package beacon

import (
	"context"
	log "log/slog"
	"time"

	"github.com/r3labs/sse/v2"
)

type Event = sse.Event

type EventSubscription struct {
	client  *sse.Client
	rawChan chan *sse.Event
	errChan chan error
}

func (se *EventSubscription) Close() {
	if nil == se.client {
		return
	}

	log.Debug("Disconnecting and destroying SSE client", "endpoint", se.client.URL)
	se.client.Unsubscribe(se.rawChan)
	se.client.Connection.CloseIdleConnections()
	se.client = nil
}

func (se *EventSubscription) Err() <-chan error {
	return se.errChan
}

func CreateSubscription(ctx context.Context, endpoint string, sink chan *Event) *EventSubscription {
	client := sse.NewClient(endpoint)
	errChan := make(chan error)
	listen := func() {
		errChan <- client.SubscribeChanRawWithContext(ctx, sink)
	}

	client.ReconnectNotify = func(err error, duration time.Duration) {
		log.Debug("Reconnecting SSE client", "endpoint", endpoint,
			"error", err, "duration", duration)
	}
	client.OnDisconnect(func(c *sse.Client) {
		log.Debug("SSE client disconnected", "endpoint", endpoint)
	})

	log.Debug("Subscribing to event stream", "endpoint", endpoint)
	go listen()

	return &EventSubscription{
		client:  client,
		rawChan: sink,
		errChan: errChan,
	}
}