/*断点续传下载接口*/
  @Streaming/*大文件需要加入这个判断，防止下载过程中写入到内存中*/
  @GET
  Observable<ResponseBody> download(@Header("RANGE") String start, @Url String url);

/**
 * 自定义进度的body
 * @author wzg
 */
public class DownloadResponseBody extends ResponseBody {
  private ResponseBody responseBody;
  private DownloadProgressListener progressListener;
  private BufferedSource bufferedSource;

  public DownloadResponseBody(ResponseBody responseBody, DownloadProgressListener progressListener) {
    this.responseBody = responseBody;
    this.progressListener = progressListener;
  }

  @Override
  public BufferedSource source() {
    if (bufferedSource == null) {
      bufferedSource = Okio.buffer(source(responseBody.source()));
    }
    return bufferedSource;
  }

  private Source source(Source source) {
    return new ForwardingSource(source) {
      long totalBytesRead = 0L;
      @Override
      public long read(Buffer sink, long byteCount) throws IOException {
        long bytesRead = super.read(sink, byteCount);
        // read() returns the number of bytes read, or -1 if this source is exhausted.
        totalBytesRead += bytesRead != -1 ? bytesRead : 0;
        if (null != progressListener) {
          progressListener.update(totalBytesRead, responseBody.contentLength(), bytesRead == -1);
        }
        return bytesRead;
      }
    };
  }
}

/**
 * 成功回调处理
 * Created by WZG on 2016/10/20.
 */
public interface DownloadProgressListener {
  /**
   * 下载进度
   * @param read
   * @param count
   * @param done
   */
  void update(long read, long count, boolean done);
}

/**
 * 成功回调处理
 * Created by WZG on 2016/10/20.
 */
public class DownloadInterceptor implements Interceptor {

  private DownloadProgressListener listener;

  public DownloadInterceptor(DownloadProgressListener listener) {
    this.listener = listener;
  }

  @Override
  public Response intercept(Chain chain) throws IOException {
    Response originalResponse = chain.proceed(chain.request());

    return originalResponse.newBuilder()
        .body(new DownloadResponseBody(originalResponse.body(), listener))
        .build();
  }
}

public class DownInfo {
  /*存储位置*/
  private String savePath;
  /*下载url*/
  private String url;
  /*基础url*/
  private String baseUrl;
  /*文件总长度*/
  private long countLength;
  /*下载长度*/
  private long readLength;
  /*下载唯一的HttpService*/
  private HttpService service;
  /*回调监听*/
  private HttpProgressOnNextListener listener;
  /*超时设置*/
  private int DEFAULT_TIMEOUT = 6;
  /*下载状态*/
  private DownState state;
  }

public enum DownState {
  START,
  DOWN,
  PAUSE,
  STOP,
  ERROR,
  FINISH,
}

/**
 * 下载过程中的回调处理
 * Created by WZG on 2016/10/20.
 */
public abstract class HttpProgressOnNextListener<T> {
  /**
   * 成功后回调方法
   * @param t
   */
  public abstract void onNext(T t);

  /**
   * 开始下载
   */
  public abstract void onStart();

  /**
   * 完成下载
   */
  public abstract void onComplete();


  /**
   * 下载进度
   * @param readLength
   * @param countLength
   */
  public abstract void updateProgress(long readLength, long countLength);

  /**
   * 失败或者错误方法
   * 主动调用，更加灵活
   * @param e
   */
   public void onError(Throwable e){

   }

  /**
   * 暂停下载
   */
  public void onPuase(){

  }

  /**
   * 停止下载销毁
   */
  public void onStop(){

  }
}

/**
 * 用于在Http请求开始时，自动显示一个ProgressDialog
 * 在Http请求结束是，关闭ProgressDialog
 * 调用者自己对请求数据进行处理
 * Created by WZG on 2016/7/16.
 */
public class ProgressDownSubscriber<T> extends Subscriber<T> implements DownloadProgressListener {
  //弱引用结果回调
  private WeakReference<HttpProgressOnNextListener> mSubscriberOnNextListener;
  /*下载数据*/
  private DownInfo downInfo;


  public ProgressDownSubscriber(DownInfo downInfo) {
    this.mSubscriberOnNextListener = new WeakReference<>(downInfo.getListener());
    this.downInfo=downInfo;
  }

  /**
   * 订阅开始时调用
   * 显示ProgressDialog
   */
  @Override
  public void onStart() {
    if(mSubscriberOnNextListener.get()!=null){
      mSubscriberOnNextListener.get().onStart();
    }
    downInfo.setState(DownState.START);
  }

  /**
   * 完成，隐藏ProgressDialog
   */
  @Override
  public void onCompleted() {
    if(mSubscriberOnNextListener.get()!=null){
      mSubscriberOnNextListener.get().onComplete();
    }
    downInfo.setState(DownState.FINISH);
  }

  /**
   * 对错误进行统一处理
   * 隐藏ProgressDialog
   *
   * @param e
   */
  @Override
  public void onError(Throwable e) {
    /*停止下载*/
    HttpDownManager.getInstance().stopDown(downInfo);
    if(mSubscriberOnNextListener.get()!=null){
      mSubscriberOnNextListener.get().onError(e);
    }
    downInfo.setState(DownState.ERROR);
  }

  /**
   * 将onNext方法中的返回结果交给Activity或Fragment自己处理
   *
   * @param t 创建Subscriber时的泛型类型
   */
  @Override
  public void onNext(T t) {
    if (mSubscriberOnNextListener.get() != null) {
      mSubscriberOnNextListener.get().onNext(t);
    }
  }

  @Override
  public void update(long read, long count, boolean done) {
    if(downInfo.getCountLength()>count){
      read=downInfo.getCountLength()-count+read;
    }else{
      downInfo.setCountLength(count);
    }
    downInfo.setReadLength(read);
    if (mSubscriberOnNextListener.get() != null) {
      /*接受进度消息，造成UI阻塞，如果不需要显示进度可去掉实现逻辑，减少压力*/
      rx.Observable.just(read).observeOn(AndroidSchedulers.mainThread())
          .subscribe(new Action1<Long>() {
        @Override
        public void call(Long aLong) {
           /*如果暂停或者停止状态延迟，不需要继续发送回调，影响显示*/
          if(downInfo.getState()==DownState.PAUSE||downInfo.getState()==DownState.STOP)return;
          downInfo.setState(DownState.DOWN);
          mSubscriberOnNextListener.get().updateProgress(aLong,downInfo.getCountLength());
        }
      });
    }
  }

}

 /**
   * 获取单例
   * @return
   */
  public static HttpDownManager getInstance() {
    if (INSTANCE == null) {
      synchronized (HttpDownManager.class) {
        if (INSTANCE == null) {
          INSTANCE = new HttpDownManager();
        }
      }
    }
    return INSTANCE;
  }

 /*回调sub队列*/
  private HashMap<String,ProgressDownSubscriber> subMap;
  /*单利对象*/
  private volatile static HttpDownManager INSTANCE;

  private HttpDownManager(){
    downInfos=new HashSet<>();
    subMap=new HashMap<>();
  }

 /**
   * 开始下载
   */
  public void startDown(DownInfo info){
    /*正在下载不处理*/
    if(info==null||subMap.get(info.getUrl())!=null){
      return;
    }
    /*添加回调处理类*/
    ProgressDownSubscriber subscriber=new ProgressDownSubscriber(info);
    /*记录回调sub*/
    subMap.put(info.getUrl(),subscriber);
    /*获取service，多次请求公用一个sercie*/
    HttpService httpService;
    if(downInfos.contains(info)){
      httpService=info.getService();
    }else{
      DownloadInterceptor interceptor = new DownloadInterceptor(subscriber);
      OkHttpClient.Builder builder = new OkHttpClient.Builder();
      //手动创建一个OkHttpClient并设置超时时间
      builder.connectTimeout(info.getConnectionTime(), TimeUnit.SECONDS);
      builder.addInterceptor(interceptor);

      Retrofit retrofit = new Retrofit.Builder()
          .client(builder.build())
          .addConverterFactory(GsonConverterFactory.create())
          .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
          .baseUrl(info.getBaseUrl())
          .build();
      httpService= retrofit.create(HttpService.class);
      info.setService(httpService);
    }
    /*得到rx对象-上一次下載的位置開始下載*/
    httpService.download("bytes=" + info.getReadLength() + "-",info.getUrl())
        /*指定线程*/
        .subscribeOn(Schedulers.io())
        .unsubscribeOn(Schedulers.io())
          /*失败后的retry配置*/
        .retryWhen(new RetryWhenNetworkException())
        /*读取下载写入文件*/
        .map(new Func1<ResponseBody, DownInfo>() {
          @Override
          public DownInfo call(ResponseBody responseBody) {
            try {
              writeCache(responseBody,new File(info.getSavePath()),info);
            } catch (IOException e) {
              /*失败抛出异常*/
              throw new HttpTimeException(e.getMessage());
            }
            return info;
          }
        })
        /*回调线程*/
        .observeOn(AndroidSchedulers.mainThread())
        /*数据回调*/
        .subscribe(subscriber);

  }

  /**
   * 写入文件
   * @param file
   * @param info
   * @throws IOException
   */
  public void writeCache(ResponseBody responseBody,File file,DownInfo info) throws IOException{
    if (!file.getParentFile().exists())
      file.getParentFile().mkdirs();
    long allLength;
    if (info.getCountLength()==0){
      allLength=responseBody.contentLength();
    }else{
      allLength=info.getCountLength();
    }
      FileChannel channelOut = null;
      RandomAccessFile randomAccessFile = null;
      randomAccessFile = new RandomAccessFile(file, "rwd");
      channelOut = randomAccessFile.getChannel();
      MappedByteBuffer mappedBuffer = channelOut.map(FileChannel.MapMode.READ_WRITE,
          info.getReadLength(),allLength-info.getReadLength());
      byte[] buffer = new byte[1024*8];
      int len;
      int record = 0;
      while ((len = responseBody.byteStream().read(buffer)) != -1) {
        mappedBuffer.put(buffer, 0, len);
        record += len;
      }
      responseBody.byteStream().close();
        if (channelOut != null) {
          channelOut.close();
        }
        if (randomAccessFile != null) {
          randomAccessFile.close();
        }
  }

/**
   * 停止下载
   */
  public void stopDown(DownInfo info){
    if(info==null)return;
    info.setState(DownState.STOP);
    info.getListener().onStop();
    if(subMap.containsKey(info.getUrl())) {
      ProgressDownSubscriber subscriber=subMap.get(info.getUrl());
      subscriber.unsubscribe();
      subMap.remove(info.getUrl());
    }
    /*同步数据库*/
  }

 /**
   * 暂停下载
   * @param info
   */
  public void pause(DownInfo info){
    if(info==null)return;
    info.setState(DownState.PAUSE);
    info.getListener().onPuase();
    if(subMap.containsKey(info.getUrl())){
      ProgressDownSubscriber subscriber=subMap.get(info.getUrl());
      subscriber.unsubscribe();
      subMap.remove(info.getUrl());
    }
    /*这里需要讲info信息写入到数据中，可自由扩展，用自己项目的数据库*/
  }

/**
   * 停止全部下载
   */
  public void stopAllDown(){
    for (DownInfo downInfo : downInfos) {
      stopDown(downInfo);
    }
    subMap.clear();
    downInfos.clear();
  }

  /**
   * 暂停全部下载
   */
  public void pauseAll(){
    for (DownInfo downInfo : downInfos) {
      pause(downInfo);
    }
    subMap.clear();
    downInfos.clear();
  }