/*
 * 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;


/**
 * Google Tasks同步管理器
 * 负责处理本地笔记与Google Tasks之间的同步逻辑
 * 实现单例模式，管理同步状态和同步操作
 */
public class GTaskManager {
    private static final String TAG = GTaskManager.class.getSimpleName();  // 日志标签

    // 同步状态常量定义
    public static final int STATE_SUCCESS = 0;              // 同步成功
    public static final int STATE_NETWORK_ERROR = 1;        // 网络错误
    public static final int STATE_INTERNAL_ERROR = 2;       // 内部错误
    public static final int STATE_SYNC_IN_PROGRESS = 3;     // 同步进行中
    public static final int STATE_SYNC_CANCELLED = 4;       // 同步已取消

    private static GTaskManager mInstance = null;           // 单例实例

    private Activity mActivity;                             // 用于获取认证令牌的Activity实例
    private Context mContext;                               // 应用上下文
    private ContentResolver mContentResolver;               // 内容解析器，用于访问本地数据库

    private boolean mSyncing;                               // 同步状态标志
    private boolean mCancelled;                             // 同步取消标志

    // Google Tasks数据结构映射
    private HashMap<String, TaskList> mGTaskListHashMap;    // Google任务列表映射
    private HashMap<String, Node> mGTaskHashMap;            // Google任务节点映射
    private HashMap<String, MetaData> mMetaHashMap;         // 元数据映射
    private TaskList mMetaList;                             // 元数据任务列表

    // 同步辅助数据结构
    private HashSet<Long> mLocalDeleteIdMap;                // 本地删除的笔记ID集合
    private HashMap<String, Long> mGidToNid;                // Google任务ID到本地笔记ID的映射
    private HashMap<Long, String> mNidToGid;                // 本地笔记ID到Google任务ID的映射

    /**
     * 私有构造函数 - 初始化同步管理器实例
     * 初始化所有同步相关的数据结构和状态标志
     */
    private GTaskManager() {
        mSyncing = false;
        mCancelled = false;
        mGTaskListHashMap = new HashMap<String, TaskList>();
        mGTaskHashMap = new HashMap<String, Node>();
        mMetaHashMap = new HashMap<String, MetaData>();
        mMetaList = null;
        mLocalDeleteIdMap = new HashSet<Long>();
        mGidToNid = new HashMap<String, Long>();
        mNidToGid = new HashMap<Long, String>();
    }

    /**
     * 获取GTaskManager的单例实例
     * 使用同步方法确保线程安全
     * @return GTaskManager单例实例
     */
    public static synchronized GTaskManager getInstance() {
        if (mInstance == null) {
            mInstance = new GTaskManager();
        }
        return mInstance;
    }

    /**
     * 设置Activity上下文
     * 用于后续获取Google认证令牌
     * @param activity 用于获取认证令牌的Activity实例
     */
    public synchronized void setActivityContext(Activity activity) {
        // used for getting authtoken
        mActivity = activity;
    }

    /**
     * 执行笔记与Google Tasks之间的同步操作
     * 这是GTaskManager的核心方法，协调整个同步流程
     * @param context 应用上下文
     * @param asyncTask 异步任务实例，用于发布同步进度
     * @return 同步状态码：
     *         STATE_SUCCESS - 同步成功
     *         STATE_NETWORK_ERROR - 网络错误
     *         STATE_INTERNAL_ERROR - 内部错误
     *         STATE_SYNC_IN_PROGRESS - 同步进行中
     *         STATE_SYNC_CANCELLED - 同步已取消
     */
    public int sync(Context context, GTaskASyncTask asyncTask) {
        if (mSyncing) {
            Log.d(TAG, "Sync is in progress");
            return STATE_SYNC_IN_PROGRESS;
        }
        mContext = context;
        mContentResolver = mContext.getContentResolver();
        mSyncing = true;
        mCancelled = false;
        mGTaskListHashMap.clear();
        mGTaskHashMap.clear();
        mMetaHashMap.clear();
        mLocalDeleteIdMap.clear();
        mGidToNid.clear();
        mNidToGid.clear();

        try {
            GTaskClient client = GTaskClient.getInstance();
            client.resetUpdateArray();

            // 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();

            // do content sync work
            asyncTask.publishProgess(mContext.getString(R.string.sync_progress_syncing));
            syncContent();
        } catch (NetworkFailureException e) {
            Log.e(TAG, e.toString());
            return STATE_NETWORK_ERROR;
        } catch (ActionFailureException e) {
            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;
        }

        return mCancelled ? STATE_SYNC_CANCELLED : STATE_SUCCESS;
    }

    /**
     * 初始化Google Tasks列表
     * 从Google服务器获取所有任务列表和任务数据，并构建本地映射
     * 处理元数据任务列表，确保其存在
     * @throws NetworkFailureException 如果网络请求失败
     * @throws ActionFailureException 如果处理JSON数据失败
     */
    private void initGTaskList() throws NetworkFailureException {
        if (mCancelled)
            return;
        GTaskClient client = GTaskClient.getInstance();
        try {
            JSONArray jsTaskLists = client.getTaskLists();

            // init meta list first
            mMetaList = null;
            for (int i = 0; i < jsTaskLists.length(); i++) {
                JSONObject object = jsTaskLists.getJSONObject(i);
                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);

                if (name
                        .equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_META)) {
                    mMetaList = new TaskList();
                    mMetaList.setContentByRemoteJSON(object);

                    // 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();
                        metaData.setContentByRemoteJSON(object);
                        if (metaData.isWorthSaving()) {
                            mMetaList.addChildTask(metaData);
                            if (metaData.getGid() != null) {
                                mMetaHashMap.put(metaData.getRelatedGid(), metaData);
                            }
                        }
                    }
                }
            }

            // create meta list if not existed
            if (mMetaList == null) {
                mMetaList = new TaskList();
                mMetaList.setName(GTaskStringUtils.MIUI_FOLDER_PREFFIX
                        + GTaskStringUtils.FOLDER_META);
                GTaskClient.getInstance().createTaskList(mMetaList);
            }

            // init task list
            for (int i = 0; i < jsTaskLists.length(); i++) {
                JSONObject object = jsTaskLists.getJSONObject(i);
                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);

                if (name.startsWith(GTaskStringUtils.MIUI_FOLDER_PREFFIX)
                        && !name.equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX
                                + GTaskStringUtils.FOLDER_META)) {
                    TaskList tasklist = new TaskList();
                    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");
        }
    }

    /**
     * 同步内容
     * 处理本地和Google Tasks之间的内容同步
     * 包括：
     * 1. 处理本地已删除的笔记
     * 2. 同步文件夹
     * 3. 处理本地已存在的笔记
     * 4. 处理Google端新增的内容
     * 5. 清理本地删除的笔记
     * 6. 刷新本地同步ID
     * @throws NetworkFailureException 如果网络请求失败
     */
    private void syncContent() throws NetworkFailureException {
        int syncType;
        Cursor c = null;
        String gid;
        Node node;

        mLocalDeleteIdMap.clear();

        if (mCancelled) {
            return;
        }

        // for local deleted note
        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;
            }
        }

        // sync folder first
        syncFolder();

        // for note existing in database
        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));
                        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 note in database");
            }

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

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

        // mCancelled can be set by another thread, so we neet to check one by
        // one
        // clear local delete table
        if (!mCancelled) {
            if (!DataUtils.batchDeleteNotes(mContentResolver, mLocalDeleteIdMap, mContext)) {
                throw new ActionFailureException("failed to batch-delete local deleted notes");
            }
        }

        // refresh local sync id
        if (!mCancelled) {
            GTaskClient.getInstance().commitUpdate();
            refreshLocalSyncId();
        }

    }

    /**
     * 同步文件夹
     * 处理本地和Google Tasks之间的文件夹同步
     * 包括：
     * 1. 同步根文件夹
     * 2. 同步通话记录文件夹
     * 3. 同步本地已存在的普通文件夹
     * 4. 同步Google端新增的文件夹
     * @throws NetworkFailureException 如果网络请求失败
     */
    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();
    }

    /**
     * 执行内容同步操作
     * 根据同步类型执行不同的同步动作
     * @param syncType 同步类型：
     *                 Node.SYNC_ACTION_ADD_LOCAL - 本地添加
     *                 Node.SYNC_ACTION_ADD_REMOTE - 远程添加
     *                 Node.SYNC_ACTION_DEL_LOCAL - 本地删除
     *                 Node.SYNC_ACTION_DEL_REMOTE - 远程删除
     *                 Node.SYNC_ACTION_UPDATE_LOCAL - 本地更新
     *                 Node.SYNC_ACTION_UPDATE_REMOTE - 远程更新
     *                 Node.SYNC_ACTION_UPDATE_CONFLICT - 更新冲突
     * @param node 要同步的节点
     * @param c 本地数据库游标
     * @throws NetworkFailureException 如果网络请求失败
     */
    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");
        }
    }

    /**
     * 添加本地节点
     * 将Google Tasks中的节点添加到本地数据库
     * @param node 要添加的Google Tasks节点
     * @throws NetworkFailureException 如果网络请求失败
     */
    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);
    }

    /**
     * 更新本地节点
     * 使用Google Tasks中的节点信息更新本地数据库中的笔记
     * @param node Google Tasks中的节点信息
     * @param c 本地数据库游标
     * @throws NetworkFailureException 如果网络请求失败
     */
    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);
    }

    /**
     * 添加远程节点
     * 将本地数据库中的笔记添加到Google Tasks
     * @param node Google Tasks节点（可能为null）
     * @param c 本地数据库游标
     * @throws NetworkFailureException 如果网络请求失败
     */
    private void addRemoteNode(Node node, Cursor c) throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        SqlNote sqlNote = new SqlNote(mContext, c);
        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");
                throw new ActionFailureException("cannot add remote task");
            }
            mGTaskListHashMap.get(parentGid).addChildTask(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<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
        mGidToNid.put(n.getGid(), sqlNote.getId());
        mNidToGid.put(sqlNote.getId(), n.getGid());
    }

    /**
     * 更新远程节点
     * 将本地数据库中笔记的更新同步到Google Tasks
     * 如果需要，还会处理任务的移动（更改父文件夹）
     * @param node Google Tasks节点
     * @param c 本地数据库游标
     * @throws NetworkFailureException 如果网络请求失败
     */
    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);

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

        // move task if necessary
        if (sqlNote.isNoteType()) {
            Task task = (Task) node;
            TaskList preParentList = task.getParent();

            String curParentGid = mNidToGid.get(sqlNote.getParentId());
            if (curParentGid == null) {
                Log.e(TAG, "cannot find task's parent tasklist");
                throw new ActionFailureException("cannot update remote task");
            }
            TaskList curParentList = mGTaskListHashMap.get(curParentGid);

            if (preParentList != curParentList) {
                preParentList.removeChildTask(task);
                curParentList.addChildTask(task);
                GTaskClient.getInstance().moveTask(task, preParentList, curParentList);
            }
        }

        // clear local modified flag
        sqlNote.resetLocalModified();
        sqlNote.commit(true);
    }

    /**
     * 更新远程元数据
     * 将本地笔记的元数据信息更新到Google Tasks的元数据列表中
     * @param gid Google Tasks节点ID
     * @param sqlNote 本地笔记对象
     * @throws NetworkFailureException 如果网络请求失败
     */
    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);
            }
        }
    }

    /**
     * 刷新本地同步ID
     * 同步完成后，更新本地笔记的同步ID为Google Tasks的最后修改时间
     * 确保下次同步时能正确检测到更改
     * @throws NetworkFailureException 如果网络请求失败
     */
    private void refreshLocalSyncId() throws NetworkFailureException {
        if (mCancelled) {
            return;
        }

        // get the latest 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");
            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();
                        values.put(NoteColumns.SYNC_ID, node.getLastModified());
                        mContentResolver.update(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI,
                                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;
            }
        }
    }

    /**
     * 获取当前同步账户
     * @return 当前用于Google Tasks同步的账户名称
     */
    public String getSyncAccount() {
        return GTaskClient.getInstance().getSyncAccount().name;
    }

    /**
     * 取消当前同步操作
     * 设置取消标志，使正在进行的同步操作能够优雅地终止
     */
    public void cancelSync() {
        mCancelled = true;
    }
}
