/*
 * 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类负责管理笔记应用的数据库，包括创建、升级和维护数据库表结构
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;

    // 定义数据库表名的接口
    public interface TABLE {
        // 笔记表名
        public static final String NOTE = "note";
        // 数据表名
        public static final String DATA = "data";
    }

    // 用于日志记录的标签
    private static final String TAG = "NotesDatabaseHelper";
    // 单例实例
    private static NotesDatabaseHelper mInstance;

    // 创建笔记表的SQL语句
    private static final String CREATE_NOTE_TABLE_SQL =
            "CREATE TABLE " + TABLE.NOTE + "(" +
                    NoteColumns.ID + " INTEGER PRIMARY KEY," + // 笔记的唯一标识，作为主键
                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 父笔记的ID，默认值为0
                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," + // 提醒日期，默认值为0
                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," + // 背景颜色ID，默认值为0
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期，默认值为当前时间戳
                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," + // 是否有附件，默认值为0
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期，默认值为当前时间戳
                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," + // 文件夹中的笔记数量，默认值为0
                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," + // 文件夹名称或笔记内容摘要，默认值为空字符串
                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," + // 文件类型（笔记或文件夹），默认值为0
                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," + // 小部件ID，默认值为0
                    NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," + // 小部件类型，默认值为-1
                    NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," + // 同步ID，默认值为0
                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," + // 本地修改标志，默认值为0
                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 移动到临时文件夹前的原始父ID，默认值为0
                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," + // gtask ID，默认值为空字符串
                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" + // 版本号，默认值为0
                    ")";

    // 创建数据表的SQL语句
    private static final String CREATE_DATA_TABLE_SQL =
            "CREATE TABLE " + TABLE.DATA + "(" +
                    DataColumns.ID + " INTEGER PRIMARY KEY," + // 数据的唯一标识，作为主键
                    DataColumns.MIME_TYPE + " TEXT NOT NULL," + // MIME类型，不能为空
                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," + // 所属笔记的ID，默认值为0
                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期，默认值为当前时间戳
                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期，默认值为当前时间戳
                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," + // 数据内容，默认值为空字符串
                    DataColumns.DATA1 + " INTEGER," + // 通用数据列1，类型为整数
                    DataColumns.DATA2 + " INTEGER," + // 通用数据列2，类型为整数
                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," + // 通用数据列3，类型为文本，默认值为空字符串
                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," + // 通用数据列4，类型为文本，默认值为空字符串
                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" + // 通用数据列5，类型为文本，默认值为空字符串
                    ")";

    // 创建数据表中note_id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 + ");";

    // 当更新笔记的父ID（即移动笔记到文件夹）时，增加目标文件夹的笔记数量的触发器
    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";

    // 当更新笔记的父ID（即从文件夹移出笔记）时，减少原文件夹的笔记数量的触发器
    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";

    // 当插入新笔记到文件夹时，增加目标文件夹的笔记数量的触发器
    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";

    // 当从文件夹删除笔记时，减少该文件夹的笔记数量的触发器
    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";

    // 当插入数据且数据类型为文本笔记时，更新对应笔记内容的触发器
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
            "CREATE TRIGGER update_note_content_on_insert " +
                    " AFTER INSERT ON " + TABLE.DATA +
                    " 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";

    // 当数据类型为文本笔记的数据发生变化时，更新对应笔记内容的触发器
    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";

    // 当删除数据且数据类型为文本笔记时，将对应笔记内容清空的触发器
    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";

    // 当删除笔记时，删除该笔记关联的所有数据的触发器
    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";

    // 当删除文件夹时，删除该文件夹下所有笔记的触发器
    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";

    // 当文件夹被移动到回收站时，将该文件夹下所有笔记也移动到回收站的触发器
    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，用于创建或打开数据库
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    // 创建笔记表的方法
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL); // 执行创建笔记表的SQL语句
        reCreateNoteTableTriggers(db); // 重新创建笔记表相关的触发器
        createSystemFolder(db); // 创建系统文件夹
        Log.d(TAG, "note table has been created"); // 记录日志，表明笔记表已创建
    }

    // 重新创建笔记表触发器的方法
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 先删除旧的触发器
        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");

        // 再创建新的触发器
        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);
    }

    // 创建系统文件夹的方法
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();

        // 创建通话记录文件夹
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建根文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建临时文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建回收站文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    // 创建数据表的方法
    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL); // 执行创建数据表的SQL语句
        reCreateDataTableTriggers(db); // 重新创建数据表相关的触发器
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL); // 执行创建note_id索引的SQL语句
        Log.d(TAG, "data table has been created"); // 记录日志，表明数据表已创建
    }

    // 重新创建数据表触发器的方法
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 先删除旧的触发器
        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");

        // 再创建新的触发器
        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);
    }

    // 获取单例实例的方法
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }

    // 当数据库首次创建时调用的方法
    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db); // 创建笔记表
        createDataTable(db); // 创建数据表
    }

    // 当数据库版本升级时调用的方法
    // 数据库版本升级时调用的方法
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // 标记是否需要重新创建触发器
    boolean reCreateTriggers = false;
    // 标记是否跳过版本2的升级过程（因为某些升级包含了从版本2到版本3的部分）
    boolean skipV2 = false;

    // 如果旧版本是1
    if (oldVersion == 1) {
        // 执行升级到版本2的操作
        upgradeToV2(db);
        // 标记跳过版本2的升级过程，因为此次升级包含了从版本2到版本3的升级
        skipV2 = true;
        // 旧版本号加1
        oldVersion++;
    }

    // 如果旧版本是2且没有跳过版本2的升级过程
    if (oldVersion == 2 &&!skipV2) {
        // 执行升级到版本3的操作
        upgradeToV3(db);
        // 标记需要重新创建触发器
        reCreateTriggers = true;
        // 旧版本号加1
        oldVersion++;
    }

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

    // 如果需要重新创建触发器
    if (reCreateTriggers) {
        // 重新创建笔记表的触发器
        reCreateNoteTableTriggers(db);
        // 重新创建数据表的触发器
        reCreateDataTableTriggers(db);
    }

    // 如果旧版本号不等于新版本号，说明升级过程出现问题
    if (oldVersion!= newVersion) {
        // 抛出异常，提示升级失败
        throw new IllegalStateException("Upgrade notes database to version " + newVersion
                + " fails");
    }
}

// 升级到版本2的具体实现方法
private void upgradeToV2(SQLiteDatabase db) {
    // 删除旧的笔记表
    db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
    // 删除旧的数据表
    db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
    // 重新创建笔记表
    createNoteTable(db);
    // 重新创建数据表
    createDataTable(db);
}

// 升级到版本3的具体实现方法
private void upgradeToV3(SQLiteDatabase db) {
    // 删除不再使用的触发器
    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");

    // 向笔记表中添加一个用于存储gtask id的列
    db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
            + " TEXT NOT NULL DEFAULT ''");

    // 创建一个用于存储回收站信息的系统文件夹
    ContentValues values = new ContentValues();
    // 设置文件夹的ID为回收站文件夹的ID
    values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
    // 设置文件夹的类型为系统类型
    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
    // 将该文件夹信息插入到笔记表中
    db.insert(TABLE.NOTE, null, values);
}