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
                    // 创建日期，默认值为当前时间（以特定格式转换后的时间戳）
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    // 修改日期，默认值为当前时间（以特定格式转换后的时间戳）
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
                    // 数据内容，默认值为空字符串
                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
                    // 额外的数据字段1，可为空（整数类型）
                    DataColumns.DATA1 + " INTEGER," +
                    // 额外的数据字段2，可为空（整数类型）
                    DataColumns.DATA2 + " INTEGER," +
                    // 额外的数据字段3，默认值为空字符串
                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
                    // 额外的数据字段4，默认值为空字符串
                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
                    // 额外的数据字段5，默认值为空字符串
                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
                    ")";

    // 创建基于data表中NOTE_ID字段的索引的SQL语句，如果索引不存在则创建
    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
            "CREATE INDEX IF NOT EXISTS note_id_index ON " +
                    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";

    /**
     * 以下是一系列数据库触发器相关的SQL语句定义，用于实现特定的数据操作逻辑关联和自动化处理

     * 当将笔记移动到文件夹时，增加文件夹的笔记数量的触发器SQL语句
     * 该触发器在更新note表的PARENT_ID字段后触发
     */
    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";

    /**
     * 当将笔记从文件夹移出时，减少文件夹的笔记数量的触发器SQL语句
     * 该触发器在更新note表的PARENT_ID字段后触发，并且只有当文件夹的笔记数量大于0时才执行减少操作
     */
    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";

    /**
     * 当向文件夹中插入新笔记时，增加文件夹的笔记数量的触发器SQL语句
     * 该触发器在向note表插入新记录后触发
     */
    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";

    /**
     * 当从文件夹中删除笔记时，减少文件夹的笔记数量的触发器SQL语句
     * 该触发器在从note表删除记录后触发，并且只有当文件夹的笔记数量大于0时才执行减少操作
     */
    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";

    /**
     * 当向data表插入类型为{@link DataConstants#NOTE}的数据时，更新对应的笔记内容的触发器SQL语句
     * 该触发器在向data表插入新记录后触发，并且仅当插入的数据MIME类型是特定的笔记类型时执行更新操作
     */
    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";

    /**
     * 当data表中类型为{@link DataConstants#NOTE}的数据发生更新时，更新对应的笔记内容的触发器SQL语句
     * 该触发器在更新data表记录后触发，并且仅当更新前的数据MIME类型是特定的笔记类型时执行更新操作
     */
    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";

    /**
     * 当从data表中删除类型为{@link DataConstants#NOTE}的数据时，更新对应的笔记内容（清空）的触发器SQL语句
     * 该触发器在从data表删除记录后触发，并且仅当删除的数据MIME类型是特定的笔记类型时执行更新操作
     */
    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";

    /**
     * 当从note表中删除笔记时，删除该笔记关联的所有data表中的数据的触发器SQL语句
     * 该触发器在从note表删除记录后触发
     */
    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";

    /**
     * 当从note表中删除文件夹时，删除该文件夹下所有笔记的触发器SQL语句
     * 该触发器在从note表删除记录后触发
     */
    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";

    /**
     * 当将文件夹移动到回收站文件夹时，移动该文件夹下所有笔记到回收站文件夹的触发器SQL语句
     * 该触发器在更新note表的PARENT_ID字段后触发，并且仅当更新后的PARENT_ID是回收站文件夹的ID时执行移动操作
     */
    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";

    // 构造函数，调用父类SQLiteOpenHelper的构造函数来初始化数据库相关信息，传入上下文、数据库名称、游标工厂（这里为null）和数据库版本号
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    // 在给定的SQLiteDatabase对象中创建note表，同时重新创建与note表相关的触发器、创建系统文件夹，并输出日志表示note表已创建
    public void createNoteTable(SQLiteDatabase db) {
        // 执行创建note表的SQL语句
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        // 重新创建与note表相关的触发器
        reCreateNoteTableTriggers(db);
        // 创建系统文件夹（此处方法未完整展示，推测是与数据库初始化相关的一些默认文件夹创建操作）
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }
    private void reCreateNoteTableTriggers(SQLiteDatabase 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);
    }

    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) {
        db.execSQL(CREATE_DATA_TABLE_SQL);
        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) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }

    @Override
    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) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }

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

    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);
    }

    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) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }
}