/*
 * 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.gtask.remote;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.util.Log;

import net.micode.notes.R;
import net.micode.notes.data.Notes;
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.NoteColumns;
import net.micode.notes.gtask.data.MetaData;
import net.micode.notes.gtask.data.Node;
import net.micode.notes.gtask.data.SqlNote;
import net.micode.notes.gtask.data.Task;
import net.micode.notes.gtask.data.TaskList;
import net.micode.notes.gtask.exception.ActionFailureException;
import net.micode.notes.gtask.exception.NetworkFailureException;
import net.micode.notes.tool.DataUtils;
import net.micode.notes.tool.GTaskStringUtils;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
/**
 * @aPackage :      net.micode.notes.gtask.remote
 * @aClassName:     GTaskManager
 * @Description:
 * GTask管理者,提供同步本地和远端的任务,初始化任务列表,同步内容、文件夹,添加、更新本地和远端结点,刷新本地同步任务D等功能
 * @aAuthor:        Li Qiushi
 * @createdate:     12/24/2023 19:31 PM
 */
public class GTaskManager {
    private static final String TAG = GTaskManager.class.getSimpleName();

    public static final int STATE_SUCCESS = 0;

    public static final int STATE_NETWORK_ERROR = 1;

    public static final int STATE_INTERNAL_ERROR = 2;

    public static final int STATE_SYNC_IN_PROGRESS = 3;

    public static final int STATE_SYNC_CANCELLED = 4;

    private static GTaskManager mInstance = null;

    private Activity mActivity;

    private Context mContext;

    private ContentResolver mContentResolver;

    private boolean mSyncing;

    private boolean mCancelled;

    private HashMap<String, TaskList> mGTaskListHashMap = new HashMap<>();

    private HashMap<String, Node> mGTaskHashMap = new HashMap<>();

    private HashMap<String, MetaData> mMetaHashMap = new HashMap<>();

    private TaskList mMetaList = null;

    private HashSet<Long> mLocalDeleteIdMap = new HashSet<>();

    private HashMap<String, Long> mGidToNid = new HashMap<>();

    private HashMap<Long, String> mNidToGid = new HashMap<>();

    private GTaskManager() {
        mSyncing = false;
        mCancelled = false;
    }

    /**
     * 包含关键字synchronized,语言级同步,指明该函数可能运行在多线程的环境下。
     * 功能:类初始化函数
     * @return GtaskManger
     */
    public static synchronized GTaskManager getInstance() {//可能运行在多线程环境下,使用语言级同步--synchronized
        if (mInstance == null) {
            mInstance = new GTaskManager();
        }
        return mInstance;
    }

    /**
     * 包含关键字synchronized,语言级同步,指明该函数可能运行在多线程的环境下。
     * @param activity
     */
    public synchronized void setActivityContext(Activity activity) {
        // used for getting auth token
        mActivity = activity;
    }

    /**
     * 核心函数
     * 功能:实现了本地同步操作和远端同步操作,用于同步Google任务列表
     * @param context-----获取上下文
     * @param asyncTask-------用于同步的异步操作类
     * @return int
     */
    public int sync(Context context, GTaskASyncTask asyncTask) {           //核心函数
       /*检查是否已经在进行同步操作(mSyncing为true)
         如果是,则记录一条调试日志并返回STATE_SYNC_IN_PROGRESS状态,表示同步正在进行中
       */
        if (mSyncing) {
            Log.d(TAG, "Sync is in progress");
            return STATE_SYNC_IN_PROGRESS;
        }

        /*
          将传入的context赋值给成员变量mContext,并获取其内容解析器(ContentResolver)赋值给成员变量mContentResolver
          将mSyncing设置为true,表示开始同步操作,将mCancelled设置为false,表示同步未被取消
          清空所有与任务相关的数据结构(如任务列表、任务映射、元数据映射等)
         */
        mContext = context;
        mContentResolver = mContext.getContentResolver();
        mSyncing = true;
        mCancelled = false;
        mGTaskListHashMap.clear();
        mGTaskHashMap.clear();
        mMetaHashMap.clear();
        mLocalDeleteIdMap.clear();
        mGidToNid.clear();
        mNidToGid.clear();

        /**
         *创建一个GTaskClient实例
         * 重置更新数组
         * 登录Google任务。如果登录失败,抛出NetworkFailureException异常
         * 从Google获取任务列表,并将其转换为本地任务列表
         * 执行内容同步工作
         */
        try {
            GTaskClient client = GTaskClient.getInstance();//getInstance即为创建一个实例,client--客户机
            client.resetUpdateArray();//JSONArray类型,reset即置为NULL

            // login google task
            if (!mCancelled) {
                if (!client.login(mActivity)) {
                    throw new NetworkFailureException("login google task failed");
                }
            }

            // get the task list from google
            asyncTask.publishProgess(mContext.getString(R.string.sync_progress_init_list));
            initGTaskList();  //获取Google上的JSONtasklist转为本地TaskList

            // do content sync work
            asyncTask.publishProgess(mContext.getString(R.string.sync_progress_syncing));
            syncContent();
        } catch (NetworkFailureException e) {  //分为两种异常,此类异常为网络异常
            Log.e(TAG, e.toString());    //创建日志文件(调试信息),error
            return STATE_NETWORK_ERROR;
        } catch (ActionFailureException e) {  //此类异常为操作异常
            Log.e(TAG, e.toString());
            return STATE_INTERNAL_ERROR;
        } catch (Exception e) {
            Log.e(TAG, e.toString());
            e.printStackTrace();
            return STATE_INTERNAL_ERROR;
        } finally {
            mGTaskListHashMap.clear();
            mGTaskHashMap.clear();
            mMetaHashMap.clear();
            mLocalDeleteIdMap.clear();
            mGidToNid.clear();
            mNidToGid.clear();
            mSyncing = false;
        }
        //根据mCancelled的值返回相应的状态(STATE_SYNC_CANCELLED表示同步已取消,STATE_SUCCESS表示同步成功)
        return mCancelled ? STATE_SYNC_CANCELLED : STATE_SUCCESS;
    }

    /**
     *功能:初始化GtaskList,获取Google上的JSONtasklist转为本地TaskList。
     *获得的数据存储在mMetaList,mGTaskListHashMap,mGTaskHashMap
     *@exception NetworkFailureException
     *@return void
     */
    private void initGTaskList() throws NetworkFailureException {
        if (mCancelled)
            return;
        //getInstance即为创建一个实例,client应指远端客户机,用于与远程服务器进行通信
        GTaskClient client = GTaskClient.getInstance();
        try {
            /*Json对象是Name Value对(即子元素)的无序集合,相当于一个Map对象。JsonObject类是bantouyan-json库对Json对象的抽象,提供操纵Json对象的各种方法。
              其格式为{"key1":value1,"key2",value2....};key 必须是字符串。
              因为ajax请求不刷新页面,但配合js可以实现局部刷新,因此json常常被用来作为异步请求的返回对象使用
            */
            JSONArray jsTaskLists = client.getTaskLists(); //通过调用client.getTaskLists()方法获取远程服务器上的任务列表,并将其存储在JSONArray对象jsTaskLists中

            // init meta list first
            mMetaList = null;
            /*
            遍历jsTaskLists中的每个元素,将其转换为JSONObject对象,并从中提取任务列表的ID和名称
             */
            for (int i = 0; i < jsTaskLists.length(); i++) {
                JSONObject object = jsTaskLists.getJSONObject(i);  //JSONObject与JSONArray一个为对象,一个为数组。此处取出单个JASONObject
                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);

                /*
                如果任务列表的名称以特定的前缀开头且不等于元数据文件夹的前缀,则创建一个新的TaskList对象,并将其添加到本地的任务列表映射中
                同时,加载该任务列表的元数据,并将其添加到元数据列表映射中
                 */
                if (name.equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_META)) {
                    mMetaList = new TaskList();                    //MetaList意为元表,Tasklist类型,此处为初始化
                    mMetaList.setContentByRemoteJSON(object);      //将JSON中部分数据复制到自己定义的对象中相对应的数据:name->mname...

                    // load meta data
                    JSONArray jsMetas = client.getTaskList(gid);
                    for (int j = 0; j < jsMetas.length(); j++) {
                        object = (JSONObject) jsMetas.getJSONObject(j);
                        MetaData metaData = new MetaData();         //继承自Node
                        metaData.setContentByRemoteJSON(object);
                        if (metaData.isWorthSaving()) {             //if not worth to save,metadata将不加入mMetaList
                            mMetaList.addChildTask(metaData);
                            if (metaData.getGid() != null) {
                                mMetaHashMap.put(metaData.getRelatedGid(), metaData);
                            }
                        }
                    }
                }
            }

            /*
            如果本地没有元数据列表,则创建一个新的元数据列表,并将其设置为默认名称
            然后,使用GTaskClient.getInstance().createTaskList(mMetaList)方法将元数据列表上传到远程服务器
             */
            if (mMetaList == null) {
                mMetaList = new TaskList();
                mMetaList.setName(GTaskStringUtils.MIUI_FOLDER_PREFFIX
                        + GTaskStringUtils.FOLDER_META);
                GTaskClient.getInstance().createTaskList(mMetaList);
            }

            /*
            最后,再次遍历jsTaskLists中的每个元素,将其转换为JSONObject对象,并从中提取任务列表的ID和名称
             */
            for (int i = 0; i < jsTaskLists.length(); i++) {
                JSONObject object = jsTaskLists.getJSONObject(i);
                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);  //通过getString函数传入本地某个标志数据的名称,获取其在远端的名称。
                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);

                /*
                如果任务列表的名称以特定的前缀开头且不等于元数据文件夹的前缀,则创建一个新的TaskList对象,并将其添加到本地的任务列表映射中
                同时,加载该任务列表的任务,并将其添加到任务列表映射中
                 */
                if (name.startsWith(GTaskStringUtils.MIUI_FOLDER_PREFFIX)
                        && !name.equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX
                        + GTaskStringUtils.FOLDER_META)) {
                    TaskList tasklist = new TaskList();     //继承自Node
                    tasklist.setContentByRemoteJSON(object);
                    mGTaskListHashMap.put(gid, tasklist);
                    mGTaskHashMap.put(gid, tasklist);

                    // load tasks
                    JSONArray jsTasks = client.getTaskList(gid);
                    for (int j = 0; j < jsTasks.length(); j++) {
                        object = (JSONObject) jsTasks.getJSONObject(j);
                        gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
                        Task task = new Task();
                        task.setContentByRemoteJSON(object);
                        if (task.isWorthSaving()) {
                            task.setMetaInfo(mMetaHashMap.get(gid));
                            tasklist.addChildTask(task);
                            mGTaskHashMap.put(gid, task);
                        }
                    }
                }
            }

        } catch (JSONException e) {
            Log.e(TAG, e.toString());
            e.printStackTrace();
            throw new ActionFailureException("initGTaskList: handing JSONObject failed");
            /*
            如果在处理过程中发生任何JSONException异常,将记录错误日志并抛出一个ActionFailureException异常
             */
        }
    }

    /**
     * 功能:本地内容同步操作
     * @throws NetworkFailureException
     * @return 无返回值
     */
    private void syncContent() throws NetworkFailureException {    //本地内容同步操作
        int syncType;
        Cursor c = null;    //数据库指针
        String gid;         //GoogleID
        Node node;          //Node包含Sync_Action的不同类型

        mLocalDeleteIdMap.clear();   //HashSet<Long>类型

        if (mCancelled) {
            return;
        }

        /*
        查询本地已删除的笔记(即类型不是系统类型且父ID是垃圾文件夹的笔记),并将查询结果存储在游标c中
        遍历游标,获取每个笔记的Google ID(gid)和对应的节点(node)
        如果节点不为空,则从mGTaskHashMap中移除该节点,并调用doContentSync()方法进行同步操作
        同时,将该笔记的ID添加到mLocalDeleteIdMap中
         */
        try {
            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
                    "(type<>? AND parent_id=?)", new String[] {
                            String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)
                    }, null);
            if (c != null) {
                while (c.moveToNext()) {
                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                    node = mGTaskHashMap.get(gid);
                    if (node != null) {
                        mGTaskHashMap.remove(gid);
                        doContentSync(Node.SYNC_ACTION_DEL_REMOTE, node, c);
                    }

                    mLocalDeleteIdMap.add(c.getLong(SqlNote.ID_COLUMN));
                }
            } else {
                Log.w(TAG, "failed to query trash folder");
            }
        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }

        //同步文件夹
        syncFolder();

        /*
        查询数据库中存在的笔记(即类型是系统类型且父ID不是垃圾文件夹的笔记),并将查询结果存储在游标c中
        遍历游标,获取每个笔记的Google ID(gid)和对应的节点(node)
        如果节点不为空,则从mGTaskHashMap中移除该节点,并通过hashmap建立联系
        然后根据节点的同步操作类型(syncType),调用doContentSync()方法进行同步操作
         */
        try {
            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
                    "(type=? AND parent_id<>?)", new String[] {
                            String.valueOf(Notes.TYPE_NOTE), String.valueOf(Notes.ID_TRASH_FOLER)
                    }, NoteColumns.TYPE + " DESC");
            if (c != null) {
                while (c.moveToNext()) {
                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                    node = mGTaskHashMap.get(gid);
                    if (node != null) {
                        mGTaskHashMap.remove(gid);
                        mGidToNid.put(gid, c.getLong(SqlNote.ID_COLUMN));   //通过hashmap建立联系
                        mNidToGid.put(c.getLong(SqlNote.ID_COLUMN), gid);   //通过hashmap建立联系
                        syncType = node.getSyncAction(c);
                    } else {
                        if (c.getString(SqlNote.GTASK_ID_COLUMN).trim().length() == 0) {
                            // local add
                            syncType = Node.SYNC_ACTION_ADD_REMOTE;
                        } else {
                            // remote delete
                            syncType = Node.SYNC_ACTION_DEL_LOCAL;
                        }
                    }
                    doContentSync(syncType, node, c);
                }
            } else {
                Log.w(TAG, "failed to query existing note in database");
            }

        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }

        // go through remaining items
        Iterator<Map.Entry<String, Node>> iter = mGTaskHashMap.entrySet().iterator();   //Iterator迭代器
        while (iter.hasNext()) {
            Map.Entry<String, Node> entry = iter.next();
            node = entry.getValue();
            doContentSync(Node.SYNC_ACTION_ADD_LOCAL, node, null);
        }

        /*如果mCancelled为假,首先调用DataUtils.batchDeleteNotes()方法批量删除本地已删除的笔记
        若删除失败,则抛出ActionFailureException异常
         */
        if (!mCancelled) {
            if (!DataUtils.batchDeleteNotes(mContentResolver, mLocalDeleteIdMap)) {
                throw new ActionFailureException("failed to batch-delete local deleted notes");
            }
        }

        /*
        用于提交更新并且刷新本地同步ID
         */
        if (!mCancelled) {
            GTaskClient.getInstance().commitUpdate();
            refreshLocalSyncId();
        }

    }

    /**
     * 功能:
     * 同步文件夹
     * 先查询根文件夹、电话记录文件夹和本地存在的文件夹,然后根据查询结果执行相应的同步操作
     * 最后,会遍历远程添加的文件夹,并将它们添加到本地
     * 在整个过程中,如果遇到网络故障,会抛出NetworkFailureException异常
     * @throws NetworkFailureException
     */
    private void syncFolder() throws NetworkFailureException {
        Cursor c = null;
        String gid;
        Node node;
        int syncType;

        if (mCancelled) {
            return;
        }

        // for root folder
        try {
            c = mContentResolver.query(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI,
                    Notes.ID_ROOT_FOLDER), SqlNote.PROJECTION_NOTE, null, null, null);
            if (c != null) {
                c.moveToNext();
                gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                node = mGTaskHashMap.get(gid);
                if (node != null) {
                    mGTaskHashMap.remove(gid);
                    mGidToNid.put(gid, (long) Notes.ID_ROOT_FOLDER);
                    mNidToGid.put((long) Notes.ID_ROOT_FOLDER, gid);
                    // for system folder, only update remote name if necessary
                    if (!node.getName().equals(
                            GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_DEFAULT))
                        doContentSync(Node.SYNC_ACTION_UPDATE_REMOTE, node, c);
                } else {
                    doContentSync(Node.SYNC_ACTION_ADD_REMOTE, node, c);
                }
            } else {
                Log.w(TAG, "failed to query root folder");
            }
        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }

        // for call-note folder
        try {
            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE, "(_id=?)",
                    new String[] {
                            String.valueOf(Notes.ID_CALL_RECORD_FOLDER)
                    }, null);
            if (c != null) {
                if (c.moveToNext()) {
                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                    node = mGTaskHashMap.get(gid);
                    if (node != null) {
                        mGTaskHashMap.remove(gid);
                        mGidToNid.put(gid, (long) Notes.ID_CALL_RECORD_FOLDER);
                        mNidToGid.put((long) Notes.ID_CALL_RECORD_FOLDER, gid);
                        // for system folder, only update remote name if
                        // necessary
                        if (!node.getName().equals(
                                GTaskStringUtils.MIUI_FOLDER_PREFFIX
                                        + GTaskStringUtils.FOLDER_CALL_NOTE))
                            doContentSync(Node.SYNC_ACTION_UPDATE_REMOTE, node, c);
                    } else {
                        doContentSync(Node.SYNC_ACTION_ADD_REMOTE, node, c);
                    }
                }
            } else {
                Log.w(TAG, "failed to query call note folder");
            }
        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }

        // for local existing folders
        try {
            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
                    "(type=? AND parent_id<>?)", new String[] {
                            String.valueOf(Notes.TYPE_FOLDER), String.valueOf(Notes.ID_TRASH_FOLER)
                    }, NoteColumns.TYPE + " DESC");
            if (c != null) {
                while (c.moveToNext()) {
                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                    node = mGTaskHashMap.get(gid);
                    if (node != null) {
                        mGTaskHashMap.remove(gid);
                        mGidToNid.put(gid, c.getLong(SqlNote.ID_COLUMN));
                        mNidToGid.put(c.getLong(SqlNote.ID_COLUMN), gid);
                        syncType = node.getSyncAction(c);
                    } else {
                        if (c.getString(SqlNote.GTASK_ID_COLUMN).trim().length() == 0) {
                            // local add
                            syncType = Node.SYNC_ACTION_ADD_REMOTE;
                        } else {
                            // remote delete
                            syncType = Node.SYNC_ACTION_DEL_LOCAL;
                        }
                    }
                    doContentSync(syncType, node, c);
                }
            } else {
                Log.w(TAG, "failed to query existing folder");
            }
        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }

        // for remote add folders
        Iterator<Map.Entry<String, TaskList>> iter = mGTaskListHashMap.entrySet().iterator();
        while (iter.hasNext()) {
            Map.Entry<String, TaskList> entry = iter.next();
            gid = entry.getKey();
            node = entry.getValue();
            if (mGTaskHashMap.containsKey(gid)) {
                mGTaskHashMap.remove(gid);
                doContentSync(Node.SYNC_ACTION_ADD_LOCAL, node, null);
            }
        }

        if (!mCancelled)
            GTaskClient.getInstance().commitUpdate();
    }

    /**
     * 功能:
     * 根据传入的同步类型(syncType)对节点(Node)进行相应的操作
     * @param syncType
     * @param node
     * @param c
     * @throws NetworkFailureException
     */
    private void doContentSync(int syncType, Node node, Cursor c) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        MetaData meta;
        switch (syncType) {
            case Node.SYNC_ACTION_ADD_LOCAL:
                addLocalNode(node);
                break;
            case Node.SYNC_ACTION_ADD_REMOTE:
                addRemoteNode(node, c);
                break;
            case Node.SYNC_ACTION_DEL_LOCAL:
                meta = mMetaHashMap.get(c.getString(SqlNote.GTASK_ID_COLUMN));
                if (meta != null) {
                    GTaskClient.getInstance().deleteNode(meta);
                }
                mLocalDeleteIdMap.add(c.getLong(SqlNote.ID_COLUMN));
                break;
            case Node.SYNC_ACTION_DEL_REMOTE:
                meta = mMetaHashMap.get(node.getGid());
                if (meta != null) {
                    GTaskClient.getInstance().deleteNode(meta);
                }
                GTaskClient.getInstance().deleteNode(node);
                break;
            case Node.SYNC_ACTION_UPDATE_LOCAL:
                updateLocalNode(node, c);
                break;
            case Node.SYNC_ACTION_UPDATE_REMOTE:
                updateRemoteNode(node, c);
                break;
            case Node.SYNC_ACTION_UPDATE_CONFLICT:
                // merging both modifications maybe a good idea
                // right now just use local update simply
                updateRemoteNode(node, c);
                break;
            case Node.SYNC_ACTION_NONE:
                break;
            case Node.SYNC_ACTION_ERROR:
            default:
                throw new ActionFailureException("unkown sync action type");
        }
    }

    /**
     * 功能:将一个本地节点(Node)添加到数据库中
     * 首先检查是否已经取消操作,如果是,则直接返回
     * 否则,根据节点的类型(TaskList或其他类型),创建一个新的SqlNote对象,并设置其内容和父ID
     * 接下来,将新创建的SqlNote对象提交到数据库中,并更新gid-nid映射以及元数据。
     * @param node
     * @throws NetworkFailureException
     */
    private void addLocalNode(Node node) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        SqlNote sqlNote;
        if (node instanceof TaskList) {
            if (node.getName().equals(
                    GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_DEFAULT)) {
                sqlNote = new SqlNote(mContext, Notes.ID_ROOT_FOLDER);
            } else if (node.getName().equals(
                    GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_CALL_NOTE)) {
                sqlNote = new SqlNote(mContext, Notes.ID_CALL_RECORD_FOLDER);
            } else {
                sqlNote = new SqlNote(mContext);
                sqlNote.setContent(node.getLocalJSONFromContent());
                sqlNote.setParentId(Notes.ID_ROOT_FOLDER);
            }
        } else {
            sqlNote = new SqlNote(mContext);
            JSONObject js = node.getLocalJSONFromContent();
            try {
                if (js.has(GTaskStringUtils.META_HEAD_NOTE)) {
                    JSONObject note = js.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);
                    if (note.has(NoteColumns.ID)) {
                        long id = note.getLong(NoteColumns.ID);
                        if (DataUtils.existInNoteDatabase(mContentResolver, id)) {
                            // the id is not available, have to create a new one
                            note.remove(NoteColumns.ID);
                        }
                    }
                }

                if (js.has(GTaskStringUtils.META_HEAD_DATA)) {
                    JSONArray dataArray = js.getJSONArray(GTaskStringUtils.META_HEAD_DATA);
                    for (int i = 0; i < dataArray.length(); i++) {
                        JSONObject data = dataArray.getJSONObject(i);
                        if (data.has(DataColumns.ID)) {
                            long dataId = data.getLong(DataColumns.ID);
                            if (DataUtils.existInDataDatabase(mContentResolver, dataId)) {
                                // the data id is not available, have to create
                                // a new one
                                data.remove(DataColumns.ID);
                            }
                        }
                    }

                }
            } catch (JSONException e) {
                Log.w(TAG, e.toString());
                e.printStackTrace();
            }
            sqlNote.setContent(js);

            Long parentId = mGidToNid.get(((Task) node).getParent().getGid());
            if (parentId == null) {
                Log.e(TAG, "cannot find task's parent id locally");
                throw new ActionFailureException("cannot add local node");
            }
            sqlNote.setParentId(parentId.longValue());
        }

        // create the local node
        sqlNote.setGtaskId(node.getGid());
        sqlNote.commit(false);

        // update gid-nid mapping
        mGidToNid.put(node.getGid(), sqlNote.getId());
        mNidToGid.put(sqlNote.getId(), node.getGid());

        // update meta
        updateRemoteMeta(node.getGid(), sqlNote);
    }

    /**
     * 功能:update本地node
     * @param node
     * ----同步操作的基础数据类型
     * @param c
     * ----Cursor
     * @throws NetworkFailureException
     */
    private void updateLocalNode(Node node, Cursor c) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        SqlNote sqlNote;
        // update the note locally
        sqlNote = new SqlNote(mContext, c);
        sqlNote.setContent(node.getLocalJSONFromContent());

        Long parentId = (node instanceof Task) ? mGidToNid.get(((Task) node).getParent().getGid())
                : new Long(Notes.ID_ROOT_FOLDER);
        if (parentId == null) {
            Log.e(TAG, "cannot find task's parent id locally");
            throw new ActionFailureException("cannot update local node");
        }
        sqlNote.setParentId(parentId.longValue());
        sqlNote.commit(true);

        // update meta info
        updateRemoteMeta(node.getGid(), sqlNote);
    }

    /**
     * 功能:远程增加Node
     * 需要updateRemoteMeta
     * @param node
     * ----同步操作的基础数据类型
     * @param c
     * --Cursor
     * @throws NetworkFailureException
     */
    private void addRemoteNode(Node node, Cursor c) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        SqlNote sqlNote = new SqlNote(mContext, c); //从本地mContext中获取内容
        Node n;

        // update remotely
        if (sqlNote.isNoteType()) {
            Task task = new Task();
            task.setContentByLocalJSON(sqlNote.getContent());

            String parentGid = mNidToGid.get(sqlNote.getParentId());
            if (parentGid == null) {
                Log.e(TAG, "cannot find task's parent tasklist"); //调试信息
                throw new ActionFailureException("cannot add remote task");
            }
            mGTaskListHashMap.get(parentGid).addChildTask(task);   //在本地生成的GTaskList中增加子结点

            //登录远程服务器,创建Task
            GTaskClient.getInstance().createTask(task);
            n = (Node) task;

            // add meta
            updateRemoteMeta(task.getGid(), sqlNote);
        } else {
            TaskList tasklist = null;

            // we need to skip folder if it has already existed
            String folderName = GTaskStringUtils.MIUI_FOLDER_PREFFIX;
            if (sqlNote.getId() == Notes.ID_ROOT_FOLDER)
                folderName += GTaskStringUtils.FOLDER_DEFAULT;
            else if (sqlNote.getId() == Notes.ID_CALL_RECORD_FOLDER)
                folderName += GTaskStringUtils.FOLDER_CALL_NOTE;
            else
                folderName += sqlNote.getSnippet();

            //iterator迭代器,通过统一的接口迭代所有的map元素
            Iterator<Map.Entry<String, TaskList>> iter = mGTaskListHashMap.entrySet().iterator();
            while (iter.hasNext()) {
                Map.Entry<String, TaskList> entry = iter.next();
                String gid = entry.getKey();
                TaskList list = entry.getValue();

                if (list.getName().equals(folderName)) {
                    tasklist = list;
                    if (mGTaskHashMap.containsKey(gid)) {
                        mGTaskHashMap.remove(gid);
                    }
                    break;
                }
            }

            // no match we can add now
            if (tasklist == null) {
                tasklist = new TaskList();
                tasklist.setContentByLocalJSON(sqlNote.getContent());
                GTaskClient.getInstance().createTaskList(tasklist);
                mGTaskListHashMap.put(tasklist.getGid(), tasklist);
            }
            n = (Node) tasklist;
        }

        // update local note
        sqlNote.setGtaskId(n.getGid());
        sqlNote.commit(false);
        sqlNote.resetLocalModified();
        sqlNote.commit(true);

        // gid-id mapping                                             //创建id间的映射
        mGidToNid.put(n.getGid(), sqlNote.getId());
        mNidToGid.put(sqlNote.getId(), n.getGid());
    }

    /**
     * 功能:更新远端的Node,包含meta更新(updateRemoteMeta)
     * @param node
     * ----同步操作的基础数据类型
     * @param c
     *  --Cursor
     * @throws NetworkFailureException
     */
    private void updateRemoteNode(Node node, Cursor c) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        SqlNote sqlNote = new SqlNote(mContext, c);

        // update remotely
        node.setContentByLocalJSON(sqlNote.getContent());
        GTaskClient.getInstance().addUpdateNode(node);  //GTaskClient用途为从本地登陆远端服务器

        // update meta
        updateRemoteMeta(node.getGid(), sqlNote);

        // move task if necessary
        if (sqlNote.isNoteType()) {
            Task task = (Task) node;
            TaskList preParentList = task.getParent();
            //preParentList为通过node获取的父节点列表

            String curParentGid = mNidToGid.get(sqlNote.getParentId());
            //curParentGid为通过光标在数据库中找到sqlNote的mParentId,再通过mNidToGid由long类型转为String类型的Gid

            if (curParentGid == null) {
                Log.e(TAG, "cannot find task's parent tasklist");
                throw new ActionFailureException("cannot update remote task");
            }
            TaskList curParentList = mGTaskListHashMap.get(curParentGid);
            //通过HashMap找到对应Gid的TaskList
            if (preParentList != curParentList) {
                preParentList.removeChildTask(task);
                curParentList.addChildTask(task);
                GTaskClient.getInstance().moveTask(task, preParentList, curParentList);
            }
        }

        sqlNote.resetLocalModified();
        //commit到本地数据库
        sqlNote.commit(true);
    }

    /**
     * 功能:升级远程meta。  meta---元数据----计算机文件系统管理数据---管理数据的数据。
     * @param gid
     * ---GoogleID为String类型
     * @param sqlNote
     * ---同步前的数据库操作,故使用类SqlNote
     * @throws NetworkFailureException
     */
    private void updateRemoteMeta(String gid, SqlNote sqlNote) throws NetworkFailureException {
        if (sqlNote != null && sqlNote.isNoteType()) {
            MetaData metaData = mMetaHashMap.get(gid);
            if (metaData != null) {
                metaData.setMeta(gid, sqlNote.getContent());
                GTaskClient.getInstance().addUpdateNode(metaData);
            } else {
                metaData = new MetaData();
                metaData.setMeta(gid, sqlNote.getContent());
                mMetaList.addChildTask(metaData);
                mMetaHashMap.put(gid, metaData);
                GTaskClient.getInstance().createTask(metaData);
            }
        }
    }

    /**
     * 功能:刷新本地,给sync的ID对应上最后更改过的对象
     * @return void
     * @throws NetworkFailureException
     */
    private void refreshLocalSyncId() throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        //获取最近的(最晚的)gtask list
        mGTaskHashMap.clear();
        mGTaskListHashMap.clear();
        mMetaHashMap.clear();
        initGTaskList();

        Cursor c = null;
        try {
            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
                    "(type<>? AND parent_id<>?)", new String[] {
                            String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)
                    }, NoteColumns.TYPE + " DESC");  //query语句:五个参数,NoteColumns.TYPE + " DESC"-----为按类型递减顺序返回查询结果。new String[] {String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)}------为选择参数。"(type<>? AND parent_id<>?)"-------指明返回行过滤器。SqlNote.PROJECTION_NOTE--------应返回的数据列的名字。Notes.CONTENT_NOTE_URI--------contentProvider包含所有数据集所对应的uri
            if (c != null) {
                while (c.moveToNext()) {
                    String gid = c.getString(SqlNote.GTASK_ID_COLUMN);
                    Node node = mGTaskHashMap.get(gid);
                    if (node != null) {
                        mGTaskHashMap.remove(gid);
                        ContentValues values = new ContentValues(); //在ContentValues中创建键值对。准备通过contentResolver写入数据
                        values.put(NoteColumns.SYNC_ID, node.getLastModified());
                        mContentResolver.update(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, //进行批量更改,选择参数为NULL,应该可以用insert替换,参数分别为表名和需要更新的value对象。
                                c.getLong(SqlNote.ID_COLUMN)), values, null, null);
                    } else {
                        Log.e(TAG, "something is missed");
                        throw new ActionFailureException(
                                "some local items don't have gid after sync");
                    }
                }
            } else {
                Log.w(TAG, "failed to query local note to refresh sync id");
            }
        } finally {
            if (c != null) {
                c.close();
                c = null;
            }
        }
    }

    /**
     * 功能:获取同步账号,mAccount.name
     * @return String
     */
    public String getSyncAccount() {
        return GTaskClient.getInstance().getSyncAccount().name;
    }

    /**
     * 功能:取消同步,置mCancelled为true
     * @author TTS
     */
    public void cancelSync() {
        mCancelled = true;
    }
}