[gps] add docs.

Author: makasim

README.md

@@ -14,6 +14,7 @@ Features:
     * [Beanstalk](docs/transport/pheanstalk.md)
     * [STOMP](docs/transport/stomp.md)
     * [Amazon SQS](docs/transport/sqs.md)
+    * [Google PubSub](docs/transport/gps.md)
     * [Kafka](docs/transport/kafka.md)
     * [Redis](docs/transport/redis.md)
     * [Gearman](docs/transport/gearman.md)

docs/index.md

@@ -4,6 +4,7 @@
 * [Transports](#transports)
     - Amqp based on [the ext](transport/amqp.md), [bunny](transport/amqp_bunny.md), [the lib](transport/amqp_lib.md)
     - [Amazon SQS](transport/sqs.md)
+    - [Google PubSub](transport/gps.md)
     - [Beanstalk (Pheanstalk)](transport/pheanstalk.md)
     - [Gearman](transport/gearman.md)
     - [Kafka](transport/kafka.md)

docs/transport/gps.md

@@ -0,0 +1,74 @@
+# Google Pub Sub transport
+
+A transport for [Google Pub Sub](https://cloud.google.com/pubsub/docs/) cloud MQ.
+It uses internally official google sdk library [google/cloud-pubsub](https://packagist.org/packages/google/cloud-pubsub) 
+
+* [Installation](#installation)
+* [Create context](#create-context)
+* [Send message to topic](#send-message-to-topic)
+* [Consume message](#consume-message)
+
+## Installation
+
+```bash
+$ composer require enqueue/gps
+```
+
+## Create context
+
+To enable the Google Cloud Pub/Sub Emulator, set the `PUBSUB_EMULATOR_HOST` environment variable. 
+There is a handy docker container [google/cloud-sdk](https://hub.docker.com/r/google/cloud-sdk/).  
+
+```php
+<?php
+use Enqueue\Gps\GpsConnectionFactory;
+
+putenv('PUBSUB_EMULATOR_HOST=http://localhost:8900');
+
+$connectionFactory = new GpsConnectionFactory();
+
+$psrContext = $connectionFactory->createContext();
+```
+
+## Send message to topic
+
+Before you can send message you have to declare a topic. 
+The operation creates a topic on a broker side. 
+Google allows messages to be sent only to topic. 
+
+```php
+<?php
+/** @var \Enqueue\Gps\GpsContext $psrContext */
+
+$fooTopic = $psrContext->createTopic('foo');
+$message = $psrContext->createMessage('Hello world!');
+
+$psrContext->declareTopic($fooTopic);
+
+$psrContext->createProducer()->send($fooTopic, $message);
+```
+
+## Consume message:
+
+Before you can consume message you have to subscribe a queue to the topic. 
+Google does not allow consuming message from the topic directly. 
+
+```php
+<?php
+/** @var \Enqueue\Gps\GpsContext $psrContext */
+
+$fooTopic = $psrContext->createTopic('foo');
+$fooQueue = $psrContext->createQueue('foo');
+
+$psrContext->subscribe($fooTopic, $fooQueue);
+
+$consumer = $psrContext->createConsumer($fooQueue);
+$message = $consumer->receive();
+
+// process a message
+
+$consumer->acknowledge($message);
+// $consumer->reject($message);
+```
+
+[back to index](../index.md)