///////// 使用方式一: 在业务代码中处理幂等 ////////////
// 接口调用方
Idempotence idempotence = new Idempotence();
String idempotenceId = idempotence.createId();
Order order = createOrderWithIdempotence(..., idempotenceId);

// 接口实现方
public class OrderController {
  private Idempotence idempontence; // 依赖注入
  
  public Order createOrderWithIdempotence(..., String idempotenceId) {
    // 前置操作
    boolean existed = idempotence.check(idempotenceId);
    if (existed) {
      // 两种处理方式：
      // 1. 查询order，并且返回；
      // 2. 返回duplication operation Exception
    }
    idempotence.record(idempotenceId);
        
    //...执行正常业务逻辑
  }
  
  public Order createOrder(...) {
    //...
  }
}

///////// 使用方式二：在框架层面处理幂等 //////////////
// 接口调用方
Idempotence idempotence = new Idempotence();
String idempotenceId = idempotence.createId();
//...通过feign框架将幂等号添加到http header中...

// 接口实现方
public class OrderController {
  @IdempotenceRequired
  public Order createOrder(...) {
    //...
  }
}

// 在AOP切面中处理幂等
@Aspect
public class IdempotenceSupportAdvice {
  @Autowired
  private Idempotence idempotence;

@Pointcut("@annotation(com.xzg.cd.idempotence.annotation.IdempotenceRequired)")
  public void controllerPointcut() {
  }

  @Around(value = "controllerPointcut()")
  public Object around(ProceedingJoinPoint joinPoint) throws Throwable {
    // 从HTTP header中获取幂等号idempotenceId
    
    // 前置操作
    boolean existed = idempotence.check(idempotenceId);
    if (existed) {
      // 两种处理方式：
      // 1. 查询order，并且返回；
      // 2. 返回duplication operation Exception
    }
    idempotence.record(idempotenceId)
    
    Object result = joinPoint.proceed();    
    return result;
  }
}

public class Idempotence {
  // comment-1: 如果要替换存储方式，是不是很麻烦呢？
  private JedisCluster jedisCluster;

  // comment-2: 如果幂等框架要跟业务系统复用jedisCluster连接呢？
  // comment-3: 是不是应该注释说明一下redisClusterAddress的格式，以及config是否可以传递进null呢？
  public Idempotence(String redisClusterAddress, GenericObjectPoolConfig config) {
    // comment-4: 这段逻辑放到构造函数里，不容易写单元测试呢
    String[] addressArray= redisClusterAddress.split(";");
    Set<HostAndPort> redisNodes = new HashSet<>();
    for (String address : addressArray) {
      String[] hostAndPort = address.split(":");
      redisNodes.add(new HostAndPort(hostAndPort[0], Integer.valueOf(hostAndPort[1])));
    }
    this.jedisCluster = new JedisCluster(redisNodes, config);
  }
  
  // comment-5: generateId()是不是比缩写要好点？
  // comment-6: 根据接口隔离原则，这个函数跟其他函数的使用场景完全不同，这个函数主要用在调用方，其他函数用在实现方，是不是应该分别放到两个类中？
  public String genId() {
    return UUID.randomUUID().toString();
  }

  // comment-7: 返回值的意义是不是应该注释说明一下？
  public boolean saveIfAbsent(String idempotenceId) {
    Long success = jedisCluster.setnx(idempotenceId, "1");
    return success == 1;
  }

  public void delete(String idempotenceId) {
    jedisCluster.del(idempotenceId);
  }
}

// 每个类的代码实现
public class Idempotence {
  private IdempotenceStorage storage;

  public Idempotence(IdempotenceStorage storage) {
    this.storage = storage;
  }

  public boolean saveIfAbsent(String idempotenceId) {
    return storage.saveIfAbsent(idempotenceId);
  }

  public void delete(String idempotenceId) {
    storage.delete(idempotenceId);
  }
}

public interface IdempotenceStorage {
  boolean saveIfAbsent(String idempotenceId);
  void delete(String idempotenceId);
}


public class RedisClusterIdempotenceStorage implements IdempotenceStorage {
  private JedisCluster jedisCluster;

  /**
   * Constructor
   * @param redisClusterAddress the format is 128.91.12.1:3455;128.91.12.2:3452;289.13.2.12:8978
   * @param config should not be null
   */
  public RedisIdempotenceStorage(String redisClusterAddress, GenericObjectPoolConfig config) {
    Set<HostAndPort> redisNodes = parseHostAndPorts(redisClusterAddress);
    this.jedisCluster = new JedisCluster(redisNodes, config);
  }

  public RedisIdempotenceStorage(JedisCluster jedisCluster) {
    this.jedisCluster = jedisCluster;
  }

  /**
   * Save {@idempotenceId} into storage if it does not exist.
   * @param idempotenceId the idempotence ID
   * @return true if the {@idempotenceId} is saved, otherwise return false
   */
  public boolean saveIfAbsent(String idempotenceId) {
    Long success = jedisCluster.setnx(idempotenceId, "1");
    return success == 1;
  }

  public void delete(String idempotenceId) {
    jedisCluster.del(idempotenceId);
  }

  @VisibleForTesting
  protected Set<HostAndPort> parseHostAndPorts(String redisClusterAddress) {
    String[] addressArray= redisClusterAddress.split(";");
    Set<HostAndPort> redisNodes = new HashSet<>();
    for (String address : addressArray) {
      String[] hostAndPort = address.split(":");
      redisNodes.add(new HostAndPort(hostAndPort[0], Integer.valueOf(hostAndPort[1])));
    }
    return redisNodes;
  }
}

public class IdempotenceIdGenerator {
  public String generateId() {
    return UUID.randomUUID().toString();
  }
}