-- This file demonstrates how to send events to subscribers of a topic
-- Detailed explanation can be found in the Aqua Book: https://doc.fluence.dev/aqua-book/libraries/aqua-dht#passing-data-to-subscribers

import "@fluencelabs/aqua-dht/pubsub.aqua"
import "@fluencelabs/aqua-dht/dht.aqua"

-- Application event
data Event:
    value: string

-- API that every subscriber must adhere to
-- You can think of it as an application protocol
service SubscriberAPI:
    receive_event(event: Event)

func call_subscriber(sub: Record, event: Event):
    -- topological move to subscriber via relay
    on sub.peer_id via sub.relay_id:
        -- resolve service on a subscriber
        SubscriberAPI sub.service_id
        -- call function
        SubscriberAPI.receive_event(event)

-- send event to every subscriber
func send_everyone(relay: PeerId, topic: string, event: Event):
    -- retrieve all subscribers of a topic
    subscribers <- findSubscribers(relay, topic)
    -- iterate through them
    for sub <- subscribers par:
        call_subscriber(sub, event)