NewEventSystem creates a new manager that listens for event on the given mux, parses and filters them.

BlocksSubscription queries hashes for blocks that are imported.

LastSubscription keeps track of the last index.

LogsSubscription queries for new or removed (chain reorg) logs.

UnknownSubscription indicates an unknown subscription type.

EventSystem creates subscriptions, processes events and broadcasts them to the subscription which match the subscription criteria.

Subscription is created when the client registers itself for a particular event.