/*
 * @(#)Installation.java		       Project:ProgramList
 * Date:2012-8-7
 *
 * Copyright (c) 2011 CFuture09, Institute of Software, 
 * Guangdong Ocean University, Zhanjiang, GuangDong, China.
 * All rights reserved.
 *
 * 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 com.githang.android.apnbb;

import android.content.Context;
import android.provider.Settings.Secure;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.UUID;

/**
 * 安装工具类，该类用于生成程序在该设备的唯一标识符。
 *
 * @author Geek_Soledad ([email protected])
 */
public class UUIDUtil {

    private static String sID = null;
    private static final String INSTALLATION = "INSTALLATION-"
            + UUID.nameUUIDFromBytes("androidkit".getBytes());

    /**
     * 返回该设备在此程序上的唯一标识符。
     *
     * @param context Context对象。
     * @return 表示该设备在此程序上的唯一标识符。
     */
    public static String getID(Context context) {
        if (sID == null) {
            synchronized (UUIDUtil.class) {
                if (sID == null) {
                    File installation = new File(context.getFilesDir(), INSTALLATION);
                    try {
                        if (!installation.exists()) {
                            writeInstallationFile(context, installation);
                        }
                        sID = readInstallationFile(installation);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return sID;
    }

    /**
     * 将表示此设备在该程序上的唯一标识符写入程序文件系统中。
     *
     * @param installation 保存唯一标识符的File对象。
     * @return 唯一标识符。
     * @throws java.io.IOException IO异常。
     */
    private static String readInstallationFile(File installation) throws IOException {
        RandomAccessFile accessFile = new RandomAccessFile(installation, "r");
        byte[] bs = new byte[(int) accessFile.length()];
        accessFile.readFully(bs);
        accessFile.close();
        return new String(bs);
    }

    /**
     * 读出保存在程序文件系统中的表示该设备在此程序上的唯一标识符。
     *
     * @param context      Context对象。
     * @param installation 保存唯一标识符的File对象。
     * @throws java.io.IOException IO异常。
     */
    private static void writeInstallationFile(Context context, File installation)
            throws IOException {
        FileOutputStream out = new FileOutputStream(installation);
        String uuid = UUID.nameUUIDFromBytes(
                Secure.getString(context.getContentResolver(), Secure.ANDROID_ID).getBytes())
                .toString();
        out.write(uuid.getBytes());
        out.close();
    }
}