Implemented event steam

[RomanovSci]

Signed-off-by: Roman Bylbas romka.bulbas@gmail.com

Summary

Implemented event steam

Checklist

• Code is properly formatted
• All commits are signed
• Tests included/updated or not needed
• Documentation (manuals or wiki) has been updated or is not required

[ihor]

@RomanovSci we need to add typing here. I guess, the most convenient way would be to have event-specific event classes. The parsing could be moved to the EventStream.

Note, that events include the standard Casper types inside of them.

[ihor]

The API is a bit confusing here:

1. We create an EventSource object and connect it to event source, which isn't logical thus isn't intuitive
2. We check if event id is not null, why? If that's part of the logic it should be handled by the library

Separatelly, we should provide possibility to start from the predefined event id, which could be passed in the event stream URL in the start_from parameter.

Note, the following possible usage:

$nodeUrl = 'http://localhost:9999';
$streamPath = \Casper\EventStream\EventSource::EVENT_TYPE_MAIN;
$startFromEvent = 12345;

$stream = new Casper\EventStream($nodeUrl, $streamPath, $startFromEvent);
$es->onEvent(
   function (\Casper\EventStream\DeployProcessedEvent $event) {
       echo json_encode($event->getDeployHeader()->getHash()) . "\n";
   }
);

$stream->listen();

[RomanovSci]

Regarding 2.
We just show how we can use abort() method

[ihor]

onEvent would be a better name

[ihor]

Why emtpy catch?

[ihor]

1. $startFrom isn't used anywhere
2. A better name would be listen

This function offers a blocking event processing. I guess it would be nice to offer an async interface. This way a consumer could subscribe to several event streams simultaneously and process all the events at once if needed. With the current approach it's not possible to process let's say main event stream and the deploys one.

[ihor]

@RomanovSci please check my comments

[mrkara]

@RomanovSci It looks like we have a small conflict on the README file. Could you please take a look?