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The reactive Postgres client
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/*
 * Copyright (C) 2017 Julien Viet
 *
 * 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 io.reactiverse.pgclient.pubsub;

import io.reactiverse.pgclient.PgConnectOptions;
import io.reactiverse.pgclient.PgConnection;
import io.reactiverse.pgclient.impl.pubsub.PgSubscriberImpl;
import io.vertx.codegen.annotations.Fluent;
import io.vertx.codegen.annotations.VertxGen;
import io.vertx.core.AsyncResult;
import io.vertx.core.Handler;
import io.vertx.core.Vertx;

import java.util.function.Function;

/**
 * A class for managing subscriptions using {@code LISTEN/UNLISTEN} to Postgres channels.
 * 
 * The subscriber manages a single connection to Postgres.
 */
@VertxGen
public interface PgSubscriber {

  /**
   * Create a subscriber.
   *
   * @param vertx the vertx instance
   * @param options the connect options
   * @return the subscriber
   */
  static PgSubscriber subscriber(Vertx vertx, PgConnectOptions options) {
    return new PgSubscriberImpl(vertx, options);
  }

  /**
   * Return a channel for the given {@code name}.
   *
   * @param name the channel name
   * 

   * This will be the name of the channel exactly as held by Postgres for sending
   * notifications.  Internally this name will be truncated to the Postgres identifier
   * maxiumum length of {@code (NAMEDATALEN = 64) - 1 == 63} characters, and prepared
   * as a quoted identifier without unicode escape sequence support for use in
   * {@code LISTEN/UNLISTEN} commands.  Examples of channel names and corresponding
   * {@code NOTIFY} commands:
   * 

   *   when {@code name == "the_channel"}: {@code NOTIFY the_channel, 'msg'},
   *   {@code NOTIFY The_Channel, 'msg'}, or {@code NOTIFY "the_channel", 'msg'}
   *   succeed in delivering a message to the created channel
   *   
   *   when {@code name == "The_Channel"}: {@code NOTIFY "The_Channel", 'msg'},
   *   succeeds in delivering a message to the created channel
   *   
   *   
   * 
   * @return the channel
   */
  PgChannel channel(String name);

  /**
   * Connect the subscriber to Postgres.
   *
   * @param handler the handler notified of the connection success or failure
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  PgSubscriber connect(Handler> handler);

  /**
   * Set the reconnect policy that is executed when the subscriber is disconnected.
   * 
   * When the subscriber is disconnected, the {@code policy} function is called with the actual
   * number of retries and returns an {@code amountOfTime} value:
   * 

   *   when {@code amountOfTime < 0}: the subscriber is closed and there is no retry
   *   when {@code amountOfTime == 0}: the subscriber retries to connect immediately
   *   when {@code amountOfTime > 0}: the subscriber retries after {@code amountOfTime} milliseconds
   * 
   * 
   * The default policy does not perform any retries.
   *
   * @param policy the policy to set
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  PgSubscriber reconnectPolicy(Function policy);

  /**
   * Set an handler called when the subscriber is closed.
   *
   * @param handler the handler
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  PgSubscriber closeHandler(Handler handler);

  /**
   * @return the actual connection to Postgres, it might be {@code null}
   */
  PgConnection actualConnection();

  /**
   * @return whether the subscriber is closed
   */
  boolean closed();

  /**
   * Close the subscriber, the retry policy will not be invoked.
   */
  void close();

}