/*
 * 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.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.IBinder;

/**
 * Google Tasks同步服务
 * 管理Google Tasks与本地笔记之间的同步操作的Service组件
 * 提供开始同步、取消同步的功能，并通过广播通知同步状态和进度
 */
public class GTaskSyncService extends Service {
    // 动作类型常量定义
    public final static String ACTION_STRING_NAME = "sync_action_type";  // 动作类型的Intent额外数据键

    public final static int ACTION_START_SYNC = 0;                       // 开始同步动作
    public final static int ACTION_CANCEL_SYNC = 1;                      // 取消同步动作
    public final static int ACTION_INVALID = 2;                          // 无效动作

    // 广播相关常量定义
    public final static String GTASK_SERVICE_BROADCAST_NAME = "net.micode.notes.gtask.remote.gtask_sync_service";  // 广播的Intent动作名称
    public final static String GTASK_SERVICE_BROADCAST_IS_SYNCING = "isSyncing";                                    // 广播中同步状态的键
    public final static String GTASK_SERVICE_BROADCAST_PROGRESS_MSG = "progressMsg";                                // 广播中同步进度消息的键

    // 同步任务相关变量
    private static GTaskASyncTask mSyncTask = null;     // 当前执行的同步任务实例
    private static String mSyncProgress = "";           // 当前同步进度消息

    /**
     * 启动同步操作
     * 创建并执行Google Tasks同步异步任务
     * 如果已经有同步任务在执行，则不重复启动
     */
    private void startSync() {
        if (mSyncTask == null) {
            mSyncTask = new GTaskASyncTask(this, new GTaskASyncTask.OnCompleteListener() {
                public void onComplete() {
                    mSyncTask = null;
                    sendBroadcast("");
                    stopSelf();
                }
            });
            sendBroadcast("");
            mSyncTask.execute();
        }
    }

    /**
     * 取消同步操作
     * 如果有同步任务正在执行，则取消该任务
     */
    private void cancelSync() {
        if (mSyncTask != null) {
            mSyncTask.cancelSync();
        }
    }

    @Override
    public void onCreate() {
        // 服务创建时初始化同步任务为null
        mSyncTask = null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // 处理传入的Intent，根据动作类型执行相应的同步操作
        Bundle bundle = intent.getExtras();
        if (bundle != null && bundle.containsKey(ACTION_STRING_NAME)) {
            switch (bundle.getInt(ACTION_STRING_NAME, ACTION_INVALID)) {
                case ACTION_START_SYNC:
                    startSync();
                    break;
                case ACTION_CANCEL_SYNC:
                    cancelSync();
                    break;
                default:
                    break;
            }
            // 返回START_STICKY表示如果服务被系统杀死，会在资源允许时重新创建
            return START_STICKY;
        }
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onLowMemory() {
        // 系统内存不足时，如果有同步任务正在执行，则取消它以释放资源
        if (mSyncTask != null) {
            mSyncTask.cancelSync();
        }
    }

    /**
     * Service的绑定方法
     * 该服务不支持绑定，因此返回null
     * @param intent 绑定意图
     * @return null
     */
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    /**
     * 发送同步状态广播
     * 通知应用其他组件同步的当前状态和进度
     * @param msg 同步进度消息
     */
    public void sendBroadcast(String msg) {
        mSyncProgress = msg;
        Intent intent = new Intent(GTASK_SERVICE_BROADCAST_NAME);
        intent.putExtra(GTASK_SERVICE_BROADCAST_IS_SYNCING, mSyncTask != null);
        intent.putExtra(GTASK_SERVICE_BROADCAST_PROGRESS_MSG, msg);
        sendBroadcast(intent);
    }

    /**
     * 静态方法：启动Google Tasks同步服务
     * 这是启动同步的公共入口方法，设置Activity上下文并发送启动同步的Intent
     * @param activity 用于获取Google认证的Activity实例
     */
    public static void startSync(Activity activity) {
        GTaskManager.getInstance().setActivityContext(activity);
        Intent intent = new Intent(activity, GTaskSyncService.class);
        intent.putExtra(GTaskSyncService.ACTION_STRING_NAME, GTaskSyncService.ACTION_START_SYNC);
        activity.startService(intent);
    }

    /**
     * 静态方法：取消Google Tasks同步服务
     * 这是取消同步的公共入口方法，发送取消同步的Intent
     * @param context 应用上下文
     */
    public static void cancelSync(Context context) {
        Intent intent = new Intent(context, GTaskSyncService.class);
        intent.putExtra(GTaskSyncService.ACTION_STRING_NAME, GTaskSyncService.ACTION_CANCEL_SYNC);
        context.startService(intent);
    }

    /**
     * 静态方法：检查是否正在同步
     * @return true表示正在同步，false表示未在同步
     */
    public static boolean isSyncing() {
        return mSyncTask != null;
    }

    /**
     * 静态方法：获取当前同步进度消息
     * @return 当前同步进度消息字符串
     */
    public static String getProgressString() {
        return mSyncProgress;
    }
}
